Voyager the Grand Tour to Interstellar Space

Home , Gary Flandro, Gliese 445, The Day the Earth Smiled

Sky at Night MAGAZINE DISCOVER SPACE The story of voyager the grand tour to interstellar space

EXCLUSIVE IN-DEPTH INTERVIEWS WITH VOYAGER SCIENTISTS PLUS, NASA TELLS US HOW THE VOYAGERS CONTINUE TO SHAPE TODAY’S MISSIONS

MARVELS AND MYSTERIES: OUR FARTHEST ENVOY: WHAT MESSAGES FOR ET: HOW THE VOYAGERS’ GREATEST VOYAGER 1 IS TELLING US THE GOLDEN RECORD COULD DISCOVERIES REVEALED ABOUT INTERSTELLAR SPACE HELP ALIENS FIND EARTH TECHNOLOGICALLYSUPERIOR

THE ALL NEW “If you’re looking for a portable heavy duty mount... the CGX-L is a worthy contender” 0bca^]^\h=^f9d]T &XbbdT GERMAN EQUATORIAL MOUNT

Celestron’s newly designed CGX-L Computerised Equatorial mount and tripod is the latest addition to the fully computerised equatorial mount series. Capable of carrying Celestron’s largest optical tubes with ease, CGX-L is designed for backyard observatories and remote imagers looking for exceptional load capacity to weight ratio, compact design, and innovative features that fully support large telescopes, imaging kits, and the latest in Additional Ports wireless tech accessories.

~4gcaP[PaVT&$[QRP_PRXch ~;PaVTa ##\\SXP\TcTa fâ\fWTT[b ~;^]VTa!& \\SêTcPX[bPSS[Tc^bd__âc [PaVTa^_cXRP[cdQTb ~AT\^cT^_TaPcX^]UaXT]S[hUTPcdaTb ~8]cTa]P[RPQ[T\P]PVT\T]c Longer Dovetail Saddle ~

2^]ca^[b^UcfPaTX]R^]Yd]RcX^]fXcW Smoother Belt Drive System

ALSO AVAILABLE THE ORIGINAL

Compact Designed Tripod ~;PaVT$$[QRP_PRXch ~0[[]TfSTbXV] BcdaSXTaP]S\âT aXVXSfXcW`dXRZTa SP\_T]X]VcX\T ~8\_aêTS\^câb P]SSaXeTbhbcT\b

Celestron® and StarSenseTM are registered trademarks or trademarks of Celestron Acquisition, LLC in the United States and in dozens of other countries around the world. All rights reserved. David Hinds Ltd is an authorised distributor and reseller of Celestron products. THE STORY OF VOYAGER 3 may be reproduced in any FOREWORD The Story Of Voyager It’s a majestic tale that’s echoed on’t join you us for the ride? Kev Lochun, Editor Lochun, Kev since 1972 – before the spacecraft were called even But ‘Voyager’. what of the NASA future? director of planetary science James Green reveals continue how the Voyagers to shape modern space exploration. through the years and is expected for a decadecontinue more.to W © Immediate Media Company Bristol 2017. All rights reserved. No part of form or by any means either wholly or in part, without prior written permission of the publisher. Not to be resold, lent, hired out or otherwise disposed of by way of trade at more than the Printed condition. mutilated in or price retail recommended in the UK by William Gibbons Ltd. The publisher, editor and products, any of respect in responsibility no accept authors goods or services which may be advertised or referred to in this in mistakes or misstatements omissions, errors, any for or issue references. or advertisements such any

www.skyatnightmagazine.com www.skyatnightmagazine.com erwin K Chris Chris

Nicholas BrettNicholas

Mandy Thwaites Mandy Eva Abramik

Marcus ArthurMarcus

Andy Marshall Andy

“Between them the Voyagers “Between them the Voyagers Jemima Dixon Jemima

visited four planets and 48 moons, 23 of which23 had we no idea existed” Tom Bureau Tom The story is one of the of Voyager

most complex there is – so as well as giving the you rundown of their myriad discoveries, asked we the people in the missioninvolved to relive it in their own words. They include Carolyn Porco, who spotted the still-unexplained spokes in the rings of Saturn and helped organise the Solar ‘family System’s mastermind Dodd, Suzanne portrait’; of the ongoing interstellar mission; and projectEd Stone, Voyager’s scientist interstellar space. It’s an astounding legacy for a pair of probes that each have 240,000 computingaround less times power than an average smartphone and aneight-track tape for a brain. ([email protected]) www.bbcworldwide.com/uk--anz/ ukpublishing.aspx Publisher Magazines and NPD Coordinator Publishing UK Director of Consumer Products and Publishing Moultrie Andrew Governance Editorial of Director Publishing Director, UK Publishing CEO WORLDWIDE BBC President of UK and ANZ PUBLISHING Publisher Managing Director Email us at: [email protected] at: us Email Like what read? you’ve

G XQFKH D inda Morabito, HƅQHRXU OO\O L G

D WELCOME through the the through cosmos for ƅQ two-thirds the of been speeding speeding been spacecraft have have spacecraft G entire Space Age. Q Derrick Andrews Derrick

The twin Voyager unt and Chris Sutch D

ob Brock ob H V R Dreamt up in those Sarah Powell Sarah ob Banino ob

R Chris Bramley Chris

QHW Tony

D O ochun S L Steve Marsh

ev obinson (0117 314 8811) K

loyd (0117 300 8276) R L The past 40 years have been revelatory.

Art Editor Art Production EditorProduction Managing EditorManaging Reprographics EDITORIAL Editor Production CoordinatorProduction Advertising Managers Advertising Neil Tony PRODUCTION Director Production CIRCULATION / ADVERTISING Head of Circulation THANKS TO Bonnie Buratti, Suzanne Dodd, Carolyn Porco, Ed Stone CONTRIBUTORS Ben Evans, Mark Garlick, James Green, Elizabeth Pearson, Ben Skuse, Paul Sutherland, Iain Todd heady, halcyon years thatpreceded the Apollo 11 landing as a ‘Grand of Tour’ WKHRXWHU LQWKH\ZHQWRQWRUH understanding of the Solar System. Between them four the visited Voyagers planets and 48 moons, 23 of which we had no idea existed. They saw new rings, volcanoes, geysers and even aurorae. 1 is pushing Now Voyager the very limit of exploration, as it ventures beyond the solar bubble our star forces out around it and into the unknown of

NASA/JPL-CALTECH/PROCESSING BY STEVE MARSH, THIS PAGE: NASA/JPL-CALTECH PAGE: THIS MARSH, STEVE BY NASA/JPL-CALTECH/PROCESSING COVER IMAGE: MARK GARLICK - FURNISHED WITH PHOTOGRAPHIC ELEMENTS © © ELEMENTS PHOTOGRAPHIC WITH FURNISHED - GARLICK MARK IMAGE: COVER THE STORY OF VOYAGER 4 LEGACY AGRAND IV PHASE 82 78 70 family 68 oftheicegiants portrait 64 56 TERRITORY UNCHARTED III PHASE 54 OLD II PHASE 28 FRIENDS I PHASE GRAND 6 IDEAS Contents CONTENTS meet theirend? meet 98 94 90 84 50 42 38 30 53 Night 26 Magazine 25 22 20 12 8 The pre-Voyager years www.skyatnightmagazine.com The chanceof lifetimes three

So long, Solar System long, Solar So Subscribe to Subscribe The Pale Dot Blue The Solar System’s TheSolar Theunknown realm fromthestars Messages

Titanic discoveries atSaturn Secrets erupt from erupt Jupiter Secrets The Voyagers’ bumpy rides Voyager’s milestones great

Anuclear-powered marvel

The voices ofVoyager: The voices ofVoyager: Suzanne Dodd Buratti Bonnie The voices ofVoyager: Ed Stone The voices ofVoyager: The voices ofVoyager: Linda Morabito Carolyn Porco H L essons from thevoyage ow willtheVoyagers’ B k t at BBC Sky

THE STORY OF VOYAGER MARK GARLICK MARK 5

CONTENTS www.skyatnightmagazine.com THE STORY OF VOYAGER 6 Tour’ a‘Grand completing spacecraft of one of prospect thetantalising System, offering the Solar sideof onthesame ranged would be planets outer 1970s, inthelate allfour extraordinary: something noticed Flandro Gary in1965, JPL intern Then B GRAND IDEAS PHASE I in1979 Jupiter with Voyagerof 1’s encounter here’smissions; hisimagining NASA many of paintings created Ken Hodges US artist IDEASGRAND www.skyatnightmagazine.com once, and Uranus and Neptune not at all. notatall. Neptune Uranusand and once, only Saturn by probes, human twice visited was patchy.giants onlybeen had Jupiter efore Voyager, ourknowledge oftheouter optimism that steeped the mission as a whole. themission asawhole. optimism that steeped to theoutergiantsinmind istestamenttothe the Voyagers were mission builtwithanextended RQO\RIƅ 1977, inAugustandSeptember launched they were DQ development was by plagued tighteningbudgets Voyager was noteasy. spacecraft Their Translating all. them intotheeventual thisidea G WH F KQ FL DOO\ERXQ LF DO F RQ F H G U IR Q V U DQ -X SL G ZKHQWKH WH U DQ G 6 DWX SU REH U Q 7 V KDW ƅQDOO\

THE STORY OF VOYAGER GRANGER HISTORICAL PICTURE ARCHIVE/ALAMY STOCK PHOTO STOCK ARCHIVE/ALAMY PICTURE HISTORICAL GRANGER 7

GRAND IDEAS www.skyatnightmagazine.com THE STORY OF VOYAGER years The pre-Voyager 6RODU6\VWHPŜHQGHGŝZLWK-XSLWHU XQ ERWK1HSWXQHDQG8UDQXVZHUH WKLQ (DUWKZHUHQRQHWKHZLVHU WLPHVEHIRUHZKLOVWZHRQ LWKDGWUDFHGRXWPLOOLRQVRI ŚWKHFRPSOHWLRQRIDMRXUQH\ LWVGLVFRYHU\\HDUVHDUOLHU ƅUVWIXOORUELWRIWKH6XQVLQFH 8 IDEAS:GRAND BEFORE VOYAGER Words: Ben Evans Words: Ben JULY 2011MARKED www.skyatnightmagazine.com ,WVHHPVVWUDQJHQRZWR N QRZQWRXVDQGWKDWWKH N WKDWRQO\\HDUVSULRU the twin spacecraft visit wouldoneday were looking wondering upand abouttheplanets System, across theSolar adventure people grand Long before scientists to satdown discuss Voyager’s Neptune’s Neptune’s DQWLTXLW\LWŝVƅWWLQJ DVWURORJHUVVLQFH DVWURQRPHUVDQG LQWKHQLJKWV WKDQSRLQWVRIOLJKW 7KH\ZHUHOLWWOHPRUH ZKDWZH ZHUHIDUUHPRYHGIURP WKHVHIRXURXWHUZRUOGV LQRXULGHDVDERXW FRQƅUPHGE\REVHUYDWLRQ H[LVWHQFHRI1HSWXQHZDV DQG6DWXUQ(YHQDIWHUWKH .QRZQWR N QRZWRGD\ N \ Galileo ﬁrst demonstrated his telescope histelescope ﬁrstdemonstrated Galileo HPHUJHIURPWKHJORRP WHOHVFRSHGLGWKHGLVWDQWSODQHWV 2QO\ZLWKWKHLQYHQWLRQRIWKH EHIDUODUJHUWKDQRXURZQ LPDJLQHGWKHZRUOGVZRXOG VRWKH\FRXOGVFDUFHO\KDYH RIPLOOLRQVRI WKDWWKHVHSODQHWVOD\KXQGUHGV WKHHDUO\VWDUJD]HUVZDVWKHIDFW Ŝ%ULQJHURI2OG$JHŝ8Q WKHJRG DVVRFLDWHGZLWK-XSLWHUŝVIDWKHU KHDYHQVRQWKHRWKHUKDQGZDV VORZPRYHPHQWDFURVVWKH PRVWLPSRUWDQWJRG6DWXUQŝV ŚZDVQDPHGDIWHUWKH5RPDQVŝ EULJKWHVWREMHFWVLQWKHV WKDW-XSLWHUŚRQHRIWKH Revelations REVHUYDWLRQVUHYHDOHGWKHP KLVKDQGFUDIWHGWHOHVFRSHRQ ,Q*DOLOHR*DOLOHLIRFXVHG WREHQDWXUDOVDWHOOLWHVŚWKH OL -XSLWHUDQGVSRWWHGIRXUVWDU N HREMHFWVQHDUE\6XEVHTXHQW revealed Jupiter’s moons in1610 Jupiter’s moons revealed design in1609.design observations His the Roman pantheon Roman the HDUOLHVW from the king of the gods in gods the of king the from largest planet, takes its name name its takes planet, largest Y Jupiter, the Solar System’s Jupiter, Solar the N QRZQIRUEHLQJWKH N N QRZQDIWHURXU LORPHWUHVDZD\ N QRZQWR N \ Z

SCIENCE HISTORY IMAGES/ALAMY STOCK PHOTO, ISTOCK, NASA X 8 THE STORY OF VOYAGER 9 WKŝ W D S ZH G HQH V H E Ŝ P J LQ RRQ 0 FRQƅU KHULF V HULW 3DVV G VS Q V R D UWKŝ PE P WH (D W S D Q WRUŚ H HWKHX I D D 6 ring and revealed that P X L Q F , T HWK (S Y L WHQFHR ike Pioneer 10, Pioneer 11’s visit to V After passing Saturn, by Pioneer 11 WXUQ L RRQ WWKHH drop in high- particles energy as it passed at by a distance of 43,000km. It inferred the H[L the ring plane, Pioneer 11 discovered thin the Titan was too cold to support life. came within 360,000km of Titan U aurorae, photographed the the photographed aurorae, northern polar regions – revealing cloud tops substantially lower than D Callisto to be 1.5 times more PDVV 20,000km past the ringed world, imaging (and almost hitting) the tiny P Jupiter had its fair share of drama. As the probe prepared to make its closest pass, a strike operators by of a diesel generator threatened to tracking Australian the down shut station to which much of Pioneer 11’s data would be sent. The station remained open, and however, the probe’s tour of the giant planet ended successfully before it headed on to 6D V V J S DV V www.skyatnightmagazine.com www.skyatnightmagazine.com G W LQ UWKŝ KL URƅOH ZHOO V Z Q V LW S P G D G (D DV LR Q Q D G WLRQ D WXUH D 5DG D HWKHƅU UWK H HU HUWK G QHWLFƅHO (D J DP H PS KHUHFRQƅU WKHH[WHQW P GRAND IDEAS: BEFORE VOYAGER BEFORE GRAND IDEAS: HF QHWLFUHO WR G E PDJ VS WURQ G OWH Q\ W V D D UH V PDJ H * HULƅH YDV LRQR RWZHUHUHWXUQH G Y V P HUWLF Q OH[ PSD V Rŝ Y D 6S , W WKH LRQHHU I G V PS G FR 3 H SD WLRQ G 5 D FR W LW\R D XUR LWHU V D ( KRZH HUWH Pioneer 10 caught Pioneer sunrise on Jupiter 10 as it approached and passed the planet largest moon, Titan, appeared Saturn’s G S WKHƅU After Pioneer 10 came Pioneer 11. It passed 130,000km Jupiter’s over V Y HQ Q X W with Jupiter. Close-range views of the including features, atmospheric *UH DV G as Pioneer 11 approached theas Pioneer planet 11 of the planet’s outer gaseous envelope. In December this 1974, second probe raised suspicions that Jupiter was a ringed world when it measured a brief a doughnut-shaped plasma torus D U U man-made machine to visit the planet. During its passage, the probe triggeredsuffered failures, false circuit 1,000 absorbed times and commands the human-lethal dose of high-energy radiation. against Yet all the odds, survived. 10 Pioneer magnetic equator, revealing an electron ƆX[WL In December 1973, three and a half centuries after Galileo peered at - , LQ 500 images revealed bright features RQ RFFXOW Pioneer 10 also took Pioneer shots 10 of Jupiter’s Great Jupiter’s Red Spot and the Jupiter’s gas bands Jupiter’s were seen in Pioneer 11 pictured the Cassini Pioneer 11 the plucky Pioneers U Ganymede, largest Jupiter’s moon unprecedented detail by Pioneer 11 Pioneer by detail unprecedented Division between A and B rings Saturn’s U U U shadow Io as seen Pioneer by 10 THE STORY OF VOYAGER although in although solid were they assumed down topin harder two mysterious ‘ears’ on ‘ears’on mysterious two 10 Z IDEAS:GRAND BEFORE VOYAGER writer $DQG%ULQJV ‘gap’ the eponymous between *LRYDQQL&DVVLQLLGHQWLƅHGDQ was it and ring S H he was seeing a triple planet atriple was seeing he so novel” to edge open partly from moved they as rings majestic its witnessing H E eventually christened Callisto surprising D children his swallowed had S that mused mythology EULHƆ\YDQLVKHG$OOXGLQJWR they when astonishment uropa aturn was encircled by a thin by athin was encircled aturn own own uygens correctly infer that that infer correctly uygens e didn’t realise it realise e didn’t escribing the sight as “so as“so sight the escribing T T The origins of the outer planets outer ofthe origins The ground for planets in its wake. its in planets for ground breeding afertile leaving exploded, that companion abinary perhaps or ‘proto-star’ cooler asmaller, was cores. Maybe theplanetary culprit toform Sun the from strips with another star tore gaseous thatpostulated a near-miss and helium. hydrogen of fusion the by powered was Sun the that inrealised 1938 until remained unanswered, energy its gained star parent our how of question the But core. dense, super-heated asuper- toform gas surrounding dust and collapsed, drawing in a gaseous ‘nebula’ that retinueits emerged from and Sun the that argued Pierre recently, when Immanuel That relatively belief changed creation. of centre the at lay Earth F Not until 1655 or millennia, humans believed that he nature of the rings was rings ofthe nature he year same hat www.skyatnightmagazine.com Several astronomers M J , G H ean Chapelain argued argued Chapelain ean - oon – and they were were they –and oon L on and he expressed expressed he and on ans Bethe , G , so unlooked aplace andaplace others anymede and I and anymede , he lightheartedly alileo wondered if 166 aturn really really aturn 1675 0 the F 0 the did Christiaan Christiaan did but he was he , but G . M before before alileo saw saw alileo any rench rench for and and -for S , o aturn . . K . ant, , . and composer composer and the rings occupied discrete orbits discrete occupied rings the forming particles the that J move across that ofcloud bands the by examining began interiors U four giants Inside the L by P was endorsed and endured rings of‘solid’ notion QXPHURXVWLQ\REMHFWV%XWWKH of up made be might they that was was WKDWWKHVXQOLJKWWKH\UHƆHFWHG $PHULFDŝV-DPHV.HHOHUVKRZHG before particles” of unconnected SUHGLFWHGşDQLQGHƅQLWHQXPEHU J I ring cast doubt on their solidity C gauzy ofthe discovery the until shared by all four giants – and –and giants by allfour shared –acharacteristic poles the at VHHPHGƆDWWHQHGRUREODWH planet the that noticed Cassini speeds different at rotate atmosphere ofits parts revealed t was the S t was the upiter’s face ames Clerk Clerk ames aplace nderstanding the outer planets’ planets’ outer the nderstanding G centre of the Universe, held sway for centuries centuries for sway held Universe, the of centre D erman U oppler , aF The geocentric model, with Earth at the the at Earth with model, geocentric The cottish scientist scientist cottish rench scholar rench - - M born astronomer shifted an approach that that , anapproach axwell who who axwell W am illi , meaning H ierre ierre erschel and , and . . . , asterisks (top) asterisks represented, as moons, largest Jupiter’s of four movements the and (above), ‘ears’as having Saturn observed U Galileo Galileo the summer of 1977. in tounlock sought Voyager probes more massive that than the Earth, times many worlds, outer four these of secrets the was It gas. nebular more tohold masses and sizes collapse, 4.5 billion years ago, ago, years billion 4.5 collapse, nebula’s the that idea the favoured formed a protostar, around which which around aprotostar, formed %\V LQ ƆRZH J assembled theirassembled chemical UH the disc cooled and formed formed and cooled disc the J of calculations early enabled this ‘failed star’ ‘failed of notions ZDVDERLOLQJƆXLGUDLVLQJHDUO\ interior planet’s the that argue astronomer sunlight incident from receives as it heat asmuch twice radiates that ofhydrogen up made predominantly a composition Saturn, planetary cores that gorged gorged that cores planetary upiter’s rotation rate rotation upiter’s G J LHQW themselves on surrounding rocky androcky gaseous. G upiter’s low density hinted at at hinted density low upiter’s material. Nebular densities The cores of Jupiter, Jupiter, of cores The was two planetary classes: classes: planetary two was at various distances further out. The result result The out. further D from the centre led to led centre the from volatiles migrated FLHQWLƅFFRQ inward and lighter chemicalthe differing elements condensed heavier planets: the compositions of V G U L D . T V Q ranus and Neptune FR his led E led his G J . S upiter being a being upiter R J I pectroscopy later later pectroscopy ichard UHZWR JDV *U V HQ nglish V P DG V X . roctor to roctor X I V X ƅFLHQW D OO\

SCIENCE HISTORY IMAGES/ALAMY STOCK PHOTO, NASA/ESA/AND A. SIMON (GSFC), NASA/JPL/SWRI, HORST ZIEGLER/CCDGUIDE.COM THE STORY OF VOYAGER . , 11 ur ur V , its aturn . . O . heir heir upiter apetus though , though , ranging I . T alilean’ G itan at S at itan toned off worlds - . Neptune’s large - , despite evidence sized T , unleashing an - ranus and Neptune stop tours of the giants riton didn’t even have riton didn’t even - , spectroscopy revealed , U upit T J uch of this uncertainty 944 M %XWWKHP\VWHULHVGLGQŝWHQG oyager probes arrived probes oyager aturn n 1 would be revolutionised the probes would raise as many questions answer as they’d DQRIƅFLDOQDPHXQWLOWKHODVW century and of nitrogen ice on its surface exact mass uncertain was WKHUH$URXQGDOOIRXUJLDQWVZHUH large retinues of moons from entire understanding of J S vanished when overnight the V 7LWDQDVWKHƅUVWQDWXUDOVDWHOOLWH known to possess a substantial DWPRVSKHUH$ERXWWKHUHVWIDU less known was moon unprecedented torrent of data about these far I whistle RSHQHGWKHƆRRGJDWHVRIKXPDQ knowledge satellites to two ‘ four er’s and planet - . -

. . 6, clever , clever , and 4 0s pointed www.skyatnightmagazine.com www.skyatnightmagazine.com 8 9 during a stellar ranus’s plain ranus’s , intensifying , while Neptune and direct mathematics mathematics observation mechanics U ° inexplicable orbital orbital inexplicable façade aquamarine 77, 8 , observations from WKDQƅFWLRQPL[RI , extending part of was interpretedwas as 9 through a stranger being a methane n 1 upiter was found in 18 infrared spectroscopyinfrared rich atmosphere rich arcs’ . I - GRAND IDEAS: BEFORE VOYAGER BEFORE GRAND IDEAS: - tilt 9 of un far S antalisingly showed that it radiated as to ‘ring the around way the planet Chile in the early 1 much heat as it receivedfrom the RFFXOWDWLRQƅYHQDUURZULQJV were detected astronomers by DERDUGWKH.XLSHU$LUERUQH 2EVHUYDWRU\%\WKLVWLPH evidence for rings had also been J at seen similar searches at Neptune T It soon Z easily seen easily both Jupiter to observers of Jupiter are A perfect this telescopic telescopic this and Saturn. In moons orbited image the four that families of of families that became evident Gallilean moons U circle projected over this Hubble shot of Jupiter reveals the giant planet’s oblateness, a trait spotted by Giovanni Cassini . z

. hour hour -

22.2 HDQG 0 N 1 upiter and J , the two oyager probes oyager upiter’s upiter’s his allowed the OLQVHUHQGLSLWRXVO\ . N erschel in 1781 . T . H arold , when bursts at 1 MH , Rupert 4 discovered telescopically telescopically , discovered 7 aturn were inconclusive 9 S illiam 1 , matching J , an icy many times before that – he largest (relative to the , z W ildt and $PDJQHWLF ranus Jupiter’s colossal magneticJupiter’s ﬁeld is t planet’s size) and strongest in the Solar System aturn sketchy was fforts to observe emissions effreys upiter’s far the is by strongest f our knowledge of .HQQHWK)UDQ ƅHOGUHPDLQHG hypothetical until ZKHQWKH$PHULFDQ DVWURQRPHUV%HUQDUG%XU Extending our reach I MH S outermost giants were a virtual blank before the V discovered radio bursts at U others led to theories of a rocky core revealed ammonia and , whilemethane the work of H J W mantle and a gaseous deep atmosphere E from until were recorded ƅHOGŝVH[LVWHQFHWREHLQIHUUHG IRUWKHƅUVWWLPH$OOIRXUJLDQWV KDYHPDJQHWLFƅHOGVEXW J and the only one that can be measured in the radio range rotation rate by – but seen and mistaken for a star exhibits a peculiar rotational THE STORY OF VOYAGER 12 lifetimes IDEAS:GRAND CONCEPT &DEVELOPMENT

NASA/SCIENCE PHOTO LIBRARY three naysayers and conﬂicting and naysayers agendasit became themission wenowknowasVoyager alignment wouldnotberepeated that 176 another for surviving After budget years. cuts, The project the‘Grand Tour’ dubbed ﬁrst fromtheaccidental grew discovery ofacosmic www.skyatnightmagazine.com The chance of Words: Ben Evans Words: Ben THE STORY OF VOYAGER , Z L 13 landro realisedlandro ranus and Neptune and ranus U ) in Pasadena, the Voyager the Voyager L NASA artwork showed how e drew his inspiration H its way through the Solar System of Jupiter and Saturn to slingshot Voyager 2 would use theVoyager gravities landro was an aeronautics F aboratory (JP THE DAWN OF THE DAWN programme came with a Eureka moment worthy of Archimedes’ bath or Newton’s apocryphal apple. In July 1965, in “a rare moment of great exhilaration” Gary F that all four of the giant planets – Jupiter, Saturn, – would be aligned along the ecliptic plane in the late 1970s and early 1980s, allowing for an unprecedented of theGrand outer Solar Tour System. It was his work that sowed the seed for one of the most remarkable history. human in adventures postgraduate at NASA’s Jet Propulsion Propulsion Jet NASA’s at postgraduate L California. another JP mathematicianfrom at Michael Minovitch, who in 1961 1961 in who Minovitch, Michael attempted to tackle the formidable www.skyatnightmagazine.com www.skyatnightmagazine.com GRAND IDEAS: CONCEPT & DEVELOPMENT & CONCEPT GRAND IDEAS: THE STORY OF VOYAGER the WKHJUDYLWDWLRQDOLQƆXHQFHVRI how exactly topredict sought 300 thrust’ ‘gravity misconceptions about RYHUDOOƆLJKWGXUDWLRQ and energy launch in savings destination toanother redirected be then to the spacecraft an incoming of course the toadjust used JUDYLWDWLRQDOƅHOGVFRXOGEH M comet satellite object a third of trajectory the perturb would the dawn of the ofthe dawn the at shift aparadigm marking 14 to years ahalf and two times: WRJHWKHUZLWKOHQJWK\ƆLJKW energies launch huge demanded )O\LQJGLUHFWWRWKHRXWHUSODQHWV adecade than less in Neptune to reach J launch in a that noting and trajectories ofpotential hundreds mapping PRGLƅHGWKHFDOFXODWLRQV DIWHUWKLVUHYHODWLRQ)ODQGUR outer the in planets multiple with 1 between M isrevealedA route spacecraft passing accelerate asthey of energy amounts small lose themselves Z IDEAS:GRAND CONCEPT &DEVELOPMENT was the fact that planets planets that fact was the W planets visiting the closer on instead focused missions early and high prohibitively were belt asteroid the beyond E less time more taking trajectory direct its outside it gravity and energy aspacecraft’s in change net no be would there that M 9 upiter’s immense gravity gravity immense upiter’s nergy requirements to travel totravel requirements nergy ‘three inovitch realised that launches launches that realised inovitch inovitch noticed that planetary planetary that inovitch noticed ars 8 H 7KLVZDVKXJHO\VLJQLƅFDQW hat wasn’t fully understood understood fully wasn’t hat 0 could achieve rendezvous rendezvous achieve 0 could ) www.skyatnightmagazine.com is work laid to rest several several torest laid is work S - to reach its destination its toreach year . un and a given planet planet agiven and un

S M , S . as

olar - - W un any engineers suspected suspected any engineers , M body problem’ assist’ assist’ an asteroid or a or anasteroid S - 1 1 orking mainly at night ercury old conundrum aturn 9 M . 9

62-1 T - S , 76-1 yielding substantial substantial yielding inovitch it called assist would carry carry would assist ystem he craft could could craft he , such as a natural asanatural such ( 9 or ‘gravity , 9

, 66 S U

78 V , pace Age ( terrestrial terrestrial ranus and and ranus rather than enus and and enus and and . could employ employ could . A few years Afewyears .

T 1 , relative relative 9 his - 76- .

