The gyros are a critical part of Hubble's pointing control system. Since then, it has been in safehold while awaiting a visit from the astronauts. Tomorrow, spacewalkers Claude Nicollier and Mike Foale will install Hubble's new main computer and a Fine Guidance Sensor. On Christmas Eve, Smith and Grunsfeld will replace a transmitter, install a digital recorder and fit Hubble with new thermal skin. In the mission's first spacewalk, astronauts Steve Smith and John Grunsfeld successfully replaced all six gyros.
Preliminary tests show the new gyros are alive and well.
Ground controllers will conduct more detailed testing tonight while the astronauts sleep. Smith and Grunsfeld are now installing improvement kits to Hubble's batteries. All systems continue to be in excellent shape and ready to support EVA 1 this afternoon. The crew is very eager to get to work. Plans are being made for starting the EVA 30 minutes to an hour ahead of schedule.