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Tbis October four spacewalki,gg will prepare tbe Hubble Space Telescopefor its next decade of observations.

by Robert Naeye

Like a fine wine, the keeps getting better with age. How can

this be, you might be wondering, when the telescope is constantly exposed to the

debilitating effects of 400° F (220° C) temperature swings, high doses of radiation,

and a constant rain of micrometeorites?

The answer is simple. Hubble was specifically designed to be serviced by space

shuttle astronauts, who breathed new life into the telescope during two previous

350-mile-high house calls. In December 1993, four spacewalking astronauts brought

the telescope back from the brink of disaster when they installed optics to correct for

Hubble's flawed primary mirror. In February 1997, astronauts installed two new

scientific instruments: the infrared camera NICMOS and an imaging spectrograph

called STIS.

If all goes according to schedule, the next Hubble servicing mission willlaunch on

October 14, 1999. On that day, an international seven-man crew will rocket into

space aboard the Discovery. Four spacewalkers, three of whom are

astrophysicists, will replace the telescope's failing gyroscopes, install a new computer, < and perform several other repairs and upgrades. This third servicing mission won't E

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..P...•* .., , "..ff +,..1. 't:.« ... " , .If. . involve radical surgery, but it will make the telescope more was a 10 to 20 percent probability that the next gyro failure reliable while paving the way for new science instruments in would occur as early as June or July 1999, one year prior to the future (see"The Future of Hubble,» page 58). the scheduled launch of Servicing Mission 3. The possibility of a one-year downtime was unacceptable." A Rescue Mission On February 19, Campbell's office asked NASA headquar- The October 1999 servicing mission was moved up eight ters if it could divide Servicing Mission 3 in two and months by necessity, not choice. NASA had planned an schedule a shuttle mission as soon as possible to replace the ambitious Servicing Mission 3 for June 2000, with six sched- gyros. On March 10, NASA complied: Servicing Mission 3 uled space walks ( known as EVAs in NASA-speak, for was split into missions 3A and 38. Because the gyros needed Extra-Vehicular Activities). Besides inserting new gyros and to be replaced as soon as possible, and the Advanced Camera, the new computer, the astronauts would install the state-of- NICMOS refrigerator, and solar arrays wouldn't be ready for the-art Advanced Camera for Surveys, a refrigerator to revive nearly a year, the 3A mission was slated for October 1999, the failed NICMOS camera, and powerful new solar arrays. while the more ambitious 3B mission was tentatively sched- For the astronauts, this was to be by far the most challenging uled for June 2001 (Campbell says there's a good chance it of all the Hubble servicing missions. will be moved up to December 2000). But NASKs plans unraveled earlier this year. Two of the telescope's six gyros had already failed, and on January 24, The EVA Ballet 1999, a third gyro began to hiccup. Hubble can't point accu- Servicing Mission 3A, designated STS-103 by the shuttle rately enough at targets to do science unless three or more program, has a veteran crew of seven astronauts who collec- gyros are functioning properly. If one more failed, Hubble tively have 18 prior space shuttle missions to their credit. would be sitting idly in space, wasting tens of millions of tax- Former US. Air Force pilot , Jn will command payer dollars. the mission. Brown, who will do the bulk of the flying, was "When the third gyro failed, we estimated odds of also the commander of 's 1998 shuttle flight. Scott between 1-in-3 and 1-in-2 that Hubble would lose another Kelly, who flew F-14s and F-18s for the US. Navy before join- gyro prior to June 2000;' says Hubble project director John ing the corps, will serve as pilot; he is the only H. Campbell of NASA's Goddard Space Flight Centen "There rookie on STS-103. (ESA) astronaut

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From left to right, the crew of STS-103 Hubble Servicing Mission 3A: , , , Curtis Brown, Jean-Francois Clervoy, John Grunsfeld, and . WASAtJSC

