Milestones in Airborne Astronomy: Fro 1920'E Presene Mth Th O St T

975609 Milestones in Airborne Astronomy: Fro 1920'e Presene mth th o st t

Wendy Whiting Dole! NASA Ames Research Center

THE ECLIPSE OF SEPTEMBER 10, 1923: ASTRONOMY FROM BIPLANES ABSTRACT One of the first airborne astronomy attempts was undertaken f airplaneo The e us astronomicar sfo l observations began ni e solaNavyS th U r r e fo beclips, yth f Septembeo e , 10 r the 1920's. From then unti earle lth y 1960'se , th almos f o l al t 1923. 2 This was an extensive effort involving sixteen Navy observations made from aircraf e purpost th wer r f fo eo e planes, including an F5-L "flying boat" biplane. Although viewing solar eclipsesadvanceo t e Du . s hi technologd yan records of all the aircraft involved are not available, the fleet increasing interest hi infrared astronomy airplanef o e us e s th , most likely also include r moro e e don DeHavilan d DH-4B for astronomy expanded during the 1960's to include biplanes. The primary objective of the expedition was to planetary observations and a wide range of other studies. This determin centerline eth eclipse th f eo e e th fro n aire O mth . paper describes some of the major milestones of airborne mornin f Septembego e aircrafth , werd 10 rt an too ef of k astronomy, from the 1920's to the present. positioned along the expected path of totality, at altitudes ranging from 5,500 - 16,500 feet. Some useful visual INTRODUCTION observations were made by the flyers, and thirty photographs were exposed e photograph t nonth bu f , o e s successfully The history of airborne astronomy goes earl e bacth yko t days recorded the eclipse. Although the expedition could be of aviation itself, with the first airborne observations made considered a failure in some ways, it was successful in from biplanes durin 1920'e g th 1930's d san . Unti 1960'se th l , attractin attentioe generae gth pres th e d th f slan n o public d an , airborne astronom s predominantlwa y y undertakee th r nfo in generating popular support for airborne science. purpose of observing solar eclipses. The aircraft's mobility Newspaper accounts credite Nave dth y with comine th o gt allowed cloud-free observing time e mosth f ,o tplacemen f o t rescue of astronomers! the instrumentation at the exact geographic location desired, and increase time dth e spen totality n i aircrafte th s a , t could notablIs i tpilot e th f seo involvethae on t192e th 3n di eclipse stay within the shadow much longer than a ground-based endeavo s Captaiwa r n Alber . Steven Arme W t th r f yo Ai s observer. A turning point was reached during the mid-1960's Corps, an accomplished aerial photographer who is considered when the invention of new infrared sensors caused infrared bfathee yth somairbornf e o rb eo t e astronomy.s hi This swa astronom flourisho yt . Also importance th , ascendinf eo o gt first airborne solar eclipse flight. He went on to participate in high altitudes into regions of cold, dry atmosphere was Honee th y Lak Nationad ean l Geographic Society airborne realized. These events, coupled with the increasing eclipse expeditions described below, as well as many other availability of jet aircraft during the 1950's and more missions from aircraft and balloons. In the 1920's Captain sophisticated telescope technologies rapie th do t extensiod le , n Stevens set altitude records from airplanes, recording the of airborne astronomy into areas other than eclipse studies, temperatures at the boundary of the stratosphere during those beginnine th s and wa f airborn go e astronom knoe w ws t yi a "aeronautse th flights f o durin d e an ,1930'e on o "t gth s swa today. ascend hi balloons durin stratosphere e "race gth th o et " .3 Countless astronomy flights have been carried out more or less continuously fro 1920'se mth researcr ,fo enjoymentd han y b , 1930: THE HONEY LAKE EXPEDITION scientists and non-scientists alike. The April 1979 issue of 1 Foeclipse th r f Aprio e, 1930 Nava28 e l th , l Observatory Life magazine r examplefo , , states that there wer t leasea t 2 1,00 eclipse 0th planer ah e f Februarfo -eth o n si , 1979y26 . organized an expedition to Honey Lake, CaliforniaJ ^This This paper describes some of the important milestones hi eclips particularla d eha y short perio totalitf do yonl- 5 y1. airborne astronom detailea y- d histor airbornf yo e astronomy is beyon scopes dit . Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