. )

distant dwarf dwarf distant planets outer the of combinations differing reach be halved visit gains gravitational potential these giant planets the of secrets the key unlocking in VXSSO\VWDWLRQŠDQGDFUXFLDO J DERXWHLJKW\HDUVŠ,QKLVPLQG in toNeptune you out took that one was the my favourite “but ƆLJKWWLPHVŠ)ODQGURH[SODLQHG and oftrajectories range whole in Neptune in 9 by DQGKDYHLWVWUDMHFWRU\GHƆHFWHG reach could ofsummer J and November November and S in dates launch that suggested YLDWKHGLUHFWURXWH)ODQGUR needed time ofthe athird in reachable became Neptune by accelerated be then Neptune to years the heliocentric longitudes After exhaustively plotting observed that during the the during that observed upiter was best “the energy upiter eptember ,IWKH\PDGHHIƅFLHQWXVHRI T 1 9 hen came the bombshell the came hen 7 8 J ° to rendezvous with with ° torendezvous , 0 upiter and and upiter the time needed to needed time the , ,

six years to years six U U . But by launching in the the in by launching But ranus in in ranus , ranus and 30 years to years 30 and ranus while while 1 1 1 9 J 9 9 77, upiter in early 86. 77, P luto 1 a spacecraft aspacecraft 9

“ U S O . , 7 1 including the the including aturn could could aturn I ranus and and ranus studied a studied 9 9 were ideal to ideal 9 were ctober . S 8 aturn 4 and 4 and 11 km/s 1 1 S 9 , 9 ,

he 16 8 1 aturn 78 9 . 0s

9 ,

a rare alignment during an internship at NASA in1965 NASA at aninternship during alignment a rare gravitational fields could be used to steer spacecraft steer to used be could fields gravitational U U Gary Flandro realised the outer planets would fall into into fall would planets outer the realised Flandro Gary Michael Minovitch’s work showed how planetary planetary Minovitch’s how showed work Michael been concentrating on missions missions on concentrating been to the inner planets – such as –such planets inner the to Prior to Voyager, to Prior had NASA Mariner 10,Mariner past flew which Venus andMercury

GARY FLANDRO/SUUNEWS, NASA/JPL/USGS X 2, NASA/JPL THE STORY OF VOYAGER , 0 , 15 luto luto 8 P - 9 ong ong Z arch L and , 25° out M 85 9 1 eanwhile ames J ong argued M 9 window L 7 upiter in in upiter 85. 9 9 88. 1 ranus in 9 U 77-1 aturn in August 1 August in aturn 9 o much so that in engineer engineer 1 . S would launch in August JPL would begin in November reaching J ecember ecember 9 and the energy afforded by 9 and S D 7 7 77, 66, he risk of particulate ring 9 9 9 9 IDVWƆLJKWDYHU\FORVHSDVVDJH RI6DWXUQZDVUHTXLUHGŠZURWH )ODQGURşZLWKWKHWUDMHFWRU\ passing between the planet’s upper cloud layers and the rings to achieve the extra gravity DVVLVWHGERRVWŠ was best for the launches that the the that D-RYLDQƆ\E\ZRXOGHQDEOH it to survey Neptune in 1 then receiving a boost of of the ecliptic to encounter Back-up plans T material impacting the spacecraft a very was real hazard 1 GT-2 1 1 in deviseda conservative plan for WZR*UDQG7RXUƆLJKWVGLUHFWHG ZHOOFOHDURIWKHULQJV7KHƅUVW GT-1, 1 . - , , oe oe . J ars oe’ oe’ J , a mission o make a -M T rand ’s advanced omer omer www.skyatnightmagazine.com www.skyatnightmagazine.com aturn’s ringsaturn’s . “ G cheek hippy S upiter’s orbit upiter’s arth - JPL might damage damage might J But the idea warm drew support from )ODQGURŝV supervisor Elliot ‘ E he major in - . T ranus U was the, was need to travel assisted , head of , and from H - deriving the name from from name the , deriving Almost immediately Almost aetano Crocco to describe a enus voyage enus he proposal drew criticism tewart tewart labelled it ‘ our’ S concepts. group design phase initiated was S V obstacle facing the mission however perilously to close WRJDLQVXIƅFLHQWLPSHWXVIRUD slingshot to one used a decade earlier by G gravity T T – some scientists poured scorn on the likelihood of building a VXIƅFLHQWO\ORQJOLYHGVSDFHFUDIW while a tongue group protested that the mission Cutting GRAND IDEAS: CONCEPT & DEVELOPMENT & CONCEPT GRAND IDEAS: NASA’s NASA’s V plans for GT-1 plans for GT-1 would have to travel it seen Pluto via Jupiter and Saturn - his his . arose only once once only arose every 176 years”every 176 . T uch uch ’s slow “Such a favourable “Such a favourable o celestial alignment celestial . S of the outer planets . T , but wrote US , ars un and in relative he he S . T , within the bounds , but three lifetimes years e doubted that the Added motivation Added H paced planetary exploration paced exploration planetary effort could be galvanised in just a decade to support such an ambitious mission that the “motivation supplied goal a by this like one could KDYHDUHDOLPSDFWRQSURJUHVVŠ they would be on the same side of the a favourable celestial alignment of the outer planets arose only once every 176 proximity to one another of one or two missions opened the possibility visiting of all them last time it during occurred was the Napoleonic W )ODQGURLWZDVDFKDQFHRI not one half a century before the discovery of Neptune THE STORY OF VOYAGER project was scaled back wasscaled project entered development when the 16 Z U IDEAS:GRAND CONCEPT &DEVELOPMENT DWPRVSKHULFSUREHV,QUHDGLQHVV of study SODQHWDU\Ɔ\E\VRUDQLQWHQVLYH between polarised opinion with DSDLURIH[SORUDWLRQURDGPDSV $FDGHP\RI6FLHQFHVDGYRFDWHG UHGXFWLRQLQƆLJKWWLPHV as it offered the greatest greatest the offered as it Concurrently TOPS prototypes had already already had TOPS prototypes www.skyatnightmagazine.com J upiter with orbiters and and orbiters with upiter the National National , the 55 VFLHQWLƅFSD\ORDG ERRPVZHOODZD\IURPWKH JHQHUDWRUV 57*V RQGHSOR\DEOH UDGLRLVRWRSHWKHUPRHOHFWULF ZRXOGFDUU\IRXUSOXWRQLXPIHG RUELWD72 IUDFWLRQRIWKDWDYDLODEOHLQ(DUWK ZDVUHFRJQLVHGWREHDPHUH 1HSWXQHŚDQGDKLJKO\IDXOW GHFUHDVLQJWREVIURP GDWDGRZQOLQ ŚFDSDEOHRID ;6EDQGKLJKJDLQDQWHQQD LQFOXGHGDPIXUODEOH HQG2WKHU72 439 around and WKHEHJLQQLQJRIWKHPLVVLRQ at sunlight of incident WKHDPRXQW VRXUFH6LQFH power nuclear ofa integration the and VXEV\VWHPV ORQJGXUDWLRQ fabrication of the included UHOLDELOLW\DQGVFKHGXOLQJŠ HVWLPDWHVRISHUIRUPDQFHFRVW DQGDOORZHGIRUşUHDOLVWLF WRLGHQWLI\IXWXUHUHTXLUHPHQWV DŜPLVVLRQŝLQLWVHOI72 SURMHFWLQ-XO\$OWKRXJKQRW DGYDQFHGV\VWHPVWHFKQRORJ\ 2XWHU DWKUHH\HDU7KHUPRHOHFWULF IRUVXFKPLVVLRQV- 7KHVH57*VZRXOGSURGXFH T 0 W his atts of electricity at of electricity atts 3 ODQHW6SDFHFUDIW 72 3 6EDVHGVSDFHFUDIW NIURP-XSLWHU 3 6WHFKQRORJLHV W N atts at its at its atts ESV missions into abloated into missions 3/ programme ballooned programme EHJDQ 3 J 6KHOSHG upiter from an idea for a for idea an from fleet of orbiters” of fleet handful of flyby of handful “The Grand Tour Tour Grand “The 3 6 and expensive and ambitious too be to proved Tour Grand the developed for technology U The TOPS TOPS The EXGJHWGHFOLQHGSUHFLSLWRXVO\ 5LFKDUG1L[RQŝVDJHQGDWKH1$6$ UHIRUPVDWWKHWRSRI 9 HYHQSHULRGLFDOO\KHDOWKFKHF KRSHGWKDWWKHV\VWHPFRXOG VZLWFKLQJWREDF and units failed isolating WKDW72 VSDFHFUDIWLWZDVLPSHUDWLYH (DUWKDQGUHFHLYHGDERDUGWKH FRPPDQGVEHLQJLVVXHGIURP PXOWLKRXUWLPHODJEHWZHHQ GLVWDQFHVWUDYHOOHGDQGWKH 67$5 FRPSXWHU WROHUDQW6HOI7HVWLQJDQG5HSDLU VXFKDWWLWXGHVZHUHQRWUHƆHFWHG IRUFHRIKHURLFGLPHQVLRQVŠEXW FDOOHGşDWHFKQRORJLFDOWRXUGH LQHDUO\WKH*UDQG7RXUZDV DQ2XWHU FRPSOH[LW\ N XOWLPDWHO\VRXQGHGWKHGHDWK SUHVHQWFRPSDQLRQWKDW 67$5ŝVGRZQIDOO WHVWVWKHWHVWHUŝSURYHGWREH WKHSHUFHLYHGZHD itself 7HVWDQG5HSDLU ŜFRUUXSWHGŝZLWKDWKUHHVWULQJ FRPSRQHQWVZHUHGHOLEHUDWHO\ PHVVDJHVJHQHUDWHGE\IDXOW\ VHOIUHOLDQW,QFDVHRISUREOHPV KDGEHHQVODVKHGDQG1$6$ funding exploration planetary FRUUHVSRQGLQJO\GURSSHGIURP weight payload its while – PLOOLRQIRUODXQFKYHKLFOHV PLOOLRQŚSOXVDIXUWKHU FRVWSHD DWPRVSKHULFHQWU\SUREHV,WV ƆHHWRIFRPSOH[RUELWHUVDQG Ɔ\E\PLVVLRQVLQWRDEORDWHG IURPDQLGHDIRUDKDQGIXORI GLGQŝWKHOSLWVHOIEDOORRQLQJ 7KH*UDQG7RXUSURJUDPPH escalate Costs QHOOIRUPLVVLRQVRI72 LHWQDP 'XHWRWKHHQRUPRXV %XGJHWFXWVZHUHDQHYHU N JWR but its size its , but 3 N : 6WHFKQRORJLHVZHUH 3 HGDWDOPRVW N ODQHWV DUDQGŜ*UHDW6RFLHW\ŝ J%\PLG : KHQ1$6$IRUPHG 3 reliability and and , reliability N the end of the ofthe end the U ZLWKWKH6RYLHW RIFRPSHWLWLRQ atool longer no exploration was 6SDFH : FRQVHUYDWLYH increasingly an by URFHVVRU : XSV,WZDV N nion KLWH+RXVH QHVVRIŜZKR RU 3 N UHVLGHQW LQJ*URXS and with with , and 3 6ŝV N THE STORY OF VOYAGER V V 17 \ QHW O\ WLRQ V E D Z O D RUFH G UO\ I S D OLF LH HUO\ G QR&URFFR -6 -6 HULRX S V D 0 WX DSS UR G WRIXUWKHU V HW S WRUHLQ D XO V G I 3/ D U H UH DULQHU-XSLWHU \* LQ P D 0D had ended due E , G 0 WRWKHRXWHU HH G V WF QŝWXQWLOWKHH V H Q D WHU -6 YHQWXUHIHDWXULQJ LQH D ariner spacecraft DV D V P 0 O V -6UHFHLYHGDEXGJHWDU\ JD M G WZ \ 0 , Q HOWL UQWWK 6ZRXOGEHXVHGE\WKHQHZ HQFRXQWHUFRXO J HQX D D V 3 G 9 DY G 7RPLQLPLVHWKHƅQDQFLDO N L QQ WRDşOHVVWKDQHQWKXVLDVWLF UHVSRQVHIURPFHUWDLQHOHPHQWV RIWKHVFLHQWLƅFFRPPXQLW\ SDUWLFXODUO\DQGWRVRPHH[WHQW &RQJUHVVŠ7KHQHZ ZRXOGGUDZRQWULHGDQG tested KDUGZDUHDQGZDVşZDUPO\ HQGRUVHGŠE\WKH6SDFH 6FLHQFHV%RDUGLQ)HEUXDU\ ULV FDSRIPLOOLRQDQG1$6$ RSWHGIRUŜLQKRXVHŝGHVLJQDQG FRQVWUXFWLRQDW- GULYHGRZQFRVWV,WZDV HVWLPDWHGWKDWKDOIRIWKH WHFKQRORJLHVWKDWDURVHIURP 72 PLVVLRQ2WKHUVLQFOXGLQJ67$5 DQGWKHIXUODEOHKLJKJDLQ to understand the necessary FDSDELOLWLHVIRUIXWXUHPLVVLRQV WRWKHRXWHU6RODU6\VWHP,Q -DQXDU\)OHWFKHUXQYHLOHG DOHVVFRVWO\ 6DWXUQ DSDLURILGHQWLFDOVSDFHFUDIW 7KH*UDQG7RXUSURJUDPPH explained he XUH P J PD QRWLRQ WZHOH XFHWU V D WKHHQHU G HUFXU\ I LQWKH 0 +RK WKL FRQƅ UH WK R 6KDG 3 H UHVLGHQW KW E J 3 WR DV Q V UO\ D Q www.skyatnightmagazine.com www.skyatnightmagazine.com Š OOƆL D D G V O ZLWK D V LWZ S HU V WFOH Y RX \LHO RUFHF V Y L I LRQ G HQHƅW H With President Nixon H] VV E stop developing TOPS developing stop L Y DVV O HQHƅW G WL D E P ZRXO O V J backing the Space Shuttle, LW\ ED D KRUWHU R NASA administrator James Fletcher (left) was forced to V WUHQ 6EDVHG*UDQG7RXU LQ XWLF D DY 3 D Q QHW U D D J O HUWXU VDY WK

VSD U Q WLFL LQ D I G S D G FKFRQ DGM Z D KRZH UH WL D J QFHR Q WU QHW V D U\RU V J DV H JD WLRQR V QURF D D D PD OH D /D LQ LWHUWR ED H O E D UR QHOOL S UWK

S N Wŝ S N KH LRQ RQ D HW G V RUW X PD HFLƅF HFWRULH L RXQWR WKH 7 Q*HU - (D VV P P , ş XOWL L DSS SDVV DM HWZHHQWKHWZR HUWXU H UHZUH KULF I I VS HORFLW\FK

PS I

DVV 'HUH Y FRXO L DP E RULHQW ( WU WKHRUHWLF Ś R FR R G P *HU L ZURWHşWKH WKFHQWXU\WK LQWR S J 0D The big challenge:Gravity assists P ZDVE\DVFLHQWLƅFFRPPXQLW\ WRUQEHWZHHQƆ\E\DQGRUELWHU DGPLQLVWUDWRU-DPHV)OHWFKHUŝV assertion to Congress that the SURJUDPPHZRXOGWULJJHUşJUHDW SRSXODULQWHUHVWŠSURYHGDKROORZ VWDWHPHQWEDF ZLWK RULQFUH D NASA/JPL X 4, ISTOCK X 2, NASA NASA 2, X ISTOCK 4, X NASA/JPL THE STORY OF VOYAGER S globe the around scattered scientists over from responses April in payloads RSSRUWXQLW\IRUVFLHQWLƅF of announcement initial An in observations UHPDLQLQJƅQDOLVWVSDUWLFLSDWLQJ actual instruments tobuild selected were which GRZQWRƅQDOLVWVDKDQGIXORI submitted formally been had payloads UK. 18 IDEAS:GRAND CONCEPT &DEVELOPMENT Z 7 WKH FRXU 6D A tale oftwo trajectories weden KH antenna WXUQ By 9 V www.skyatnightmagazine.com V H H R\ , including the the including D G D J DJ UHWKHƅQ X , Q uly

W EE G , HU were discontinued were . WKHQ

est est , T H

77 VSD G hese were whittled whittled were hese Ŝ -67 proposals for for proposals G .

FHFU 7 D ermany and the the and ermany 1 OWZRWU LW 9 ŝZ D , 72 with the DI US, Q 2 DV received received 00 W DI E

F 9 DM WHUZKLFKLW RXQ rance R\ HFWRULH DJ 5 Mar 19795 Mar rendezvous Jupiter Voyager 1 G MJS .

I HURQ RU ,

- V

X 5 Sep 19775 Sep Launch Voyager 1 I RU S LWHU from ofa capable by a3 dominated be would spacecraft VFLHQWLƅFLQVWUXPHQWVDQG with bristling be would that antennas ofwhip apair and booms deployable three with equipped be would probes the at Neptune but a NASA-run competition in March 1977 March in competition aNASA-run but D E “Navigator was name, apotential new 12 1980 Nov rendezvous Saturn Voyager 1 ach of the ofthe ach J ŚL ZRXO HQWLUHO\ ZRXO .7 upiter m high I D G G came out in favour in out came Voyager” of P . OH W

, I dropping to L 115.2 n addition DN VV DY 1 9 - 0 LRQH[WHQ gain antenna HLWWR R\ HWKH - sided sided kb/s downlink DJ 20 Aug 197720 Aug Launch Voyager 2 HUŝ - S X O MJS , D both of both S V V QHR 1 LWHU LRQZ SD 4 .

4kb/s WKF I ,

6D WKH DV WXUQ D J OOH S U O D D G 25 Aug 198125 Aug rendezvous Saturn Voyager 2 D QWH QHW Q -6; G 9 Jul 19799 Jul rendezvous Jupiter Voyager 2 G WKHQ V ŚRQ WR Z O ZRXO D DV XQFKH 8 WKH U G D R QX thermoelectric generators all the the capabilities of the ofthe capabilities the farbeyond evolved quickly by 7RXURSSRUWXQLWLHVLGHQWLƅHG line with the optimum optimum the with line S T A namechange G Y argeted to launch inAugust to launch argeted eptember V 25 Aug 198925 Aug rendezvous Neptune Voyager 2 V 24 Jan 1986 Jan 24 rendezvous Uranus Voyager 2 ƅU HUW ORZHUR F D landro – the –the landro V Q DN WWK G - important radioisotope HLWLQWKH 1 H D I WKHWZR S Wŝ WXQH V 1 9 E 77 HF – precisely in in –precisely D DV 2GG MJS X V WHURL 9 HLW R\ O\ twins twins (JSX TRAJECTORY) VOYAGER 2 (JST TRAJECTORY) VOYAGER 1 V M G DJ WU 9 G rand rand ariner ariner R\ DM E HU . HOW

HFWRU\ DJ - HU THE STORY OF VOYAGER 19 f

. I ’ ranus V U JST JSX . But if , its twin aturn to S , dubbed ‘ promised to carry 1 succeeded 2 from , JSX problematic births, the Voyager oyager oyager rare alignment of the outer giants Despite their relatively rushed and and rushed relatively their Despite realised trajectory in its stead V could execute a unique mission exploration of V in order to complete the DQG1HSWXQHIXOƅOOLQJWKH*UDQG 7RXULQPDJQLƅFHQWVW\OH probes were able to capitalise on the , - , . aturn S aturn -S www.skyatnightmagazine.com www.skyatnightmagazine.com R\DJHUKDG itan encounters itan 1 fail at upiter trajectory – then o and T I oyager 2 could conceivably V (JST) itan itan oyager hould hould – adopting a J WKHƆLJKWSDWKRI9 nine months to be adjusted Neptune and instead undertook the both V visit the two outer planets S T GRAND IDEAS: CONCEPT & DEVELOPMENT & CONCEPT GRAND IDEAS: NASA’s NASA’s U experience with enabledTOPS development the Voyager of ‘in-house’ . , . upiter upiter ranus illiam t came came J aturn’s aturn’s us and U . I W ranus run run 77 upiter’s upiter’s rand - 9 U ran 1 G A , but at the U S . o and S oyager’ arch 1 relinquished V R\DJHUƆHZ director 9 ars mission and , although it was . JPL M he original original he , its velocity would be oyager o I . T V aturn , it would depart the S upiter’s moon I upiter’s n spite of the name change J But if I itan oyager remained tied to ickering had already suggested aturnian system in the wrong aturn too early to achieve a our still was possible

&RQYHUVHO\LILWƆHZFORVHWR T S direction to encounter chanceany to go to gravity that it would reach S suitable rendezvous with increased so much J by PRRQ7LWDQ,I close to hoped that changing political and budgetary winds might see WKH8UDQXVDQG1HSWXQHƆ\E\V restored spacecraft V and expense of getting close views of T P ‘Navigator’ as a potential , but name a NA new competition in M out in favour of ‘ originallywas the name of an unrealised VHHPHGHQWLUHO\ƅWWLQJIRUDQ expedition to the very edge of human knowledge NASA, NASA/JPL X 7, ISTOCK 7, X NASA/JPL NASA, THE STORY OF VOYAGER marvel times less than the average the than less smartphone” times measly 240,000 memory of –around 68kb are used to explore a planet’s aplanet’s toexplore are used of magnetometers pairs boom short other to the attached batteries’ ‘atomic the from aspossible away as far them tokeep booms short ofthe one on mounted are instruments science of the ofa pair whip antennas (2. short two (12 long –one booms deployable arethree buses identical 20 Evans Words: Ben Voyager spacecraft were nearing completion severaland trips back to thedrawing board, the twin thespringIn of1977, 12 after Flandro’s years revelation A nuclear- IDEAS:GRAND THE SPACECRAFT average jpeg image average jpeg an for enough approximately or smartphone average the than around – edge in 1 was cutting that technology high of the 3 isthe structure in diameter 4 ‘bus’ that’s spacecraft’s core is a core spacecraft’s 722 weighing and car sizeofasmall the about each measly a have systems computer crafts’ the while recorder tape aneight on isstored data much outdated tothanks 16 towards pointing is kept THE VOYAGER PROBES VOYAGERTHE PROBES T S T “The probes’ computer systems have computer probes’ a “The prouting out of the probes’ probes’ ofthe out prouting he long boom holds two two holds boom long he he two probes contain contain probes two he www.skyatnightmagazine.com 68K , nuclear 9 2 77 40 - . D B of memory B ofmemory gain antenna , which small thrusters small 7 but is now very very isnow but 4m 000 times less times ,000 cm high and and high cm ominating each each ominating . F – as well as ) –aswell .7 - or instance powered twins powered m . powered - m kg wide dish 1 0 and ) and . M At each . At each - . which , which sided sided E - arth arth 1.8 track are ost ost . - m , , includes alow includes and platform scan asthe known is batteries atomic the carry T i PDJQHWLFƅHOGDQGKRZLW to the public to the sold what is ultimately produced cameras these that ofthe images camera angle ahigh and camera nteracts with the solar wind solar the with nteracts he short boom that doesn’t doesn’t that boom short he . . T - S res wide res olar he spectacular spectacular he - res narrow res S ystem ystem - V angle angle oyager oyager . - pyro shocks and acoustic up to it stands well how see to platform scan the test engineers U NASA plutonium a last planets other wave toinvestigate subsystem plasma the house electricity by thermocouples electricity heat in available ofsunlight cent per four barely panels at J solar fallson that of sunlight two spacecraft the for source asapower option pellets FRQWDLQLQJ thermoelectric generators hundred RXWƅWWHGZLWKWKUHHPXOWL NA present be might that any rings densities and masses FRPSRVLWLRQJUDYLWDWLRQDOƅHOGV atmospheric planets’ the toexamine employed are also the micr T its magnetospheric dynamics of gaining deeper insights into hope the in toaplanet enough near they’re when densities astronomy radio planetary for are used a‘three and spectrometer an ultraviolet to Neptune to Neptune it make hopefully would of them G Going nuclear from the mission the from ultraviolet photopolarimeter ƅHOGVDQGSDUWLFOHVVXLWH spacecrafts’ the constitute systems investigation plasma cosmic and low by aphotopolarimeter areobserved moons near and abundances in atmospheres radiated heat and constituents chemical temperatures planetary toexamine spectrometer and radiometer million km from the the from km million be travelling to travelling be he iven that the V the that iven T S T T S - o each V o each he whip antennas also also antennas whip he he two whip antennas antennas whip two he he scan also platform carries S ometeoroid detector and energy charged particle V A’s decision to delete a A’s todelete decision which is converted to isconverted , which un - - oyagers’ radio signals signals radio oyagers’ particle interactions at at interactions particle minute addition following following addition minute . T solar energy wasn’t an wasn’t energy ) solar -W hese decay to produce toproduce decay hese -2 . T , interferometer upiter’s distance is distance upiter’s att radioisotope radioisotope att - E ( - 3 oyager probe is ray detectors ray 4 in arth’s orbit hey record electron electron record hey . T oxide in pressed pressed in 8 oxide . P .5 N - . T JRIƅVVLRQDEOH billion km from from km billion J one’ infrared he system was system he article article oyagers would would oyagers upiter . he amount - wave wave S un as well as , aswell while , while (778 and one one ) and , . and , and , each

. . V .

NASA/JPL-CALTECH, ILLUSTRATION BY MARK GARLICK GRAND IDEAS: THE SPACECRAFT The Voyager instrument suite

The Voyagers launched with an armada of instruments capable of examining atmospheric chemistry, PDSSLQJPDJQHWLFƅHOGVGHWHFWLQJDXURUDHDQGPRUH6RPHRIWKHPFRXOGHYHQDQDO\VHFKDQJHV LQVSDFHLWVHOILQRUGHUWRWHOOXVZKHUHWKHVRODUZLQGJLYHVZD\WRLQWHUVWHOODUVSDFH

Infrared Radiometer/Interferometer/Spectrometer (IRIS) Three-in-one instrument to detect temperatures, LGHQWLI\FKHPLFDOFRPSRXQGVDQGUHƆHFWLYLW\VWXGLHV hydrogen abundance and atmospheric dynamics Ultraviolet Spectrometer (UVS) Photopolarimeter System (PPS) 'HWHFWVXOWUDYLROHWOLJKWVWXGLHV 0HDVXUHVOLJKWSRODULVDWLRQVWXGLHVSDUWLFXODWHV atmospheres, rings and aurorae in atmospheres, rings, lightning and aurorae

Plasma Spectrometer (PLS) Imaging Science System (ISS) Measures lowest-energy particles 7ZRWHOHYLVLRQW\SHFDPHUDVZLWK LQSODVPDVWXGLHVVRODUZLQG HLJKWƅOWHUVRQHZLGHDQJOHDQG and the termination shock one narrow angle THE STORY OF VOYAGER Cosmic Ray System (CRS) Measures high-enery particles Low-Energy Charged LQSODVPDVWXGLHVWKHRULJLQDQG Particle Instrument (LECP) dynamics of cosmic rays, and 0HDVXUHVORZHQHUJ\SDUWLFOHV planetary magnetospheres VWXGLHVFRVPLFUD\VVRODUƆDUHV and particles of planetary origin Radio Science System (RSS) Uses comms system to determine WKHSODQHWŝVSK\VLFDOSURSHUWLHV

Bus The Golden Record Houses electronics 7KHŜPHVVDJHLQDERWWOHŝIRU DQDGYDQFHGDOLHQFLYLOLVDWLRQ

Radioisotope Thermoelectric Generators (RTGs)

Magnetometer Experiment (MAG) 7KH9R\DJHUVŝDWRPLFEDWWHULHV 0HDVXUHVFKDQJHVLQWKH6XQŝV PDJHQWLFƅHOGDQGWKHH[WHQW of any others - Planetary Radio Astronomy Investigation (PRA) Listens for radio signals emitted by the planets - Plasma Wave Subsystem (PWS) 0HDVXUHVHOHFWURQGHQVLWLHV studies particle interactions and magnetospheres

www.skyatnightmagazine.com 21 THE STORY OF VOYAGER 22 The Voyagers’ GRAND IDEAS: THE LAUNCHES www.skyatnightmagazine.com bumpy ridesbumpy launchpad the on sat rocket Centaur V planets giant four toexplore mission amulti that gambled Evans Words: Ben frantic period ofclose calls high and drama the beginning oftheVoyager mission wasa from Florida’sweeks apart Cape Canaveral. But spacecraftBoth were successfully just launched S the take usbeyond and Complex 4 at Cape Canaveral’s sweltering that on question another with Y long so for ever survived had HYHUƆRZQVRIDUQRVSDFHFUDIW real acutely was offailure fear the that sailing away from the plane of plane the from away sailing November in that would it see arrive at ashort for was set following be would probes the trajectories different before launching ON 20AUGUST ystem could be asuccess be could ystem et people were preoccupied preoccupied were et people oyager oyager T T M here were so many unknowns many unknowns so were here he answer is because of the ofthe isbecause answer he arch LIFT OFF LIFT , LAUNCH VEHICLE VEHICLE LAUNCH dozens of their moons moons oftheir dozens 2 1 9 and its its and FROM 5 September 19775 September 1) (Voyager 1 , S 1 7 few would have have fewwould : why was . 9 aturday morning No spacecraft had had spacecraft No 9 and 9 and 8 0 Launch profile , before then then before

1 V T 9 , S 20 August 1977 August 20 2), (Voyager . oyager oyager fast course course fast 77,

itan aturn in in aturn V Cape Canaveral, Florida Canaveral, Cape L oyager oyager - V as aunch decade oyager oyager IIIE- S olar J 1 . ? upiter . 1

Titan IIIE-Centaur continue its mission almost asplanned almost mission its continue J LUUHOHYDQWEHLQJƅUVWWRDUULYHDW VFKHPHEHLQJƅUVWWRODXQFKZDV S the 4 the ignited motors rocket T fed by ahalf fed core central rocket’s of the HQJLQHVRIWKHƅUVWVWDJHŚSDUW kg of thrust a combined crystal 1 in twin its overtake 1 faster the while Because order? launch reversed the U those outermost giants outermost those toreach trajectory best the on probe the put would date launch the planets allow it to continue out towards out tocontinue it allow take longer would was on would set off off set would 9 upiter was the main prize main was the upiter aturn sooner itan ranus and Neptune and ranus Despite problems before and after after and before problems Despite 77 At At S . After After o why not simply renumber renumber o why simply not V and reach reach and 1 8 oyagers in response to the tothe response in oyagers launch, Voyager 2 was able to Voyagerlaunch, to 2wasable IIIE- 0 m - .2 clear - 9am local time 9am local 112 tall booster into the the into tall booster Centaur’s two solid two Centaur’s .

seconds T - F and he path . lorida skies with with skies lorida

16 I - J n NA moving upiter and and upiter days later days - half mixture mixture half D S , . the dual dual the ecember

V , 1.1 T A pushing pushing oyager oyager he earlier ' s grand s grand . million million ,

the the V , oyager oyager but but . ,

, it - 2

THE STORY OF VOYAGER Z . 23 the , A when , ebruary ebruary HQ 78. F Y 9 H 1 in in ropulsion he problem V P T day timer

. - t possible for aboratory et ' ortunately L (JPL) to California fully rectify a potentially catastrophic that situation in occurred April series of minor J F

. it wasn it WƆHZRQO\ The wide-bodied Centaur permanently losing its , , IIIE booster (below) with a 2 rocket (top) links to the Titan tapering inter-stage adaptor G H G launch levels of sensitivity of levels launch - Although these obstacles were were obstacles these Although oyager RXQ ŚDVDIHW\PHFKDQLVPGHVLJQHG headaches culminated in in culminated headaches V the onboard seven main radio receiver innocuously rather began all expendable launch vehicles vehicles launch expendable all and the by time the Titan IIIE- Centaur was being readied for its maiden voyage on 11 its death1974 knell had already V engineers at the times, with the twoVoyager probes being its swansong. and misaligned VSDFHFUDIWŝVƆDVKRIIKHDWHU reversed this problem and returned the instrument to its pre overcome Voyager 2, 2, Voyager www.skyatnightmagazine.com www.skyatnightmagazine.com U encased in its launch capsule, is winched into atop position IIIE- Titan the Centaur rocket GRAND IDEAS: THE LAUNCHES THE IDEAS: GRAND

V .

he he

, . upiter upiter 7E T

J 3 t been . KXWWOH ' - 6 robotic was the mainwas prize” tar ' ƅFXOWLH being first launch to FH I S course was irrelevant; Being irrelevant; was L causing 9km/s onto 9km/s , - G ’s 1. first Jupiter arrive to at 2 which 6SD , “In NASA's grand“In scheme, NASA's protection KH - another a was , 7 which hadn protection system , his caused was but there would be a - , month trek to

T , bound velocity bound G -

UXQLQWR s scan platform had oyager . - he glitch turned out 3 V 2'

T 2 KH , DG

V '. fuelled motor burned for - upiter HWK ne of the bumps was ƅQL J N seconds to add O After the jettisoning the oyager oyager he infrared infrared he DV 5 ’s imaging ’s led to the mirrors inside the warped becoming spectrometer T radiometer interferometer and spectrometer ŚDFUXFLDO of element V 2 VXLWHŚDOVR suffered a period of degraded sensitivity theby crystallisation of some material bonding it to drift slightly off indicated the boom the carryingindicated V not deployed that thruster manoeuvring ended up pointing the wrong propellant spraying and way onto the spacecraft 4 its few more bumps along the way solid spent motor then was discarded and the could begin saw its fault report unexpected readings described some by as vertigo to be the fault a sensor that erroneously system itself system Centaur programmed to recognise the launch conditions and reported an issue though even everything expected as proceeding was into the Solar System. These billion-dollar the of both included sent landers and orbiters Viking to Mars in 1975. But the Titan URF even before its development Z was widely expected to replace

V out , 2 well ,

000kg 000kg . , LRQ but stage stage ts ts , I

VV . . he turn turn he L 00 5 T

P . 4km/s oyager 1 Hŝ

. the solid core and so V , off - he probe had DS IIIE F T

V . energy Centaur Centaur energy 0 and nitrogen 0 seconds - uelled liquid by -5 F 21

itan itan until that too was . could support a ,

tall Centaur wider was T 2 UWKH - m (D whose single engine , Ŝ .6

upiter J arth orbit and onto a course he mission only was minutes ight minutes into the mission J E T At two minutesAt E S’s inventory.S’s Standing 16 oyager he Centaur’s initial burn ollowing the cancellation of of cancellation the ollowing

storeys tall, it was capable of ƅULQ shortsightedness the Saturn V rocket, the Titan most the became IIIE-Centaur powerful launch vehicle in the U Success andSuccess F weighing up to 3,700kg, deep Titan IIIE-Centaur: IIIE-Centaur: Titan lengthy period of coasting to performance maximise VHFRQGEXUQODVWHGƅYHDQGD half minutes and accelerated the spacecraft to over velocity escape beyond Problems arise Problems T established a temporary ‘parking orbit’ and demonstrated that V suffered a double computer failure on the launchpad old but already it running was problems into during its ascent another glitch of propulsive yield WHWUR[LGHŚURDUHGLQWROLIH almost out punching of Aerozine required a tapering inter adapter to connect them rocket motors were discarded and the vehicle continued to climb under the impulse of its core jettisoned a little four over minutes afterlift the 9 oxygen and hydrogen at very low cryogenic temperatures the than for then came for the core’s second stage burned for the second stage separated and the high upper stage prepared for a pair of burns to heave of NASA/JPL X 2, NASA/JPL-CALTECH/KSC 2, X NASA/JPL THE STORY OF VOYAGER as much as9 as much by toslip frequency the caused deep PRYHPHQWVDQGƆXFWXDWLQJ as well as as well the around motion and complicated by E was frequency correct the probe the with communicate to order in frequency right the precisely at to transmit forcing and deaf XSUHFHLYHURIƆLQH back take the and functionality full toback receiver main the toreturn undertaken were efforts and was found solution 24 Z GRAND IDEAS: THE LAUNCHES back the tofailin acircuit caused had back toits switched and failed had receiver main the by assuming control ground from command reset to zero with contact to guard against loss of loss against to guard 7KHGLIƅFXOW\LQƅQGLQJ www.skyatnightmagazine.com - - - up receiver up up space temperaturesspace that without receiving a receiving , without . V But an electrical short short anelectrical . But oyager oyager V oyager oyager 6H E arth – ran down –randown arth z length leaving it tone it , leaving . At responded 2 responded JPL arth 2 ’s own engineers ' s rotation s rotation S un , a , . - - workable back workable EHUHOD\HGKRPHE\DƆDZHG\HW 9 – counting and decades four – lifetime operational ofits rest mission entire the tosupport receiver back the just with was left launch after months it killing effectively receiver main the in fuses both process At At followsOne two 5 S rose from L from rose V result was that was that result RISURSHOODQWXQEXUQHG7KH than more left hardware QRUPDOO\DIDLOXUHLQWKH7LWDQ of ascent appeared to proceed ride But DWRSWKHƅQDO7LWDQ,,,(&HQWDXU its Centaur were not travelling travelling not were Centaur its R\DJHUŝVVFLHQWLƅFGDWDZRXOG oyager oyager D 8.56 eptember Although the early phase phase early the . Although uring this uring switching V oyager oyager am local time on on time am local . Remarkably an electrical short blew blew short , anelectrical left E 2 left aunch Complex 4 Complex aunch , 16 was in for a rough arough for in 1 was - V up receiver up days after after days arth oyager oyager . O , V the team team , the for the the , for nly oyager oyager and 1 and 5 40kg . - up 1 quicker path to Jupiter to path quicker 1 , follow a different but but adifferent follow Voyager 1 lifted off off Voyager 1lifted after Voyager 2, to after t LQWRWKH by falling launch after few hours a mission its ended have 2 would the outer S outer the E the from away barrelled probes of image aremarkable acquired scan platform ajammed with ownissue its weathered already having and occurred with V ZDVSUHWW\FORVHŠ DQDLURIXQGHUVWDWHPHQWş7KDW couldn error for margin asmaller had trajectory its only natural satellite satellite natural only its and world our had before Never JPL WLPHUHPDLQLQJş origin behind two ,WVHUYHGDVDƅQDOIDUHZHOODVWKH entirety their in together seen time the at crescents had only 3 only had WKH&HQWDXUƅQDOO\VKXWGRZQLW own engines for slightly longer slightly for engines own its burning and shortfall the for by compensating day the saved Centaur’s computer onboard enough fast hey encountered hey arth on their missions to explore toexplore missions their on arth 7KLUWHHQGD\VDIWHUODXQFK H D ,WZDVDQDLOELWLQJWLPH E D arth and the the and arth ad a similar malfunction malfunction asimilar ad espite the early problems problems early the espite V oyagers left their place of place their left oyagers irector Bruce M Bruce irector ' t have rescued it rescued t have even the Centaur Centaur , even the 3 DFLƅF2FHDQ . 4 seconds ofburn 4 seconds olar . F never toreturn , never , V ortunately back and captured andcaptured back S the same frame in frame same the oyager oyager Voyager 1 turned Voyager 1turned oyager oyager ystem M : Moon appear in appear Moon this image – the –the image this , both V As it left Earth, Earth, itleft As ﬁrst where our our ﬁrst where planet and the the and planet oon RZŠUHPDU their entirety urray ) been . 2, ( . V below ( 1 both whose whose the , the oyager oyager , with oyager oyager : - . KHQ N . ). . HG V

