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Final Hubble servicing mission set for October 8 |
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Written by Derek Kessler on
Sunday, 25 May 2008
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 Postponed by a delay in the manufacturing of the problematic external fuel tanks, the space shuttle Atlantis will blast off from the Kennedy Space Center in Cape Canaveral, Florida, on October 8th, 2008. The mission commanded by veteran astronaut Scott Altman, will be the last shuttle mission sent to the 18-year-old Hubble Space Telescope and should ensure operation of the storied telescope through 2013.
Normally, NASA’s Michoud Assembly Facility where the external fuel tanks are assembled would have been able to cope with the launch schedule, but the unique requirements of the Hubble mission required an additional fuel tank be prepped. Following the loss of the space shuttle Columbia in 2003 (which was scheduled to service Hubble in 2005), NASA decided to limit all the remaining space shuttle flights to the International Space Station, where if damaged beyond repair the crew could seek refuge while an emergency rescue shuttle was prepped. Because of this requirement, a planned Hubble servicing mission was scrapped.
At the time, the Hubble Space Telescope was still operating as designed. Then in 2004 the telescope’s spectrograph (used to determine the chemical composition of light-emitting or reflecting sources) failed, followed by the main optical camera failure in 2006 and a backup electronics power failure in early 2007. Right now, both the ultraviolet and visible light systems are inoperable, limiting Hubble to only the solar blind channel. Additionally, Hubble’s solar-array charged batteries are beginning to show their age and two of the six gyroscopes used to stabilize and orient the telescope have failed, with more predicted to fail in the next few years. If left alone, the Hubble would likely reenter the Earth’s atmosphere sometime in 2010. Because of the sizeable mass and density of components like the main mirror, several large pieces of the telescope would survive to impact the surface, with odds of up to 1-in-700 of human fatality resulting.
Faced with pressure from politicians and the public to keep the popular telescope operational, along with scientific pressure from astronomers, NASA rethought the decision to cancel the Hubble servicing mission. The telescope’s successor, the James Webb Space Telescope, isn’t planned for launch any sooner than 2013, and even then the new telescope will only make observations in the infrared, while Hubble in peak operating condition covers the ultraviolet, optical, and near-infrared spectrums.
The decision to send a space shuttle mission to Hubble meant that a second shuttle had to be standing by, ready to launch at a moment’s notice if Atlantis were irreparably damaged. This is where the delay comes in, as Michoud had to produced two post-Columbia redesigned tanks in the time that they usually take to produce one. The redesign is quite a bit trickier to manufacture and Michoud has routinely encountered delays in producing the fuel tanks much earlier than their deadlines.
Atlantis will launch from Launch Complex 39A, while Endeavour will be standing by just over a mile away at Launch Complex 39B. If needed, Endeavour will be ready to be fueled and launched immediately as contingency mission STS-400 to rescue the crew of Atlantis. And if all goes well, Endeavour will be designated STS-126, loaded with supplies and equipment for the ISS, and launched no earlier than November 10.
Atlantis’ servicing mission to the Hubble Space Telescope will be a marathon of repair work and replacements for the telescope. The crew will replace all six gyroscopes, which are installed in pairs and both battery modules (each containing three batteries), replace insulation blankets, and install a new cooling system. They will also swap out the Corrective Optics Space Telescope Axial Replacement (COSTAR) for the new Cosmic Origins Spectrograph. COSTAR was installed during the first servicing mission in 1993 to correct the mirror aberration that crippled use of the telescope since its 1990 launch. The Cosmic Origins Spectrograph will operate in conjunction with the currently installed spectrograph, which will be repaired. Wide Field Camera 3 will also be installed during the Atlantis mission. WFC3 will be the most advanced and powerful camera installed on Hubble, capable of viewing in the ultraviolet, visible, and infrared spectrums.
A new fine guidance sensor to control Hubble’s orientation will be installed, along with a new ‘soft capture mechanism’ that will allow a future unmanned spacecraft to dock with the telescope and guide it into a controlled atmospheric reentry. The original pre-Columbia disaster plan had been for the space shuttle Columbia to recapture the telescope and bring it back to Earth (Hubble was originally launched from the space shuttle Discovery) in 2009, but with NASA’s revised safety requirements, shuttle retirement deadline, the loss of Columbia as the designated retrieval vehicle, and the estimated up-to-$500 million cost of such a mission, that plan was scrapped along with the original fourth servicing mission.
The Atlantis crew will also be taking an IMAX camera into orbit with them to chronicle the repair effort for a future IMAX film that will cover the entire story of Hubble. Upon release, the HST's orbit will have been sufficiently boosted to minimize the effects of atmospheric drag for several years.
STS-125 will be the fourth shuttle to service the Hubble Space Telescope, the thirtieth flight for Atlantis, and the last space shuttle mission not destined for the ISS. It is scheduled to last 11 days, with five spacewalks. If STS-125 is successful, Hubble is estimated to be operational until at least 2013, and possibly until 2020.
Discuss: TrekUnited Forum
The Hubble Space Telescope docked with the space shuttle Discovery in 1999.
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"Captain Proton would never walk away from a mission like this."
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