seconds -" and a narrow ground shadow. Because of these 1932: THE NATIONAL GEOGRAPHIC SOCIETY / ARMY constraints, not many astronomers made plans to observe the AIR CORP SECLIPS- E PHOTOGRAPHYR FROAI E MTH event. However, it offered a good opportunity to observe the exact centerlin eclipsee th f eo , neede mako dt e correctiono st Building on the experience of the 1923 eclipse and the Honey the lunar s almanactailor-madwa d an , o exploit e e th t Lake expedition, Albert Stevens undertook his third airborne advantages of observing from aircraft. eclipse expeditio 1932.n i This expeditio joina s t nwa effor t Arme oNationae fth r Corp th yAi d san l Geographic 4Society. Two naval aircraft, a Sikorsky PS-3, and a Vought O2U-1, The National Geographic Society had a ground party in place were secure expeditione th r dfo Sikorske Th . uses ydwa o t to study the eclipse, and was interested in recording the transport peopl equipmend ean Honeo t y Lake Voughe Th . t positio shadoe th movet f i n o ws a d acros earthe sth , whics hwa 02U-1 was equipped with an Akeley motion picture camera best done from high altitude. for recording the eclipse shadow on film. The pat f totalitho r thiyfo s eclips s oveewa r Mainew Ne , Hampshir Canadad ean . Captain Stevens too frof kof m North Conway Hampshirw Ne , eclipsn eo e day, with three cameras on board: a long focal-length camera for photographing the corona, and a medium focal-length camera and a short focal- length camera for photographing the shadow. In addition, an electroscop onboars measuremene ewa th r dfo cosmif to c rays.

e eclipsTh e photograph altitudn a s carriet a f y wa t eo dou 27,00 thosn I . e0ft days, flyin t sucga higha h altituda s ewa challenge in itself. Captain Stevens was in the back of the airplane manipulatin camerase gth communicated an , d with the pilo shory b t t shrieks r "yips" o yip,o sTw .mean t turn right. More double yips meant keep turningp rightyi e on , meant turn left, and so forth. The plane was open cockpit, and keeping warm was a major problem. The aviators bundled up, head-to-toe, in layers of wool, down, and leather clothing, but Photograph from the archives of Dr. Eric R. Craine still reported problems wit e coldhth , particularly frozen fingers and toes. The crew used oxygen, but Captain Stevens Figure 1. The O2U-1 flying over Honey Lake. reported that nevertheless, it was easy to become disoriented in helo flightt pd reminan , d himsel f cruciao f l procedures, The expeditio successa s groune nwa Th . d observers, through wrote instruction largn i s e letter tapn o s e attachee th o dt breake cloudsth n i s , recorded film that showed thae th t apparatus. ground station was within the shadow. The film obtained from the Vought O2U-1 recorded the approach of the shadow Captain Stevens, by quick sequential manipulation of the three and was used to verify the correctness of the predicted path. cameras onboard, captured a series of excellent photos of the moon's shado approachedt i ws a durind ,an g totality obtaineda photograp solae th f rh o coron a usin infraren ga d filter. These photos were publishe Nationan di l Geographic Magazine's November 1932 issue. The National Geographic article, written by Captain Stevens, describes in detail the difficulties encountered during this flight, including a tangling of his oxygen hose with the camera losa , enginf so e power causesnaggine th e y dth b f go pilot's glove on the throttle and ensuing dive to recover control, and the numbing of his hands as they struggled to operat camerae e bitteth e th n rsi cold. 1945: ROYAL CANADIA FORCR NAI E "OPERATION ECLIPSE" For the eclipse of July 9, 1945, the Royal Canadian Air Force (RCAF) carried out observations from four aircraft: a Spitfire, a Mitchell, and two Ansons.5 This effort was part of a series Photograph from the archives o: of ionospheric observations sponsored by the Canadian Radio Wave Propagation Committee. Although the focus of this Figure 2: Chief photographer (left) and pilot on the O2U-1 expedition was not strictly on astronomy, it's included in this aircraft used during the Honey Lake eclipse mission. Akeley paper because it is a good illustration of the technology that motion picture camera is in the background. was in use during the 1940's, which had improved very much sinc 193e eth 2 eclipse observations described above. Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

