Amazing Effort Does Not Come Without Complications

STS-125 mission specialists Mike Massimino and Mike Good completed the mission’s fourth spacewalk Sunday at 5:47 p.m. EDT. The spacewalkers continued repairs and improvements to the Space Telescope Imaging Spectrograph (STIS) that will extend the Hubble’s life into the next decade.

In the sixth longest spacewalk in history, Astronauts Mike Massimino and Michael Good tackled the intricate task of removing and capturing 111 screws to be able to revive the Hubble Space Telescope’s two-dimensional spectroscopy capability.

In the 8 hour, 2 minute spacewalk, Massimino and Good repaired the Space Telescope Imaging Spectrograph (STIS) by replacing a power supply board. STIS, installed on the Hubble Space Telescope in 1997, stopped working in August 2004 due to a power supply failure and was in a “safe mode.”

Though the removal of the many screws was expected to be difficult, a handrail gave Good and Massimino trouble. The handrail was obstructing the path of a fastener capture plate and one stripped bolt prevented it from coming free. Massimino followed steps developed quickly at the Goddard Spaceflight Center to carefully bend and break the handrail free so that the fastener capture plate could be installed. At about three hours into the spacewalk, Massimino broke the handrail free allowing the spacewalkers to proceed with the day’s tasks.

The initial aliveness test reported the STIS as working properly. The initial functional test was ended when the telescope put itself into “safe mode,” having reached a low thermal limit. The STIS is believed to be in good shape. Ground controllers will start the functional tests over again, once the telescope reaches a good temperature.

The STIS separates light into its component colors to reveal information about the chemical content, temperature and motion of planets, comets, stars, interstellar gas and galaxies. The information it can provide will help scientists better understand the physical properties of the material universe – putting the physics in astrophysics.

Massimino and Good were unable to get to the installation of the New Outer Blanket Layer (NOBL) on the outside of the telescope’s bay 8. Mission managers have asked Mission Specialists John Grunsfeld and Andrew Fuestel to add the installation of a partial set of blankets on bay 8 during Monday’s spacewalk. If time permits, the two may get to install the full set.

The crew was due to wake up Monday at 0431 to conduct the fifth and final spacewalk of the mission.

NASA has updated their plans for the Fifth spacewalk, "Our goal is to get the spacewalk done on time, which is scheduled to last 5 hours, 45 minutes. Batteries and the Fine Guidance Sensor tasks are our priorities for tomorrow's spacewalk. We will make a real time call where we are in the timeline after those tasks are complete on the go forward plan for the Bay 5 & 8 New Outer Blanket Layer installation tasks. For the baseline plan, we would do a partial Bay 8 and then go to the other side and do a full Bay 5."

FMI: www.nasa.gov