"Im just gonna watch John come out slowly and listen to his voice and see the look on his face because its gonna be his first spacewalk and its gonnabe a really special moment for him."
Lead flight director Linda Ham said there is a chance the pair could get started up to one hour early if theyre ahead of schedule to perform some "get-ahead tasks."
Some of the work Smith and Grunsfeld may get started on include inspecting cables and installing handrail covers. Due to the shortened mission, one of the EVAs was cancelled and the space agency has been studying how to squeeze in a few extra tasks.
Smith, a veteran of the 1997 mission, will precede Grunsfeld out the door and keep an eye on his colleague.
"Im just gonna watch John come out slowly and listen to his voice and see the look on his face because its gonna be his first spacewalk and its gonna be a really special moment for him," Smith said in an interview before the mission.
More than 300 miles above the Earth, at the end of the cargo bay, the 12.5-ton, 43.5-foot tall Hubble Space Telescope awaits the astronauts. The telescope should be a sight with its glistening silver-colored Mylar insulating blanket.
First order of business will be to place a post between the telescope and cargo bay to hold the telescope firmly. After that, the duo will set up tools and aids for the remaining two EVAs.
Smith and Grunsfeld will open the doors on the Hubble and begin the 2.5-hour task of replacing the six gyros, which are housed in pairs in three rate sensor units.
Grunsfeld will be mounted on the shuttles robot arm which is controlled by Jean-François Clervoy while he assists Smith, who will have to squeeze into the tight and delicate area inside the Hubble.
"Its very tight quarters and theres several very fragile pieces in there, so rather than have me climb in there, John will rotate me on my back and stick me in the Hubble Space Telescope," Smith said.
While Grunsfeld uses the power ratchet tool to loosen bolts, Smith will loosen the electrical and data connections. When the old gyro-unit is extracted, Smith hands it to Grunsfeld who stows it and retrieves a new one to install.
The process is repeated until all three gyro-bearing rate sensor units are installed. To replace one of the units, it will be Grunsfeld who will venture into the telescope.
As the astronauts work, Hubble Controllers at Goddard Space Flight Center will begin testing the new gyros.
"As soon as the first rate sensor unit is plugged in, which has two gyros, we will begin doing an aliveness test," said Hubble Project Manager John Campbell. "Those aliveness tests are designed to make sure the electrical connectors are connecting and the pins are connected properly."
Campbell said that the test gives about a 90 percent confidence that the gyros will function properly. More detailed tests will follow as the astronauts perform other tasks.
Grunsfeld, making his first spacewalk, plans on being extra cautious inside the Hubble.
"Weve been told once were in the telescope to be a statue and not touch anything other than the gyroscopes," Grunsfeld said in an interview before launch. "Its a very delicate activity for something that was planned to be routine."
Though the telescope contains delicate components, most were designed to be replaced in orbit.
After the gyros are replaced, Grunsfeld will spend about 20 minutes opening valves to drain remaining nitrogen from the now-dormant NICMOS or Near Infrared Camera and Multi-Object Spectrometer in advance of the 2001 mission to Hubble. That crew will add another cooling package to the instrument to put it back in service.
The camera lost its coolant soon after installation in 1997 by Smith and astronaut Mark Lee.
The spacewalking pair will finish the day by installing three improved voltage regulators designed to work with more advanced solar arrays to be installed on a later mission. This task should take about 90 minutes.
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