Jean-Frangois Clervoy of France will operate the shuttle's mission. Like Grunsfeld, Foale and Nicollier both have Canadian-built robotic arm. advanced degrees in astrophysics. A pair of two-man teams will do the EVAs. Steven Smith, Two days after launch, Brown will deftly maneuver a former electrical engineer who performed three space Discovery into position to rendezvous with Hubble. "The . walks during the February 1997 servicing mission, will be main thing we worry about is the fragile solar arrays, says paired with John Grunsfeld, an astrophysicist who studies Brown. "We're flying an orbiter that weighs 230,000 pounds, high-energy objects such as x-ray pulsars and black holes. and we're very precisely maneuvering within tolerances of British native Michael Foale, who spent 134 days on the inches as we slowly move into position so that the robotic Russian space station in 1997, will do EVAs with ESA arm can grab the telescope." astronaut Claude Nicollier of Switzerland. Nicollier operated On the third day of the 10-day mission, Smith and the robotic arm during the December 1993 servicing Grunsfeld will venture outside the shuttle to perform the first of four 6-hour EVAs. The two astronauts will install a kit The skin on Hubble's sunward side is cracking and peeling. The astro- that protects the batteries from overcharging, but their main nauts will place large metal "Band-Aids" over the skin. NASA•JSC chore will be to replace all six gyros. As Smith says, "It's the single most important thing we're doing." Because NASA anticipated that the gyros would eventually ML*$ *0• fail, they were designed to be replaced. But this EVA is hardly a leisurely afternoon stroll in the park. "It means going right ./=. Uei into the bowels of the telescope, right into one of the most 1 .t sensitive regions," says Grunsfeld. Smith and Grunsfeld will -=\4 « -1 1. take turns guiding each other into passageways that are just > .= barely wide enough to accommodate an astronaut in his 036't «- .. I . Standing virtually motionless like statues for three 1 ,» t-•b. 46 half-hour shifts, they will have to disconnect three boxes )*,%% , 4 B. *LE + containing the old gyros and replace them with three new 11 I * t=••. .. . /A boxes. "We're told we can't touch anything, except for the . box we're replacing," says Grunsfeld. "You have to remember 4, 4 1,4 that when you take a box out, it might be a $5-million or 16 Fi 1 $10-million box that you're holding, and that you're working VJ . inches away from a $5-billion astronomical resource." 4, .4.1*... + d The next day, it's Foale and Nicollier's turn. They will -..,.'.--" replace Hubble's "ancient" computer, which is based on

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Astronauts Claude Nicollier and Michael Foale float in a giant water Steven Smith removes the Solar Array 3 Diode box from its protective tank as they simulate changing out the Advanced Computer. NASAtJSC enclosure in the same practice tank. N•s••sc

1970s technology, with a computer based on early 1990s technology (it has a 486-class processor). The new computer The Future of Hubble will pay immediate dividends by reducing operating costs. Foale and Nicollier will also replace one of Hubble's three If all goes well with the 3A mission, Servicing Mis- onboard Fine Guidance Sensors that allow the telescope to sion 38 will install the $50-million Advanced be pointed precisely at an astronomical target. The new Camera for Surveys (ACS), which will have roughly sensor was brought down to Earth during the previous serv- twice the resolution and field of view of Hubble's icing mission and then refurbished; the sensor being taken current visible light camera, the Wide Field/Plane- down on this mission will be refurbished and brought back tary Camera 2 (WFPC2). ACS will provide roughly up on a later mission. 10 times more information per picture than WFPC2. During the third EVA, Smith and Grunsfeld will install a Servicing Mission 4 is currently scheduled for new transmitter to replace one of the two that failed last year. 2003. Besides replacing the gyros again, astronauts NASA didn't anticipate such a failure, so the transmitter will install two powerful new instruments that will wasn't designed to be replaced. To remove the old unit, shed light on the evolution of the universe, the Wide Grunsfeld will use common hand tools to take out eight tiny Field Camera 3 and the Cosmic Origins Spectrograph. bolts and washers and three cables with subminiature "The way we create new science is [often] with new connections - a difficult task with the large, balky gloves of instruments," says Steven Beckwith, the new director his space suit. Grunsfeld will have to make sure he collects of the Space Telescope Science Institute. "Every time each bolt and washer, so they don't float around inside the you put a new set of instruments on an old telescope, telescope. "Some people have trouble replacing these with you just rejuvenate it completely." bare fingers. It's a challenging task - it's very hand-intensive and tiring - but I think we've worked out a good system so I'm confident it will go okay;' says Grunsfeld. E : *m/:: + 1/:I:mil/11'/I/:11:'Mi/9.vil/mil 'll'lill Smith and Grunsfeld will also replace an old-fashioned 2 3.,1,1.ID-Jil k...IG:.·..i,;;• reel-to-reel tape recorder with a new solid-state data recorder. The new recorder has 10 times more data storage capacity, which will be essential once the Advanced Camera Ft'' ··•''• •,9 -1 .15 - .·'' : ..3-•••'•' .lar•,A .t/, ...* is installed on the 3B mission and two new science instru- /, . .r•.:- ,5 '' · '·-·• ..i,' ' •'·'• 'fe ments (the Wide Field Camera 3 and the Cosmic Origins Spectrograph) are installed on Servicing Mission 4 in 2003. In addition, Smith and Grunsfeld will attach stainless steel "cookie sheets- to parts of Hubble's skin in the middle ./ S ' I .t..1 / ....,..."I...... 4 7 .m.».7. '-t:/ ...,-*,1.'. 't,." 'i section that have been scorched by sunlight, causing cracking and peeling. The ACS is scheduled to be installed in 2001. Johns Hopkins University On the fourth and final EVA, Foale and Nicollier will affix rolls of wallpaper-like sheets to the forward sections of Under current plans, the Next Generation Space Hubble's sunburned skin near the light shield. Foale and Telescope will be launched in 2007. Hubble will be Nicollier will stretch the limit of the robotic arm to reach the decommissioned and possibly brought back to Earth top of the telescope, providing an exceptional view of in 2010, where it might eventually be put on display Hubble, Discovery, and Earth. at the . - R.N. Just because one pair of astronauts is outside doing an EVA doesn't mean the other pair gets to take the day off. The