NASA/JPL X 2 h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h h THE STORY h OF VOYAGER h h h h h h h h h h h h h h h h h h h 25

h h h W HU WHU V Y D W O V ƅU V WH V V h h h LRQŝ ranus. It It ranus. RQWK WKHƅU VV U P L WKHƅU P DSV DV Q V V WKH I WKL HU HUK P DJ DJ R\ R\ KRWRR planetary encounter, a a planetary encounter, portrait of Jupiter from away. km million 57.6 WITHIN FIVE YEARS 2 isVoyager expected to space. interstellar reach 25 AUGUST 1981 2 arrivesVoyager at Saturn and passes closer to the planet than its twin, 41,000km. with coming JANUARY24 1986 9 with encounter discovers 11 new moons and two rings, plus reveals Miranda to be the weirdest moon in the Solar System. 25 AUGUST 2012 interstellar enters 1 Voyager to able only is NASA space. FRQƅU 19 DECEMBER19 1977 1 overtakesVoyager 2,Voyager passing its belt. asteroid the twin in 6 JANUARY 1979 9 S after a coronal mass ejection from the Sun catches up with the spacecraft. Words: Kev Lochun Kev Words: \ E H WKH G P Q D WWL V UWK (D www.skyatnightmagazine.com H P RUWKHƅU I H WWL V V FOR yperion. The spacecraft now S BY 2025BY Both Voyagers are expected to have exhausted their plutonium batteries and all its instruments shutdown. been have will 14 DECEMBER14 1980 1’sVoyager Saturn encounter comes to an end with observations of the moon H begins moving away from the planets. the of plane 25 AUGUST 1989 photographed is Neptune X 2 fromVoyager 5,000km. The spacecraft ferocious records winds and a massive storm system – the Great Dark Spot. 2012 AUGUST 13 2 gainsVoyager the title of spacecraft,longest-operating breakingthe 12,758-day record in 6 Pioneer by set previously 2000. December 18 SEPTEMBER 1977 As 1 leaves Voyager Earth, it planet its home photographs from 11.7 million It’s km away. WKHƅU 5 MARCH 1979 1 makesVoyager its closest approach to Jupiter, 206,700km over the planet’s cloud tops. The gas giant is unexpectedly found to have faint, slender and dusty rings. Moon have been seen in a single frame shot from a spacecraft. GRAND IDEAS: MISSION TIMELINE MISSION GRAND IDEAS: O W W D V V

WKHƅU WKHƅU WKHƅQ V V V

Wŝ RW , XLUH W VS T G DI F Q D T. D U

FHFU JV HU ort Cloud. It could take O VSD DJ R\ 9 MARCH 1979 30 AUGUST 2007 AUGUST 30 2 passesVoyager the and shock termination heliosheath. the enters TIME YEARS’ 300 1 isVoyager expected to reach the shepherd moons. shepherd 14 FEBRUARY 1990 9 40,000 years to pass through it. Volcanism is discovered on on discovered is Volcanism the Galilean moon Io, from a photo only taken to navigate WKH NOVEMBER 1980 12 1 alsoVoyager passes within 64,200km of Saturn’s cloud tops. The probe reveals new rings, new ‘gaps’ between WKHULQ 5 SEPTEMBER 1977 Voyager 1 follows its sister spacecraft skyward, launching from Cape Canaveral at 12:56:00 images of the mission, a ‘family portrait’ of our Solar System; among them is the Pale Blue Dot, in which Earth appears as a speck trapped in a sunbeam. time volcanism has been seen beyond Earth.

the entire Space Age and could continue for another decade Age Space and continue could the entire U The highlights from a mission that has lasted for two-thirds of that for has two-thirds lasted a mission from The highlights lorida lorida

T atop

milestones Voyager’s great Voyager’s U

h h h 9 JULY 1979 9 JULY at 14:29:00at IIIE-Centaur, Titan a 17 FEBRUARY 199817 the heliosheath. the ahead of Voyager 1 owing atmosphere is intriguing. is atmosphere oss 248.oss h h h Cape Canaveral in in Canaveral Cape R to its slower trajectory. slower its to Voyager 2 launches from Voyager 2 makesVoyager its Voyager 1 overtakesVoyager 20 AUGUST 1977 the moon’s surface, but it’s a boundary zone called closest approach to Jupiter, Pioneer 10 to become the at a much greater distance 570,000km. of from Earth at this time. this Earth at from most distant human-made distant most object in space; it is A 69 12 NOVEMBER 1980 12 1 makesVoyager its pass of Titan, only 4,000km above its clouds. The atmosphere is too thick for the probe to see The Voyagers pass close to other stars. 1 will Voyager sail within 1.6 lightyears of Gliese 445, while 2 will Voyager 1.7 lightyears within travel of 40,000 YEARS’ TIME YEARS’ 40,000 17 DECEMBER17 2004 1 passesVoyager the where shock, termination the intensity of the solar wind starts to diminish. It enters h h h

h h h

h h

h h h h h h h h h h h h h h h h h h h h h h h h h h h h Sky at Night MAGAZINE SAVE WHEN YOU SUBSCRIBE TO THE DIGITAL EDITION

Available from The perfect addition to your stargazing, BBC Sky at Night Magazine is your practical guide to astronomy, helping you to discover the night skies, understand the Universe around us and learn exciting techniques for using your telescope.

Enjoy our Premium App experience now available from

Sky at Night MAGAZINE THE STORY OF VOYAGER

MARK GARLICK WKDW F HQRX V 6 28 T OLD FRIENDS IIPHASE OLD FRIENDS Z RX DWX LU

UV O www.skyatnightmagazine.com L U 6 Q J H Q DWX J KWR

KHƅ WZR DQW WKH EHOW L 7 W V KH\ U * P Qŝ LT V UV J ZDOORZ V V X U DOODQ D HDW W RI V UL L V W\ HQWED V Q JL WR JV F 5 PLJ DQW ORX SV H ZH G V G IR WKH HYH G V FN KW\-X 6S U N HID U L WKH W QRZQWRKX F U RWŚDQDQW V P DO(D OR V U DMH V X SL P HX 9 UJL R\D WH R U V WK W Q U S U H LF J OD V J LP F UL V H R 7 UJ P WR Q LF UV D PS KH\ J \ J DQ H UPV ZH H F V H G OH[WKDQZH ORQHOD W V NL ZR U RI-X S U DQ HYHDOH Q HWKH ODQHWRI G U G VL O G RI UJ Q SL F G H WH H U ŝ V KD FU ƆRH F Z WKH ZD , ZD Q KD L H V WK G WHD V V GL U V 9 WKH U D P WH FU HDO R\D F 7 G R D WH G KH RIƅQ U V FNV LV WRWKH HHQR H UV J H U H S Z G HZ DQ UV ODQHW DQ L HQ GL WKDOO UL UP G W Q G 9 L F V J Q WKDW-X RX R\D V W RXQWH J ŝ G ULS P P RIWKHWH[WERR V HD WKDQZHHYH J H DQQH RRQ H V G U U ED H LF SU SL V G \ WKDW U REH WH DE RI UU FU U HQKX ŝ X V T V U V RD P EH X U W HDOO\ LUNV V U D G DQ VNV LP NV J J F QHWR Ś DQKH D G D O V V V D JL V LN X RRIWHQ WRI DWHOO USULV F QH HRX VS W U L G H YHODYD KH %XW L H WH U RZQ U G H V L W THE STORY OF VOYAGER 29

The Voyager probes probes Voyager The revealed the beauty and OLD FRIENDS OLD complexity of Saturn’s rings Saturn’s of complexity www.skyatnightmagazine.com OLD FRIENDS: JUPITER Secrets erupt Jupiterfrom

In January 1979, after a journey of 15 months, Voyager 1 began to photograph the ﬁrst planet on its Grand Tour, the gas giant Jupiter. Voyager 2 followed a few months later, and together they rewrote THE STORY OF VOYAGER STORY THE almost everything we thought we knew about the Jovian system – not least the fact that volcanism exists beyond Earth Words: Ben Evans

AT FIRST GLANCE, it resembled trajectory to Saturn, three- temperatures soared up to nothing more than a blemish on quarters of a billion kilometres 200°C higher than the Voyager 1’s lens. But as 26-year- and 20 months away. She had surrounding terrain. Four months old engineer Linda Morabito MXVWPDGHWKHPRVWVLJQLƅFDQW later, on 9 July, Voyager 2 peered closer at the image of discovery of the entire mission. revealed that Pele had fallen Jupiter’s moon, Io, she realised The long-exposure shot, taken dormant, although several other she was looking at something a day earlier, viewed Io from a volcanoes remained active. extraordinary. The blemish was parting distance of 4.5 million actually a faint, bluish crescent km. Analysis revealed the Big surprises that was protruding from beyond crescent to be a plume – rising It was a big surprise on a natural the moon’s limb. over 280km into space – from a satellite with a size and density This all occurred on 9 March volcano. Later named ‘Pele’ after roughly equal to that of our 1979, four days after the probe the Hawaiian goddess of geologically inactive Moon. had made its closest pass – YROFDQRHVLWZDVWKHƅUVWRI Io’s proximity to its giant host 349,000km – of the broiling hundreds of such features to be (it orbits just 421,800km from Jovian cloudtops. Morabito was found on Io. As the days wore on, Jupiter’s centre) forces it to part of the optical navigation infrared data pinpointed regions bear the brunt of a punishing team, plotting Voyager 1’s rich in sulphur dioxide, where PDJQHWLFƅHOG7KLVLVKXQGUHGV Z

30 www.skyatnightmagazine.com THE STORY OF VOYAGER

NASA/JPL/PROCESSING BY STEVE MARSH STEVE BY NASA/JPL/PROCESSING 31 (right) they as and Jupiter on pass betweenit (left) and Europa 13 February 1979 Voyager 1 spies Io Voyager OLD FRIENDS: JUPITER FRIENDS: OLD www.skyatnightmagazine.com www.skyatnightmagazine.com THE STORY OF VOYAGER from the volcanoes on Io’s on volcanoes the surface from north then south then north WKDWULVHVDQGIDOOVƆRSSLQJ ahuge in outwards equator ƅHOGLVLQƆDWHGDWWKHPDJQHWLF DORQJPDJQHWLFƅHOGOLQHV7KH forth and back plasma energetic transporting vast quantities of J E shaped ‘torus’ of charged of charged ‘torus’ shaped VHFRQG7KLVIRUPVDGRXJKQXW every moon the from of mass sweeps past RQH$V-XSLWHUŝVPDJQHWLFƅHOG J URWDWLRQSHULRG 32 U Z identiﬁed on Io (inset) be to ﬁrstvolcano was the by Voyager 1,Pele, spotted OLD FRIENDS: JUPITER upiter’s interior every upiter and and upiter arth’s ‘co and of times stronger than than stronger of times 7KHUHODWLRQVKLSEHWZHHQ Streams of lava snake out snake out lava of Streams www.skyatnightmagazine.com , pushing the plasma plasma the pushing I o is a complex o isacomplex I o it strips o it strips - rotates’ with with rotates’ , during each each during , tilted ‘sheet’ ‘sheet’ tilted 1 1, 0 hours 000kg ,

gaze WRPD begin was maintained torus this ofhow process the did volcanism particles achieve such intensities DWXOWUDYLROHWZDYHOHQJWKV7R brightly glowed atoms sodium RIVXOSKXUGLR[LGH VSHFWURVFRSLFƅQJHUSULQWV sputtering I around cloud sodium neutral REVHUYDWLRQVDOVRLGHQWLƅHGD E\ H[WHQWRIZKLFKZDVƅUVWLQIHUUHG 1 tosurpass have temperatures U erupting from Ionian volcano Loki volcano Ionian from erupting o 00 , Not until the discovery of discovery the until Not formed by atmospheric Voyager 1 catches a plume aplume Voyager 1catches 3 , 000°C and radiate a trillion atrillion radiate and 000°C LRQHHU*URXQGEDVHG , twice N HVHQVH8QGHU , the existence and and existence the , as well as the asthe aswell - ionised oxygen and and oxygen ionised 9 R\DJHUŝV , electron I o ' s cloud belts Jupiter'sof infront hangs of layers of sulphur, of basalt layers of and frost sulphur-dioxide U V Io’s plains are vivid in colours, thought to be the result result the be to Io’s incolours, thought vivid are plains Tiny Io Io Tiny VL]HRIRXUSODQHW ofthe athird only being and KDYLQJDƅIWKDVPDQ\KRWVSRWV combined volcanoes asallof energy much 6RODU6\VWHP,W\LHOGVWZLFHDV volcanically active place in the LGHQWLƅHG,RDVWKHPRVW M Lava lakes andlights F ZLWKGDU pockmarked was ofwhich cent surface dynamic and young its on craters impact out in wide arcs wide in out RUDQJHODYDƆRZVVRPHIDQQLQJ DURXQG tube rom these snaked red and and red snaked these rom orabito’s chance discovery discovery orabito’s chance 9 R\DJHUIRXQGYLUWXDOO\QR , but missed its centre by centre its missed but N Ɔ\WKURXJKWKLVƆX[ FHQWUHGYROFDQRHV 9 N R\DJHUWULHGWR P PDJQHWRVSKHUH , W others forming forming others , into just a few per afewper just the power the DŜƆX[WXEHŝ atts – double –double atts generating 86ŚDORQJ the entire entire the of potential , despite despite J E upiter’s arth’s -

NASA/JPL X 7, NASA/JPL/PROCESSING BY STEVE MARSH THE STORY OF VOYAGER Z 33 as th th , upiter’s upiter’s 17 km gulf J - R\DJHU both before 9 , s rotation ' prompted prompted R\DJHUGLG , million 9 upiter upiter J 778- R\DJHUVVSHQWPRQWKV J LFWXUHVUHFHLYHGGXULQJ 9 3 arth and observed the spot inhabits the , E ovies made with overlapping overlapping with made ovies M HZLVHEHWZHHQ$SULODQG LQFHQWYDQ*RJK R\DJHUWUDQVPLWWHGGDWD N the boundary rhythmically rhythmically boundary the ƆDVKHGLQDQGRXWLQUHVSRQVH WRVRODUZLQGSUHVVXUH PDJQHWRVSKHUHŚ UHFRUGHGERXQGDU\FURVVLQJV 7KLVVKRZHGWKHYDULDELOLW\RI size magnetosphere’s the showed clouds swirling around around swirling clouds showed the edge of the planet’s famous *UHDW5HG6SRWDQGFOLSSLQJ DORQJDWPV7ZLFHWKH of size Moving pictures Moving 7KHWZR of photos telescopically since the century southern hemisphere and rotates examining examining DQGDIWHUWKHLUFORVHVWSDVVHV )URP-DQXDU\XQWLO$SULO 9 across the WR(DUWKZKLOH OL $XJXVW those periods showing how the differential rotation of atmosphere produces a colourful latitudinal display of bright ‘belts’ and dark ‘bands’ comparisons to the work of 9 OLD FRIENDS: JUPITER FRIENDS: OLD

V www.skyatnightmagazine.com www.skyatnightmagazine.com OLWFKH enter the J - pull dynamic dynamic pull H - V KH 7 40 million km beyond then re 7 , 4 had compressed the PV 7 9 WH 1 exit , V \ of Jupiter’s radiationof Jupiter’s belts V R\DJHUGDWDFRQƅUPHGWKHWDLOŝV D sunward boundarysunward and a continuous push repeatedly spacecraft both saw enter 9 existence and showed that it extended WKHSODQHWDVIDUDV6DWXUQŝV RUELW,QFUHDVHGVRODUDFWLYLW\ since W GD KW J Images taken the by Cassini spacecraft ortunately, 2 passed Voyager years later revealed the variable nature F The made Voyagers it through Z led to some photographs being taken 40 seconds too which early, induced high-resolution of loss the and blurring images of Io and Ganymede. Jupiter at a much wider distance than its twin so its problems were correspondingly lessened. Its computer had alsobeen reprogrammed to hour. every automatically, synchronise of complications the fashion, this In image-smear the by high radiation avoided. largely were levels the radiation belt but not wholly experienced 1 unscathed. Voyager a ‘timing offset’, which caused its onboard clock to slow down. Moreover, its two computers drifted out of and each other synchronisation with WKHƆL Voyager 1 Voyager U took this picture on 5 March lightning 1979; can be seen in the centre of the image, as can aurorae on limb Jupiter’s

, as far as Saturn’s orbit”as far plume plume - R\DJHU “Voyager confirmed Jupiter’s“Voyager magnetosphere extended 740 wide wide million km beyond the planet, adiation-resistant adiation-resistant - 9 R which , put together , R\DJHULPDJH 9 00km 2 000km across its , ights’ also picked L

like like shaped sulphur of lake -

H - N while while , R\DJHUZHQWRQWR

9 lightning ‘superbolts’ 9 1 ovian

J upiter’s magnetosphere is a upiter’s torus offered a As well as building a plasma- J J ioneer probes revealed its elesurrounded was a by arth’s volcanoes arth’s oki – more powerful than all of

wave instrument to analyse this this analyse instrument to wave worked engineers environment, to toughen probes’ the Voyager electronics ahead of their visits to Jupiter and Saturn. The radiation problem Before 1970, it was theorised that might dust abrasive of quantities large endanger a spacecraft as it attempted belt asteroid the through pass to between Mars and Jupiter. Several years later, when the Pioneer probes crossed the belt, they showed the dust was no danger. But upon their arrival at Jupiter, a new problem emerged: the Pioneers’ circuits had been fried and savage the by darkened optics their endured belts. radiation They’d Jovian 1,000 times the human-lethal dose of high-energy protons and electrons. were tantalum, including materials, reliability, their maximise to tested before being added into each of the areas spacecraft. sensitive Particularly spot-shielding. additional received ‘magnetotail’ LQLWVZD ZKLOH ORFDWHHLJKWDGGLWLRQDOƆDVKHV WUXO\FRORVVDOSRZHUKRXVH7KH P extentsunward and raised speculation of a bullet north polar region and generated extraordinary ‘whistling’ radio HPLVVLRQV7KH out massive electrical discharges from HUXSWLRQE\WKHWLPH ZDVDEOHWRREVHUYHLW contributing reservoir of particlesenergetic VSLUDOOHGDORQJPDJQHWLFƅHOG lines to fuel the planet’s VSHFWDFXODUDXURUDH2QHGLVSOD\ extended 30 WKDWFRQƅUPHGWKHH[LVWHQFHRI the ‘ L E – had increased in magnitude and evolved into a two dioxide DVHULHVRIWZLVWLQJWHQWDFOHV P hoofprint THE STORY OF VOYAGER T ( waves pressure toanchor continents region ofahigh hallmarks bands at the spot’s southern rim southern spot’s the at bands of ‘thinning’ anotable revealed of distance V complex turbulence altered considerably had latitudes temperate south attendant clouds its and spot the within colour 34 OLD FRIENDS: JUPITER Z and do and anticyclonically he oyager oyager Red Spot while observing Jupiter in 1665 in Jupiter observing while Spot Red U old great ofan glimpse a fresh the Royal Society Royal the the in 1665. and 1664 between it recorded and seen tohave believed are whom of both Cassini, Giovanni the or scientist English to the discovery is usually either attributed for more than three centuries. Its telescopically observed been has and equator Jupiter’s of south 22° lies south, the enigmatic Great Great enigmatic the south, diameter and half as much north- in east-west its Measuring 26,000km the feature’s presence “in the largest largest the “in presence feature’s the www.skyatnightmagazine.com P Giovanni Cassini sketched the the Great Giovanni Cassinisketched ioneer probes saw uniform uniform saw probes ioneer . ,

J W ) endure for centuries for endure Philosophical Transactions of upiter’s storms can can storms upiter’s F 2 ith no solid surface or or surface solid no ith ranco-Italian astronomerranco-Italian hurtled past at a at past hurtled 576, 000km and and 000km , bearing many bearing , but by but - +RR . pressure pressure ,

producing producing I n J uly N 1 R HL 9 obert obert , 7

G W 9 .

HQWLƅH R riting ed Spot ,

H ooke G M sizeofour the each and earlier VSRWVƅUVWVHHQIRXUGHFDGHV way steadily eastwards way steadily colour of evenness agreater and east a spreading at V S the in planet massive J 11 At A ringisrevealed upiter is the biggest and most most and biggest isthe upiter ystem oyager pegged its composition composition its pegged oyager per cent helium cent per oon 87 1, 300 times the sizeof the times 300 per cent hydrogen and and hydrogen cent per , . reason for its colour remains a mystery. amystery. remains colour its for reason the although cloud-tops, the at colder D tobe it revealed Voyager observations diameter. in to40,000km stage one mellow ruddy brown and swelling at toamore hue brick-red extraordinary an from ranging colour: and size in both changed has it then, Since 1831. H until 1713, before seemingly vanishing. oftenth Jupiter”. and noted that diameter “its is one- Jupiter” of belts observed three the of had also worked their their worked also had

T KL . to engulf Earth several times over times several Earth engulf to and long-lived storm big enough isaviolent Spot Red Great The einrich Schwabe saw it again in

The spot was seen intermittently up up intermittently seen was spot The I hree ovalhree nfrared data from from data nfrared J K - out of clouds to the tothe ofclouds out S UH VV , - with trace trace with XUHUH shaped white white shaped S olar . J E LRQ arth V L , J

QLƅF D movies make short to stitched together planet were the of pictures seen when be could bands Jupiter’s cloud of movements U QWO\ The The R the giant long-lived storms planets, settled into a semi-stable state. state. asemi-stable into settled Great the energy, storm’s the todissipate continents of absence the and atmosphere the of depth immense tothe thanks that seems It eddies. and spots smaller other by gobbling simply size their accrue they that perhaps or below, or features draw energy from the sides R Great the as league same the in not although Neptune, and Saturn on I ed Spot. It’s possible that such such that possible It’s Spot. ed WKL Due to the lack of solid surfaces on on surfaces solid of lack tothe Due V amounts of methane amounts rings U didn’t end there than expected south least at extended W interior the in deep work was at of material disc its across crisply moved belts and bands its within eddies mass of clouds rock and ammonia W\ ranus were known to have to have known were ranus estward Before Before S , HK indicating that the motion motion the that indicating ; theoretical models of models theoretical , far closer to the poles poles tothe farcloser DY 1 H 9 - , E blowing zonal winds winds zonal blowing 7 rather than energy R HHQL 9 ed Spot has , only . , But the surprises surprises the But storms and and storms . G 6 HQWLƅH . S 0° north and and north 0° A seething Aseething aturn and and aturn , water G ,

THE STORY OF VOYAGER

, Z o

I . 35

. more , olar olar wide wide - S itan T slightly slightly ,

oon to almost . 000km , M 0km . heavily cratered , a 4 uropa and Callisto , 5,27 E

ars , level pressure on oyager spacecraft anymede is the largest - uncovered the aturn’s moonaturn’s M egio 1 V G S with equatorial an R , mages the taken by dancing points of light I ,

. anymede with a pressure iant iant he dominant feature on G G T anymede anymede’s surface is the alileo oyager he two arth ystem V E ancient areas and brighter youthful patches intersected by furrows and ridges diameter of pipping presence of a thin atmosphere on equivalent to just one billionth of the sea probe showed a terrain split dark between T as big as planetary satellite in the S revealed them to be four distinct worlds that varied in size from smaller than our as tiny WKHƅQHVWWHOHVFRSHVRIWKHHUD were only capable of showing G G G OLD FRIENDS: JUPITER FRIENDS: OLD

, ven E

. . The storm responsible for producing the Great Red which ts main body , www.skyatnightmagazine.com www.skyatnightmagazine.com I his prompted

U Spot is believed to have been years raging for over 150 . T

like” – andlike” its . . - upiter implied that implied that upiter J revealed the ring to 2 alilean moons 000km the above , G 0 oyager probes unveiled unveiled probes oyager torn apart by tidal forces” tidal by torn apart petered out into the darkness background 18 ovian system in its entirety ‘gossamer’ ring ‘gossamer’ V planet’s cloud tops of dust and an outer J oyager V was joinedwas interior an by ‘halo’ “jupiter’s main“jupiter’s ring might have he he New view, new details new view, New evolved from an ancient moon, ancient moon, an from evolved T the IRUWKHƅUVWWLPHDQGVKRZHGXV the vast differences between the four also revealed a red surface on the elongated and cratered Amalthea moon speculation that the ring might have evolved from an ancient moon torn apart tidal by forces and argued it was that Adrastea could provide a suitable reservoir of material for it young quite was it be quite narrow – one scientist “ribbon called it proximity to

Amalthea, Amalthea, U known to exist since 1892, was found to be extremely red

. was able to catch a glimpse of its narrow ring – the orange streaks in the left of this picture hours With 2 Voyager Jupiter in shadow, 17 rocky grains when a , , etis and range imagery range - made its M

1 , ong L

hat prediction was . hebe T T

. oyager V term stability had not - t was intrinsicallyt was dark and Different meteorological characteristics persist at different latitudes on Among the myriad atmospheric features were brown oval ’barges’ like I upiter

composed of tiny composed of with a reddish hue similar to the surfaces of the newly found moons Adrastea photo taken to search for new moons picked out a tenuous ring only 30km wide proven wrongproven just approach closest long predicted to exist any at J after U U Jupiter, which leadJupiter, to the formation of the planet’s distinctive bands this one (left) and an array of white storms close to the Great Red Spot (right) NASA/JPL X 8 X NASA/JPL THE STORY OF VOYAGER craters exhibit dark rays dark exhibit craters upheavals G a tantalising of glimpse T writing new the through show original the allow that parchment medieval ofreused pieces nicknamed ‘palimpsests’ punctuated by craters G oval vast 4 the 36 OLD FRIENDS: JUPITER Z ones lighter newer, the from out standing old regions dark, with dramatically, contrasts crust Ganymede's dark patch big enough tocover enough big patch dark he region and its craters offer offer craters its and region he anymede’s past tectonic tectonic past anymede’s is crust primordial anymede’s www.skyatnightmagazine.com 8 adjoining adjoining , partly erased work to work erased partly - shaped remnant of remnant shaped .

E lsewhere US states , younger younger ,

, after after .

T his .

the surface the kilometres across of hundreds for extending Callisto moon An old are far enough from from are farenough half and half are approximately similar to be G than diameter inequatorial smaller cent per eight anymede seen here towards the western western the towards here seen limb of Callisto, is surrounded Callisto, of issurrounded limb , The Valhalla crater,The impact although although - rock and rock by a vast system of rings of by avastsystem , . was expected was expected , as both moons moons asboth , unlike J upiter - water water I o ,

tectonic activity activity tectonic of a lack suggests Callisto on craters of number history tectonic moon’sthe onto a window provide Regio Galileo huge in Ganymede’s V U The small small The craters The altered the ability of its thin thin ofits ability the altered composition had somehow thattheories Callisto’s ice absent diameter craters 4 themselves giant planets ofthe stages accretional as the asfarback stretch may origin whose aworld revealed terrain concentric rings of array surrounding its and of the of the .5 globe V billion years ago years billion crust to support them tosupport crust ast tracts of heavily pitted pitted ofheavily tracts ast by the by the PRRQDVDKLJKO\UHƆHFWLYH at the time of the ofthe time the at , , V , the smallest smallest the exceeding however ravines but dominated dominated but ravines reminiscent of a reminiscent encounters alhalla impact crater crater impact alhalla , two spacecraft saw saw spacecraft two were conspicuously conspicuously were mountains or deep DUJXHGWKDWLFHƆRHV to serious escape of this size of this ofyears over millions obliterated craters craters obliterated SUREDEO\ƅOOHGDQG surface without high high without surface 6 magnetospheric journey and found a found and journey As for for As outward leg of its ofits leg outward bombardment 00km Callisto on the the on Callisto V oyager oyager . ,

leading to leading 15 - E wide bullseye , . uropa it was it G ‘ 0km in in 0km . L alilean alilean 1 arge’ arge’ saw saw V , . some - ,

oyager oyager the the E rock rock . ven ven

THE STORY OF VOYAGER - 37 V along , . robots ; millions of , olcanism on on olcanism V

. upiter for the J its encounter withJupiter knowledge of the gas giant Voyager 1 cameVoyager away from oyager robots V having markedly increased our colossal polar aurorae , o next quarter of a century kilometres from home from kilometres ZKRVHƅQGLQJVUHZURWHWKH textbooks on “being in the crow’s nest of a ship during landfall and passage through an archipelago of islands” strange with unknown and unseen rings and moons could never have EHHQFRQƅGHQWO\SUHGLFWHG before turned we our knowledge to over capabilities gathering the I

. OLD FRIENDS: JUPITER FRIENDS: OLD

. utch utch it it , M lifetime - A’s a S ystem had www.skyatnightmagazine.com www.skyatnightmagazine.com - S homas homas in experience NA associate administrator for space science T likened it to - olar olar S for the largest , oyager scientists V or the had been a once planet in the begrudgingly surrendered only a handful of the mysteries it held F unpredictability planetary of exploration Europafrom afar (inset) and up close (above); heavily the scored surface is riddled with stress fractures U

, , “The Voyagers’ “The Voyagers’ underlined the

N , t I

. wyll while P , unpredictability of of unpredictability .

shaped discoveries Jupiter at . wyll impact impact wyll - P wide wide planetary exploration” planetary - shaped bands while the side , - km the ,

. which faces away 26 , for iceberg , wedge , wrapped baseball” wrapped - upiter characterised was nicknamed ‘maculae’ nicknamed oyagers’ discoveries , J V uropa is upiter underlinedupiter the E nterestingly J I ne of the he he uropa’s interior

ZHUHLGHQWLƅHGDVSRWHQWLDO upwellings from deep within E by huge long kilometres many of the moon from seemed to have occurred on a particularly thin portion of the crust subsurfacechunks of material SURWUXGHGIURPLWVƆRRU'DU areas More to discover More to discover T at “string was a descriptionwas inspired the by striking linear features moon’s from its scalloped ridges to that stripes dark meandering crisscrossed the surface for kilometres of thousands mysterious ‘triple bands’ made up of two ridges parallel few craters on bright by surrounded is which rays of ejecta that run for hundreds of kilometres out from its central basin separated by a depressed gorge central O NASA/JPL X 7 X NASA/JPL THE STORY OF VOYAGER 38 FRPS moons of Jupiter, using a the and stars of locations exact the out working to dedicated ateam of part I was by: IainInterviewed Todd OLD FRIENDS: THE VOICES OFVOYAGER catalogue dated to a particular toaparticular dated catalogue F moons tothe relative position aspacecraft’s to determine W needed a new star catalogue. we locations To the out work ago long from totechnology back harkening was a camera the then Back doable! the time T tosub taken we had images the in bodies ofthose centres ofthe locations W sized room. VOYAGER or that you need a star a star you need that or his was asking quite a bit at at abit quite was asking his e need accurate star positions positions star accurate e need the toknow e needed In the days after Voyager thedays In 1’s Jupiter encounter themission’s made she mostfamous Linda Morabito joined theVoyager mission engineer asan in thenavigation team. www.skyatnightmagazine.com X V discovery: revealed aplumethat theGalilean moonIowasvolcanically active WHU idicon , but it was certainly was certainly it but WKDW - pixel accuracy , . which is really isreally which ƅ OOHG D THE VOICESOF Linda Morabito JRRG .

extra layers ofclothing! layers extra bullpen area area bullpen the navigation team cooled tobe had I than my mini computer. far more computing power reasonable quality today has of laptop any that I suspect privileged to do no O to the Jupiter encounter. prior sleep much We get didn’t exciting! very was E alltimes fansat its from coming an enormous amount of noise what isexactly that and ƆDZOHVVO\ that spacecraft to navigate W doing we were work the knew ofusor heard highest accuracy possible tothe positions true the knew we that so catalogue a star creating in toassist California L and colleague task our to accomplish we needed accuracy the us with provide could that existence in catalogue star wasn’t asingle move relative tous move relative they and stars tothe relative we move because motions epoch t took up an entire room and and room anentire up t took ick very time time very ur job was to make sure that that sure was tomake job ur e just wanted wanted e just - one ever one O , bservatory in northern then you apply proper proper you apply then I had to step inside inside tostep had I had to put on on toput had . I

had to go to the tothe togo had . , so there was there so .

