First Hubble Spacewalk Meets Main Objectives
Frank Morring, Jr. morring@aviationweek.com
Johnson Space Center, Houston
Astronauts John Grunsfeld and Drew Feustel overcame a balky latch bolt to accomplish their main tasks on the first extravehicular activity (EVA) of the STS-125 mission to service the Hubble Space Telescope.
Before returning to the relative safety of the space shuttle Atlantis, the pair pulled out the 16-year-old Wide Field Planetary Camera 2 (WFPC 2), inserted the more powerful Wide Field Camera 3 (WRC 3) in its place, and swapped out the data-handling computer that forced a seven-month delay in the mission when it failed last September.
They also installed the docking mechanism that may be used in the future to capture a robotic spacecraft bringing a propulsion system that can deorbit the telescope safely once its service life ends. But thanks to the work done Thursday, that day should be at least five years in the future.
By replacing the Science Instrument Command and Data Handling (SI C&DH) unit that failed last September with a flight-qualified ground spare, the two spacewalkers restored the redundancy NASA managers considered so important that they pushed the mission back seven months, delaying work on the vehicles that will follow the shuttle into space accordingly.
The task itself was straightforward, and took less than an hour. The door-mounted plate holding the six avionics boxes making up the SI C&DH came off easily, and Feustel was able to install the new unit while Grunsfeld stowed the bad one in the payload bay. A quick aliveness test verified the connections and allowed controllers at Goddard Space Flight Center to start work on a more detailed functional test.
With Fuestel spending most of his first EVA riding the orbiter's robotic arm and two-time Hubble-servicing veteran Grunsfeld moving more freely around the payload bay, the pair overcame an early snag when the bolt latching WFPC 2 into the telescope wouldn't turn. Working carefully to avoid damage that might have made it impossible to install WFC 3, Feustel broke torque on the bolt and got it loose.
Using a temporary handhold, Feustel pulled the camera out of the telescope, and then reversed the process to install the 890-pound WFC 3 in its place with Grunsfeld calling clearances.
Grunsfeld made quick work installing the capture mechanism for a future deorbit motor, turning the single bolt that unlatched it from the payload bay turntable where the telescope is mounted, and attached it to the telescope.
The only snag came at the end of the seven-hour, 20-minute spacewalk when Feustel wasn't able to install a kit designed to hasten opening and closing one of the telescope doors. After discussion among engineers in Mission Control here, the job was abandoned and the affected door was closed with a repaired latch.
"In traditional Hubble fashion, Hubble threw us a few curves," Grunsfeld said in thanking his colleagues for their help in the successful EVA.
Photo credit: NASA TV