Three of the aircraft involved in the RCAF operation were OPEN-DOOR OBSERVATIONS DURIN ECLIPSE GTH E outfitted with a total of seven standard cameras, of the type OF JUN , 195E30 4 commonly used at that time for aerial photography. The second Anson carrie a dmotio n picture camera. eclipse Th Junf eo e 30,195 observes 4wa d fro opee mth n door Spectrographic and polarization measurements were made, as of a special Lincoln aircraft flying at an altitude of 30,000 ft.7 wel visuas a l infrared an l d photograph solae th f rs o coron d aan Photographs obtaine flighn di t were use derivo dt e coronal prominences. brightnes polarizationd san , along witbrightnesy hsk d an s polarization, and their variation with altitude. Details of the Ther severae ear l notable differences between this efford an t operation are only briefly described in a lengthy article by the expeditions described above altitude aircrafe Th th . f eo t D.E. Blackwell, published in Monthly notices of the Royal ranged between 17,000 ft and 34,000 ft. The cameras were Astronomical Societ 1955 n yauthoi e Th . r make assertioe sth n mounted behind special plate glass windows l excepal d tan , that airborne astronomy observations should be made from an one were adjuste o automaticallt d y take exposures, once open port in the aircraft, not through an aircraft window. started. Threaircrafe th f eo t wer propeee kepth n to r heading Regarding observatio 195e th 4f no eclipse authoe th , r notes using a modification to the pilot's gun sight; the pilot kept the founs wa tha dt "i tmos t convenien folo aircrafe t dth t door sun centered on the sighting rings, which kept the cameras mouno t bac d camere opeke an tth th nn a i doorwa sucn yi ha pointing at the sun. The spectra obtained during the mission way that it could be guided in altitude and azimuth". may be the first ever taken from an aircraft. Althoug aircrafe h th capabl s wa t fligh43,00f o et o p u t 0 e ft.th , observing altitud limites ewa 30,00o dt 0 ft.givo t , e "the best compromise between sky darkening on the one hand, and 1948: THE NATIONAL GEOGRAPHIC SOCIETY'S aircraft stability and observer alertness on the other hand." "OPERATION ECLIPSE" EARLY 1960'S: EVENTS COINCIDE TO CREATE A For the annular solar eclipse of May 8, 1948, the National MAJOR TURNING POINT IN THE HISTORY OF Geographic Society organized an expedition unprecedented in AIRBORNE ASTRONOMY size. Observers were statione groune th n Burmado n di , Siam, China, southern Korea ,Aleutia e Japanth d an ,n Islands. A remarkable serie eventf so s durin earle gth ya 1960'o t d sle Two B-29 aircraft were also stationed in the Aleutians, as a rapid increase of activity in airborne astronomy. In 1963, the backue grounth o t pd observers, because higth hf o e first major eclipse mission aboard a jet aircraft was probability of bad weather. successfully carried out. Sponsored by the National Geographic Societ Douglad an y s Aircraft Company, this A t turnei s d outweathed ba , r interfered withe mosth f o t mission prove feasibilite dth usefulnesd yan observationf o s s ground observations, a major disappointment, especially for fro t aircraftmje . an operatio sizes it f n.o However, observers aboar- B e dth 29's, ascendin 27,00o gt 29,00d an t 0, werf 0 ft e successfun i l Also durin e earlgth y sixties s performin, wa Fran w kLo g obtaining photographs during totality. pivotal experiments that would expan e windodth r wfo infrared observations, up to 1000 microns. The invention of These observations were mad spit n riskei a f eo y situation that Gallium-dopee th d Germanium bolometen ri detectow Lo y rb develope optical-glasflighte n di th s a , s domes that housee dth 19618, and his efforts in performing observations using open- cameras began to crack. Both aircraft experienced the trouble, port instruments on aircraft, were vitally important hi the loud groaning sounde glasth s a scracke d causing furtherin developmene gth airbornf to e astronomy. considerable tension amongst the observers. Luckily, the domes held, and both aircraft landed safely, having 196e Th 3 signin Atmospherie th f go c TesTreatyn tBa , which successfully recorded the eclipse. The National Geographic banned the testing of nuclear weapons in the atmosphere, article about this event reports on the "triumphant crews" prompted scientists from the Los Alamos Scientific landing at Amchitka after the eclipse mission. Laborator proposo yt alternatn e a thref o e e eus NC-13 5 test readiness aircraft. They suggested that the aircraft, originally The ultimate purpos Nationae th f eo l Geographic Operation intended for use as airborne laboratories kept in readiness Eclipse was to make measurements that could be used to should nuclear testing again become necessary, be used for determine more accurately the relative locations of points on solar eclipse observations. Their proposa approveds lwa d an , the earth's surface. Again, the focus was not on astronomy. three th e aircraft were made availabl highla r efo y successful However, it was an important milestone in the history of series of solar eclipse missions, carried out from 1965 to 1980. airborne eclipse observations, becaus e succese eth th f o s Each of the events described above is written up in more detail airborne observations stood out in such contrast to the largely in sections below. unsuccessful ground operations e stor f Th Operatioyo . n Eclips 47-pagwrittea s ei n i p nu e articlMarche th n ei , 1949 And finally, the period from January 1,1964, to December 31, editio Nationaf no l Geographic magazine authoe Th . r offered 1965 was designated the International Quiet Solar Year two conclusions aircraff o e r whicf o us fo ttha s e e htwa th ,on (IQSY) predictee ,th d minimu solar mfo r activity. Durine gth astronomical observations held great promise, as a kind of IQSY, scientist ovel worlsal e rth d participate coordinaten di d "eclipse insurance" for future expeditions. The importance of measurements of solar phenomena. airborne observations was again shown, with high public visibility. Perhap above consequenca th s f a seo l evental d f o ean s circumstances feweo n , r than four 4-engin t aircrafeje t were deployed to the South Pacific for the solar eclipse of May 30, 1965 Atomio -tw c Energy Commission (AEC) NC-135's were Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

stationed in Samoa, and the newly-acquired NASA CV-990 Forcr Ai an en da KG-13 5 were statione Hawaii.n de i th r Fo eclips f Novembeo e r 1966 e aircrafthirC th ,s AE d wa t 9 deployed l fival ed aircrafan , t participate a massiv n i d e coordinated effort, which also included simultaneous rocket experiments.10