T ' s little s little myself ‘what that?’ is here here “I believed what Iwas believed “I over and over again” over and over . A so I seeing wasseeing real… was .

I t

I just kept asking asking kept I just .

I nervous you need and second every errors ofany because not although coming in late was somewhat the navigation team of rest the with runner the for ofimages them capture and satellites the view to place right the exactly in were we that toensure encounter be made prior to the tothe prior made be manoeuvres to that needed 7KHUHZHUHDFWXDOO\DIHZƅQDO received. been had across where the it street, Communications Complex Goldstone Deep Space the from Voyagerus data bring to We arunner had saw was beyond imagination. beyond was saw we that detail of level the at but the appearance of Jupiter yet, seen we haven't things describing of job amazing 6 to was supposed it when happen could direction trajectory the that so data the for waiting we were while else everyone and me at looking at my manager and my manager still haven’t forgotten looking looking forgotten haven’t still FLH Q . FH But when you’re counting you’re counting when But . ƅ All these years later years these All FWLR QZ .

I . extremely everybody by make going seconds the based data with combined be to data that

recall waiting waiting recall ULWHUV . J

T E upiter he data arth GR - D , ,

Q ,

THE STORY OF VOYAGER

Z . o’s o’s 39 I had and , 0km 0km I

- , here began I tone 27

T . was was here

. S I . we , and so T

. d . over and over , o E but I ,

. thought that that thought I so it actually , of course , was seeing was was I just kept asking I think think I so so ,

. now we know now we that it , And the object was . one after the other , t was alsot was umbrella I

. it about was a quarter of , in the sense that it belonged , he object had a phase angle asked myself that question T By the end of the day f course I began making educated possibility that eliminate had to also had to eliminate the believed what had the answer to the extent that project scientist sent commands to one of the instruments to detect further possible evidence that this was DYROFDQLFSOXPH,KDGWRƅQG out the latitude and longitude occur to me! But had its own crescent and its own illuminated dark portion an offsetwas in the orientation of this crescent compared to crescent people who contacting started were familiar with the camera systems and artefacts no idea what it and was very short on sleep it associated with huge the size of the crescent in the image shaped and raining back down O a plumewas rising about theabove surface of One after another, I contacted the people who I thought could give me the answer on the spot, because I felt I didn’t have a lot of time and I wanted to know what I was looking at. I guesses were blemishes in most images things that weren’t real I I possibility that it a newly was discovered satellite because like looked it what that’s myself “what is that?” over again to my datato my if HQRXJKWKHDQVZHUZRXOGƅQDOO\ I performed what’s known as images the on stretch linear a to bring out the contrast and pick out small variations in moment, that At brightness. a gigantic objectappeared off the limb of the moon. I real they had been taken anyway them processing J

, Q o I so so , GL he he By so so . , T

. ƅQ accuracy accuracy - WUH www.skyatnightmagazine.com www.skyatnightmagazine.com had read I oyager had had oyager Q much like , V lit satellite - FH . \ was astonished was But that’s not I . upiter were pretty J UDF was using was based was X I made the decision oon rom what I and

, F .

M . DFF came in and displayed the I arth’s arth’s think nearly think every member knew that the high what found we The images I had were designed to show me only what I needed to see for the KLJK think you would know what to to what know would you think expect VFLHQWLVWVZHUHSUHWW\FRQƅGHQW that would we see an object with craters that could be somewhat dead geologically E To be honest,To they had a very low priority. I of the imaging team had left and returned to their home point that institutions at then everybody really thought that the wonders appeared as a crescent revealed of much behind us! pictures because the phase angle didn’t result in fully lit satellites software on having a fully I FHQWUHƅQGLQJZDVQŝWJRLQJWR happen that the images were useless in terms of the purpose for which OLD FRIENDS: THE VOICES OF VOYAGER VOICES THE FRIENDS: OLD Linda with U colleagues in navigation the image team’s processing where room, the discovery of active volcanism took place Io on

he he .

. T .

. but o you’d o you’d , S

. remember upiter as as upiter I J caused , arth o s about the E ' I but , ll never forget o up close I our images I' range from black ,

, . did go home and I ystem had the opportunity oon is from I S s about the same size of ' M he colours of T

his is an object that’s a moon . olar olar d been working so hard that

hadn’t had a chance to view was seeing: was what appeared to almost couldn’t believe what

to see the fruits of our labour the images of WKHQƅQDOO\,VDZWKHPGXULQJD press conference somewhere in the laboratory – the sight of that moon took breath my away sulphurby dioxide at various temperatures sleep I it to orange to yellow to blue during the very brief periods of that time I' be one of the strangestobjects humanity has seen ever in the S that the I our and own that As navigators As I way scientists described it – and the described way we it at the time – caught on very quickly: it looked a mouldy like pizza Seeing Io – a world we had never seen before incredible. was – T same distance from weren’t in colour LINDA MORABITO, NASA MORABITO, LINDA THE STORY OF VOYAGER

BILL PETERS/WWW.BILLPETERS.CA, NASA stuff ofdreams stuff any individual one than important ismore science discovery of this terms in tome belonged that ones only the were morning the T with the image. alone afew moments I had those initial enquiries and came when I began making The most memorable part feature that with up lined longitude of what and latitude the moment the on heart large ofthe top on about just position the object the position to subtraction and addition longitude and latitude spacecraft the you have once But not or limb the was behind it because of cloud the appearance the upon based extrapolate to had then and spacecraft 40 Z wasrevealed plume Io’sin which volcanic image the displays Linda’s computer OLD FRIENDS: THE VOICES OFVOYAGER on hose moments very early in in early very moments hose I o www.skyatnightmagazine.com I . o directly beneath the the beneath o directly -

I shaped volcanic feature volcanic feature shaped don’t think think don’t I didn’t know whether whether know didn’t , it’s just takes a simple takes asimple just it’s , because because , because the the because . I I

was seeing was seeing . ’ll ever forget ’ll ever forget I

t was the t was the I t landed t landed ,

I . knew .

all likelihood I J Voyager 1arrived. before Io on been a of prediction volcanism had there but it, realise I didn’t before seen ever had was seeing something that something was seeing ust before the encounter the before ust , no human being being human no .

, in revelatory photo revelatory this snapped that probe the of Voyager 1, amodel of front V Linda sits in sits Linda but there were a lot ofpeople alot were there but S of predicting that apaper published had Barbara U seeing at H dissipation tidal through heated humanity forward humanity move tosomehow my dreams: privileged to part of KDGVRPDQ\ƅUVWVWKDW,ZDVVR happening it we saw DOLYH7KLVZDVWKHƅUVWWLPH come and heat internal generate worlds way tomake amazing I course ofthe portion A good textbooks the T incredible opportunity. of moments were These was seeing he what heartbeat a in knew eyes: he his in it see S prediction the up to back evidence any for possible looking including including now teach is on tidal forces tidal ison teach now tanton tanton tone was called in was called tone hey often say we rewrote werewrote say often hey niversity ofniversity California e anticipated what we were we were what e anticipated S tan’s paper at the time the at tan’s paper P E I eale from the the from eale o d .

I S was unaware was unaware tone .

Y I o was being o was being es . , , we did who were were who , you could you could . V

. T

V hose were were hose , oyager oyager

S anta .

. W

, hen an ,

FROM THE MAKERS OF ONLY £9.99 EACH INC FREE P&P*

The Apollo Story is your complete guide

Discover the story of over 50 years of ,PPHUVH\RXUVHOILQWKHZRQGHURIWKH manned space exploration in this lavish, QLJKWVN\ZLWKHotshots: Volume 1. In 116-page special issue. With articles by LW\RX OOƅQGDPD]LQJSKRWRVSOXV OHDGLQJVSDFHƆLJKWZULWHUVDQGUDUHO\VHHQ expert imaging tutorials covering the photos of astronauts and their spacecraft. most popular targets. ORDER ONLINE www.buysubscriptions.com/skycollection Or call our hotline: 03330 162 138† Please quote code: SKYSPEC †Calls from landlines will cost up to 9p per minute. Call charges from mobile phones will cost between 3p and 55p per minute but are included in free call packages. Lines are open 8am -6pm weekdays and 9am – 1pm Saturday for orders only *Subscribers to BBC Sky at Night Magazine receive FREE UK postage on these special editions Prices including postage are: £11.49 each for all other UK residents, £12.99 each for Europe and £13.49 each for Rest of the World. Please allow up to 21 days for delivery. OLD FRIENDS: SATURN THE STORY OF VOYAGER STORY THE

Four of Saturn’s many moons can be seen in this Voyager 2 image. Tethys, Dione and Rhea ﬂoat in space while Mimas hangs just below the rings, near the planet’s western limb

42 www.skyatnightmagazine.com THE STORY OF VOYAGER - 43 at at aturn , -S closest closest Saturn Saturn Hyperion but , Z ystem

. S approach so close to

upiter

“to break , hours 2 , J olar olar S the only natural , t was indeedt was a QRZQWRSRVVHVV I was following was a Earth occultation zone N 1 Enceladus SUN Words: BenWords: Evans Dione oyager V

itan’ so it coulditan’ observe . aturn meetings aturn 200,000km S communications encounter?” move bold dauntingly there a clear was rationale for it T quartersclose satellite in the GHƅQLWLYHO\ a dense atmosphere route known as ‘ Rhea EARTH Mimas Titan Tethys . OLD FRIENDS: SATURN FRIENDS: OLD arth -

itan E , T Sun occultation zone Now . www.skyatnightmagazine.com www.skyatnightmagazine.com urray urray M upiter ” , J 4 billion km from 1. the spacecraft tiny , it having was its critical , sn’t it risky it sn’t I “ arth more than E with link communications intentionally severed so the craft could be turned towards asked at one of the last pre was threewas years into an epic mission exploration of that had already rewritten the textbooks on After all closest closest Saturn Saturn

approach 2 hours 2 Titan The probes' V paths through through paths Saturnian the system saw (below 1 Voyager left) pass much closer to Titan than 2 Voyager (below right) Sun occultation zone Dione

Tethys ,

. , Rhea SUN 200,000km EARTH discoveries at

. aturn Earth occultation zone though though , S asadena Enceladus of ropulsion P P silent less than a , , in in 0 et past Titan, still the only moon we know of with a thick atmosphere atmosphere a thick the only moon we know of with still past Titan, Mimas 8 J then serving as 9 , 1 (JPL) was not was alone in fell abruptly , 1 urray M Hyperion than anyone had imagined. While it was in the neighbourhood, Voyager 1 skimmed 1 skimmed Voyager the neighbourhood, was in it While than anyone had imagined. VOYAGER 1VOYAGER 2 VOYAGER oyager aboratory November November

Long regarded as the ‘wow’ planet of the Solar System, Saturn proved more magniﬁcent magniﬁcent more Saturn proved planet of the Solar System, regarded as the ‘wow’ Long

ON THE EVENING

Saturn Titanic L California 6 week before reaching V having expressed consternation theover hazardous manoeuvre that about was place to take not unexpectedly not Bruce Bruce director of the NASA/JPL THE STORY OF VOYAGER VXEVWDQWLDOWKDQDQWLFLSDWHG WKHVŚZDVIDUPRUH GHWHFWHGVSHFWURVFRSLFDOO\LQ 7LWDQŝVDWPRVSKHUHŚƅUVW LQYHVWLJDWRUVWRVKRZWKDW 7KHVLJQDOŝVŜRFFXOWDWLRQŝDOORZHG UHDSSHDULQJDIWHUPLQXWHV IDGHGDQGWKHQYDQLVKHG RUDQJHFORXGVJUDGXDOO\ WRƆ\ZLWKLQ DZD\IURPLWVORF WRUHSRVLWLRQLWVHOIDTXDUWHUWXUQ DFFRPSOLVKWKDW WKUXVWHUVZDVQHHGHG$QGWR ƅULQJRIWKHVSDFHFUDIWŝV KD]HDWUDMHFWRU\FRUUHFWLQJ FDQRS\RIJDVHVDQGSDUWLFXODWH 44 SDVVHGWKURXJK7LWDQŝVWKLF WKHVSDFHFUDIWŝVUDGLRVLJQDO VRRQDIWHU(DUO\RQ1RYHPEHU 7KHƅUVWGLYLGHQGZDVSDLG Investigations begin OLD FRIENDS: SATURN Z PLQXWHVODWHU FRPPXQLFDWLRQVZHUHUHVWRUHG 7RHYHU\RQH VLPPHQVHUHOLHI UHDOLJQHGLWVHOIZLWKRXUZRUOG WKH7LWDQƆ\E\7KHSUREHWKHQ LWDVOLJKWVLGHZD\VQXGJHIRU DOPRVWPLQXWHVDIIRUGLQJ IXHOOHGWKUXVWHUVKLVVHGIRU DZD\IURP(DUWK,WVK\GUD]LQH URWDWLQJLWVKLJKJDLQDQWHQQD WUDF DQGWKH6DWXUQLDQV\VWHP WKHLPPHQVHJXOIEHWZHHQ(DUWK IRUWKRVHFRPPDQGVWRFURVV WUDYHOOLQJDWWKHVSHHGRIOLJKW VSDFHFUDIW,WWRR UHTXLVLWHFRPPDQGVXSWRWKH &DOLIRUQLDGXO\WUDQVPLWWHGWKH 7KH'HHS6SDFH1HWZRU 9 I f it was f it R\DJHUUHVSRQGHGFULVSO\ N www.skyatnightmagazine.com LQJVWDWLRQLQ*ROGVWRQH N PRI7LWDQŝVVRXSOL N N 9 RQ(DUWK PLQXWHV R\DJHUKDG N N H N ŝV SDUWLFXODWHVPLJUDWHIURPRQH ZDVDEOHWRVKRZWKDWJDVHVDQG : 7LWDQ VFORXGV GLVWLQFWVHDVRQVDQG LQQHUPRVWSODQHW WKDQWKH6RODU6\VWHPŝV DQGWKDWERWKPRRQVDUHELJJHU PDUJLQDOO\WKHODUJHURIWKHWZR DVFHUWDLQWKDW*DQ\PHGHLV GDWDLWZDVSRVVLEOHWR WKLF UHJDUGLQJWKH RISUHFLVHGHWDLO ELDVHGE\DODF WKLVƅJXUHZDV VXJJHVWHGDQRSWLFDOVL]HRI IURP(DUWKDIHZ\HDUVHDUOLHU $QRFFXOWDWLRQRIRXU WKDQ-XSLWHUŝVPRRQ*DQ\PHGH LQWKH6RODU6\VWHPODUJHUHYHQ ZDVWKHELJJHVWQDWXUDOVDWHOOLWH HUURQHRXVDVVXPSWLRQWKDWLW RSDTXHYHLOKDGVSDZQHGWKH WKHXQ ZDVDVLJQLƅFDQWƅQGDVXQWLO GLDPHWHURIDURXQG WKHPRRQWRKDYHDQHTXDWRULDO WHPSHUDWXUHRIŚ RIDVROLGVXUIDFHZLWKD GDWDUHYHDOHGWKHH[LVWHQFH / DWHUDQDO\VLVRIWKHVLJQDO DWHUDQDO\VLVRIWKHVLJQDO LWK 7LWDQŝVHTXDWRULDOWLOWFDXVHV 7KHUDGLRVLJQDODOVRVKRZHG N QHVVRI 9 N R\DJHUŝV PEXW N QRZQVL]HRI7LWDQŝV N 0 hydrocarbon lakes and and lakes hydrocarbon HUFXU\ p & 9 0 plausibly considered R\DJHU RRQVHHQ N for the first time” first the for seas on Titan on seas was P7KLV “the existence of of existence “the the moon haze shroud that of layers the (above) shows shot colour closer, false- Voyager 1’s from afar (inset); featureless blob Titan's imaged U Voyager 2 QRUWKDQGDXWXPQLQWKHVRXWK ŚDWWKHWLPHLWZDVVSULQJLQWKH JOLPSVHRIWKHVHDVRQDOYDULDWLRQ EULJKWHUVRXWKDQGSURYLGHGD FRQWUDVWHGVWDU KD]HRYHUWKHQRUWKSROH7KLV PDQ\RIZKLFKZHUHGHWHFWDEOH K\GURJHQF\DQLGHDQGDFHW\OHQH WUDFHFRQVWLWXHQWVLQFOXGLQJ DWRPVUHFRPELQHLQWRDUDIWRI RIQLWURJHQDQGPHWKDQH7KHLU VRODUZLQGVHSDUDWHPROHFXOHV DQGXOWUDYLROHWSKRWRQVIURPWKH 6DWXUQŝVƅHUFHPDJQHWRVSKHUH SHUFHQW,QIDFWSURWRQVIURP PHWKDQHRQO\DFFRXQWVIRUDIHZ GDU ZKLFKVZHSW 1HLWKHU EURDGGLIIHUHQFHVLQDOEHGR DWPRVSKHUHWKLVKLJKOLJKWHG ZLWKWKHVKHHUGHQVLW\RIWKH KHPLVSKHUHWRWKHRWKHU$ORQJ WKHPXU WUDFHRIDVROLGVXUIDFHWKURXJK 7LWDQLQ$XJXVWVDZDQ\ 7KHPRRQŝVDWPRVSKHUH N EURZQŜKRRGŝRIGHWDFKHG N 9 EXWWKH\GLGLGHQWLI\D R\DJHUQRU N O\ZLWKWKHIDU ZDV WXUQVRXWWKDW DOWKRXJKLW SUREHVDUULYHG WKH ORQJEHIRUH PHWKDQH WRFRQWDLQ 9 N N 9 PSDVW R\DJHU QRZQ R\DJHU THE STORY OF VOYAGER Z 45 P P N N N LRQHHU 3 PWKLF N 7KUHHULQJVGXEEHG$%DQG QRZQWRDVWURQRPHUVORQJ DUDGLDOEUHDGWKRI HTXLYDOHQWWRWKUHHTXDUWHUVRI WKHGLVWDQFHEXWDUHEHOLHYHGWR EHQRPRUHWKDQ &WRJHWKHUZLWKWKH ZLGH&DVVLQL'LYLVLRQZHUH N EHIRUHWKHGDZQRIWKH6SDFH $JH,Q6HSWHPEHU IRXQGWKH)ULQJZKLFK UHVHPEOHGDFRQWRUWHGWDQJOHRI OLD FRIENDS: SATURN FRIENDS: OLD O\\HOORZ N www.skyatnightmagazine.com www.skyatnightmagazine.com PSDVWWKHVLF R\DJHUKXUWOHG N 9 HVDQGVHDVZDVSODXVLEO\ The rings million as seen 2 from limb km; can just 3.3 Voyager by Saturn's (LJKWHHQKRXUVDIWHUOHDYLQJ N OD FRQVLGHUHGIRUWKHƅUVWWLPH 7LWDQ FORXGWRSVRI6DWXUQWKH 6RODU6\VWHPŝVPRVWYLVXDOO\ VSHFWDFXODUSODQHW,WVLQWULFDWH ULQJVZKLFKVRSX]]OHG*DOLOHRLQ EHIRUHWKH\ZHUHFRUUHFWO\ GHVFULEHGDQGLGHQWLƅHGE\ &KULVWLDDQ+X\JHQVLQKDYH U be seen through the C ring and inner part of the in the B ring, lower right Tethys, Tethys, U Enceladus and Mimas are visible around ringed Saturn in this mademosaic, images from million taken 18 away km P N VIRU N P u PWR u R\DJHUVŝLQIUDUHG 9 R\DJHUVREVHUYHGFRROHU ZKRVHSDUWLFXODWHVYDU\ 9 N Voyager 1 spotted Voyager F Ring (top), kinks in Saturn’s QRZQDVŜWHPSHUDWXUHLQYHUVLRQŝ

U WKLF LQVL]HIURP 'XULQJWKHLUUDSLGWUDQVLWV WKH WHPSHUDWXUHVQHDUHUWKHPRRQŝV DQGZDUPHURQHVLQWKHKLJK WURSRVSKHUHDSKHQRPHQRQ N ,WŝVGULYHQSULPDULO\E\XOWUDYLROHW VXQOLJKWDQGFRQWULEXWHVWR 7LWDQŝVDOUHDG\FRPSOLFDWHG SKRWRFKHPLFDOSLFWXUHZKLFK LVGRPLQDWHGE\DGHQVHOD\HU RIK\GURFDUERQŜVPRJŝ A complicated pictureA complicated (YHQLQLWZDVDUJXHGWKDW WKHVHSDUWLFXODWHVFRXOGŜVQRZŝ RQWR7LWDQŝVVXUIDFHDQGVR WKHH[LVWHQFHRIK\GURFDUERQ LQVWUXPHQWV+\GURJHQF\DQLGH SOD\VDQLPSRUWDQWUROHLQWKH V\QWKHVLVRIDPLQRDFLGVDQGLWV GLVFRYHU\DW7LWDQWULJJHUHGHDUO\ WKHRULHVWKDWWKHPRRQPLJKW KDUERXUWKHEXLOGLQJEORF WRWKH FRPSOH[RUJDQLFFKHPLVWU\ ,QGHHGLWPD\HYHQPLUURU FRQGLWLRQVRQWKHLQIDQW(DUWK DVLWZDVELOOLRQVRI\HDUVEHIRUH OLIHHYROYHGKHUH which suggested that moonlets were responsible the Cassini for ring ‘shepherding’ material. In 2010, spacecraft allowed scientists to see how Prometheus and Pandora (also discovered do Voyager) that by just NASA/JPL X 5, NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE SCIENCE NASA/JPL-CALTECH/SPACE 5, X NASA/JPL THE STORY OF VOYAGER Nine months later months Nine slender exceptionally dusty the locate detail great in them toexamine unable was probe the that meant defective photopolarimeter the LQƆXHQFHGWKHVWUXFWXUHRI possibly and straddled P moonlets later kilometre ring material million along its anchored ‘moonlets’ oftiny existence possible the at strongly hinted data its 46 OLD FRIENDS: SATURN maintained by shepherd moons moons by shepherd maintained are edge ring the to parallel features linear the that thought it's Aring; the of edge outer The Z Why does Saturn does have rings? Why grand such andora narrow strands S till F www.skyatnightmagazine.com ,

ring V F ,

V oyager oyager or over three centuries, from from centuries, over three or the observations earliest by oyager oyager , both of which ofwhich both . - ,

or ‘shepherded’ P Galileo Galilei and Christiaan Christiaan and Galilei Galileo , long tracks U which somehow rometheus and and rometheus . nfortunately H 1 uygens, Saturn was was Saturn uygens, discovered the the discovered 1 . managed to managed

D believed to be the M ,

ring and the the and ring V oreover only planet to have tohave planet only oyager oyager . G A year Ayear ring rings. Morerings. , a , the the , recently,

. 2

- its threeits giant Cassini Cassini rings the in anywhere existed fewgaps very that showing of hitherto groups toresolve managed and photopolarimeter functioning encountered fragments rocky and ofdust mass a vast by populated tobe out turned Brings Aand bright the separates ofwhich band dark rings iswater rings T The rings' origins under sizefrom in ranged particles spaced closely most the that PHDVXUHPHQWVFRQƅUPHG he principal constituent of the ofthe constituent principal he E ven the notionally ‘empty’ ‘empty’ notionally the ven a given planet would be torn apart apart torn be would planet a given E solve. help could Voyagers the hoped was it mystery a was systems ring of endurance and creation the Saturn, of those than grandiose less far being Despite assemblages of dust and grains. rocky own their revealed have cousins UH R by tidal forces and the debris might might debris the and forces by tidal 1 cm to H oche, that postulated small moons D V Two main theories took centre-stage centre-stage took Two theories main I L RUH ivision settle into rings. The second, by second, The rings. into settle G . - LQ

R unseen ‘ringlets’ unseen J Pierre Pierre adio - S 1 ice 0m or more or 0m D aturn with a fully afully with aturn , W K the broad the . VS

- ant, argued thatant, the rings I science t makes up up t makes 7 L formed at the same time time same the at formed HFLƅF KHƅU aplace and Immanuel as Saturn, in a process aprocess in Saturn, as ,

V G similar to how the the tohow similar . W , L

V ,

E W Solar System D . \

QFH (G formed from formed RX V I a large a large D UR Saturn's rings that traverse ‘spokes’the revealed images of Voyager U U G P disc. Sequences Sequences FRROH hand, other the on Saturn, systems. ring expansive less and darker far their toassemble which from volatiles early in their evolution, leaving mainly their primordial gaseous discs quite that Jupiter, a relatively benign environment. implying that the rings have thrived in Saturn, at radiation ambient of levels low exceptionally Voyagers revealed this. than older much were they if atmosphere the into pulled been have would they that grains) tosand-like boulders car-sized (from small so are particles Some years. million hundred afew than older no – that they seemed contaminants wholly water-ice, with some trace almost –formed pristine and bright so were rings the in particles discrete their encounters, the Voyagers also During rings. brilliant more far produce eventually and tocondense vapour This contributed to early theories theories toearly contributed This Voyager probes, by the viewed As uncovered much more intricate G detail, from spokes and kinks to kinks and spokes from detail, gravitational orbital mechanics gravitational with areinconsistent that spokes and kinks including features radial uncovered probes formation rings the behind force driving asthe forces gravitational VFLHQWLƅFFRQVHQVXVIDYRXUHG silicates or tholins as such ofimpurities presence in places V UHƆHFWLYHDOWKRXJKERWK dazzlingly so them makes what 99 dissipation lifecycles dissipation and formation spokes’ the S of one during of images images showed them to be tobe them showed images V aturn’s rotations that revealed revealed that aturn’s rotations oyagers saw discolouration X ringlets and shepherd moons, moons, shepherd and ringlets V . 9 per cent of the rings and is and rings ofthe cent 9 per I oyager oyager ƅFLHQWO\H than had been expected. been had than U ranus and Neptune lost , perhaps due to the tothe due perhaps .

Y 1 took a sequence asequence took et the et the D UO\ F urthermore, theurthermore, . I

RUZ V U oyager oyager ntil ntil .

T D he 1 WHU 9 8 ,

0 , '

THE STORY OF VOYAGER

, , 47 ap was was till till , S km in in km G

with with . , 2 LPDV ivision ivision 87 wide wide 0 - eeler D K per cent km upiter t’s thought 6 uygens uygens J I ovian

25 oyagers deep deep oyagers . H J

V . ames J the composition , measuring 4 , ike itsike larger cousin images L 2

. ap in the A ring and G aturn’s atmosphereaturn’s was S nexpectedly oyager aturn shown was to radiate ncke ncke Another gap diameter and named in honour astronomer of – are thought to be controlled in SDUWE\WKHLQƆXHQFHRI other openings in the rings – including the Cassini and the narrower V keeping it free of particles to be responsible for ‘scalloping’ the edges the of 3 E detected the by within the A ring of distinct quite from abundances helium smaller and a larger relative share of hydrogen – about 9 compared to the cent per S Giant stormsGiant U

- , . OLD FRIENDS: SATURN FRIENDS: OLD 990 1 .

www.skyatnightmagazine.com www.skyatnightmagazine.com the walnut . , rometheus anus P J

. imas orbital mechanics” orbital ivision are thought M particles near was found in , , The rings and moons were seen casting shadows on the planet D whereby particles , orbiting moonlets orbiting up ring material – and - an U and particles bordering , - P radial features, including spokes and kinks, are that andora lent credence to P lsewhere t had been argued that I moonlet Another E “the Voyager probes uncovered “the Voyager inconsistent with gravitational inconsistentwith gravitational he discovery of pimetheus and charged particles that levitated theabove rings shaped following an analysis of old divisions within the rings were formed the by process of orbital ‘resonance’ ZHUHFRQƅQHGWRVSHFLƅFUHJLRQV theby gravitational attraction of moons shepherd neighbouring T and idea this Cassini the WREHLQƆXHQFHGE\WKHSUHVHQFH of the moon the edge of the A ring are ‘sharpened’ the by moonlet Atlas – its astonishing equatorial ridge might represent a deposit of swept theby co E Saturn has its own red albeit spot, smaller than Jupiter’s Ribbon-like wave structures were clouds seen in Saturn’s A tiny speck 2 image in a Voyager (top) was later

U U U revealed to be moon Pan. Investigations performed by the Cassini probe showed it to be walnut-shaped (above) NASA/JPL X 17, NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE SCIENCE NASA/JPL-CALTECH/SPACE 17, X NASA/JPL THE STORY OF VOYAGER OHVVREYLRXV%XWWKHZRUOG much isalso banding latitudinal LWPLJKWƆRDWRQWKHZDWHU,WV found be could bathtub large LGLRPWKDWLIDVXIƅFLHQWO\ massive J characteristic of all four giants ofallfour characteristic that equator bulging SRODUƆDWWHQLQJDQGRXWZDUGO\ axis its upon rapidly rotates it and sunlight it absorbed from incident 48 Z OLD FRIENDS: SATURN upiter more heat into space than than space into heat more 10km deep and 130km across) covers covers across) 130km and deep 10km Mimas’s fact, In seen. ever size totheir proportion showcase the biggest craters in which water-ice, predominantly both intriguing are Tethys and Mimas, Most moons. other Saturn’s on craters many generated to have thought are epochs youth.Those its in epochs of meteoroid bombardment savage two endured had –that craft Voyager by both distance a great crater-scarred and seen only from globally atmosphere, ‘sensible’ diameter. in 1,530km at size the rocky was largest Next Titan. planet-sized the being them among largest the visited, Voyagers the before Saturn to orbit Around a dozen moons were known MOONS NOT SHOWN TO RELATIVE SCALE I n a further contrast to contrast n afurther www.skyatnightmagazine.com It was was It ,

S , leading to the famous famous tothe leading aturn is 30 per cent less less cent per is30 aturn A growing moon menagerie A growing R hea – stripped of a of –stripped hea , generating the the generating Rhea H erschel crater (almost U R ' The two Voyager probes provided our best shots of Saturn’s moons until the Cassinispacecraft Saturn’s the of until shots moons best our provided Voyager probes two The s a curious s acurious hea, one-third ,

Titan .

Phoebe Tethys S DQHOOLSWLFDOZKLWHVSRWQHDU visits the before century an inactive place by means no of Bringer and of father fabled to the homage pays ZKRVHQDPH VWRUPVDWZRU oflarge sightings periodic astronomer aturn’s equator aturn’s O Dione ld Age is Age ld , comedian and amateur amateur and comedian ( material could be responsible. leading hemisphere by darkened preferential bombardment of Iapetus’s that suggesting halves, two the transitional zone300km-wide between ameandering, Voyagers revealed The other. the on dark face, one on L Cassini Giovanni abewildered which terrain. its of fraction awide spans feature, called ancient more ashallower, boasts Tethys apart. moon the broken almost have must impact causative its that enormous so diameter, its of a third of ‘cryovolcanism’. suspicions early raising and satellite it the brightest-known natural allvirtually incident rendering sunlight, G O V HQWLƅH Then there’s enigmatic Iapetus, HZKHUHLF\ J upiter W N ill G DV , H one of several ofseveral one .

