Walter Watts
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Hubble Servicing Mission 4 Update (06.16.2006)
« on: 2006-07-17 09:48:06 » |
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Given the flawless performance of STS-121, which was launched July 4, 2006 and returned this morning, the possibility of HST SM4 (Hubble Space Telescope-Servicing Mission 4) looks very promising indeed.
This is very good news for us Hubble fans! 
Walter
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Servicing Mission 4 Update (06.16.2006)
The Hubble Space Telescope Program, resident at NASA's Goddard Space Flight Center in Greenbelt, MD, continues to work toward a possible Servicing Mission 4 (SM4) in late-2007 or early-2008.
Prior to an HST SM4 being approved by the NASA Administrator, the Shuttle must perform two consecutive successful flights: STS-114, which flew in July of 2005, and STS-121, which was launched July 4, 2006. An engineering risk analysis also must demonstrate a high degree of safety for the Shuttle and its crew in an SM4 flight to Hubble. Because the study will be partially informed by the STS-121 experience, it will not be completed until some period of time after that mission has landed.
Given the possibility that SM4 might occur as soon as 18-24 months from now, preparations for the mission cannot be delayed until after the Shuttle has demonstrated its robustness in the manner just described. Accordingly, and in response to direction from the NASA Administrator, the Hubble Program has for the last year been proceeding with normal planning and preparations for a possible SM4.
If SM4 becomes a reality, EVA astronauts would perform a number of tasks not only to keep Hubble operational until at least 2013, but to expand greatly the scientific power of the telescope. Key to putting Hubble at the “apex” of its capabilities will be the installation of two new scientific instruments: the Cosmic Origins Spectrograph (COS) and the Wide Field Camera 3 (WFC3). Each instrument contains advanced technology sensors which far surpass what has been available on Hubble to-date, and improvement factors of 10X-70X are expected in certain key performance areas.
Operating Hubble to 2013 will require the installation of some new engineering hardware, specifically batteries (6), gyroscopes (6), and a refurbished Fine Guidance Sensor (FGS). The current batteries should have enough capacity to last at least until 2009, allowing ample time to conduct an SM4 mission. The current gyros were installed in December, 1999, and are approaching “gyro old age.” Four gyros are still operational, with two currently being used for day-to-day operations and two being held in reserve as spares. Hubble should have enough working gyros to keep it in “science mode” through late-2008. The telescope holds three FGS units (along with the gyros, FGSs are part of Hubble’s pointing control system), and recent servicing missions have been replacing them one at a time in “round robin” fashion with refurbished units.
If SM4 is approved, the astronauts may also attempt the repair of the Space Telescope Imaging Spectrograph (STIS), which was installed on Hubble during SM2 in 1997. STIS is the most advanced spectrograph ever flown in space, but it ceased operations due to failure of an electronic component in August of 2004. The capabilities of COS and STIS complement each other extremely well, and should STIS be repaired, the pair of instruments would bring a “full set” of spectroscopic tools to Hubble for use by astrophysicists in their research. Key to fixing STIS is the on-orbit replacement of one electronics board inside the main electronics box. The Hubble Program and NASA astronauts have been working together to develop manual techniques that astronauts would use to change out the board in orbit.
This page will keep readers apprised of future developments in the march toward a possible SM4.
http://hubble.nasa.gov/missions/intro.php
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