1963: NATIONAL GEOGRAPHIC SOCIETY DOUGLA- S AIRCRAFT COMPANY ECLIPSE EXPEDITION

The National Geographic Society (NGS) and Douglas Aircraft Company collaborate organizdo t majoea r airborne expedition Jul e fo, 196th ry 20 3 eclipse11. Fifty-five scientists operated 25 scientific experiment DC-a n so 8 aircraft, whic beed hha n Douglas Aircraft Photo leased from. Delta Airlines for the event. This was an international mission, involvin ga doze n organizationn i s Figur . e 3 InterioAPEQeth f o rS DC-8, showing addition to the NGS and Douglas Aircraft company. instrumentation installed alon righe gth t side. The project was called APEQS - Aerial Photography of the The APEQS scientific director and author of the National Eclipse of the Quiet Sun. All seats on the right side of the Geographic magazine article describin evene gth t wrote th f eo aircraft foud an r,lefte rowth , n wero s e remove mako dt e "far-reaching conclusions thaalreadn ca t drawn..e yb . that room for science instruments. Among these was a 700 Ib point to a new era in astronomical observation." A quote spectrograph to be used for recording a spectrum of a narrow from one of the scientists onboard the mission ends the article. band of the sun's corona. The spectrograph was mounted on a He said, "In such an observatory, astronomers could 6-inch telescope that received light fro mgyro-stabilizea d conveniently conduct many valuable experiments...in addition heliostat tracking mirror. Thi stabln s kepsu image e tth th f eo to those concerning eclipse sun.e th f "so accurac n minutec a ar o t 1 f y.o Coincidentally, the scientific director of the Douglas/ NGS The DC-8, flying at 525 miles per hour in the direction of the eclipse expeditio s Wolfganwa n . KlempererB g n a , shadow's movement ove earth e altitudn rth a t a , 40,50f eo 0 ft, aeronautical engineer who helped design the National stretched the time of totality to 142 seconds, compared to 100 Geographic - U.S. Army Air Corps stratospheric balloons in seconds see observery nb grounde th n so . Amon mane gth y 1934-35. Albert Stevens, mentioned earlier in this paper as observations made were infrared measurements of the sun's th earliese pilofleth o n wo twh t airborne eclipse expeditions, upper atmosphere. flew on the stratosphere balloon flights in 1934 and 1935. observere Althougth l al t thei t sme hno r flighte goalth r ,sfo Klemperer's assistant at the control desk of the DC-8 during overall it was a highly successful mission. This was a the 1963 eclipse fligh Robers wa t t Camero Douglaf no s significant milestone in the history of airborne astronomy, Aircraft. Dr. Michel Bader of Ames Research Center directed demonstrating clearly the potential of using jet aircraft for one of the science teams aboard the aircraft. Bader and airborne astronomy aircrafe Th . t prove dstabla e platforr mfo Cameron (who later went to work for NASA) became key science instruments and could fly fast at high altitudes. participants in the start-up of NASA's airborne science program.

Douglas Aircraft Photo Figure 4. DC-8 aircraft leased from Delta Airlines for the National Geographic Society - Douglas Aircraft APEQS solar eclipse mission in 1963 Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

1965: THE BEGINNINGS OF NASA'S AIRBORNE ASTRONOMY PROGRAM ABOAR E CV99TH D 0 The Galileo I was used for astronomical observations during GALILEO OBSERVATORY the late 1960's and early 1970's. The major Galileo I airborne astronomy missions are summarized inTable 1. From their experience historie th n so c National Geographic- Douglas Aircraft expedition in 1963, scientists at NASA Ames Table 1. NASA CV-990 Galileo I astronomy missions were convinced of the potential for the use of high-flying jet aircraf r astronomyfo t . Throug efforte hth f teao s m leader Year Galileo I Mission Michel Bader Convai,a aircraf0 purchaser99 s wa t NASy db A 5/65 Solar eclipse in 1964 for use as an airborne science platform. Thirteen 10/65 Comet Ikeya-Seki apertures capable of holding optical-quality glass were 10/66 Solar eclipse installed along the upper left side of the fuselage. Its first mission was the solar eclipse of May 30,1965. 1967o t IR sola planetard ran y 1969 observations From the beginning, the NASA airborne science program was 8/6 10/67& 7 Solar constant studies open to scientists from around the country and the world. 8/71 Mars opposition expedition Settin stage gthisth r 196e fo ,th 5 mission included scientists 10/72 Giacobinid meteor shower from the US, Switzerland, the Netherlands, Italy, and expedition Belgium. Professor Guglielmo Righini from Itals wa y 1972 Solar eclipse onboar eclipse th d e flight. During totality lookee t h ,a t dou the eclipse and spotted the brighter moons of Jupiter, the first scientiste On th CV-99e f eo fleth o n wso wh 0 Galiles wa oI objects seen by Galileo with his telescope. Dr. Righini Gerard P. Kuiper, Director of the Lunar and Planetary Lab at immediately suggested thae CV99th t givee 0b name nth e the University of Arizona, who was interested in obtaining "Galileo"13. His suggestion was quickly approved by NASA. near-infrared spectra of bright planets, free of contamination The CV-99 operates 0wa d from 196 19735o t , when tragically from the Earth's atmosphere. Flying on the CV-990, using a the aircraft and everyone onboard were lost hi a mid-air telescope with a gyro-stabilized heliostat to achieve accurate collision while attempting to land at Moffett Field, CA. pointin guidingd gan . KuipeDr , r obtaine dremarkabla f o t ese NASA replace e Galiledth o with another CV-990, called near-infrared spectra of Venus, showing that the clouds of Galileo II, which was used very little for airborne astronomy, Venus wer madt e no beewaterf d eo ha n s widel,a y believed. as, by then, the Learjet and the Kuiper Airborne Observatory During another mission in 1971, Dr. Kuiper's team, and were in operation. another group from Cornell University made observations of Mars during opposition.