H ay observed ay observed ŜWZRWRQH V banding is less obvious obvious less is banding alf a oyagers oyagers ( Janus O than jupiter's, but it's it's but jupiter's, than QFHO “Saturn's latitudinal “Saturn's dysseus, which also Mimas R - DG ugged Dione scale by no means an inactive place” inactive X G V ŝŚ Epimetheus UHƆHFW Iapetus E UL J KW V Hyperion ƅ this carry –could tomoonlets grains from rings– the within particles innumerable of presence the but FRQƅU P Today, Pan. that known it’s including others, of detection tothe led work on theirEarth-based imagery later Voyagers and by the found Prometheus and Pandora) were (Atlas, moons more Three opened. D Janus of observations range asteroid. aseized represent could Phoebe blob-like and remnant of an ancient collision shaped potato- while moon, companion aco-orbital topossess shown was Q J RUHWK W G XUHLQWRWKHWKRX ith the Voyagers’ close- (S P MHWVWUHDPVZKLFKSHD latitudes above latitudes SRZHUIXOSRODUDXURUDHDW uncovered spacecraft both latitudes higher at JUHDWHUZLQGVZHUHDOVRFORF than those on L P H D H G Qƅ HWKHX yperion might be the the be might yperion RU Enceladus N Y PKŚƅYHWLPHVIDVWHU E H LW G V V WKHƆRR R]HQ H[L VD V E W P Q arth 65 D GV gusting gusting HDVWZDUG 1 on planet the past 9 RRQ W 9 . R\DJHUƆHZ °N 6D GJD

81, RU W D . 25

, M ata from from ata V WXUQ together together hen it revealed revealed it N E ZLWK August August WH arginally arginally HGDW H\RQ V N G HG THE STORY OF VOYAGER

, t I

. 49 V

. planet as a crescent WR8UDQXVWKH N The Voyagers showedThe Voyagers the equator to the poles us that Saturn's banding thatus Saturn's stretches all the way from ,WZDVDƅQDOSDUWLQJJLIW7KHQ Voyager 1 lookedVoyager back at Saturn R\DJHUŝVLQVWUXPHQWVZHUH four days after its close encounter to give a fresh us perspective – the VHHPHGDVLI6DWXUQZDVELGGLQJ LWVYLVLWRUVIDUHZHOOE\RIIHULQJ up one more mystery to perplex and astound us ƅYH\HDUWUH timing had almost been poetic the magnetosphere rapidly rapidly magnetosphere the EDOORRQHGRXWZDUGVLQOHVV than six hours 9 deactivated and the spacecraft entered hibernation for its lonely

, OLD FRIENDS: SATURN FRIENDS: OLD upiter R\DJHU HGO\ J 9 N aturn on S www.skyatnightmagazine.com www.skyatnightmagazine.com R\DJHU 9 as the , PE\ hen N T

. much smaller than the enormous cavity encapsulates that EXWZDVVWLOOVKRZQWRVSDQRYHU WZRPLOOLRQ 1LQHPRQWKVODWHUZKHQ DUULYHGVRODUZLQGSUHVVXUHV KDGKHLJKWHQHGDQGPDU FRPSUHVVHGWKHVXQZDUG boundary departed spacecraft WKHRXWZDUGOHJRILWVMRXUQH\LWV instruments detected a sudden GURSLQVRODUZLQGSUHVVXUHDQG Saturn's Saturn's U north polar region was seen to be littered with small- bright, spots cloud scale

, itan

. T ZLWK p PDERYH N LORPHWUH N latitudes he strong strong he - aturn and T

. S R\DJHUVREVHUYHGD 9 LRQHHUWKDWƅUVW 3 he planet’s magnetosphere is is magnetosphere planet’s he

respect to its rotational poles ZKLOHWKH strange ‘torus’ of positively charged hydrogen and oxygen LRQVDERXW T ,WZDV detected the unusual alignment RI6DWXUQŝVPDJQHWLFƅHOGZKLFK LVWLOWHGE\OHVVWKDQ the cloud tops HPLVVLRQVDVVRFLDWHGZLWKWKLV WRUXVZHUHPHDVXUHGE\WKH ƅHOGVDQGSDUWLFOHVLQVWUXPHQWV UHYHDOHGDPLOOLRQ ZLGHŜVKHHWŝRISODVPDSHUKDSV atmospheric supplied by from material ZLWKXOWUDYLROHWHPLVVLRQVRI hydrogen at mid A parting gift NASA/JPL X 13 X NASA/JPL THE STORY OF VOYAGER 50 by: IainInterviewed Todd OLD FRIENDS: THE VOICES OFVOYAGER I 8UDQXVƆ\E\LQWKUHH\HDUVŝWLPH I Voyager’s imaging team. graduated I was added to I as soon as and rings Saturn’s on my thesis I did the on how that’s and on thesis my todo my into hands fell of the of the I where department academic O by Saturn. Voyager passed when student agraduate I was analyse it all it analyse to people enough had teams of the none that information much so was back was sending probe the that images ofthe some T VOYAGER had done my thesis on on my thesis done had the for toprepare was helping was studying was a member was amember was studying hrough him him hrough ne of the people in the the in people ofthe ne www.skyatnightmagazine.com The imaging theCassini team for leader mission looksback atSaturn onherdays V V oyager imaging team oyager project V . spent analysing photographs fromtheVoyagerspent analysing photographs mission, led that work

I oyager science science oyager S got to work on on towork got ome nice topics to herdiscovering thespokes lie that within thegasgiant’s rings THE VOICESOF . .

I T got got here here Carolyn Porco .

to our destination to our toget rowing aboat in years I Homeric epic. a Voyager like was rings planet’s the of made observations all the for was responsible that team imaging the within group small conquest and triumph and conquest to Neptune we reached the next port ofcall port next the we reached until ofpaddling years more for boat the in back getting expert U around found eventually were that ofrings type exact the there was a crazy week or two two or week was acrazy there then and destination to our W t was like spending three three t was like spending ranus e would spend years getting getting years spend e would . By the time time Bythe , so I , was the team’s was the

I was leading the the was leading

. , then it was it then V oyager got got oyager , before before .

Voyager’s data discuss to US TV on appear to leader, prepare team imaging Voyager’s Brad Smith, V Carolyn and and Carolyn planning the next one next the planning previous encounter we’d that the data from got the and images the analysing iswe’d be encounters between the two the of amarathon duration the for tosprint asked O different was entirely Cassini on so and science the discuss to and meetings planning for ayear times three maybe W planning each day. and Voyager analysis a room doing nothing but in We together all weren’t continually observations making and data was gathering probe the when n Cassini e would be called together together called be e would - week long long week , . it was like being was like it being

D uring the years years the uring .

I t was like taking t was like taking , V as well as aswell oyager oyager .

. THE STORY OF VOYAGER

51 . hey were T Back then

. . Z numbered And then I . . giving me four , which , . decided to categorise them I ut of that popped obvious an o had two intermediate piles see what in was them Every picture had a time stamp, so I decided to a spectral analysis. O periodicity showing the spokes coming and going in their intensity and their aerial coverage on the rings coming and going in a period that equal was to the magnetic ƅHOGSHULRG7KLVZDVP\ƅUVW discovery genuine categories could look at hundreds of images once at I noticed how Saturn’s ring spokes changed in their number. and intensity S putting images with very few spokes in a pile on the left and images with lots of spokes in a pile on the right I betweenin it was the only format in which

. inch -

. ,

as it , 4x4 , www.skyatnightmagazine.com www.skyatnightmagazine.com oyagers took turned out they were left for Cassini to discover In the days we of Voyager, dealing were V one of which aturn’s moonaturn’s , S oyager but o we mighto we have V RXWKRZWRƅ[LW S

N . ’s scan’s platform got 1 GXULQJWKHƆ\E\VRZH N put out these small oyager nceladus somehow hands got my on enhanced enough that you could could you that enough enhanced Because of that glitch there were some sequences of images that never got taken a sequencewas of the southern of hemisphere E seen the tiger stripe fractures with sooner glossy prints that were made of every image the I them and they were contrast with hard-copy images. hard-copy with JPL We actuallyWe lost the chance during images some take to encounter. Saturn the V VWXF KDGWRZRU OLD FRIENDS: THE VOICES OF VOYAGER VOICES THE FRIENDS: OLD Carolyn U (centre) joins scientists including Carl Sagan (seated on the desk) and Ed Stone (seated, far right) to analyse images of Neptune’s Triton moon

how fix to it.” ,

. so so , “Voyager 1’s scan “Voyager platform got stuck got platform

oyager . 3 years! V 1 so we hadso we work to out very much during the Saturn flyby, during flyby, the Saturn , oyager mission uring the green and blue , V D

, was made was the imaging I there wasn’t really any , hat’s still the case

encounters and making them last continuously for All are eyes on the images presenting you’re when results to the public. T team leader on Cassini days attempt to get the pictures looking the best they could worryingby about the colours putting red it one was cardinal of my goals when images images together aligning them so they could sit on top of one another and framing the picture so that it looks a work of art like to the resentment of other scientists Nothing that like done was when were processingwe images during the CAROLYN PORCO X 2, CORBIS/CONTRIBUTOR 2, X PORCO CAROLYN THE STORY OF VOYAGER

NASA/JPL-CALTECH/SSI of the of the usapicture gave and there out I like. was System Solar the what everyone showing in act opening Voyager the was around rings ofthe cousins kissing S the within rings the studying was actually contribution discovery V theywhen think me and about we got there with Cassini with there we got before for at fondly looked the surface and that there was there that and surface the we’d that scratched just feeling that we needed to go back sense keen avery uswith left I VFLH my was biggest spokes the of discovery the say I wouldn’t it knows who one you’re only the U the about truth a fundamental uncovered who’s just priestess nature something about mother of thrill that comes from knowing you athrill give would that ofthings lots asthat! heady it about anything knows who planet the on person you’re only the that other people T livescientists for. Eureka moments that 52 Z OLD FRIENDS: THE VOICES OFVOYAGER know in the eyes of the public eyes ofthe the in know t allowed us to survey what was what ustosurvey t allowed aturn system that were the the were that system aturn It was just one of those those of one just was It here’s a time before you tell you tell before atime here’s oyager niverse and for a brief period period abrief for and niverse www.skyatnightmagazine.com Q WL S , . in the case of case the in

ƅ Y U olar . , Nothing can be as be can Nothing they think of that ou feel like a high like ahigh feel ou F ranus . But But , FR but this was the kind kind was the this but S , Q when you know you know when ystem that we that ystem WULE I . Y ’d say my biggest ’d my biggest say

ou can imagine imagine can ou X

WLR 2 3 years 3 years S aturn Q .

I t ; a ,

. issues that had tremendous had that issues H[DPSOHWKHUHZHUHVFLHQWLƅF system to planetary one particular were that things about just not and tolearn… more much so far got the biggest set ofrings set biggest the got past the in cosmos the throughout everywhere was happening what about alot said we studied planetary systems have systems planetary other allthe everything got S our in system planetary rich I my life. in role a special played certainly has Saturn space but also into the future the into also but space across only not out reaching carries message that wonderful us outlive will it because explorers interstellar how UHGHƅQHGKXPDQLW\WKDWŝV was like anodyssey land promised the in immersion asumptuous been has Cassini different projects. Voyager very and are Cassini Cassini with there back go to we going were that learned after after S studying initially in out lucked atmosphere like atmosphere the in moon ofmoons collection diverse and large avery got isasinteresting atmosphere not asornate not t’s the most phenomenally phenomenally most the t’s olar aturn and then a few months afew months then and aturn - reaching implications reaching , , I so tospeak so in the future and now and future the in think ofit think V S oyager was over we oyager ystem because it’s it’s because ystem .

I n the case of case n the S , as olar .

I T , t made us t made J but but itan’s S upiter’s . ystem has an has ystem .

. No other other No V

I t was us V oyager oyager S . oyager oyager aturn

. . I

really really I . I t’s

. t

W . I .

. t’s

I , , hat

ts if , , for for

Earth Smiled Earth the Day The image: this with Pale Blue Dot reimagined the U Cassini see stars in the ‘ the in stars see picture take the V the for proposal the in phrase ofstars” a “sea ofthe a picture ‘ H envisioned. originally had Sagan what is image [above] from Cassini Smiled’ Earth The Day ‘The ofthe exploration the and we doing were to what attention topay people to get DWƅQGLQJWKDWHPRWLRQDOKRR Carl pure love you everyone and you know was everyone ofdust mote this on that noting perspective human a more Carl ofspace blackness the and isolation the dramatising away far the see thinking of how it would to look W human condition. into an allegory for the image Dot’ Blue ‘Pale the turned who Sagan Carl was It with the communicate and to connect to longing ofour asymbol it’s Cassini about say wouldn’t gesture a beautiful ofyears billions for it carry and it of uson up it picks T ‘ in stars we see do to the cosmos to the P he oyager project oyager e was hoping that the the that e was hoping ale Blue Blue ale ith the ‘ the ith E S arth arth agan saw the image from from image the saw agan S , U with all the planets planets allthe with ; olar he was the master master was the he P , D niverse around us niverse S there’s a bit ofall abit there’s ale Blue Blue ale miled’ ot’ picture would be be would picture ot’ S . . ystem from very very from ystem V

I H E . f anybody ever f anybody P , oyager will will oyager

urging them to them urging W arth awash in arth e put that that e put ale Blue Blue ale . . S

T , T hile we don’t we don’t hile Earth which you which D olar he V hat was hat ot’ . D But But , S V

I ay ystem was oyager oyager D .

. , I But But

ot’ t’s . N ,

. THE STORY OF VOYAGER 53 www.skyatnightmagazine.com www.skyatnightmagazine.com OLD FRIENDS: THE PALE BLUE DOT BLUE PALE THE FRIENDS: OLD Carl 1994 Sagan, The Pale Blue Dot Blue Pale The in a sunbeam.” us. On it everyone you love, everyone you know, know, you everyone love, us. On you it everyone ever was ...ever was every saint and sinner in the history of everyone you ever heard you everyone every human of, being who

our species lived there suspended of dust – on a mote

“Look again at that dot. That’s here. That’s dot. home. That’s that That’s “Look at again NASA/JPL THE STORY OF VOYAGER

MARK GARLICK 54 TERRITORY UNCHARTED III PHASE TERRITORY UNCHARTED ice giantin1989ice the with encounter its during Neptune of views ﬁrst close-up its humanity Voyager 2gave www.skyatnightmagazine.com THE STORY OF VOYAGER W 55 F

HREMH G D n 2012 it did P I t also detected I DQ P W UV WKHƅ J Q nly Voyager 2 carried on to nly Voyager the outer giants Uranus and Neptune, that had worlds hitherto only been seen as PL R F UNCHARTED TERRITORY RŚEH www.skyatnightmagazine.com previously undiscovered rings and new undiscovered previously the two addmoons planets’ to to already 1, meanwhile, tallies. Voyager impressive from the plane of the planets, raced away reach eventually in the hope that it would the edge heliosphere. of the V O faint blobs through a telescope. The plucky craft be them to markedly revealed different from their closer cousins – one bland, almost serene; the other a frosty realm of roaring winds stronger than any others in the Solar System. to enter interstellar space. UNCHARTED TERRITORY: URANUS & NEPTUNE

The unknown realm of the

Words: Ben Evans ice THE STORY OF VOYAGER STORY THE

In January 1986 and August 1989, Voyager 2 ﬂew giantspast the outer giants Uranus and Neptune – becoming the ﬁrst spacecraft to visit either. In its brief visits, these cold worlds almost beyond the reach of the Sun’s warmth were revealed to be every bit as mysterious as their closer cousins

Having gathered a vast amount of scientiﬁc data at Uranus, Voyager 2 took this parting shot of the planet’s crescent before heading on to Neptune

56 www.skyatnightmagazine.com UNCHARTED TERRITORY: URANUS & NEPTUNE

U Ground-based telescopes had provided our best views of Uranus (left) and Neptune (right) until Voyager 2’s visit. Much about these distant worlds remained a mystery as a result, including the number of moons in orbit around them

PERHAPS THE TOUGHEST discoverer, William Herschel, with predictions and telescopic kind of exploration is studying Ariel and Umbriel observed by observations of Johann Galle, a pair of planets about which William Lassell in 1851 and tiny Urbain Le Verrier and John virtually nothing is known with 0LUDQGDLGHQWLƅHGE\*HUDUG Couch Adams in 1846, there certainty. In February 1984, Kuiper in 1948. Some 1.6 billion existed only the most general

several dozen scientists gathered km beyond Uranus, Neptune and sweeping awareness of THE STORY OF VOYAGER in Pasadena, California, to was attended by Triton and either planet. They were known consider the scant level of 1HUHLGƅWWLQJO\QDPHGDIWHU WREHQHDUWZLQVLQVL]HZLWK knowledge about Uranus and V William classical deities of the sea. All equatorial diameters around Neptune. These two giants, Herschel found were barely detectable with 50,000km, four times bigger which reside on the fringe of our Uranus in 1781; (DUWKEDVHGLQVWUXPHQWVEHIRUH than Earth and over 15 times planetary system, had only been he also spotted the Voyager 2 probe arrived. more massive. The probe its ﬁrst known discovered in the preceding moons Titania Following Uranus’s discovery in FRQƅUPHGK\GURJHQDQG two centuries. And as Voyager 2 and Oberon, DQGWKHƅQGLQJRI1HSWXQH helium as their predominant journeyed towards them for in 1787 thanks to the mathematical constituents. Uranus’s plain Z KXPDQLW\ŝVƅUVWHYHUYLVLWV neither had revealed itself as much more than a fuzzy blob in an ocean of emptiness.

Worth a visit The desire to travel to Uranus and Neptune originated with NASA’s Grand Tour programme, but a subsequent rescoping of the mission led to a revised focus on Jupiter and Saturn. Nevertheless, in 1976 NASA approved an extension to Uranus on the condition that all primary objectives were met. $PRGLƅHGLQIUDUHGGHWHFWRU was built to achieve the necessary resolution at Uranian distance – 2.6 billion km from Earth – but when the Uranus Ɔ\E\IRUPDOO\EHJDQLWGLGVR with a greatly reduced budget and a leaner workforce. By that time Uranus was NQRZQWRSRVVHVVƅYHPRRQV named after characters from the works of William Shakespeare DQG$OH[DQGHU3RSH7KHƅUVW pair, Titania and Oberon, were

ISTOCK, NASA/JPL-CALTECH, SEBASTIAN VOLTMER/CCDGUIDE.COM, ROBERT SCHULZ/CCDGUIDE. SEBASTIAN VOLTMER/CCDGUIDE.COM, NASA/JPL-CALTECH, ISTOCK, PHOTO WORLD STOCK ARCHIVE/ALAMY HISTORY COM, found in 1787 by Uranus’s own

www.skyatnightmagazine.com 57 UNCHARTED TERRITORY: URANUS & NEPTUNE

“Travelling at 64,000km/h, Voyager 2 had only six hours to make its close-range observations of Uranus”

Z aquamarine colour and the where the spacecraft would be richer, sky-blue façade of at each point in time,” recalled Neptune also betrayed the Voyager imaging team member presence of ammonia, methane Andrew Ingersoll. “We told the and hydrogen sulphide. engineers what latitude and longitude we wanted to look at U The blue- Data gathering and they told the camera to take green tint in to wryly dub themselves ‘the Travelling at 64,000km/h, a picture. These commands had Voyager 2’s imagining team’. However, Voyager 2 had only six hours to be worked out and radioed to true-colour infrared data revealed clouds images of on 24 January 1986 to make the probe weeks in advance.” beneath a high-altitude layer of Uranus (left) its close-range observations of Due to Uranus’s 98° axial is indicative of hydrocarbons and the probe’s Uranus. But to maximise the tilt, Voyager 2 approached the methane in its radio-science and ultraviolet VFLHQWLƅF\LHOGRILWVƆ\E\WKH planet’s sunward-facing south atmosphere. instruments revealed uniform probe took measurements of pole and generated time- False-colour temperatures throughout the

THE STORY OF VOYAGER STORY THE the planet continually for 16 lapse movies to track cloud images (right) atmosphere of around –216°C. show an orange weeks from November 1985 movements and wind speeds. Theories abounded that this spot that might until February 1986. A similar Unlike on Jupiter and Saturn, be dense smog atmosphere might extend more campaign was adopted at there was little evidence of over the pole than 3,000km beneath the cloud Neptune from June to October storms or latitudinal banding, tops, perhaps terminating in a 1989. “We had a prediction of which led the imaging team slushy ocean of water, ammonia

U Voyager 2 imaged the varied surfaces of the moons of Uranus. Umbriel (left) is dominated by craters, while canyons and faultlines score the surface of Titania (middle). Oberon (right) has a mix of new and old surface material, which suggests some form of volcanic activity

58 www.skyatnightmagazine.com UNCHARTED TERRITORY: URANUS & NEPTUNE

U Giant radio telescope arrays in Canberra (left), Madrid (middle) and California (right) combine to make NASA’s Deep Space Network Beefing up the Voyagers from the ground

Orbitting billions of kilometres beyond Australia, the remote foothills west Saturn, the outer giants Uranus and of Madrid in Spain and in California’s Neptune inhabit a gloomy region of Mojave Desert) received a $100 million the Solar System, requiring Voyager 2 facelift to boost Voyager 2’s ever- to examine worlds where high noon is weakening signal, which by January dimmer than dusk on Earth. One 1986 was a billion times fainter than a scientist likened the problem to watch battery. All three stations had

photographing a pile of charcoal their 64m antennas augmented for THE STORY OF VOYAGER briquettes lying at the foot of a Uranus, electronically synchronising Christmas tree, lit by a single-Watt bulb. them to strengthen the signal. Further Stability was crucial, but even turning upgrades to 70m were implemented for its tape recorder on and off was enough Neptune and two additional tracking to induce a disruptive ‘nodding’ effect stations in Japan and New Mexico were in Voyager 2. Its gyroscopes could keep called into duty. the instruments reasonably steady, but Due to the position of Uranus in engineers had to halve the duration of Earth’s skies in the winter of 1985-1986, WKUXVWHUƅULQJVWRDOORZWKHSUREHWR Canberra was the main tracking station, settle after manoeuvres. At Neptune, following Voyager 2 for 12 hours per longer exposures of 96 seconds and U The DSS-14 antenna at Goldstone was day and allowing a 21.6kbps downlink WKUXVWHUƅULQJVXQGHUIRXUPLOOLVHFRQGV widened from 64m to 70m in 1989 to help rate. In support, a 400km microwave became necessary. Image motion it pick up Voyager 2’s weakening signal connection was established with the compensation allowed Voyager 2 to Parkes radio telescope in New South UHVROYHƅQHUGHWDLOEXWDWWKHH[SHQVH Back on Earth, the three tracking Wales, bolstering it by 25 per cent and RISLFNLQJRXWLUULWDWLQJRSWLFDOƆDZV stations that make up NASA’s Deep allowing up to 50 extra photographs to including dust on its lenses. Space Network (located in Canberra, be returned every day.

and methane, girdling an its magnetometer to measure $OOƅYHPRRQVDSSHDUHG Earth-sized rocky core. A similar Uranus’s day at 17.25 hours and intrinsically dark, suggesting situation is also thought to exist Neptune’s day at 16.1 hours, that radiation had broken down at Neptune. Voyager 2 was which in turn helped provide any methane on their surfaces unable to prove the existence of wind-speed estimates. within a few tens of millions such oceans, but did detect radio of years, darkening them and V Ridges and signals induced by interactions The dark of the moons leaving a thick, charcoal-like troughs were between the solar wind and seen on the To great surprise, Uranus’s dusting. Umbriel is by far the electrons in the planets’ surface of the PDJQHWLFƅHOGH[WHQGHG darkest, although it does PDJQHWLFƅHOGV7KLVHQDEOHG moon Ariel only 600,000km sunward, exhibit a few splotches of bright but wound backwards, like a material, including an enigmatic JLDQWFRUNVFUHZPLOOLRQǻP ‘Cheerio’ in the crater Wunda at beyond the planet. Ultraviolet its equator. As for its siblings, observations of polar aurorae Titania – the largest, at 1,580km VKRZHGWKDWWKHƅHOGZDVWLOWHG across – is marred by huge faults at 59° to Uranus’s rotational and winding canyons, pointing to axis – a curiosity that, on Earth, a violent tectonic past. Oberon would be equivalent to having revealed bright and dark regions, our north magnetic pole in not unlike our Moon, indicating the Florida Keys – and bore a meteoroid bombardment and powerful sting in the guise of perhaps the volcanic extrusion trapped, high-energy radiation. of subsurface material. This clearly manifested itself on But it was Miranda and Ariel Z NASA/JPL-CALTECH X 10 NASA/JPL-CALTECH the surfaces of Uranus’s moons. to which Voyager 2 devoted

www.skyatnightmagazine.com 59 UNCHARTED TERRITORY: URANUS & NEPTUNE

Z the most attention. The latter is the brightest Uranian moon, with an ancient and heavily cratered terrain that features rolling plains, parallel ridges and troughs lying tens of kilometres apart. Miranda, less than 500km in diameter, was the most closely inspected, principally due to WKHƆ\E\JHRPHWU\QHHGHGE\ Voyager 2 to reach Neptune. It revealed unmistakable evidence of billions of years of impacts, which tore Miranda apart, then hammered it back together, gouging out 20km- deep canyons, at least three enormous, oval-shaped ‘coronae’ and broad terraces of old and member). Another object was UZ Miranda’s young, bright and dark, lightly photographed by the probe, but cliffs, canyons and heavily cratered terrain. One went unrecognised as a moon and craters (right), hint at a area, the 200km-wide Inverness XQWLO,WZDVƅWWLQJO\QDPHG past that saw it Corona, showed a bright ‘Perdita’, the Latin word for lost. smashed to chevron-like feature between Something that had already pieces and then dark layers, possibly a result of been seen at Saturn was the reassembled. reaggregated bits of Miranda’s pivotal role tiny ‘shepherd’ The Inverness original crust, poking out from moons play in anchoring ring Corona appears as a bright the present surface. material. Several narrow rings ‘tick’ (above) had been detected around New moons Uranus by ground-based Voyager 2 also found 10 new observers in the 1970s, but moons, ranging from 160km- Voyager 2 uncovered another wide Puck to diminutive Cordelia, pair. The probe revealed the new about an eighth as large. A pair to be relatively insubstantial, small subset that share similar although the brighter ‘Epsilon but only two – Cordelia and orbits, surface colouration and ring’ achieved a maximum Ophelia – were detected, lying generally elongated shapes extent of 96km. astride and ‘binding’ the inner ZDVFODVVLƅHGDVWKHŜ3RUWLD Up to 18 shepherd moons were and outer edges of the Epsilon

THE STORY OF VOYAGER STORY THE Group’ (named for its biggest predicted to exist at Uranus, ring. The general darkness of the

The bullseye planet Z With its 98° tilt, Uranus is unlike any other planet in Uranus is unique among the the height of Uranian summer the Solar System planets in our Solar System in January 1986 and casting their thanks to its extraordinary northern extremities into rotational tilt of 98° – Uranus a 21-year-long winter season. presents itself to observers as a How Uranus’s axial tilt came world tipped on its side. Its poles about remains a mystery, lie where its equator should be although a collision with an and receive a correspondingly Earth-sized impactor has been higher level of incident sunlight. proposed. The fact that the Situated 2.8 billion km from the moons circle within its equatorial Sun, Uranus circles its parent plane implies that they formed star every 84 years, with each much later from debris placed into pole rhythmically illuminated, orbit by this impact. Moreover, before being plunged into frigid Uranus radiates hardly any heat darkness, every four decades. into space – its temperatures dip When Voyager 2 viewed the as low as –224°C, giving it the planet only the southern pole coldest planetary atmosphere ZDVLQGLUHFWVXQOLJKW,WVƅYH in the Solar System – and it's main moons orbit their giant possible that whatever hit the host within its equatorial plane, planet caused it to expel much placing their southern halves at of its primordial heat.

60 www.skyatnightmagazine.com UNCHARTED TERRITORY: URANUS & NEPTUNE

could themselves someday be resolve any surface detail, much torn apart and incorporated less measure its rotational into the system. characteristics. 9R\DJHUFRQƅUPHGWKH Before it found any rings, it existence of six new moons was hoped that Voyager 2 would at Neptune, including potato- Ɔ\ZLWKLQNPRIWKH shaped and heavily cratered planet’s largest moon, Triton, Proteus, which is thought to be which ground-based almost big enough for gravity observations had shown to to pull it into a spherical shape. possess nitrogen ices on its Eccentric-orbiting Nereid, surface. To avoid the risk of discovered by Gerard Kuiper in colliding with ring particles, the 1949, was also seen by the probe, probe’s trajectory was altered to but at a distance of 4.7 million carry it 4,950km over Neptune’s km it was still too far away to north pole – the closest Z “Rings were eagerly anticipated rings underscores their extreme U Lanes of at Neptune, with ground-based youth, for they are probably no dust particles more than 600 million years can be seen in studies suggesting that old. Data from Voyager 2’s this 'close-up' of incomplete ‘arcs’ might run

the Uranian THE STORY OF VOYAGER photopolarimeter and other rings, imaged part-way around the planet” instruments revealed them to from a distance be so sharp that the Epsilon of 236,000km component can’t be greater than 150m thick. Z Neptune was Rings were also eagerly found to be anticipated at Neptune, with tempestuous, ground-based studies between with a 'Great 1968 and the early 1980s Dark Spot' and howling suggesting that incomplete winds ‘arcs’ might run part-way around the planet. Numerous theories postulated that the arcs were held in place by tiny shepherd moons or maybe new rings were in the process of forming. With just two weeks to go until Voyager 2’s arrival, their true nature was revealed. A pair of incomplete arcs did appear to exist, with three shepherd moons (Galatea, Larissa and Despina) interacting with them. V Voyager 2 Building rings showed that full As the probe drew nearer, it rings encircle became apparent that more Neptune (below) and rings extended around the that they’re formed planet. Their uneven ‘clumpiness’ by uneven ‘clumps’ of dust (below right) and irregularly distributed particles offered an early explanation for why arcs had been suspected for so long. Indeed, Neptune’s outermost ‘Adams’ ring revealed several clods of material, up to 50km wide. It was argued that debris from ancient moons could have contributed to this unequal distribution of mass and a pair of

NASA/JPL-CALTECH X 8, ISTOCK X 8, NASA/JPL-CALTECH tiny moons, Thalassa and Naiad,

www.skyatnightmagazine.com 61 UNCHARTED TERRITORY: URANUS & NEPTUNE

brightness was a key reason why such a tiny, distant body was found telescopically by William Lassell in October 1846, just weeks after Neptune itself.

Freeze-thaw effect The probe imaged a third of Triton’s surface, uncovering a greenish landscape, nicknamed ‘cantaloupe’, due to its similarity U Proteus (left) was among the new moons found by Voyager 2; it's 400km to the scaly skinned melon. It across, bigger than Nereid (right), which had been known of since 1949 was crisscrossed with circular depressions, Z planetary encounter achieved supporting thin “dark streaks across each around by either Voyager craft – on 25 nitrogen-ice Triton’s southern polar 25km wide, August 1989. It then plunged clouds and haze and long, south, passing within 39,800km at an altitude cap indicated that interconnecting RI7ULWRQƅYHKRXUVODWHU of 13km. volcanism was ridges were Circling Neptune in a highly Voyager 2 thought to inclined ‘retrograde’ orbit, the strongly hinted commonplace” be the result moon proved smaller than that these of epochs of predicted, at just 2,700km constituents originated from melting and refreezing. This across, and a stellar occultation the evaporation of surface ices, reinforced the notion of Triton allowed Voyager 2 to measure with winds transporting dust as a captured Kuiper Belt object its 800km-deep atmosphere, particles up to 50km across and that the tidal heating from all the way down to its surface, its terrain. Triton is the most Neptune's gravity had left its the coldest known in the Solar spectroscopically diverse object LQWHULRUƆXLGIRUDELOOLRQ\HDUV System at a frigid –236°C. In fact, LQWKH6RODU6\VWHPUHƆHFWLQJ underpinning these complex Triton’s tenuous mix of gases over 85 per cent of incident internal processes. and particulates is virtually sunlight – eight times more than Voyager 2 also revealed a

a vacuum, barely capable of our Moon – and this extreme pinkish southern polar cap, X 8 NASA/JPL-CALTECH

A world of wild weather

Four-and-a-half billion kilometres from with a chevron-shaped, westward- Elsewhere in the sky-blue atmosphere its parent star, recipient of half as much moving cloud feature, whose rapid were cirrus streaks of methane-ice,

THE STORY OF VOYAGER STORY THE sunlight as gloomy Uranus and with 16-hour transit around Neptune’s which cast shadows, tens of kilometres temperatures as low as –218°C, Neptune atmosphere generated the nickname long, on Neptune’s cloud deck at low should be an inactive world. Yet of ‘Scooter’. The Great Dark Spot, northern latitudes. How such wild Voyager 2 revealed it to be surprisingly in keeping with its name, was 10 per weather can manifest itself on such energetic, with the oval-shaped Great cent darker than its surroundings a cold planet must be related to its Dark Spot observed at a latitude of and hustled northwards through the dense interior and the fact that it emits 22°S. This counter-clockwise-rotating atmosphere at 1,100km/h. At its edge 2.6 times as much heat as it receives vortex bore many uncanny parallels was a hovering, shape-shifting ‘bright from incident sunlight. It has been with Jupiter’s Great Red Spot, in terms companion’ cloud. The spot lay 50km suggested that temperature differences of relative size, motion and position below Neptune’s main cloud deck, with between Neptune’s internal heat and within the atmosphere. the companion at a slightly higher its cold atmosphere could trigger As the probe drew closer, a second, altitude, creating analogies with instabilities and induce large-scale smaller dark spot was found, together lenticular cloud formations on Earth. meteorological phenomena.