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NOVEMBER 1999 ASTRONOMY • 59 , 8@ '9' Ii, ® 1'ill @*@

The star was the search NASA SUCCESS Hubble needs a mini- overheating. Additionally, target because the planet mum of three working the astronauts opened a there was already known - gyroscopes to keep itself coolant line on the disabled it was one of the approxi- A Hubble properly oriented. While in infrared camera, NICMOS. mately 30 extrasolar planets safe mode, Hubble kept its Shuttle-bay-door latches whose presence has been solar arrays perpendicular to that resisted closing made inferred by their gravita- Makeover the sun by rotating about this space walk the second tional tugs on stars. # The Hubble Space Tele- once an hour - negating longest in history. Cameron's team calculated scope awakened from its the opportunity for any pre- Two days later, American the planet is about eight five-week electronic hiber- cise aiming ofobservational Michael Foale and Swiss times the mass ofJupiter nation after space shuttle equipment and rendering astronaut Claude Nicollier and 1.8 times the diameten Discovery's astronauts per- Hubble virtually blind for performed "brain" surgery Astrophysicist Adam formed needed repairs in this period. Working or not, in space when they replaced Burrows of the University of late December. The $3- Hubble costs about $25 Hubble's computer with·a said that in some billion Hubble shut itself million a month to operate. radiation-resistant Intel sense, it probably does not down and entered a "safe Because the main gyro- 80486 DX2 processor. The matter which team is right mode" on November 13, scopes didn't function replacement computer is 20 about having spotted the 1999, when the fourth of six properly, simply snagging times faster than its prede- planet. Now, more searchers gyroscopesfailed because of Hubble challenged Discov- cessor and gives Hubble's willlikely enter the fray, corroded wires. ery's crew members. A memory a six-fold increase. perhaps with better equip- Before Discovery could straightforward approach to While today's computer ment, and observe this and launch to remedy the situa- grabbing Hubble was technicians consider the other planets, tion, the shuttle encountered impossible. Its off-kilter DX2 obsolete, NASA prefers And collecting more its own set of problems, position required Discov- time-tested equipment. light to achieve better including damaged wiring, a ery's pilot, Curtis Brown, Jr., During the third and spectra will open the door contaminated engine, a to finesse his 's final space walk on Decem- to doing actual scientific dented fuel pipe, welding position to align with the ber 24, Smith and Grunsfeld investigations. Says Butler: irregularities, and inclement orbiting observatory. Mean- returned to the shuttle bay. "The direct detection of a weather. After a record nine while, backup gyroscopes Installation ofa solid-state planet's spectrum would be delays, Discovery finally fired to eliminate the tele- recorder allows Hui)ble to a great triumph and would began its 27th mission on scope's rotation and keep its record 10 times as much give us unique physical and the evening of December 19. solar arrays properly data as before. A new radio chemical information Astronauts worked through- oriented while.Brown transmitter replaces a about the planet, including out the Christmas holidays maneuvered Discovery into backup unit that took over orbital inclination, mass, repairing or installing nearly position. European Space in 1998. Designers never radius, density, tempera- $70 million worth of Agency astronaut Jean- expected the radio trans- ture, rotational period, and updated equipment and Fran•ois Clervoy then mitters to fail, so working chemical composition." - allowing Hubble to open its grabbed Hubble with the on them required special DAVID GRAHAM eyes again. shuttle's robotic arm. tools and a redesigned On December 21, space- replacement unit. Astronaut Steve Smith waves to a crewmate inside Discovery's cabin walkers Steve Smith and Grunsfeld's hands tired during the first spacewalk to repair the Hubble Space Telescope. John Grunsfeld spent more easily in the bulky gloves than eight:hours performing during the procedure, -n repairs - half of which was which lengthened the time spentreplacing Hubble's six needed to complete the . . -- ... :/ 1 24-pound gyroscopes. task. After the men hooked 1 Despite the fact that several up an electronic unit to the 4,114' * of Hubble's systems were 1 de L 1 pointing system andhung *, malfunctioning or shut two 4x5-foot stainless steel down, Grunsfeld was solar guard panels over impressed with HST's over- cracked and peeling « 7 all condition. Once you got insulation at Hubble's base, 0 7- .. -11 1 past the superficial blem- NASA declared the mission * 1 ishes and looked inside, a success. ... -, Hubble looks absolutely Discovery touched down. . . - pristine, he says. Smith and in on December 27, 11 , 1 Grunsfeld also installed six 1999, with just one day to C , --= < voltage regulators on spare before possible Y2K W Z I '. ,- Hubble's batteries to prevent problems. - CAROL RYBACK

26 • ASTRONOMY APRIL 2000 1