Figur NAS. S e A CV-99 0Galile- : oObservatioI n window seee b nn alonsca uppee gth r left side of meluseiager as well as special ports in me passenger windows. 5 Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

Before ratifyin e 196th g 3 Nuclear Testreatyn Ba t , which prohibited nuclear tests in the atmosphere, outer space and underwater, Congress required that certain safeguards be put in place. One of these was that the U.S. should maintain the abilit resumo yt e nuclear tests quickl necessaryf yi shoulr o , d there be any abrogation of the treaty. To satisfy at least part of this requirement, the Atomic Energy Commission obtained joint interest in three NC-135's maintained by the Air Force, and modified them for use as flying laboratories.14 To keep the aircraft crews activ capabld ean f faseo t deploymente th , AEC performed exercises using simulations instea reaf do l weapons tests.

The aircraft were made available to the Los Alamos Scientific Laboratory (LASL, late becomo t r s AlamoLo e s National Laboratory) e Sandith , a Laboratory e Lawrencth d an , e Livermore Laboratory. These three laboratories were each NC-135'se assigneth f o e d,on although they were availablo et the other labs and used interchangeably, as programmatic and science needs dictated. The individual histories of each of these aircraft, and their use by each of the laboratories, is beyon scope dth thif eo s paper. Included her summara s ei f yo NASA photo the Los Alamos Scientific Laboratory's use of the NC-135's Figure 6. Robert Cameron and Earl Petersen on NASA's for a series of eclipse missions. Galile wit, oI Questaha r telescop gyro-stabilized ean d heliostat used during the Comet Ikeya-Seki mission in 1965. The same yea treate s signedth r ywa scientisto tw , s from LASL traveled to Northern Canada for the eclipse of July 20, 1963. Frustrate cloudy db s which obscured theire vieth f wo eclipse and swarms of stinging mosquitoes, and aware of the succes NGS/Douglae th f so s Aircraft mission, they proposed that the AEC NC-135's be used for airborne observations during the May 1965 eclipse. - There was much popular support amongst the scientists15 a1t6 LASL for this proposal, as they wer t findineno simulatioe gth n exercises particularly satisfying e proposaTh .s accepted seriee wa lth f d o s an , eclipse flights was born.

The aircraft were already equipped with the best communications equipment available, and windows for various types of observations; they were well-suited for airborne eclipse studies. In May of 1965, two of the three AEC NC-135's were deployed to American Samoa for solar eclipse observations by LASL and the Sandia Laboratory. The first LASL mission was led by astrophysicist Arthur Cox; hi preparation for the mission, Cox and his fellow scientists worked feverishly to install special equipment for solar observations, including stabilized platforms for the HA SphotA o instrumentation. The mission was a success, and LASL Figure 7. Gerard P. Kuiper (second from left) onboard scientists went on to carry out six more eclipse expeditions, in NASA's CV-990 Galileo observatory. With Dr. Kuiper are 1966,1970, 1972, 1973,1979, and 1980.17 (left to right) Dale Cruikshank, Ferdinand DeWiess, and Godfrey Sill. On manf eo y notable aspect firse th tf sLASo L eclipse mission wa firse sth t airborn 10-inca f o e heus diameter, 80-inch focal 1965 TO 1980: AIRBORNE OBSERVATIONS WITH length refracting telescope calle "Rube dth e Goldberg", after ATOMIC ENERGY COMMISSION NC-135 AIRCRAFT the popular cartoon contraptions of that name. Designed by a Donalgrouy b d ple d Liebenber LASLf go "Rubee ,th s "wa An interesting chapte histore th n f airborni ry o e astronomy modified extensively ove yeare rth incorporato st ideaw ene s concerns the use of three NC-135 aircraft operated by the and technologies, and was considered the workhorse of the Atomic Energy Commissio solar nfo r eclipse observations. LASL eclipse missions.18 Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