U Tumultuous Neptune up close: its Great Dark Spot; its smaller dark spot; the ’Scooter’ cloud pattern; and cirrus-like methane-ice clouds

62 www.skyatnightmagazine.com THE STORY OF VOYAGER

, 63

which , Neptune is , ” exulted one V , breathlessly , ow southern polar cap Dark dust deposits W Y “ became the only . streaks across the pink methane-ice on Triton’s Triton’s on methane-ice 2 hat a way to leave ystem!” from geyser plumes form S W “ . twins are thought to have olar olar - oyager S V as planetary scientist spacecraft in historyvisit to four planets the the near similar compositions marginally more massive LQƆXHQFHVLWVPDJQHWLFƅHOGDQG heat internal espite espite D

. www.skyatnightmagazine.com whose outward , ranus belied a times as much U And although the 2.6 . ranus infrared data showed it , roviding a backdrop to these U P un GLVFRYHULHVZDVPDJQLƅFHQW itself Neptune similarity to far more active world its greater distance from the S to radiate heat from incident sunlight as UNCHARTED TERRITORY: URANUS & NEPTUNE & URANUS TERRITORY: UNCHARTED Voyager 2 Voyager U took one last shot of Neptune heading before on towards the edge of the System Solar

, riton’s riton’s

T arth and . E tinged crustal were known - , while other , only only , o I 9

even in this even , forcing exotic ices , 8 , . 9 1 nitrogen and water , ne geyser was arth O as strong as a moderate ,

E . indicative of the presence gas’ andgas’ build pressure , - And it from was within the . n August I 4km/h riton: erupting geysers ystem upiter’s moon upiter’s gale on on gale observed hurl carbonaceous to material an altitude to of several metres thousand measurements allowed local wind speeds to be clocked at 5 to harbour active volcanism indicated southern polar cap that such phenomena were commonplace IDUƆXQJFRUQHURIWKH6RODU S J but dark streaks across ices polar caps that a moderate greenhouse effect could have nurtured been before prompting one of the at most discoveries surprising T of methane to ‘de abutted a blue by region THE STORY OF VOYAGER 64 by: IainInterviewed Todd UNCHARTED TERRITORY: THE VOICES OFVOYAGER team at the time the at team ofthe member M completing my PhD. Iwas while Voyager data I working started on the everything needed to tease My work amounted to doing Neptune and from coming data the analysing on focused became and team photopolarimeter stage V I P for that project 7KLVZDVWKHƅUVWELJUHVHDUFK of moons icy ofthe some from was coming that light the at quantitatively me for project VOYAGER continued to work on the the on towork continued Bonnie Buratti’s storied onNASA’s career seenherwork has Cassini, Horizons New and ropulsion ropulsion oyager mission oyager y advisor . Rosetta missions, started butshe outonVoyager and thenerves remembers –and

W www.skyatnightmagazine.com hen I was working with the the with was working I came toNA came , L

J aboratory aboratory I took responsibility responsibility took oe . J excitement ofwaiting all ﬂybys too Neptune well and theUranus for , which was to look was tolook which upiter and and upiter V V . oyager imaging But at that that at But . everka

H e had a e had U (JPL), THE VOICESOF S ranus , A’s A’s was a S Bonnie Buratti aturn J

et .

been that way with Cassini too Cassini with way that been especially in thebeginning especially night and day work GDWDƅUVWFRPHVLQ\RXMXVW in Neptune and and I was happening what see really I planet. the of surface the off scattered light the how understand to trying and manipulatingstart them to had then and images Voyager, receive Iwould on working Iwas When W much working 24/7. the planets you’re pretty During the encounters with typical for graduate students time! allthe worked so then any back have kids apartment to Cornell apartment my from in little walking after about working I data analysis routines built in. have didn’t we had computers computers back then and the We didn’t have personal to followanything cookbook a have really you don’t is that knowledge new you’re creating T data. the of out results the with the data relationship intimate a more did that on aday on that did n many ways n many ’d create models so we could we could so ’d models create he thing about research when when research about thing he e reached e reached I continued that right up to up right that continued ; you don’t really have have really you don’t 1 9 U . 8 ,

ranus in in ranus it was like we had was like it we had I 9 1 was pretty much much was pretty , 4 hours a day aday 4 hours and when the the when and . - to .

T I t’s kind of kind t’s . -

hat’s pretty I day basis day 1 didn’t 9 86 . and and I just just

. . ,

and 1980sand 1970sduring the magnetic tape relied on Laboratory Propulsion NASA’s Jet at storage data and V Computing Computing it todecode ofprocedures lots ones I numbers. as data We received with to observe that want people spacecraft the on instruments other the with tocooperate you’re going how take you and can volume spacecraft WRƅJXUHRXWZKHUHWRSRLQWWKH the time time the in that aspect career experiments any ofthe designing involved in I t’s basically a bunch of zeros and and of zeros abunch basically t’s n those early stages early n those .

T he data comes down to down comes data he , and then it goes through through goes it then and I became more involved involved more became I was working at at was working , how much data data much how .

L ; when you have you have when ater on in my in on ater . ,

I wasn’t wasn’t JPL.

THE STORY OF VOYAGER 65

. . . Z But . . ou’re ou’re Y

. in suspense in , because there’s the , uiper Belt object there a possibility was , K it takes a while to , waiting , hen when it does come riton’s thin atmosphere thin riton’s riton is a massive moon irst of all t has this giant polar cap that I seasonal is think on and we that cap saw we all these plume deposits and three active plumes of gases being expelled into T put the images together For me, the most awesome discovery was that there were at least three active Triton. on plumes T of Neptune and probably a captured T through then seeing realise you you’re something that no human has seenever before and it makes all the drudgery worthwhile light travel time and it takes hours for the data to come from these distant planets the data from Uranus and arrive. to Neptune F that the encounter hadn’t worked out sitting

. e

. it’s more , UVW www.skyatnightmagazine.com www.skyatnightmagazine.com . r even r even ƅ O that you’ve discovered the most important things didn’t discover discover didn’t activity on (QFHODGXV WKH oyager encounter oyager oyager mission and . IRU V V SODFH ione and several of all the D D HGLGRQHƆ\E\RI(QFHODGXV itan either itan time, doesn’t mean you’ve you’ve mean doesn’t time, everything… discovered ZKHUHDVZHKDGƆ\E\VRILW GXULQJWKH&DVVLQLHQFRXQWHUƅYH of moons major other being learned I’ve lesson The involved in these two missions is just because been you’ve WR than a hundred times greater : during the QXPEHURIƆ\E\VDQGHQFRXQWHUV had withwe’ve Cassini during the didn’t the discover we lakes on T The was a great deal of suspense while waited we for JPL scientists U gather on 25 August 1989 anticipation in Voyager’s of approach close to Neptune UNCHARTED TERRITORY: THE VOICES OF VOYAGER OF VOICES THE TERRITORY: UNCHARTED in suspense” in

, so so ,

hen hen , and data to come from come to data , W

. . these planets. distant whereas You’re sitting, waiting, waiting, sitting, You’re “it takes hours“it takes for the n Cassinin , O

. 000 pixels 000 1, pace Network and which turn it into S , Nowadays can we . 000x

, 1, was was eep eep telling how you bright it I , D his then gets turned into an ’s T hen hen

. oyager

now we justnow we put everything on a website EHPXFKPRUHHIƅFLHQWDQGJHW much more work done the imaging camera captures roughly there are a million pixels working on V image a computer by was everything phone by done and had you to photocopy and everything mail it out to people each has a number associated it with is really have Computers changed how missions operate. today W to give a current example you lookyou at the staggering JPL computer through goes it then algorithms a grid of numbers BONNIE BURATTI, NASA/JPL-CALTECH, RGB VENTURES/SUPERSTOCK/ALAMY STOCK PHOTO STOCK VENTURES/SUPERSTOCK/ALAMY RGB NASA/JPL-CALTECH, BURATTI, BONNIE THE STORY OF VOYAGER

NASA/JPL-CALTECH E ƅUVWYLHZRIYROFDQRHVEH\RQG was the discoveries amazing J of moons the at look DQG1HSWXQHDQGWKHƅUVWWR : PLVVLR exploratory the as mission; ashistory the reconnaissance in down go Voyager will H[SHFWHGWRƅQGRXWWKHUH we’d that objects cratered the expected we than usway more showed it ZHZHUHWKHƅUVWKXPDQVWRVHH and was known ofthat None moons ofthe alot on faults again together come and disrupted been had at O past. the in active appeared to have been The Uranian moons all body active avery tobe seems cells convection and systems weather see we could S the from I on Jupiter. found Spot Red Great the to a dark spot similar ‘Scooter’, that it was maybe some sulphur sulphur some was maybe it that was why that 6FLHQWLVWVFRXOGQŝWƅJXUHRXW shadow when that observed had Astronomers been seen before seeing something that had never we were that realising it: about dark dust amysterious with covered 66 Io. on volcanoes the Linda Morabito discovered after best it said Stone Ed dioxide sulphur out spewing behold there we got when And volcanoes the predicted that apaper wrote colleagues his encounter surface the on was condensing that atmosphere the in dioxide Z UNCHARTED TERRITORY: THE VOICES OFVOYAGER t amazed us that a body so far so abody usthat t amazed upiter up close arth o there’s hardly any sunlight but but any sunlight hardly o there’s . Then there was Neptune’s ne of them

HZHUHWKHƅUVWWRVHH8UDQXV T M hat’s what was so thrilling thrilling was so what hat’s www.skyatnightmagazine.com iranda , on I o came out of out o came Q , . we saw active volcanoes ,

it seemed tobrighten seemed it S S ; DV . J everal days before the the before days everal they weren’t just just weren’t they

, un could still be active be still could un W

upiter’s moon , S it looked like it looked it tanton tanton WKH hen we looked we looked hen ,

. U Now we know we Now know . mbriel

. T ƅ

O . here were also also were here

UVW T ne of the most most ofthe ne P he moons moons he . Neptune Neptune eale and and eale J S , was upiter’s aturn and and aturn , lo and and lo I o .

. .

for an announcement on on anannouncement for watching it and you’re and copy hard there the you have aswhen as much I and media social on it’s now but interested! an orbiter around around an orbiter W anorbiter istosend process the in step next mission reconnaissance a you do After planet the orbit and back go on mission a study doing currently ayear once planet toevery missions sending ofmoney amounts LVPRQH\,IZHKDGLQƅQLWH O missions. follow-up for worthy Uranus and Neptune are slower alot moved things and world no web was there because website toyour them post you couldn’t and images allthe showing up made lithographs W remember. cycle, news 24-hour internet and the the of days the before was This newspaper ofevery page front the on apicture got KLVWRU\(YHU\Ɔ\E\ W were thinking involved were who scientists all ofthe what summarised mission” agreat been has H I Voyager. destroy to have never we’ll Cassini, Unlike aswell Neptune be a habitable environment environment ahabitable be could we’ve what since found name of planetary protection the in spacecraft of the rid to get think somehow it doesn’t sink in in sink doesn’t it somehow think n the case of Cassini case n the e remarked: “ e remarked: ur big constraint at NA at constraint big ur e’re also looking at putting putting at e’re looking also e had to have these these tohave e had making e were U ranus to ranus . But . ,

the the . I

t was a very different different t was avery I think that that think . , T , wow… were people wow… people were

. rather than waiting waiting than rather

T hey still aretoday still hey .

here are scientists arescientists here T . .

his

P , luto and and luto we would be be we would Neptune, and the first first the and Neptune, , “We were the first to first the were “We we have we have to at look moons of Saturn and Jupiter Jupiter Saturn and S T A witter see Uranus and and Uranus see ,

. close up” by the press by the use for prints lithograph turned into were Neptune of shots U Voyager’s a great voyage ofdiscovery a great mountain ofthe side missionmost extraordinary Voyager the as upon I look aswe can long as for tothem we’ll listen But out run eventually generators their that or them tohear able S the arethat constraints aswe can aslong for probes tothe listening keep we’ll so prospect that to face spacecraft by the contaminated being from environment that toprevent –we have molecule oforganic kind some usually is –which offood a source water E the icy crust on on crust icy the under ocean saltwater the in it so exciting mission the on like that many people so we had and charismatic was so V in the mission larger do with it I T think Carl Carl think nceladus pace Network might not be be not might Network pace hat’s what makes it human it makes what hat’s everka W ith , - a source ofenergy asource than . V ,

was one ofthem one was I oyager think that’s what made made what that’s think .

. T

S - I here were a lot of alot were here f there’s liquid liquid f there’s life involved people agan had a lot to alot had agan . . V

M .

S , we never have have we never y advisor on the other other the on know what’s to to want genes our in to explore of humanity I with. involved I’ve been that aturn’s moon aturn’s moon t’s the nature nature the t’s . .

I T t was he two two he D ,

, . eep

J H ; it’s . oe

e .

THE STORY OF VOYAGER the of edge towards the heading J with encounters successful its 65, in the the in home ofour aportrait produced itself around to gaze back at at back togaze around itself and ofNeptune orbits the beyond away km billion six almost ‘ ofthe image 68 UNCHARTED TERRITORY: THE FAMILY PORTRAIT an iconican set ofimages tookhome system and looked back atits 1990 Voyager 1 On Valentine’s Day portrait family The Solar System’s BY 1990, VOYAGER BY 1990, P upiter and and upiter ale Blue Blue ale O 000km/h S n www.skyatnightmagazine.com P olar VENUS EARTH luto 1 G 4 alaxy F S ebruary , the spacecraft turned turned spacecraft the D ystem at close to close at ystem ot’ S .

, aturn E I including an iconic t was then . arth known as the asthe known arth

, when it was it when , that it

1 was , after after ,

a snapshot of six planets ofsix a snapshot W during neighbourhood planetary beam home to months take three would that by either of the ofthe by either taken pictures last –the images of asequence collected before seen been never had that usaview give and leaving was it ofworlds family the a planet as regarded still was then which glare M within the camera’s optics camera’s the within FDXVHGE\VXQOLJKWUHƆHFWLQJ oflight aray in caught speck included the the included ercury was lost in the the in was lost ercury T hen combined hey were transmitted back back transmitted were hey , while while M , were too small to show to show small too were arch M . A valentine to our toour Avalentine E , ars and and ars April and and April arth asatiny arth SUN V , they produced produced they oyager probes – JUPITER P luto S M 6 un’s .

0 . ay I . t

. .

I t during the exposure the during moved they because smeared up P V damage could it feared and exercise ofthe point P managers at NA opposition from mission against up came they But the from ofthe member Carolyn Carl populariser astronomer and science people two from came T Great minds… Words: Paul Sutherland asadena ropulsion ropulsion he idea for this family portrait portrait family this for idea he oyager project in in project oyager “ .

S U oon after after oon ranus and Neptune look look Neptune and ranus P U orco , who failed to see the the tosee failed who niversity ofArizona niversity L SATURN aboratory aboratory , I then a young ayoung then joined the the joined V S S V oyager team team oyager agan and and agan A’s A’s oyager oyager O . ctober J et , (JPL) the the 1. 1 in 9 8 .

3 THE STORY OF VOYAGER n

, 69 O ”

. .

small hat’s hat’s , . H T V ups ups N

. - . nstead I arth

it revealed . hat’s us hat’s , everyone E ot’ have , n a book of I T

. . this project he later wrote: , ot’ , niverse suspended in the , D U pace probes are each exposed to , S

the family portrait . , oyagers’ 40th ale Blue everyone ever you V , as much detail as possible lived out their lives But from a distance of every human being who P , . , hat’s home hat’s URANUS ale Blue T

. NEPTUNE P n the agan dubbed the picture n many ways S I O ook again at that dot L ever was heard of heard you know here it everyone you love the same name same the “ the world know we best – our closeown – was to invisible LQƅQLWHYRLGRIVSDFH the ‘ GHƅHGFRPPRQVHQVHOL looking the wrong way through a telescope meant to bring us close of unexplored worlds occupying less than a pixel in shot the the fragile nature of and vulnerable around six billion km bring out the detail within quite distinctquite anniversary and the ‘ lost none of their power to bring home the unknowablyvast spaces of the

, Voyager 1’s famous family portrait captures 1’s Voyager and Mars are missing.The individual frames

. . .

. stand out because they were taken at different six planets; of the Solar only System’s Mercury un exposures and through ﬁlters various to capture who upiter upiter the , , S J

. arth ” . the , E ’s Candy’s ansen he worked worked he www.skyatnightmagazine.com www.skyatnightmagazine.com arth before JPL S H E

. the biggest , is an odd one at ƅUVWJODQFH5DWKHU hown above hown combined picture than a single S panorama orco explains orco individual frames are Looking back Looking P was chosen was because it 1 ” , bright it would be oyager imaging team’s team’s imaging oyager \MREZDVWRƅJXUHRXWKRZ so weren’t we sure how V worked on designing the observation of 0 I ş “ ansen on making ithappen oyager orco worked with out the commands to turn the spacecraft from one planet to next the long the exposures had to be Believe it or not FKDOOHQJHZDVƅJXULQJRXWKRZ to expose correctly on No one had taken this kind of P H V would be able to capture free from the glare the of with observations responsiblewas for executing the image sequences UNCHARTED TERRITORY: THE FAMILY PORTRAIT FAMILY THE TERRITORY: UNCHARTED Carl Sagan, V below, worked worked below, with Carolyn Porco to NASA convince of the beneﬁt of Voyager using 1 to create a ‘family portrait’ of the Solar System neighbourhood” to ourto planetary probes — that would would probes — that take three take to months “voyager 1 collected a “voyager sequence of 60 images by either of the Voyager either by of the Voyager beam home. A valentine agan agan — the pictures last taken S thought I he mission arth and

. T E

. “ . turn around looked at 1 orco JPL ystem’ for the ” .

A couple of years P , S . ruly ruly oyager was crazy was because T olar olar I while V , S ” says learned that Carl , I A agan went to S S ichard ichard

started promoting the idea of spoke to him about

had also proposed this ‘portrait of the having having same reasons and he got the same response I a pictureto take of all the other planets me like there no was science in doing so – all these objects would be a pixel across or less – and the engineers didn’t to waste want resources to make a useless observation later it and decided we to join forces LWZRXOGEHDPDJQLƅFHQWŜZH are here’ look at our cosmic place at managers I the very top persuading NA administrator R to agree to the picture NASA/JPL/SPACE SCIENCE INSTITUTE X 7, NASA PHOTO/ALAMY STOCK PHOTO STOCK PHOTO/ALAMY NASA 7, X INSTITUTE SCIENCE NASA/JPL/SPACE THE STORY OF VOYAGER Solar 70 UNCHARTED TERRITORY: THE FINAL FRONTIER ISTOCK, NASA/JPL www.skyatnightmagazine.com System So long, ﬁrst glimpseﬁrst ofinterstellar space? itself: could thespacecraft give usour unknown, anewopportunity presented more. and for asthey spedinto But realms women atmissionand control hoped had Voyagers delivered had all themen that With theouter behind planets them, the Words: Ben Skuse Words: Ben THE STORY OF VOYAGER

A , U) S Z ay ay 71 was

D 2 As As .

, oyager - . hen hen

in in 40 A 40 et at . , ( V Y one oyager W

. . so NA so . , V

, more un’s sphereun’s away oyager ortrait - S the longest hey highlight ot and V P , But they also U) . T 990 alentine’s alentine’s

. 1 . V A nterstellar nterstellar 0s when when 0s oyagers would I

1 . 6 V 3 9 ( was born was un’s grasp un’s while amily 1 on on , S 1 F A engineers tasked with a ‘gust’ of subatomic a ‘gust’ , un oyager spacecraft S ioneer probes ioneer S ortrait images taken V oyager (VIM) P P ystem environment and V S oyager probes ended their a mission capable of , oyager V hey were travelling much V billion km n the late 7KHƅUVWSKDVHRIWKH After the I T ission ission oyagers’ interstellar mission mission interstellar oyagers’ heir cameras were turned off olar olar .6 amily 990 are among the most iconic THE PALE BLUE BLUE PALE THE from thefrom such sustaining itself long enough to reach interstellar space seen was as little more than a pipe dream for the NA building the spacecraft the beginning of was around six billion km planetary mission had lasted less than three and a half years was beingwas planned A long reach 7KH6XQŝVLQƆXHQFHVWUHWFKHV far beyond the planets the two began their interstellar mission they were within reach of the 6XQŝVPDJQHWLFƅHOGDQGWKH wind solar plasma particles released from its atmosphere F V lasted a decade well over by 1 from the mission the scale of our home in the vastness of space represent the moment when the exploration of the planets and began a new adventure that would them take into interstellar space both probes were blinded T permanently to save power and memory for the instruments needed to investigate the environment in the darkness beyond the so the a slightly closer but still substantial 4 then the than faster the that knew EHWKHƅUVWKXPDQPDGHREMHFWV to pass beyond the RILQƆXHQFH,QGRLQJVRWKH\ ZRXOGSURYLGHXVZLWKRXUƅUVW opportunity to study the outer S M distant

www.skyatnightmagazine.com of Earth has been before Voyager 1 is our farthestVoyager man- region of space that no emissary made spacecraft; it is exploring a UNCHARTED TERRITORY: THE FINAL FRONTIER FINAL THE TERRITORY: UNCHARTED sphere of influence” of sphere “NASA knew that the Voyagers the knew“NASA Voyagers that would bewould the first human-made objects to pass beyondthe Sun’sobjects pass to THE STORY OF VOYAGER 72 Z UH The boundary between the bubble Solar ofthe Edge The UNCHARTED TERRITORY: THE FINAL FRONTIER one merges into the other where zone aphased but edge, LQWHU LRQVDQGHOHFWURQV7KHVH 6XQŚVWDUWHGWRGHWHFWHQHUJHWLF 9 VSDFHFUDIWXQWLOPLGZKHQ FKDQJHGIRUWKH RIURXJKO\$8SHU\HDUOLWWOH 6XQ LQ PDGHREMHFWIXUWKHVWIURPWKH RYHUWD DQG WUDQVPLVVLRQZDVVHQWLQ PLVVLRQHQGHG LWVƅQDO which time the the time which R\DJHUŚQRZ$8IURPWKH 'HVSLWHFRYHULQJDGLVWDQFH D www.skyatnightmagazine.com O 9 P V R\DJHUPDQDJHGWR N WHOO R H INTERSTELLAR MEDIUM MEDIUM INTERSTELLAR heavier elements, as well as aswell elements, heavier hydrogen, helium and some some and hydrogen, helium between stars in the Milky Milky inthe stars between I 3 Though barren, the space space the barren, Though WKH LRQHHUDVKXPDQ D of the heliosphere. tail the down ﬂow and back turn to wind solar the causing medium, interstellar the from pressure the balances wind solar weakening the is where System, it Solar the of border outer the considered Often HELIOPAUSE It contains gas clouds of of clouds gas contains It Way is far from empty. empty. Way from isfar U dust and cosmic rays. cosmicrays. dust and VSD 6 9 P XQŝ R\DJHU ioneer layers of the heliosphere. outer the against medium interstellar water, the from it’s by pressure caused through pass asthey by boats created wave bow the to Similar edge. outer the on forms shock abow space, interstellar through plows heliosphere the As BOW SHOCK BOW FHL V LQƆXHQFH V QRW

D FOH

D D Q U WKHWHUPLQDWLRQVKRF ZDVQHDULQJDUHJLRQ SDUWLFOHVVXJJHVWHGWKHSUREH DUHVXOWWKH LWVHQFRXQWHUZLWK6DWXUQ$V VWRSSHGZRU PHDVXULQJWKHVRODUZLQG KDG WKHLQVWUXPHQWEHVWVXLWHGWR 9 GLIƅFXOWWRFRQƅUPEHFDXVH WKHLQWHUVWHOODUPHGLXP GRZQDQGEXQFKXSDVWKH\KLW VRODUZLQGSDUWLFOHVDEUXSWO\VORZ G R\DJHUŝVSODVPDGHWHFWRU 8QIRUWXQDWHO\WKLVZDV 9 N LQJLQGXULQJ , 0 WHDPKDGWR N N ZKHUH QRZQDV VOYAGER 1 VOYAGER 2 becoming denser and hotter. and denser becoming andbunchesup,slows abruptly wind solar the where heliopause, and shock termination the between heliosphere, the of region outer The XQGHUWD \HDUVSDLQVWD 2YHUWKHQH[WWZRDQGKDOI 3RVVLEOH VXVWDLQHGVSL ZKHQWKHUHZDVDODUJH VWHDGLO\URVHXQWLO'HFHPEHU UHYHDOHGWKDWWKHZLQGŝVLQWHQVLW\ RIWKHVRODUZLQG7KHLUHIIRUWV LQGLUHFWO\PHDVXUHWKHSDUWLFOHV E\XVLQJLWVRWKHULQVWUXPHQWV UHDFKHGWKHWHUPLQDWLRQVKRF LQIHUZKHWKHUWKHVSDFHFUDIWKDG HELIOSHEATH wind abruptly slows to subsonic subsonic to slows abruptly wind N The point at which the solar solar the which at point The interstellar wind, causing a interstellar speeds as it encounters the the asitencounters speeds HQE\WKH TERMINATION SHOCK N shockwave-like effect. FR N HLQ LQJZRU Qƅ 9 9 R\DJHUŝV , UPDWLR 0 N WHDPWR ZDV N Q

THE STORY OF VOYAGER

0 , 73 9 H ROW N 9 Q R\DJHUV Z 9 R\DJHU7KH GHFOL DQGHQWHULQJ 9 N Sun’s heliosphere heliosphere Sun’s DWWVRI : WKH J Q L evaporatingfrom the Orion much the like one beyond the LQJOLYHVWKHSODQHWDU\ Z by LL Orionisby collides with gas DWWVSHU\HDU Nebula to create a bow shock, N The vigorous solar wind emitted ,QDQHIIRUWWRSURORQJWKHLU %\$XJXVWWKH OR : '&SRZHUEXWDVWKHSOXWRQLXPŝV UDGLRDFWLYLW\GHFD\HGSRZHU KDGEHHQVWHDGLO\GHFOLQLQJDW ZRU UDGLRDVWURQRP\LQYHVWLJDWLRQ LQVWUXPHQWZDVGLVDEOHGRQ ERWKSUREHVDVZDVWKHLQIUDUHG VSHFWURPHWHURQ SRZHUZDVDOVRFXWRQYDULRXV QRQHVVHQWLDOV\VWHPV WKDQSUHGLFWHG2QHSRVVLEOH H[SODQDWLRQIRUWKLVLVWKDW HQHUJ\LVWUDQVIHUUHGWRFRVPLF UD\SDUWLFOHVWKDWDUHDFFHOHUDWHG WRKLJKVSHHGVDWWKHVKRF WHDPIDFHGDQHZFKDOOHQJH ZHUH\HDUVROG'XULQJWKHLU OLIHWLPHVWKH\KDGHDFKUHOLHG RQWKUHHSOXWRQLXPIXHOOHG UDGLRLVRWRSHWKHUPRHOHFWULF JHQHUDWRUV 57*V DVDSRZHU VRXUFH$WODXQFKWKH57*V SURYLGHG 6 $IWHUSDVVLQJWKURXJKWKH WHUPLQDWLRQVKRF WKHKHOLRVKHDWKZKHUHWKHVRODU ZLQGVORZVGRZQGUDPDWLFDOO\ DQGEHFRPHVWXUEXOHQWWKH N LV N ZDYH ZDYHDW N N www.skyatnightmagazine.com www.skyatnightmagazine.com R\DJHU \HQRXJK DOPRVWWKUHH 9 N N QRWDQRUPDO VKRF DOO,QDQRUPDO VKRF IDVWPRYLQJ PDWHULDOVORZV GRZQDQG IRUPVDGHQVHU KRWWHUUHJLRQ KHUH R\DJHUFURVVHGWKH R\DJHUIRXQGLWVHOI : R\DJHUDOVRUHYHDOHG 9 9 9 )DUWKHUEHKLQGEXWZLWKLWV 7KLVFUXFLDO$8GLIIHUHQFH VRODUZLQGGHWHFWRULQWDFWDQG ZLWKVFLHQWLVWVOXF WREHOLVWHQLQJDWWKHFUXFLDO PRPHQW WHUPLQDWLRQVKRF \HDUVODWHURQ$XJXVW ŚDOWKRXJKWKLVWLPHWKHFURVVLQJ RFFXUUHGDWDGLVWDQFHRI$8 IURPWKH6XQ EHWZHHQWKHSUREHVŝFURVVLQJV SURYHGDORQJOLYHGWKHRU\ WKDWWKH6RODU6\VWHPLVQRW SHUIHFWO\URXQGEXWDFWXDOO\ VTXDVKHG FURVVHGWKHWHUPLQDWLRQVKRF WKHORFDOLQWHUVWHOODUPDJQHWLF ƅHOGSXVKHVLWFORVHULQWRZDUGV WKH6XQ WKDWWKHWHUPLQDWLRQVKRF DVLWHQFRXQWHUVDQREVWDFOH,Q FRQWUDVW LQRQHWKDWZDVPXFKFROGHU UNCHARTED TERRITORY: THE FINAL FRONTIER FINAL THE TERRITORY: UNCHARTED “Voyager 1 and 2’s “Voyager actually squashed” HELIOSPHERE HELIOSPHERE The immense magnetic bubble made the by solar wind emanating from the Sun. It contains our Solar System and the entire solar ﬁeld. magnetic perfectly round, but perfectly crossing points proved the Solar is not System a long-lived theory that 0 , 9 HQZKHQLW N

WHDPFRXOG ƅQDOO\DQQRXQFHWKDWWKHSUREH KDGUHDFKHGWKHƅUVWPDMRU ERXQGDU\RIWKH6RODU6\VWHP UHDGLQJV7KHVSDFHFUDIWZDV $8IURPWKH6XQEXWWKH LQWHQVLW\RIWKH UHDGLQJVZDV HTXDOWRWKRVH WD ZDVDPHUH $8IURPWKH 6XQLQ,W PHDQWWKH

HERITAGE TEAM (STSCI/AURA) TEAM HERITAGE NASA/JPL-CALTEHCH, NASA AND THE HUBBLE HUBBLE THE AND NASA NASA/JPL-CALTEHCH, THE STORY OF VOYAGER S 122 in what the the what respectively the and S ƅHOGQRORQJHUFRPHIURPWKH magnetic and wind the which heliopause 74 boundary the hit 7RWU\DQGFRQƅUPZKHQWKH\ The crossing Z UNCHARTED TERRITORY: THE FINAL FRONTIER that could be measured be could that intensity aconstant at appear uniformly VSHHGRIOLJKW ƅOOWKHKHOLRVKHDWK WRDVPXFKDVƅYHSHUFHQWRIWKH up are sped and ionised become shock termination ofthe out ( the from rays cosmic that instruments low and on relied plasma detector wasn’t working wasn’t detector plasma the heliopause: the at again faced onceannouncement them shock termination the blighted EHFDXVHWKHVDPHGLIƅFXOW\WKDW solar wind particles that leak leak that particles wind solar un olar Y J et the mission continued and and continued mission et the A uly , www.skyatnightmagazine.com but from nearby supernovae supernovae nearby from but U, S ystem boundary: the the boundary: ystem 2

V - 0 M energy charged particle oyager oyager V . 12, VIM

ilky ilky H oyager oyager .

at a distance of adistance at . I ence . At least t’s the point at at point the t’s

T team thought team W heir reasoning was reasoning heir ay 1 , , the the they would would they hit its second second its hit 1 ’s cosmic ray ray ’s cosmic G , alaxy that’s VIM .

