Wednesday, May 20, 2009

Lifeline for Hubble

A long drama finally came to a close this week, as the crew of the space shuttle Atlantis released the Hubble Space Telescope back into orbit after 8 days of grueling repairs. Headlines have understandably been dominated by the overwhelming success of the servicing mission -- but behind the scenes there was another story, with a more human dimension, that most people never knew about.

After the tragic loss of the space shuttle Columbia and its crew in February 2003, everything in orbit that relied on the shuttle program came to a grinding halt. The future of the final Hubble servicing mission was suddenly very uncertain. It took nearly 29 months before the shuttle returned to the skies in July 2005, and another year before it continued regular operations in July 2006. During these three and a half years, the primary concern was whether NASA could ensure the safety of shuttle crews -- so in August 2004, administrator Sean O'Keefe commissioned a study to determine the viability of a robotic servicing mission to Hubble. This idea was ultimately rejected in April 2005 by the next administrator, Michael Griffin, who finally approved the servicing mission in October 2006. In the meantime, Hubble was gradually losing many of its scientific functions.

Throughout this period, the life of Hubble was extended again and again by the heroic efforts of the scientists and operators at the Space Telescope Science Institute in Baltimore. Every time a component of Hubble failed, these men and women figured out a way to continue limited science operations on whatever was left. For many, their jobs literally depended on it -- without Hubble they would have nothing to do until the launch of the James Webb Space Telescope in June 2013 (at the earliest). So they were determined to keep Hubble working, and they did. The servicing mission was finally scheduled for October 2008, but Hubble's on-board computer system failed just two weeks before launch. It took weeks for engineers to design a short-term fix, and months for astronauts to incorporate the replacement computer into their long-rehearsed training routine.

Which brings us to this week -- when all of that training was finally put to good use, and the long-anticipated repair mission has come to a successful conclusion. The main digital camera on Hubble was replaced with a newer model, and the old corrective lenses it received in 1993 to fix its fuzzy vision were replaced by a new light-splitting spectrograph that will peer to the very edge of the observable universe. Two of the other scientific instruments, STIS and ACS which have been dead or crippled since power supply failures in 2004 and 2007, have now been restored. These science upgrades were complemented by a host of routine repairs including: the installation of new gyroscopes for the telescope's pointing system, new batteries which are charged by Hubble's solar panels for 60 minutes of each orbit and supply all of the power during the remaining 36 minutes on the dark side of the Earth, and a new insulating outer blanket that helps protect the satellite from harmful radiation and space junk. With the installation of a replacement on-board computer system and an external dock to support the future robotic capture of the telescope for disposal at the end of its life, the servicing mission was complete.

Hubble is now expected to continue its marathon of ground-breaking discoveries well into the next decade -- and most importantly, until the next space telescope is operational. The dozens of people at the Space Telescope Science Institute whose jobs depend on this mission can now breath a collective sigh of relief.