Photo fro archivee mth Williaf so m Regan NC-13C FigurAE : Alamo5s 8 e useLo y db s National Laborator eclipsr yfo e missions from 196 19805o t .

configuration 1-ince Th . h thick quart- z windowCV e th n so 990 only allowed transmission of infrared radiation out to about 5 microns; in addition, the 12-inch windows restricted telescopee size th f th eo s used. During 196 s colleagu1967d hi 6an d , an Fran ew CarkLo l Gillespie started experimenting wit 2-incha h telescope aboard U.Sa . Navy Douglas A3-B bomber. researcserie4 1A 91 f so h flights were performed, usin helium-coolega d Germanium bolometer mounted on a ball-and-socket fixture in a canopy of aircrafte th . Flyin t altitudega s from 40,00 44,00o 0t 0e ftth , first far-infrared airborne observations were made, recording the solar brightness temperatur wavelengta t ea f 1mmho . Just after the solar measurements were made, the A3-B and its crew were transcontinenta losa n to l flight. n 1966I , recognizin open-porn a e nee gr th dfo t airborne telescope for far-infrared observations, Frank Low, at the suggestion of Gerard P. Kuiper, approached Michel Bader at Figure 9: The Rube Goldberg telescope used during eclipse Ames Research Centerdecisioe th d mads ,an n wa submi o et a t mission NC-13sC aboarAE e 5d th aircraft . proposal for installing an open-port telescope on a NASA Ames Learjet proposae Th .accepteds wa l 12-inca , h open- port reflecting telescop s designeewa installed dan a n di 1968: NASA'S LEARJET OBSERVATORY TAKES TO passenger window location, and the first astronomical THE SKIES observations aboar Learjee dth t took place hi October, 1968. During the pioneering early flights of the Learjet observatory, Encouraged by the infrared observations made on NASA's major obstacles were overcome, including researchind gan CV-990 aircraft, scientists at NASA Ames began planning for solvin probleme gth s associated wit open-porn ha t airborne a larger telescope that could be installed in an open port telescope, and the invention of the first chopping secondary mirror for subtracting of sky brightness from the signal. Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

buildin a gmuc h larger open-port telescope, which were eventually realized wit e developmenth h e Kuipeth f o tr Airborne Observatory (KAO) Learjee Th . t continuey fl o dt astronomy missions long after the KAO was put into service in 1974. Between 1968 and 1984, over seventy papers were published in astronomy journals, using data obtained on the Learjet. The NASA Learjet is still available for astronomy missions today.

1973 MINUTE4 :7 TOTALITF SO Y ABOARE DTH CONCORDE 001 On Jun, 197330 e , scientists aboar e British-Frencth d h Concorde 001, traveling at nearly 1300 miles per hour at altitudes over 50,00 , experience0ft drecord-breakina 4 g7 minute f totalityo s e aircraftTh . , laden with scientific instrument observerd san s from France, Englan U.S.e th d , dan too fro f Palmas k of Canarme La th n si y Island fled swan 1800 miles across Africa, interceptin e moon'gth s shadow over Mauritania and landing hi Chad, central Africa. scientiste On th Concorde'e f eth o n so s historic flighs wa t Donald Liebenberg, leader of the team that built the "Rube Goldberg" telescope, and vetera LASL'f no s NC-135 eclipse NASA photo missionsConcordee flighs th hi n r o t Fo . , Liebenberg useda Figure 10: Carl Gillespie with NASA's Learjet telescope. specially-designed 3-inch telescope, whice h th lookef o t dou aircraft through one of five silica quartz windows installed in Flyin 45,00t ga 50,000o t cabia 0d ftnan , altitud f 18,00eo o 0t the Concorde' aircrafte speee th th f so do t roofe , whicDu . h 25,000 ft, observers aboard the Learjet discovered a host of nearls movemene wa th fass ya s moon'a te th f to s shadow over bright infrared sources; this work showed the usefulness of the earth, observers on board were able to view the eclipse hi airborne infrared astronom r planetaryyfo , stellar galactid ,an c slow motion. The moon moved across only 20 km of the sun's studies. Discoveries during the early flights of the Learjet atmosphere per second, compared to 200-300 km per second telescope include: the first measurement of the internal for observers on the ground. This, for example, gave the energies of Jupiter and Saturn, far-infrared observations of the airborne observer second0 s5 vieo s t 100e wregioth m 0k f no great nebul Orionn ai , studie staf so r formation regione th d san the sun's atmosphere, compare onlo dt secondy3 groundr sfo - bright IR sources at the center of the Milky Way galaxy. based observers. Another objectiv researche th f eo , made e earlAlsoth yn i , 1970's, near-infrared spectroscopa y yb possible by the long time spent in totality, was to look for NASA Ame sJamey teab d msle Pollac Edwid kan n Erickson oscillations in the sun's corona that occurred on a time scale of showed that the clouds of Venus are made from sulphuric acid about five minutes. Compared to ground observers, who droplets pulsatione woulon e Liebenberg'dse d an , s colleagues aboard the NC-13 woulo approximatel5e wh dse yminute4 two7 e ,th s totalitf o y aboar Concorde dth e would allow observatio2 1 f no pulsations.