W team team , S

hen un ,

indeed happen further and again came back came again and further even dipped intensity the later T again rose intensity the later days afew but plummet would intensity the and space interstellar into escape would ions these that was expected V U hree weeks weeks hree oyager oyager T Voyager 1’s increasing plasma readings indicated the probe was beyond the heliosphere heliosphere the wasbeyond probe the Voyager 1’s indicated readings plasma increasing his did did his 1 hit the boundary the hit .

Frequency (kHz) ,

2 3 1 Nov 2012 1 Jan 2013 1 Mar 2013 1 May 2013 1May 2013 1 Mar 2013 1Jan 2012 1 Nov had interstellar space reached “the plasma around around plasma “the provided the readings NASA NASA readings the provided the spacecraft wasthe needed to prove Voyager 1 prove to needed ejection on 6 March 2012 6March on ejection , it vibrating like a like vibrating The Sun’sThe mass coronal .

guitar string” Voyager 1 plasma wave science wave Voyager 1plasma

LQWHUVWHOODUVSDFHDQGƅQDOO\ in tosee expected had they was environment probe’s the string like aguitar vibrating was spacecraft the around I signal the up picked instruments the spacecraft toreach burst the for wait ananxious after they needed M the from RIVRODUZLQGDQGPDJQHWLFƅHOG mass ejection plasma environment spacecraft’s the measuring VIM T Making sure T density plasma’s the determine to scientists allowed pitch their and sounds into turned interstellar space interstellar that adding further evidence the from those than energetic more the from rays ofcosmic set of adifferent O since again risen not has and cent per by 90 dipped intensity F t showed that the plasma plasma the that t showed inally o be certain though certain o be o the o the n the same day same n the arch T hese vibrations could be be could vibrations hese S team needed a way of away needed team V un oyager oyager , on 2 VIM , 0 dramatically increased dramatically S M 12 25 un team’s delight ilky ilky provided just what what just provided . August August )

that erupted in in erupted that O 1 ( had entered entered had , W a massive burst burst a massive

n 9 April n 9April V 0.05 0.10 0.15 1 the density density the I the heliosphere the insideobserved been had than denser times 40 tobe revealed ay oyager oyager . , 3 t was exactly exactly t was the intensity intensity the - , month which arefar which . , 2 A coronal Acoronal the the

3 0

Density (cm ) 12 2 1 0 their their ’s ’s ,

1 . 3

. Z

. ,

. .

NASA/SDO/AIA, NASA/JPL-CALTECH/UNIVERSITY OF IOWA, ILLUSTRATION BY MARK GARLICK THE STORY OF VOYAGER 75

(1990) (2016) (1998) (1990) Operational Operational Disabled Disabled Disabled Disabled Disabled (2008) (2008) (2008) Low-Energy Charged Voyager 1: 1: Voyager Voyager 2: Voyager Voyager 1: 1: Voyager Voyager 1: 1: Voyager Voyager 2: Voyager Voyager 2: Voyager Particle Instrument (LECP) Instrument Particle Disabled Disabled Operational Operational Imaging Science System (ISS) System Science Imaging Ultraviolet Spectrometer (UVS) Ultraviolet Planetary Radio Astronomy Astronomy Radio Planetary (PRA) Investigation 1: Voyager 2:Voyager Plasma Subsystem Wave (PWS) 1: Voyager 2: Voyager www.skyatnightmagazine.com UNCHARTED TERRITORY: THE FINAL FRONTIER FINAL THE TERRITORY: UNCHARTED in phases of the as the probes’ power batteries continues fade to (2007) (1991) (1990) (1998) (1990) (1980) (1979) Disabled Disabled Disabled Operational Operational Operational Disabled Disabled Operational Operational Defunct Defunct Disabled Defunct have failed,have others been have intentionally disabled and those that remain will be shut down After 40 years in space, the Voyagers are showing some wear and tear. Some some are showing and wear After of their tear. 40 instruments years in space, the Voyagers The Voyagers’ Slow Shutdown Slow The Voyagers’ Infrared Radiometer/Interferometer/Spectrometer (IRIS) Radiometer/Interferometer/Spectrometer Infrared 1: Voyager 2:Voyager Magnetometer Experiment (MAG) Experiment Magnetometer 1: Voyager 2:Voyager Voyager 2:Voyager Cosmic Ray System (CRS) 1: Voyager Voyager 2:Voyager Plasma Spectrometer (PLS) Plasma 1: Voyager Radio Science System (RSS) 1: Voyager 2:Voyager Voyager 2:Voyager Photopolarimeter System (PPS) System Photopolarimeter 1: Voyager THE STORY OF VOYAGER galactic cosmic rays cosmic galactic the protecting in is heliosphere the important how revealed existence tenuous our into an insight exploration of space history the in to mark interstellar traveller 9 D than more from 76 when say toconclusively fareasier be plasma instrument it should years’ time two or one –in medium interstellar the and wind solar the between boundary – the heliopause the heliosheath V roughly Behind crossing A clearer UNCHARTED TERRITORY: THE FINAL FRONTIER Z allowed the team to claim that that toclaim team the allowed R\DJHUZDVKXPDQLW\ŝVƅUVW oyager oyager NA Not only was this a moment amoment was this only Not S www.skyatnightmagazine.com - olar and ozone and V 1 0 per cent slower cent 0 per 2 oyager oyager . S

V remains in the the in remains V ystem , oyager oyager it also provided provided also it . oyager oyager

I t is expected to hit tohit t isexpected .

W 75 1 - , and travelling travelling and shielding us shielding destroying ith its working working its ith per cent of cent per 2 . 1 reaches reaches had had . Pluto’s orbit ,

unimaginable distance over is probe the E toreach hours speed ofits terms in turns wind solar the ofhow details reveal also and heliopause the ago years heliopause the through passed having spacecraft the take around faint signals temperature and density But this is not the case the isnot this But space in interstellar indeed VFLHQWLƅFFRPPXQLW\WKDWLWLV the in isconsensus there that V former ninth planet or even the even the or planet ninth former the farbeyond stretches gravity begins space S our where tobe thought S ystem ends and interstellar interstellar and ends ystem arth because because arth un than oyager oyager T P oday luto , it would be easy to assume toassume easy be would it 2 0 billion km away km 0 billion The Oort Cloud Cloud Oort The , 3 200,000 AU ,

1 V .5 ’s ’s oyager times closer to the tothe closer times 17 , but the the but

, was once was once “In 2020, the remaining 2020, remaining “In the S science instruments instruments science . , . un’s and with with and At this S . will need to start need will , olar being shutdown” being

the boundary for candidates suggested as allbeen have Cloud Oort the and Belt Kuiper orbit, the Pluto’sdebated. is begins space where interstellar V Exactly The Kuiper Belt Belt Kuiper The 60-100 AU result QHDUE\PDJQHWLFƅHOG$VD VXUSULVLQJO\VWLOOLQƆXHQFHVWKH boundary heliopause the at ishalted wind solar the heliopause the from different issubtly sand invisible the DPDJQHWLFLQƆXHQFHLVZKHUH the which O 7KH V predicted theoretically comets 30 A O a result Cloud in 300 years 300 in Cloud oyager oyager ort Cloud – the birthplace of birthplace –the Cloud ort thers suggest the point at at point the suggest thers S U- olar , ƅQ the probe continues to continues probe the distant distant , some believe that the the that believe some , magnetic line in the 1 S might reach the the reach might S DO ystem ends ystem , because although although because un no longer has has longer no un The Sun The VWHSV K uiper Belt uiper At earliest the the boundary A 5, S the to envelop ystem some some ystem U . 000– away –is away S olar .

T 1 00 his , it . As O , 000 ort ort .

THE STORY OF VOYAGER

; 77

. team V un’s un’s S ystem VIM S KHUHŝ V 7

. the , olar olar V and elucidating ; S UH D HƆ J U WLPH D ŝ by listening by to plasma , n these eight remaining years I HDUV ey aims include:ey understanding XHQWO shedding light on the interstellar wind oscillations caused coronal by ejections mass the interaction of the atmosphere with winds in interstellar space by watchingby it peel open as the probes travel farther away of useful science will be rushing to learn as much as possible about the outer reaches of the K KRZWKH6XQŝVPDJQHWLFƅHOGLV wrapped around the heliosphere T WLPH ŝ UH I ort Cloud is thought to surround O \ HO\ HDUV Y n I

WL . D . DJHU when \ arth 25, 9R E 0 will stop except , 2 www.skyatnightmagazine.com www.skyatnightmagazine.com 2 RXWUHO V \ this is likely to LW ,

and . VS 1 At that At point both DJHU DJHU . W THE OORT CLOUD 248 ROSS \ \ D oss 248, 10.3 lightyears is a dim away, red dwarf star Though never directly observed, a shell of billions of icy objects known as the the Solar System. It’s so vast, that it’s thought that the couldVoyagers take 40,000 years to pass through it. Y 9R Y 9R R WK some (inconclusive) evidence that this star has a large large a has star this that evidence (inconclusive) some companion. brown-dwarf-sized or Jupiter oyager

the remaining science , V nfortunately 0 Z Z 2 U 0 WLPH WLPH occur at about the same time that with communicating for periodically emitting faint electronic blips to indicate each of their positions for a few more years to come KDYHƅQDOO\DQGXQGHQLDEO\ reached interstellar space 2 instruments will need start to being shutdown to save power in order to last until WKHƅQDOVFLHQFHLQVWUXPHQWZLOO be turned off probes will fall silent ŝ ŝ HDUV HDUV UNCHARTED TERRITORY: THE FINAL FRONTIER FINAL THE TERRITORY: UNCHARTED \ GLIESE 445 \ DJHU \ DJHU

, \ 9R 9R - will will 1 wind un need need un - it should S , occasional , But detailed . oyager V

for those who sign it should be just about visible to the naked eye. it should be just about visible to the naked eye. , , Currently lightyears 17.6 from the Sun, Gliese 445 is white dwarf (Sirius It’s B). 8.6 lightyears from Earth. of a main sequence star (Sirius A) and a companion is truly in the ‘pristine’ a main sequence star in Camelopardalis. It’s moving towards Earth and, at the point Voyager 1 passes by, towards Earth and, at the point 1 passes Voyager by, 1 Voyager 2 willVoyager eventually pass the brightest star in the night which sky, is in fact a two-star system, consisting SIRIUS CANIS (ALPHA MAJORIS) Where next for the Voyagers? n eight years’ time I oyager

be pointing in the right direction LQƆXHQFHGPDJQHWLFƅHOGQHHGV to turn roughly 40° investigations have revealed WKDWWKLVLQƆXHQFHLVZDQLQJDQG WKHƅHOGLVVORZO\WXUQLQJ to cease and the solar transmit peculiar magnetic ƅHOGUHDGLQJV7RVKRZWKDW V disturbances from of waves magnetism from the interstellar medium meaning that meaning boundary magnetic the to up interpretation OORT CLOUD: MARK GARLICK, ESA_AOES MEDIALAB, ISTOCK, NASA, NASA/ESA AND G. BACON (STSCI) BACON G. AND NASA/ESA NASA, ISTOCK, MEDIALAB, ESA_AOES GARLICK, MARK CLOUD: OORT THE STORY OF VOYAGER WR close be probably It’ll college. 78 heliopause was the where we know didn’t because space interstellar we’d that and this reach never of tocome going was nothing I us. cancel they’d thought we when times were There project manager I going be WKHPLVVLRQLQLWZRXOGVWLOO I the Cassini missions – including I 1HSWXQHƆ\E\7KHQLQ Ɔ\E\DQGVWD\HGRQIRUWKH I 10 more years. 9R Pearson Elizabeth by: Interviewed UNCHARTED TERRITORY: THE VOICES OFVOYAGER VOYAGER never thought that when when that thought never various did and off went the before hired was n the early early n the ’d be able to come back asa back ’d tocome able be \ P engineer on the Uranus and Neptune encounters. Neptune engineer and Sheleft in ontheUranus 1990 to onother work projects, returning later to some20 years oversee theVoyager Interstellar Mission M www.skyatnightmagazine.com DJHU \ ars ars Suzanne Doddjoined theVoyager mission straight from college, working asan ODVW Z 2 O 0 years later and that that and later 0 years DV bserver and and bserver MRE 2 000s P . LI

\ƅ I . wasn’t on the the on wasn’t LW , they thought thought they UVW ODVWV U THE VOICESOF MRE S ranus Suzanne Dodd pitzer IRU I DIWHU left left ,

Along with that the from coming ofparticles drop rapid I T 2 say and backtrack we could together W later months eight about until take we couldn’t that plasma the on measurements some toget able were we and space interstellar from particles in increase large arather we saw in August it happened termination shock the and Neptune between V mid review the had never subsonic to ultrasonic from went particles termination shock when –was mission interstellar of the terms –in happening interesting T to interstellar space. probes might be getting close the think to we began that 2000s mid the until wasn’t It years tothree two every funding for toask have it for preparing were review atermination for charts tomaking wayup all the project at thatproject time n 004 hat started to get interesting toget started hat he start of something of something start he oyager oyager 2 hen we put those two pieces pieces two those we put hen 0 25 2 12 , 000s for both probes both for 000s after after V August August

V oyager crossed the the crossed oyager oyager oyager . 1 S

crossed in in crossed T un hat happened in the the in happened hat 1 4 years of travelling oftravelling 4 years .

2 1 , 0 saw a really areally saw

12 . ; .

when when

was when was when “We lose 4Watts“We ayear F , for turning things off” things turning for . but it went went it but or

, D but they they but W power source, so we sowe source, power ecember 2 V e still e still have to make plans have plans to make . 00

oyager oyager T from our nuclear hey 7. .

V phase encounter planetary the during increasing was plasma ofthe density the board on instrument plasma aworking have doesn’t 7KH space interstellar in travelling started and 9R predicted to happen ƅUVWKLQWEXWEHFDXVH space interstellar from coming particles in increase an we got that time same the the T ray spectrometer space came from the cosmic Voyager interstellar in 1was VSDFH so when it reaches interstellar F measurement of the plasma. WRJHWKHUZLWKZKHQVRODUƆDUHV that detect could instrument radio our and plasma the vibrated RI direction the in travelling be reached had it discovered or he particles coming from from coming particles he oyager oyager 9 \ V S R\DJHU7KHVRODUƆDUH DJHU ƅ .

oyager oyager un dropped way off at at off way dropped un P ) UVW Z we couldn’t see that that see we couldn’t utting that piece of data of data piece that utting H 1 L crossed the heliopause heliopause the crossed ŝ , OO Q which was what was was what which KDV GLFDWLR KDYH 1, the way we way the WKDW happened to just and earlier 1 emitted was VRODUƆDUHWKDW a through was space interstellar . .

3 months 3 months D T .

Q hat was the was the hat GLUHFW . L ( Q WKDW it broke broke it 9 VWU R\DJHU X PH Q

W THE STORY OF VOYAGER

, 79 But . . \ But it . we’ll be we’ll rather , , YHU e might Z

. . Q W

atts a year . W UHPDL e lose 4 think we can say we really say we can we think I W SUREHV

. here are some people who T e mostly monitor the power H[SHUWVLQWKHƅHOGKDGVHYHUDO discussions about it healthy for senior citizens. citizens. senior for healthy W now from ournuclear power source so have we to make plans for turning things off in a couplemore years turning off instruments because don’twe have enough power to keep them all on turn off a heater and eventually than being out in the ocean those models have since been has plasma the as debunked EHHQSUHWW\VWHDG\6RDIWHUƅYH years had various models suggesting that weren’t we in interstellar space were just – we seeing the ripple on the shoreline are in interstellar space wasn’t like seeing like wasn’t a picture 7KH

, f I YRWH

1. the D , oyager un un S -V WR e didn’t have www.skyatnightmagazine.com www.skyatnightmagazine.com his was T W so that

, nce got we

. . ZQ . oyager O

V hat gives . GR T

. a chance to cross 2 FDPH oyager science team V oyager un’s activityun’s is decreasing ou could see the drop in than it was for you lookyou at solar cycles S so the distance the heliosphere stretches out to should be decreasing a little bit because the pressure from the has reduced V was very exciting a little bit sooner There was a lot of discussion we whether consider to had actually crossed into interstellar space or not. It DOPRVW Y charged particles KXPDQLW\ŝVƅUVWFURVVLQJLQWR interstellar space of theany other information to then it with go the data back on the plasma the non some with along scientists who were considered Suzanne with Suzanne U a memento from memento a her ﬁrst stint with – a Voyager sheet that shows the timeline of commands for 2 Voyager during its close to approach Neptune on 25 August 1989 UNCHARTED TERRITORY: THE VOICES OF VOYAGER OF VOICES THE TERRITORY: UNCHARTED

, W Qŝ told

\ , .

GLG 2 VD H , which W , Z t’s already X W I

. E X oyager e still haven’t E . along with the V , W

. QŚ HDUV HDU here are a lot of \ T

is in the heliosheath \\ . YH 2 e saw a subtle change in Qƅ GLUHFWLR W HYHU

. LWKL HOG oyager hat’s based on the fact the

between the termination shock and the heliopause been thicker for WKDW V direction but not a big one Our best guess is that 2 Voyager space interstellar in be will Z seen that seen theories about didn’t see we why that T PDJQHWLFƅHOGRILQWHUVWHOODU space would be coming from a steeper incline We also expectedWe to see a magnetic in change shape ƅ would be a marker for being in interstellar space us that the spacecraft in was a more dense plasma were happening particle drop in the plasma NASA/JPL-CALTECH THE STORY OF VOYAGER

NASA/JPL X 2 will go farit how want tosee and it P general public. the with popular been always it’s because lucky been Voyager always has P W it? found have might beings it? found have W record in say say in record tothat happen will what about sounds and images ascertain well we like music as –what it on planet the ZLOOWHOOZKRHYHUƅQGVLWDERXW that record this we have that mission tothe gravity lends it I carry the Golden Record. they because particular, ambassadors for in Earth, great they’re I think totry left nothing be there’ll spacecraft the torecover ofthings a lot anymore transmitter the tooperate power enough have we don’t that mean likely would it anything hear we don’t probes the from asignal get longer we no until them operate out runs gradually power asthe systems functioning the allof between trades to manage though ofthem out years I towards pointed antennas the tokeep thrusters the doesn’t freeze hydrazine the that so warm lines W cold. very that’s a place because the probes are in though, off we turn what W Voyager probes. the for party anniversary a50th have to is goal My spacecraft ofthe each on condition thermal the and power both conserving about careful pointings antenna we’ll the and lose drift eventually 80 Z UNCHARTED TERRITORY: THE VOICES OFVOYAGER f we don’t t gets a lot of romancing and and ofromancing alot t gets eople are always interested in in interested are always eople that in areinterested eople We have to be careful about about We careful be to have e need to keep our propellant propellant our tokeep e need e hope to get at least least at toget e hope hat willhat they think of us? here will it be? it will here www.skyatnightmagazine.com .

. W .

As engineers I t’s to interesting think hen you talk about you talkabout hen , the probes will will probes the , E but at some point point some at but arth and the people people the and arth 5 , because we need we need because 00 million years million 00 W W hat other .

. I

ho will S t takes work work t takes o we’re very o we’re very .

, we have we have W e’ll try e’ll try V 1 . 0 more 0 more

oyagers oyagers W .

E . e’ll e’ll arth .

I f .

very are margins those Now it? on of margin :KH surprise nasty a in result don’t they that hope RXUƅQJHUVDQG we cross and make decisions E important 1 think they’re to going do take on passed have engineers early the back togo hard design numbers their in put they margin much was designed something margins power low with we’re playing T ailments. of set adifferent has spacecraft the of each because concerns always are there said, That going missions these to keep willpower ofpolitical alot takes reasons whatever for them funding stop or them cancel to ofopportunity alot there’s decades last that missions decided we needed to turn turn to we needed decided the propellant lines and we of one in heaters of side aredundant we had 2011, in 0 very day we day very here are concerns now that that now areconcerns here , W so you can’t ask them how how them ask you can’t so , very very atts and there’s there’s and atts Q 12 ,

ƅ W .

T UVW atts or does it take it does or atts . he mission is so old it’s it’s old isso mission he

FDPH , but do what we what do but . . A fair number of number Afair

D point there’ll be nothing nothing be there’ll point oes it really really it oes EDFN spacecraft, at but some 2

things to recover the to the recover things W . atts atts “We’ll try alot of “We’ll

, R or how how or Q .

I t .

left to try.”left before broadcast hours just afew taken been had of Triton that viewers images show to able was Suzanne Voyager Update U During the the During

and it all worked well allworked it and a spacecraft’ on working what’s with tamper a certain philosophy of ‘don’t the side we haven’t used for 3 for used we haven’t side the T decision. a risky was power. save It to off that to the other side other to the back switch we could working wasn’t ifit and there switch W you done? have what work… been never had that side to the W side other we’ve the used never lifetime its beyond getting it’s we’rethat because on side the off we turn do or years he question was: do we turn off off we turn was: do question he e designed it so that we could we could that so it e designed toswitch deciding up e ended edition of JPL’s of edition Suzanne presented the 5am the Suzanne presented 1989 Neptune the share to programme on 25 August 25August on programme encounter with the public the with encounter . But it all worked allworked it But Voyager Update Voyager .

and it doesn’t doesn’t it and of ifyou switch that question always there’s forward going lifetime longest us the give would that used because T , here was here even though even though . V , but but 5

THE STORY OF VOYAGER

MARK GARLICK 82 V LEGACY A GRAND IV PHASE LEGACYA GRAND V territory thisunexplored analysing on, willcontinue probes The few years. inthenext to gointerstellar it’s expected star, theheliosphere; away within fromourparent isstill Z whoknows? And the cosmos. of aglimpse foreverwill carry in the Golden and, spacecraft the way for later System, paved theway we theSolar changed thinkabout theVoyager but out, Thismission has goon. will legacy into the stars all those years ago. ago. years allthose into thestars itout whosent ofthepeople for thedescendants RID L OOƅQ www.skyatnightmagazine.com U I G U R WKDW space. Voyagerspace. approximately 17.1 2, billionkm into interstellar ahead forging the Sun, than away fromourplanet farther times 138 roughly oyager 1isnow over from billionkm 20.7 P KR V P O L YH HXQW U RIRX L OWKH U FL LU Y L S O LV OXWRQ E M DW arth as it was in 1977 in asitwas in1977 arth aybe another species species another aybe L RQDQ L X P EDWWH G F R P UL HORR H R V ƅQDOO\ ecords, E NL arth, arth, Q J U XQ THE STORY OF VOYAGER 83

continues into interstellar space our Solar System but its journey passed beyond the boundary of Alone in the dark: 1 has Voyager A GRAND LEGACY www.skyatnightmagazine.com THE STORY OF VOYAGER RILQƆXHQFHZLWKLQDIHZ\HDUV ofthe limits outer the in twin pioneering its to join space interstellar stars: the between region mysterious the entered and system planetary our left ever gone before gone ever –has hands by human touched else anything –or spacecraft no where travelling and operating two the exploration greatest achievements in ofthe asone remembered 84 the Voyager legacy remains unfulﬁlled missions of followed howpart that –and how theprobes wentonto inspire the the Voyager programme. Here heexplains about thelastingat NASA, inﬂuence of director science ofplanetary Green, James askedDr We voyage Lessons from the LEGACY:A GRAND LESSONS LEARNED VOYAGER WILL BE WILL VOYAGER I n August n August www.skyatnightmagazine.com .

V V oyager oyager oyager probes are still arestill probes oyager . As you read this you read As 2 0 12, 2 . is expected isexpected

V S oyager oyager un’s sphere un’s sphere

inspired WRUHƆHFWRQWKHYLVLRQWKDW beginning mission ofthe anniversary 40th km mark achievements and its enduring V than more space into launched were craft two the Neptune planets wondrous J of knowledge our transformed close RIPRRQVLWDOVRJDYHXVRXUƅUVW upiter oyager oyager T he - , up look at the strange and and strange the at look up

V , V

S oyager mission not only only not mission oyager V oyager oyager . 2 .

aturn and their dozens dozens their and aturn As we approach the the we approach As I oyager , has hit the the hit has n the 40 years since since years 40 n the it 2 0 billion km 0 billion ' s worth pausing pausing s worth 1 , has travelled travelled has its greatest greatest its U ranus and ranus and 17 , billion billion while while missions today FRQWLQXHWRLQƆXHQFH1$6$ they how and followed that DQGWKHLUƅQGLQJVLQVSLUHGWKRVH probes two the –how legacy stars beyond our our beyond stars Blue our on explorers audacious when an era from capsule time a one –each ambassadors V to think that by the forged home another for nest’ the ‘left have will and E giant ared become now from atime about I Ambassadorial duties n my quieter moments n my quieter arth will no longer be habitable habitable be longer no will arth oyagers will still be be still will oyagers I t ' , s humbling and inspiring inspiring and s humbling in order tosurvive order in Words: Dr James Green James Words: Dr D The success of Voyager helped Voyager of success helped The ot reached out to the tothe out ot reached shape subsequent spacecraft spacecraft subsequent shape , when our our when , , even then even billions of years ofyears billions V , following a path apath following . oyager missions oyager

and mission design mission and S olar . Bythen S E un has has un arth’s , S humans humans , ,

the the ystem I think P , ale ale

THE STORY OF VOYAGER

85 , ’s 1 Z

, ince ince S having having

; . . oyager he same same he V

arth T .

. E the swivel that , pportunity O he same platform platform same he T

EUROPA CLIPPEREUROPA Launch due: Early 2020s ars exploration rovers exploration ars CASSINI CASSINI Launched: October 1997 oyager missions were two strategy punch’ the was 78. - V M 9 1 By having two spacecraft we . pirit and t quickly became clear that this moves itsmoves cameras and the the Ɔ\E\VDQRPDOLHVWKDWZRXOG require a lot of time to diagnose and correct could result in us missing an encounter and all the science that might derive from it could increase the odds of the successmission’s S strategy employed was with the two rovers notonly provides a redundancy and gives us a error for margin bigger instruments and looks for commands from became stuck for several weeks in instruments from side to side to side instruments from best one to adopt platform scan Always have a plan B have Always I ‘one

. A S oyagers? A history ne of the Collectively S V . www.skyatnightmagazine.com www.skyatnightmagazine.com O and imaged imaged and places more than other any spacecraft in NA a condition that down all science typically shuts , GALILEO GALILEO Launched: October 1989 ’m often’m asked is: I oyager missionas was discovered more moons mode , many anomaliesmany that would put them in safe V oyagers visited more V he he T oyager an early was NA ambitious as it gets the planets were therewhy two questions V PLVVLRQDWDWLPHZKHQƆLJKW systems were known to suffer A GRAND LEGACY: LESSONS LEARNED LESSONS A GRANDLEGACY: JUNO JUNO Launched: August 2011 Mars rover Z Spirit had a twin too: Opportunity. Doubling up was a fail-safe born strategy of the Voyager program .

. “By having two “By two having VOYAGER 2 Launched: August 1977

the , ecords 11 ” agan agan mission’s success” mission’s . R S spacecraft we could we spacecraft ecords were the , increase the odds of the 0 and oyager R 1 olden olden V G As Carl . in in olden olden , G ioneers he launching of this P T “ , hile Not only has the science W oyagers’ he twin phonograph records arth that to anyone might

each carried small metal plaques detailing theirorigin and date of launch ambitious more considerably noted ‘bottle’ in the cosmic ocean says something very hopeful about life on this planet discover them discover V T brim with images and sounds that provide a snapshot of the diversity of life and culture on E the form the of produced the by beenmission captivating captured themselves probes the world’s by imagination each carrying a greeting for extraterrestrial civilisations The Voyagers inspiredThe Voyagers NASA of generations each spacecraft, beneﬁtting narrower from purviews more and technology advanced NEW HORIZONS Launched: January 2006 VOYAGER 1 Launched: September 1977 NASA/JPL-CALTECH X 8, ISTOCK 8, X NASA/JPL-CALTECH THE STORY OF VOYAGER second craft asaback craft second redundancy and having a of value the reinforced problems S at results fantastic produced S with approach closest its from away was pulling spacecraft the 86 LEGACY:A GRAND LESSONS LEARNED Z geysers on on geysers erupting and winds powerful Neptune’s ƅQGLQJRIDFWLYHYROFDQRHVRQ,R rings and moons unknown ofpreviously discovery was the mission’s accomplishments the science ofnew a bonanza S outer the in planets giant four the Ɔ\E\VWKRXJK,Q planetary last probes’ the with wind termination shock ƅUVWPHDVXUHPHQWVRIWKHVRODU space interstellar into boundary the yet tocross which interstellar space WKHJDODFWLFPDJQHWLFƅHOGIURP and rays ofcosmic intensity full WKHƅUVWPHDVXUHPHQWVRIWKH heliosphere the leave EHFDPHWKHƅUVWVSDFHFUDIWWR aturn despite the technical technical the despite aturn aturn olar became stuck on on stuck became $VWKHƅUVWPLVVLRQWRWD T he discoveries didn’t stop stop didn’t discoveries he www.skyatnightmagazine.com S , at the time ofwriting time the at . ystem

F ortunately ortunately , but the anomalies anomalies the but G T reat reat riton ,

V oyager produced D . , .

provided the the provided

V ark V oyager oyager V oyager oyager , oyager oyager delivering 9 S - pot and and pot R\DJHU up .

. Among . , N

the the 2, HLQ 2 , has has

2 ’s as as ’s

planets was the principle of principle was the planets V to be been has which paradigm science planetary the IXUWKHUVWXG\$VƆ\E\PLVVLRQV for priorities our on decide and there out what’s us tosurvey the VWHSV,QGHHG next take the usto enabled Ɔ\E\VWKDWKDYH with way the T this paradigm of instigators the and party scouting the – tobe continue ways some T rove samples return and 6\VWHPƆ\E\RUELWODQG ofthe exploration its for D NA party Scouting next fewyears next within the space in interstellar : stars? other from winds solar the tasting begin and companion hey forged forged hey he oyagers’ tours of the outer outer ofthe tours oyagers’ ivision follows a paradigm aparadigm follows ivision HKRSHLWZLOOMRLQ Critical to the success of the ofthe success tothe Critical W S V V hen will will hen V A’s A’s , oyagers reinforced the the reinforced oyagers allowed spacecraft oyager tremendously successful tremendously oyagers were – and in in –and were oyagers P lanetary V oyager oyager .

. , and continues continues and S 9 cience cience flyby, rove orbit, land, R\DJHU R\DJHU 2 and return samples” return and follows aparadigm: join its its join .

S “NASA’s Planetary olar Science Division ,

. alter its orbit its alter repeatedly to them used probe Saturn the how see can you here Cassini mission; the of part an integral also became Voyager to vital assist concept U The gravity- The V to destination its IURP-XSLWHUŝVJUDYLW\26,5,65(; P 6\VWHP1HZ+RUL]RQVƆHZE\ outer the in destinations toreach takes it oftime amount the reduce dramatically and fuel tosave assists gravity employed have missions U totour assist ofaspacecraft trajectory and speed the toalter space in object another or of aplanet mass the –using assist gravity but to slow it down it toslow but up spacecraft the tospeed not M hand DW(DUWKDQG M into placed being before itself from assists separate orbit enter successfully luto two years ago with a boost aboost with ago years two luto oyager oyager ranus and Neptune and ranus essenger used gravity assist assist gravity used essenger ercury’s orbit S ince then . ,

mission planners for for planners mission M essenger received assists assists received essenger 2 nailed the gravity gravity the nailed , 9 a number of anumber J HQXVDQGWKUHH upiter .

more rapidly it to slingshot 22 IURP(DUWKRQ assist a gravity Bennu DVWHURLG for bound .