Figur : NASe11 A Learjet exterior, showin telescope'e gth s open-port configuration. Photo fro archivee mth Williaf so m Regan Success on the Learjet encouraged scientists at NASA to Figur Donal: e12 d Liebenber LASLf go , showin locatioe gth n continue with their plans, underway since late 1965, for of silica quartz windows on a model of the Concorde 001. Copyright© 1997, American Institute Aeronauticf o Astronauticsd san , Inc.

NASA photo Figur : Kuipe14 e r Airborne Observator flightn e i y Th . telescope cavity door, located forward of the wing, is open. Another uniqu e differencth n i es telescopewa e designe th n O . CV-99 othed 0an r airborne observatories KAO e prioth o t r, gyro-controlled flat mirrors were often used to provide a Photo fro archivee m Donal. th Dr f Liebenber. so d H g steady image into the telescope. This allowed the positioning of long focal-length telescopes down the length of the aircraft. Figure 13: Donald Liebenberg of LASL, aboard the Concorde The KAO telescope was designed to balance on a 16-inch with instrumentation use durindn i 197e gth 3 eclipse. diameter spherical ah- bearing (believelargese th e b t suco dt h airbearing hi existence) entire th d e an telescop, gyros ewa - stabilized. The air bearing was imbedded in a pressure 1974 TO 1995: NASA's KUIPER AIRBORNE bulkhead separating the open port from the crew cabin. The OBSERVATORY bent-Cassegrain Nasmyth configuration allowed light from the telescop paso et s throug ahe h-th bearinreceivee b d gan y db The next step in NASA's airborne astronomy program was the instruments in the cabin, making it unnecessary for those installatio a 36-inc f o n h open-port reflecting telescope onboard to wear oxygen masks during entire observing onboar a dLockhee d C-141 Starlifter e projecTh s . wa t missions. approved by NASA in 1969, and the telescope design begun immediately originae Th . instalo lt pla s telescope nlth wa n eo the CV-990 Galileo I observatory. It was later decided that the C-141 woul mora e db e suitable platform; this changn ei plans also allowed the CV-990 to continue with important atmospheri meteorologicad can l research already underway. The C-141 was purchased and delivered to NASA in early 1972; test flights bega Aprin i n f e firs1973o lth t d ,an astronomical research fligh s conductewa t d hi Januarf yo 1974. In May, 1975, the observatory was dedicated as the Gerard P. Kuiper Airborne Observatory (KAO), in honor of Dr. Kuiper's contributions to infrared and airborne astronomy. Although built using the experience gained on the CV-990 and Learjet observatories, there were critical differences hi the design of the KAO that made it a far more versatile and efficient platfor astronomyr mfo mose Th .t obvious difference aircraft e telescopes sizth e it if sth d e o C-14an e , a Th .s 1i large, four-engin t transporeje t wit mucha h larger capacity than the Learjet Even with the installation of the three-times NASA photo larger telescope hi the forward section of the aircraft, and associated electronics rack controd san l consoles C-14e th , 1 Figure 15: Close-up of the KAO open port. This photograph was capabl f carryino e g approximatel scientist0 y2 d an s was ground e taketh n no techniciaa ; seee b nn insidnca e eth telescope crew in its cabin. The Learjet only had space for telescope cavity. two scientists. In addition, the typical KAO flight was 7.5 hours long, compared to a maxium of 2.5 hours on the Learjet. Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.

Figure 17: Photograph of SOFIA, now under development.

ACKNOWLEDGMENTS Much thank Bilo st l Regan, Public Information Officer during the LASL eclipse missions, for photographs, written materials and hours of conversation regarding the LASL flights. Thanks also to Donald Liebenberg for photos and written correspondence about the Concorde 001 flight and LASL NASA photo missions. And, Haughnethanku Lo o st timr yfo e spent poring over photos from the NASA archives, and for sharing his Figure 16: KAO telescope at NASA Ames, before installation recollection earle th yf s o CV-990 flightsO , LearjeKA .d an t aboard the C-141.