O M ,

so it could could it so S n the other other n the ercury’s , .

eptember S M aturn , ercury will get get will S olar ,

THE STORY OF VOYAGER Z . 87

. it it , Daphnis

. PRIWKH N Consequently . oyagers had limited Helene Calypso V oyagers set the agenda agenda the set oyagers V he he hile the T IURP(QFHODGXVEULQJLQJWKH SUREHZLWKLQ moon’s icymoon’s surface Raising the bar W programmable memory programmable proved to be a critical resource that used was extensively and reprogrammed on a number of occasions all subsequent planetary missions were given large memories programmable future planetaryfor exploration Atlas his was Hyperion

. 2 &DVVLQL www.skyatnightmagazine.com www.skyatnightmagazine.com N oyager V

and produced , , riton PDERYHWKHSODQHWŝV T Epimetheus N Voyager 2's closest ﬂyby 2's was within Voyager 5,000km of Neptune; NASA was U ,QRUGHUWRREVHUYH1HSWXQHŝV later able to program above Enceladus Cassini to ﬂy (above) at 15km VLJQLƅFDQWVFLHQWLƅFUHVXOWV moon SHUIRUPHGDYHU\FORVHƆ\E\RI Neptune that saw it pass about inaccessible north polar cloud tops the closest trajectory that any spacecraft had followed around one of the outer planets and initiated the development of precision trajectories for future Ɔ\E\VWKDWZRXOGEHHYHQFORVHU 2QHVXFKƆ\E\WRR through the plumes bursting up A GRAND LEGACY: LESSONS LEARNED LESSONS A GRANDLEGACY: The Voyagers The Voyagers used gravity assists to speed but theyup, can also be used to slow down; Messenger the probe to Mercury thatdid just as it passed Venus U Janus Telesto Prometheus Pandora aturnian aturnian S his has T

. enus and one each Methone V itan to continually Cassini has mastered the . T Cassini received two gravity aturn Phoebe

moons that would be otherwise reshape its orbit allowed Cassini to obtain new views of many of the assists at art of gravity assists and uses FORVHƆ\E\VRI6DWXUQ VODUJHVW moon DW(DUWKDQG-XSLWHUHQURXWHWR S Cassini's use of gravityCassini's assists allowed it to get close views of many of major moons Saturn’s NASA/JPL-CALTECH X 16 X NASA/JPL-CALTECH THE STORY OF VOYAGER and the relatively low volume volume low relatively the and missions ofthose instruments moons their and giants ice the about 88 LEGACY:A GRAND LESSONS LEARNED Z Jovian moon of the same name same the of moon Jovian icy the on life signsof for look will Clipper Europa in-development The T images itinto process and data the download can anyone meaning instrument, science citizen mission’s the isa camera pole; main Jupiter’s south over spacecraft Juno The hough they taught us much usmuch taught they hough www.skyatnightmagazine.com , the relatively primitive primitive relatively the ,

questions than answers than questions more raised returned of data more we appreciate what we what we appreciate more we know more ofthe case T he V oyager mission was a mission oyager .

, the the Return journeys from assist by agravity again once concepts including orbiters including concepts mission ofpotential a variety pre covers S to come years the in change could that since unexplored remained have Neptune T priority to G J of NA anumber for way the paved need to learn a gravity assist from from assist a gravity to T evidence of life beyond oflifebeyond evidence seek also but surface the explore could that successor alogical be would mission lander subsequent early the in launch V from gained experience the on builds also that is anorbiter development under currently the New New the of ŜFRPSOHWHGWKHVHWŝZLWKDƆ\E\ tours upiter cience cience he ice giants icegiants he he oyager alileo and and alileo W P U S - luto in aturn with decadal survey explored explored survey decadal ranus or Neptune as a top asatop Neptune or ranus hile the the hile E ' J didn’t include include didn’t uropa Clipper mission Clipper uropa S upiter , 2 . A missions: both the the both A missions: and the Cassini mission mission Cassini the and A recent NA Arecent 0 . D . Clipper is scheduled to isscheduled Clipper

H T 1 ecadal 3– orizons mission mission orizons J he current current he uly of uly J . V 2

uno missions to missions uno . As such 0 oyagers , U appropriately 22, ranus and and ranus S V 2 lists a return areturn lists urvey oyager oyager 2 0 P 0 S 15 J luto 2 P A ' ,

upiter – aided –aided

0s and a and 0s ' lanetary grand grand - V E led , which which oyager oyager arth ,

2, , ,

but but .

, ,

THE STORY OF VOYAGER

89 . it it but ,

, was was . I Any Any term .

hoisn’t

, - . ranus V W olar olar arth U

. . S E yearn seen by R\DJHUƆ\E\V I ,

, 9 they also he time it took , ot T

. D e were compelled A’s director of A’s S W niverse aturn’s rings aturn’s from a distance of six 1 S U to go back to , ale Blue oyager probes not only as NA P , A scientists involved with V oyager also taught us the S V As a graduate student graduate a As oyagermission out there oyager here are still legacies of the he he ystem and Neptune and even discover more about the ice giants to return to the outer S T V ZDLWLQJWREHIXOƅOOHG V billion km? billion km? to repeat that experiment with Cassini viewed as we through that that art of patience for the probes to complete their investigations required that the NA the mission make a long would be worth the wait planetary science T investment in the project JUDWLƅFDWLRQWKDWFDPHIURPLW would be severely delayed as history has show shown WUDQVƅ[HGE\WKH Now transformed our view of science and the changed us as people awestruck and humbled the by iconic image of our home planet FRPSHOOHGWRH[SORUHWRƅQGRXW whatlies beyond the next hill

. we’re we’re , www.skyatnightmagazine.com www.skyatnightmagazine.com so visiting the , Curiosity is . As humans As . ystem S NA D olar olar e also still have much to S W oyager’s 40thoyager’s anniversary OHDUQDERXWWKHƅQDOIURQWLHURI the heliopause with a more capable mission bucket is on list my minds Enquiring V LVWKHLGHDOWLPHWRUHƆHFWRQ what drives us to understand our origins and what our future may hold in our A GRAND LEGACY: LESSONS LEARNED LESSONS A GRANDLEGACY: what’s beyond the next hill” compelled explore, to find to out The New Earth seen within the rings of Saturn, a homage to 1’s Voyager Pale Blue Dot “Curiosity is in our DNA. As humans, we’re U Horizons probe fulﬁlled one of the Grand discarded Tour’s in objectives – a brief 2015 visit to Pluto

. and , .

HU\ .

, 9 riton’s riton’s But e have 0s . T 2 ranus bserver W 0

U . O

2 . o . I ionosphere ionosphere rontiers line - 003 F oyager found 2 aside from what , V

, ranus’s atmosphereranus’s U which is about three with an , , oyagers piqued our o A’s New A’s V I cold surface cold S - oyagers’ discoveries also also discoveries oyagers’ he he V T Also puzzling are Neptune’s ranus’s oyager encounters more upiter’s fascinating volcanic volcanic fascinating upiter’s

inspired a future mission to J moon listed as one of the priorities NA in of missions in curiosity about the internal structures and compositions of the giant planets ultra little is known about the PDJQHWLFƅHOGVDQG of magnetospheres questions remain about their magnetosphere KHDWƆRZZKLFKLVDURXQG times larger than expected nitrogen geysers erupting into the stratosphere from much to learn about their polar regions and the origin RIWKHLUPDJQHWLFƅHOGV learnedwas through the V than two decades ago coupling processes and their link to the aurorae and moons U times greater than anticipated But the causes are unknown At Neptune and Neptune Ɔ\E\VDQGSUREHVWKDWZRXOG into dive to study its composition possibly in the late

PHYSICS LABORATORY/SOUTHWEST RESEARCH INSTITUTE RESEARCH LABORATORY/SOUTHWEST PHYSICS NASA/JPL-CALTECH X 3, NASA/JOHNS HOPKINS UNIVERSITY APPLIED APPLIED UNIVERSITY HOPKINS NASA/JOHNS 3, X NASA/JPL-CALTECH THE STORY OF VOYAGER to the stars Messages 90 Skuse Words: Ben nature intrepid humanity our and a‘record’word of every senseofthe future, they are, in ﬁndtheminmay the extraterrestrials that interpreted byany Records are Voyager’s Golden matterNo how mixtape, invitation. Ambassador, message, LEGACY:A GRAND GOLDEN THE RECORD www.skyatnightmagazine.com communicate with to power enough have longer the message will be received be will message WKHKRSHUHPDLQVWKDWRQHƅQDO from to and signals regular even though But acentury half almost lasted mission that ZLOORIƅFLDOO\PDU far asNA a from capsule V civilisation extraterrestrial on NA anyone at for intended IN AROUND 10 oyager spacecraft is a time isatime spacecraft oyager 12- P T E erched on each of the ofthe each on erched he message in question is in not question he message V arth inch gold inch oyager spacecraft will no no will spacecraft oyager , but for an advanced anadvanced for but S A is concerned E , by then by 1 - arth will cease will arth 9 plated copper disc 77 years’ time years’ N WKHHQGRID in the form of form the in E arth , will have have will . . ,

As this . S ,

A or A or , .

THE STORY OF VOYAGER

H .

and LQJ . N . SETI N LO\ Z

N . oon oon omberg as S , HDQGD L

WDO - N HZKRƅUVW N N 77. including , ioneer ioneer 9 H6DJDQDQG 1 P oyager N but if agan and , ORULVWVDUWLVWV which were V , S N he images came 'UD T

N . arth ahal to a picture of omberg selected the anuary E L J A approved the idea M S HG6DJDQ'UD along with symbols aj aj , N on on National Geographic National

T J , NA , HKDGGHVLJQHGWKHSODTXHV A A had two astronomers N S S 7KHWHDPVHWWRZRU ociety in in ociety and ethnomusicologists well as consulting with political andgroups documentarians Artist of pictures highly diverse: from an image of the fallen leaves WRKLVWRULDQVIRO from various sources FRXOGQŝWƅQGDQDSSURSULDWH LPDJHRUGLDJUDPKHRU'UD simply drew it themselves NA Sports Illustrated DQGWDV committee included that artists and authors to depict as much of our existence as possible on the record in a matter of months Earth in a groove ,WZDV6DJDQDQG'UD suggested a more ambitious message for the probes during a meeting of Astronomical American the S after 'UD used for the earlier providing information about the origin of the two spacecraft mission – a pair of gold anodised aluminium panels that pictured a nude man and woman IRXQGHU)UDQ ZDVQRPHDQIHDWEXWOXF NA experienced in sending physical messages into space: famed astrophysicist and science populariser Carl

8, QRZQ and 3 , N DJHV pure -2 N - Also Also . www.skyatnightmagazine.com www.skyatnightmagazine.com WKHLUPHVVDJH Voyager probe Voyager N in its aluminium allowing the age of the 7KHSDF are completed by ultra samples of the isotope uranium arth on a record protective sleeve, sleeve, protective is mounted onto a E One of the records, into which are etched which are into , ortraying the diversity of life P The nickel-plated master record is inspected before used toit’s press the discs oyagers to be determined DVW\OXVWRSOD\EDF V through radioactive dating diagrams and binary code containing all the information them play to needed inscribed on them is the location RIWKH6XQLQUHODWLRQWR pulsars so that the origin of the records can be deduced should DQ\RQHƅQGHLWKHURQHRIWKHP aluminium and culture on A GRAND LEGACY: THE GOLDEN RECORD THE GOLDEN A GRAND LEGACY:

. A

S . comprehend the would bewould able to technology easily” advanced civilisation civilisation advanced minute minute and NA , “NASA believed an that 12- a , ecords’ might be R -

, olden olden olden olden G greetings he technology behind , G T

languages . ach ach analogue 55 E Production begins on the Golden Records for the probesVoyager June in 1977 The gold-plating gold-plating The is applied to the copper records Instructions are etched into the protective sleeves he records are mounted in ecord carries carries ecord arth and 90 minutes of music

R a wealth of information including 116 encoded images in montage of natural sounds from E T protective sleeves made from believed that an advanced civilisation would be able to comprehend it easily enough but it is a simple one antiquated by modern standards by antiquated these ‘ a phonograph record containing a glimpse of our planet as it was then NASA/JPL-CALTECH X 7 X NASA/JPL-CALTECH THE STORY OF VOYAGER wife S languages invarious greetings acquiring 92 Z pulses. the of frequency the deﬁnes code binary 14 to The pulsars. relation in Sun our of location The =~1 side one time: hour Playing Record Golden of view Elevation cartridge of view Elevation Golden Record the of view Plan spacecraft) on (supplied record play to stylus with cartridge of Outline seconds/rotation) (3.6 speed playback correct deﬁning code Binary LEGACY:A GRAND GOLDEN THE RECORD alzman M for reasons of inclusivity. religion were also omitted aggression. Politics and of asign as interpreted theyconcerns could be to due out left were war interesting. Images of as just is included not cities appear, but what’s mountains, seas and deserts, Earth’s of Shots SCENES The etchings on the records’ protective sleeves serve as playback instructions –here’s they what mean instructions asplayback sleeves serve protective records’ the on etchings The eanwhile www.skyatnightmagazine.com , artist and writer writer and artist , was in charge of charge was in A snapshot of the contents of the Golden Golden ofthe contents ofthe A snapshot .

D ,

ue to the time time tothe ue S agan’s then how to playhow record agolden Messages from Earth Messages from L inda inda - programmer in New York. acomputer from message aSwedish included it so and happy Earth on people keeping in exercise an more was it But it. key todecipher a with language one sent have would team Sagan’s understood by anyone, tobe intended truly were If of this greetings selection GREETINGS constraint instruction on what tosay what on instruction communities surrounding the and Cornell from were , S many of the speakers speakers ofthe many agan’s university .

G iven little R ecords, the time capsules carried on the Voyager probes ,

is about a peasant revolt. apeasant about is song the that found team offensive the associations, to ensure there were no latter piece, ‘Tchakrulo’, Translating the lyrics of this traditional music. Georgian Sengalese percussion and to Bach and Beethoven from music: of sorts all The Golden MUSIC R ecord holds The two lowest states of a hydrogen atom; atom; ahydrogen of states lowest two The the vertical lines with the dots indicate the the indicate dots the with lines vertical the spin moments of the proton and electron. electron. and proton the of moments spin The transition time from one state to the the to state one from time transition The (512 vertical lines per complete picture) (512 complete per lines vertical General appearance of wave form of of form wave of appearance General other provides the fundamental clock clock fundamental the provides other reference for the sleeve’s the for instructions reference from –ranging eclectic were results from the children of planet ofplanet children the from in saying Nick to the one to the video signals found on the records the on found signals video indicates time of each scan sweep sweep scan each of time indicates Video image frame showing the the showing frame image Video image to appear will be acircle be will appear to image direction of a scan. Binary code code Binary ascan. of direction to undergo an EEG scan. scan. EEG an to undergo and so Druyan volunteered idea, the liked members team other the and Sagan could exist;thoughts technology to decode the with acivilisation if wondered had Druyan Druyan’s brainwaves. Ann of sound the was An inclusion unexpected A EXPERIMENT THOUGHT S and record’s pictures. decoded agan’s six If properly decoded, the ﬁrst Binary code deﬁning time of the scan (~8 milliseconds) (~8 scan the - word E nglish “ - , minimalism minimalism year Scan triggering - old son G reetings reetings E arth”

THE STORY OF VOYAGER 6 9 A

S , 93

, the , NA the the . . o the olden olden T drinking G solar spectrum;solar oyagers from V

V . he probes will T

. A administrator to sign S ncluding the records I ecords were sent anyway all times’ in the space between the grooves and the label works just after theyhad ƅQLVKHGFXWWLQJWKHPDVWHUE\ adding the inscription ‘ makers of musicall worlds — quality control rejected the record as with the inscription it no longer matched the design VSHFLƅFDWLRQV,I6DJDQKDGQŝW hastily produced a waiver for the NA records would have to have been replaced with blank discs transformed the robotic explorers into interstellar ambassadors likely never reach alien hands but the fact that the R speaks volumes for the hope humanity harbours of one day discovering that are not alonewe

, ,

, oode’ oode’ ere imothy imothy the G ozart H refused 8 23 5 T , But Classical . . M agan also also agan EMI, www.skyatnightmagazine.com www.skyatnightmagazine.com S

. erris writer and and writer Rolling Stone editor F music features prominently excerpts with from but , ohnny B J A permission to use un’ he Beatles’ ‘ traditional songs S S , the team thought , T but to give a sense of , nce the content was O despite the Beatles themselves , erris threw a spanner in the the hard part over was F Bach and Beethoven among others the range of music humanity has to offer from various cultures and even Chuck Berry’s ‘ were also included requested Comes the band’s record company to grant NA it being in favour of its inclusion assembled A GRAND LEGACY: THE GOLDEN RECORD THE GOLDEN A GRAND LEGACY:

. 4 7 1 to grantto NASA

, permission use to it” Beatles’ ‘HereBeatles’ Comes “Sagan requested“Sagan The the but EMI Sun’, refused esponsibility oversaw the , R

. ” . as well as human , the project’s arth’ recordings , E a chimpanzee’s call greetings were not the , , ave ave H how are ruyan , D This is a small selection of the images encoded on the Golden chosen Records, to describe our planet, our region of space and riends of riends of f course ounds of agan’s third wife third agan’s

F S

U and animal noises such as a cry baby’s Sounds and music O erupting volcanoes and crashing ocean waves and bark a dog’s for the music fell to science only audio sent into the heavens Ann Ann include thunderstormswhich creative director and later S of “peace” in Aramaic or the bizarre Amoy greeting that as translates “ space all? you ‘ you eatenyou Come yet? visit us haveif you time human race: [1] Male andhuman female race: forms; [1] [2]The UN building; [3] Children with globe; [4] House construction in Africa; [5] The [6] The structure Earth of Earth; from space [7] [8] Sprinters at the Olympic Games [9] A demonstration of licking, eating and NASA/JPL-CALTECH X 12, ISTOCK X 2 X ISTOCK 12, X NASA/JPL-CALTECH THE STORY OF VOYAGER 94 once at thing one at look only WLPHGXULQJDƆ\E\DQGZHFRXOG of amount alimited had we only Bbecause Aor todo decision a tomake we had when times were there but together well we discovering were things the and journeys probes’ two the public tothe encounters the reporting in to take alead then and FRRUGLQDWHWKHVFLHQWLƅFHIIRUWV steering group science the was called what spacecraft the on instrument particular teams PLVVLRQWKHUHZHUHVFLHQWLƅF F SURMHFW thereafter I became the shortly and 1972 July in began VoyagerThe project Pearson Elizabeth by: Interviewed LEGACY:A GRAND THE VOICES OFVOYAGER VOYAGER or the planetary part of the ofthe part planetary the or Ed Stone –the‘face’ ofVoyager beenthemission’s –has project scientist since 1972. G He looksback atthechallenges ofthemission days oftheearly howthetwin and enerally www.skyatnightmagazine.com , , leading them through through them leading each of which had a had ofwhich each VFLH space probes continue to explore theedgeofheliosphere beyond and .

, T everyone worked worked everyone Q he teams formed formed teams he WLVW .

M y role was to was y role THE VOICESOF . .

do next E RUOHVVƆRZQE\FRPPDQGVIURP P WKDW spacecraft automated fully WKH because probes, the building we were while alot We learned worked quite well things that away such in efforts what to do S of deciding that launch” ready for you’re deciding of “Everything is systematically is “Everything organised arth that toldarth them what to o we had to make decisions of decisions tomake o we had revious spacecraft were more more were spacecraft revious a model of Voyager of in1977a model and colleagues with stands left, from second Ed Stone, Ed Stone as there are many steps in the process process the in steps many are as there 9R FR \ . X

DJHUV F OG or , Ɔ\ but we organised our our we organised but V oyager we wrote wewrote oyager Z WKHPVHOYHV HUH . WKH ƅ UVW machines in space machines advanced most the were they quite primitive standards computers 7KH\Ɔ\XVLQJVPDOORQERDUG autonomous tobe built were spacecraft asthese new really –was something computers the for programming even the – tested and integrated to be had that ofinstruments array spacecraft then executed programs computer , the computers are computers the . By today’s Bytoday’s , but at the time time the at but . , which the the which .

T he .

THE STORY OF VOYAGER Z 95

, But

. . it was ; HUDQGWKH OG N X FR or example or F

LW 2. oyagers and each LI V but it hadn’t Z , R Q N oyager W V Qŝ e had no experience with we hadwe two W anything that old in space We hopedWe that the spacecraft would last long enough to get we but space, interstellar to GLG with with just passing some by dust some bright dust specks would Ɔ\SDVWWKHVWDUWUDF spacecraft would begin to act as if it had been bumped by something

, But FDUH uring - . N D

hat hat ]. in fact in T , - ’s fault www.skyatnightmagazine.com www.skyatnightmagazine.com 2 to bring the thing [ oyager V here were some other T combination back within those limitsback those within of itself and everything came back online and orientated itself peculiar things that happened its launch protection system reported things weren’t as expected HYHU\WKLQJZDVƅQH,WWRR it turned out that because was it being was launched! caused some confusion as the spacecraft in was fault protection mode when A GRAND LEGACY: THE VOICES OF VOYAGER VOICES THE A GRAND LEGACY: The science Ed Stone leads a press closestbrieﬁng for Voyager’s approach ofJupiter in 1979 U steering group for the Voyager mission (then called MJS-77) at JPL in 1972, after their ﬁrst Ed meeting. Stone stands fourth left from

, he he T

. RWKHU WLPH Q\ D your UVW , oyager has \ 000 times times 000 , V ƅ 40 OLNH YHU LQJLWDOOƅW 2 f something I N WKH

. DV . WV Q IRU \Z WKHVH or instance or today could you – which launched was , F PH 2

GD . X Ɔ\ FK but one that has lot a of WR VWU , Q L Z XQ f course oyager oyager verything is systematically upiter second – had onboard

V ƅUVWEHFDXVHLWZDVRQDVORZHU trajectory and would reach J computer programs that faults detected outsidewas of expected limits the programs would make a change and keep on changing WKLQJVWRƅQGWKHULJKW complicated, automated automated complicated, VSDFHFUDIW We were constantly learning learning constantly were We KR E organised as there are many steps in the process of deciding that ready you’re for launch attention because the launch is one of the most critical parts missionof any countdown is a very exciting time /D which gives an idea you of the FKDOOHQJHRIPD smartphone has more memory than O do much better with the instruments than could we with V We had a ratherWe good payload RI NASA/JPL-CALTECH THE STORY OF VOYAGER volcanoes in the the in volcanoes active only the point that until realm usual our within not were that things revealing doing: ofwhat symbolic though out stand does on ofvolcanoes discovery moment favourite one out day next the for ready toget and back got we’d what just understand and totry afternoon every convene D discovery. of a day for it for substitute could that another we had system one on failed subsystems of its (YHU another about for data sending tokeep it toallow power enough has it that sure pretty space interstellar reached far how space interstellar toreach totravel have would farthey how or last would the long in space years 40 last could that anything old was only age space the W things will work. thatoptimistic somehow be to you have space in I think if you’re doing research spacecraft other 96 Z LEGACY:A GRAND THE VOICES OFVOYAGER surface and the polar cap on on cap polar the and surface S the in bodies the diverse how just todiscover ajourney on were T volcanic than activity J of amoon –just was amoon on here were before seen we had unlike anything circularised was orbit its and was captured I amoon became and Neptune P P T T surprised. We getting kept t had a different history as it as it history adifferent t had upiter – that had had –that upiter riton olar luto before it was captured by captured was it before luto luto one had redundancy on many hat’s when we really realised we realised we really when hat’s he last object we visited was we visited object last he uring the encounters the uring hen .

www.skyatnightmagazine.com W . \ And . S

, I e had no experience with with experience no e had which is about the sizeof the isabout which . V GD t probably was a sibling of was asibling t probably ystem are ystem

, Y because because oyager was launched . ou could see the icy icy the see could ou

V W \ , ofcourse oyager spacecraft spacecraft oyager RI . e didn’t know how how know e didn’t

T .

E riton was a body was abody riton I D t’s hard to pick topick hard t’s arth Ɔ\ . . S .

V , Now we know we Now know V so if anything ifanything so olar 1 E . oyager oyager oyager was oyager And yet here yet here And 0 times more more 0 times , \Z we had the the we had E , S we would we would .

arth DV 1 ystem ystem I 2 0 years t was 0 years 0 years . . 1

. W

U o has has T .

p he e’re ,

. and electrons and I plasma ofionised pocket a giant bubble called the heliosphere temperature frozen was T interstellar space. Voyager 1 had entered Eventually we realised cold severe the despite so cap polar that on W [ zero above absolute 40°C about T geologic activity occurring activity geologic speeds supersonic until space more and 6RLWƅOOVPRUH the from further gets it as weaker gets is outside is heliosphere the inside density W anyout further it can’t push coming from other stars other from coming t’s hydrogen mainly – riton was nitrogen he 27 1 e saw two of them erupting erupting ofthem two e saw e know that the plasma plasma the that e know 00 times less dense than it it than dense less times 00 3°C , S eventually un creates this huge huge this creates un , but it it but ], so even the nitrogen nitrogen even so the S , where the plasma is plasma the where un . But even at that that even at But , there were geysers were there .

, pushing out at at out pushing . ,

there was still was still there ,

, I protons protons t was cold “Voyager was at right planetary missions” us how to all mount how us its time and ittaught and its time the cutting edge for for edge cutting the .

W . e saw e saw the subsequent subsequent the ,

Golden Records the for greeting of a message who provided Jimmy Carter, President meets U Ed (left) Ed (left) per cent the speed oflight speed the cent per ZLQGLVDFFHOHUDWHGWRDERXWƅYH solar ofthe some heliosphere the space interstellar entered and 9 when 40 ofabout by afactor a jump inside particles would disappear disappear would particles inside before we’d that seen never an intensity out back them sweeping keeps wind oftheir stripped been have T rays. cosmic was space when it reached interstellar Voyager 1saw thing Another outside ofthem none but heliosphere the point that at ion anenergetic called hese are heavy ions that that ions areheavy hese R\DJHUƅQDOO\OHIWWKHEXEEOH T , he other clue was that inside inside was that clue other he but we saw them jump to jump them we saw but .

T .

[ W . here’s lots of those inside inside ofthose lots here’s

in the plasma density plasma the in W e’d predicted that the the that e’d predicted e saw them disappear them e saw because the the because S the into getting KDYHGLIƅFXOW\ ago years 5-1 that occurred supernovae come from electrons olar 0 million 0 million S ystem ystem . .

T I T t’s hey hey ] .

. THE STORY OF VOYAGER

, .

. Q L ilky here 225 T M

making making . , RDW Ɔ

. V . WKDW hey’ll be out there but can we today , T

. at least not very e can’t measure the , W

. DWRPV ou can do things better o we are limitedo we Y S

. telling whoever might . , UDO X e can only measure charged ay for billions of years oyager right was at the cutting he probes will remain in orbit DW arth better V edge for its time and it taught us how to mount all the subsequent planetary missions space. interstellar W particles ƆRZRIWKHZLQGRXWVLGHWKH heliosphere accurately – especially the faster winds with the technology that’s that’s technology the with emerged in the last 40 years can’t we things some are There measure with the Voyager probes, though, such as the Q are some things that couldn’t we measure then The Voyager missionThe Voyager reallywon’t end. ƅQGWKHPDERXWWKHSODQHW from came they T around the centre of the carrying from messages their E W an orbit about once every million years

, .

. but hat hat , T

. hat’s hat’s we know , ystem T o

S . ome of I

. www.skyatnightmagazine.com www.skyatnightmagazine.com . S

they’ve . , olar olar sensors are , S V \ oyager completely completely oyager E alileo did V

G . Ɔ\ venthough they started E

. PRUH hey’re quitehey’re different from each eptember this year this eptember nceladus that were discovered ou still discover interesting and n terms of planetary science evolved differently evolved Cassini by and how each of them has had history. geological unique a T other out insimilar ways them are still active is active with its volcanoes there are geysers erupting from E now is the time to go into orbit so that can we explore these objects in much more detail Y phenomena unexpected Looking forwards, I think the the think I forwards, Looking not to is consensus general GR I whatwas what Cassini will be doing until S did we With pretty Voyager, much everything could you do at the time. Now technology is much more computational – advanced power is greater changed our view of planets and our view of the A GRAND LEGACY: THE VOICES OF VOYAGER VOICES THE A GRAND LEGACY: Journalists U question Ed regarding Voyager’s encounter with 1986 in Uranus

. 2

1 the , oyager . o we sawo we V t did jump I

S .

oyager . V un has created but instead , S . or example or F so it still has a few

, . HƅJXUHGLWZRXOG But because it’s but it didn’t change . , and that’s what we , : e also predicted that the W

. he only signature we T t’s still inside the heliospheric plasma density would be higher and saw we that too is passing through is a different size to section that when went outside we and the outside particles would be at a maximum saw bubble that the greatestVoyager’s legacy is the diverse how just revealing bodies of the Solar System are didn’t see a change was in the PDJQHWLFƅHOGGLUHFWLRQZKLFK expectedwe to differ intensityin GLUHFWLRQ change direction just becameit stronger enter won’t 2 Voyager interstellar space for a while. I part of the heliosphere through passed following a different trajectory already seeingwe’re things that different are the signatures that expected we itself around years to go THE STORY OF VOYAGER instruments their down toshut have will another for power provide able be should thermoelectric generators the probes’ radioisotope T need to conserve their energy birthdays 40th totheir get spacecraft two the closer the the space agency hopes agency space the enough –long aspossible long as for going both them keep 98 LEGACY:A GRAND THE END MUCH LIKE AGING he meet their end?

V www.skyatnightmagazine.com oyager team estimate estimate team oyager , the more they they more the 1 , one by one one 0 years How will the Voyagers V , oyager oyager but NA but athletes , , to for for S A , .

between A one that you realise until much ƅJXUHVPLJKWQRWVRXQGOL approximately of adistance at from us while uswhile from astronomical units expected to transmitted space in interstellar join and heliosheath V T hey’ll be far enough away that that away farenough be hey’ll oyager oyager U I f the last science data is data science last f the is equivalent to the distance distance tothe isequivalent 2 E ,

to punch through the the through topunch V arth and the the and arth oyager oyager V 15 E oyager oyager 1 arth in arth 4 0 million km 0 million 2 ( 1 A . A

will be be will V U. U) oyager oyager 2

2 away S T will be be will 0 un hose N 25 H 16 ,

as . 9

THE VOYAGERS VOYAGERS THE 20.7 billion km km billion 20.7 Location: RIGHT NOW? 17.1 km billion VOYAGER 2 VOYAGER 1 WHERE ARE ARE WHERE heliosheath Interstellar Interstellar Distance: Distance: Location: (139 A (139 (114 A (114 space U U The The ) )

Words: Ben Skuse Words: Ben their abyss carrying the into hurtle asthey down them slow can the from nothing life in the the life in is there that know them let and civilisations alien spacefaring envoys encounter just might odds bottles in messages expensive become pass by they environments the record to meet them to meet No longer able to measure and and tomeasure able longer No , G it’s possible our interstellar interstellar our possible it’s olden .

, the the D espite the inconceivable M ilky ilky V R oyager probes will . ecords V W S ay and it wants wants it and ay olar .

S ystem ystem ,

BACKGROUND: MARK GARLICK, VOYAGER: YAY MEDIA AS/ALAMY STOCK PHOTO TECHNOLOGICALLYSUPERIOR NEW TELESCOPES Smartphone Adapter Removable Flashlight FROM CELESTRON

Get inspired by Celestron! The ultimate telescope for the novice to intermediate astronomer, the Inspire range is loaded with exciting new features. The innovative lens cap converts to a universal smartphone adapter for imaging with your phone. The mount has a built in red ﬂashlight to illuminate the accessory tray. Conveniently, the ﬂashlight is Inspire 100AZ Refractor also easily removable for use independently. Available apertures: 70mm, 80mm and 100mm

Celestron is not only changing the way we experience astronomy, but we’re also changing the way you interact with the night sky. The Astro Fi range can be controlled with your smart phone or tablet using the free Celestron SkyPortal app! It’s never been more fun to explore the universe!

Available apertures: 90mm, 102mm and 130mm iPAD and iPHONE SHOWN NOT INCLUDED.

Available from: F1 Telescopes 01795 432702 First Light Optics 01392 791000 Green Witch 01924 477719 / 01767 677025 Grovers OpticsShop 01609 898098 Astro Fi 130mm Newtonian Harrison Telescopes 01322 403407 Rother Valley Optics 01909 774369 Sneezums 01284 752 634 Tring Astronomy Centre 01442 822997 The Widescreen Centre 020 7935 2580

Celestron is distributed in the UK & Ireland by David Hinds Limited. Trade enquiries welcomed. www.celestron.uk.com @David_Hinds_Ltd

Celestron®, InspireTM and Astro FiTM are registered trademarks or trademarks of Celestron Acquisition, LLC in the United States and in dozens of other countries around the world. All rights reserved. David Hinds Ltd is an authorised distributor and reseller of Celestron products. The iPhone®, iPad® and App Store are registered trademarks of Apple Inc. Google Play is a registered trademark of Google Inc. TECHNOLOGICALLYSUPERIOR

THE NEXSTAR EVOLUTION KEEPS EVOLVING

Now paired together, enjoy the EdgeHD 8” optics and NexStar Evolution 8” EdgeHD StarSense AutoAlign on the Evolution Mount. All controlled with StarSense AutoAlign from your favourite iOS or Android phone or tablet with the new SkyPortal App. iPAD and iPHONE SHOWN Upgrade your NexStar Evolution for longer NOT INCLUDED. exposure astrophotography with the new Evolution equatorial wedge.

NexStar Evolution 6” SCT NexStar Evolution 9” SCT

Equatorial Wedge

Available from specialist astronomy retailers and selected other dealers nationwide. Celestron is distributed in the UK & Ireland by David Hinds Limited. Trade enquiries welcomed. www.celestron.uk.com

Celestron® and NexStar® are registered trademarks of Celestron Acquisition, LLC in the United States and in dozens of other countries around the world. All rights reserved. David Hinds Ltd is an authorised distributor and reseller of Celestron products. The iPhone® and iPad® are trademarks of Apple Inc., registered in the U.S. and other countries.