From fle197 O averagn w a 19954o researc t 0 KA 7 e f eth o , h REFERENCES flight yearr spe , fro homs mit e bas NASt ea A Ames Research Center, and as science needs dictated, from remote locations 1. Wheelwright, J. "Tracking our Last Eclipse of the Century" around the world. Life (April 1979): 110-118. Scientific output from the KAO was prolific. Some examples 2. Craine, Eric R. "The Beginnings of Airborne Astronomy: of scientific findings based on KAO observations are: 192 0193- Historican 0A l Narrative", NASA Conference discovery of the rings around the planet Uranus; detection of Publication #2353 Airborne Astronomy Symposium - water vapor in comets; discovery of Pluto's atmosphere; the Proceedings of a Meeting sponsored by NASA and the ASP composition, structure, and dynamics of Supernova 1987a; (July 11-13, 1984). luminosity, dust, and gas distributions in the Galactic Center; emission by shocked gas components of the interstellar 3. Stevens, Albert W. "Exploring the Earth's Stratosphere" medium e structurth d an ; f star-formineo g clouds. Other National Geographic (December 1926): 755-776. benefit programO sKA froe n additioi th e m, th o t n contribution o sciencet s , were e developmenth : w ne f o t 4. Stevens, Albert W. "Photographing the Eclipse of 1932 instrument and other technologies, the training of young from the Air", National Geographic (November 1932): 581- scientists particularl- d an ,las e th t n threyi O e yearKA f so 586. operations - an education program that included flight opportunities for schoolteachers. Millman. 5 , Pete "R.C.A.F. rM . Operation 'Eclipse'", Skd yan Telescope 47 (September 1945): 8-9,15. The KAO was grounded in October 1995, after a long and productive lifetime, in order to allow work to begin on the 6. Kinney, William A. "Operation Eclipse: 1948" National Stratospheric Observator Infrarer yFo d Astronomy (SOFIA). Geographic (March 1949): 325-372. Decade reviews of NASA's airborne astronomy programs 21 22 were give symposin i 198n ai 1994.d 4an - . Blackwell7 , D.E OuteStude A ." th f yro Corona Froma High Altitude Aircraft at the Eclipse of 1954 June 30" Monthly Notices Royale ofth Astronomical Society Vol5 1 . THE FUTURE OF NASA's AIRBORNE ASTRONOMY (1955): 629. PROGRAM: SOFIA Alien. 8 , Davi Infrared,. dA AstronomyThw eNe Halsted NASA's next-generation airborne observatory is now under Press, 1975. development Stratospherie Th . c Observator r InfrareyFo d Astronomy (SOFIA), Boeina wil e b l g 747SP modifieo dt 9. Cox, A.N., Liebenberg, D.H., and Stone, S.N "Thirty-Six carry a 2.7 meter telescope. SOFIA is being jointly developed MileShadowe Telescopeth d n si an y "Sk (August 1965):72- by NASA and the German Space Agency, DARA. Science 75. flights will begin on SOFIA in the year 2001.

10. Cox,'A.N., Liebenberg, D.H., Brownlee, R.R., Rudnick, Robertsond an , P. , M.M. "Racin Moon'e gth s Shadow" Sky and Telescope (February 1967): 85-89. 11. Klemperer, W.B., "The Solar Eclipse From a Jet" National Geographic (November 1963): 785-796. 12. DeVorkin, D.H. Stratosphere,Racee th o t Manned Scientific Ballooning in America Springer-Verlag, 1989.

13. Haughney, L.C. "History NASA's Airborne Astronomy Program" NASA Conference Publication #2353 Airborne Astronomy Symposium - Proceedings of a Meeting sponsored by NASA and the ASP (July 11-13,1984). 14..Regan, W. and Zimmerman, E. "The Diagnostic Air Force", The Atom, Los Alamos Scientific Laboratory (October 1964): 19. 15. Regan, W. "Progress in Sun Missions" The Atom Los Alamos Scientific Laboratory (September 1972):20.

16. Zimmerman Ordinaro "N . E , y Thermometer: LASL Scientists Develop Special Instrument Eclipser sfo " The Atom, Los Alamos Scientific Laboratory (May 1965): 7. Mulkin. Flight17 n Alamos "I Stor. e Lo ,B :f Th yo s Eclipse Missions" Los Alamos Science (Winter/Spring 1981): 39. 18. Ibid. :40. 19. Low "Airborn. ,F e Infrared Astronomy Earle :Th y Days" NASA Conference Publication #2353 Airborne Astronomy Symposium - Proceedings of a Meeting sponsored by NASA and the ASP (July 11-13,1984). 20. Storms, B. "74 Minutes of Totality Aboard a French Concorde" The Atom Alamos Lo s Scientific Laboratory (September 1973): 14-18. 21. NASA Conference Publication #2353 Airborne Astronomy Symposium - Proceedings of a Meeting sponsored by NASA and the ASP (July 11-13,1984). 22. ASP Conference Series, Vol. 73 "Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to DusF. Edited by Haas, M.R., Davidson, J.A., and Erickson, E.F. (1995).

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