STS-103 Extravehicular Activities

Four astronauts performed three space walks over three days to service the Hubble Space Telescope. NASA calls a space walk an "extra-vehicular activity", or EVA. Each of the space walk servicing periods is an EVA Day, although these "days" span two "Flight Days". For example, EVA Day 1 begins two days and 19 hours into the mission, and it ends in the second hour of the third mission day. The tasks were arranged in order of importance and efficiency. The space walkers worked in teams of two, with each pair going out on alternating days.

EVA Day 1
Steven Smith, John Grunsfeld
Actual Time: 8 hours, 15 minutes
Actual Start Time: 12:54 p.m. CST, December 22, 1999
Actual Finish Time: 9:10 p.m. CST, December 22, 1999
The first team replaced Hubble's three Rate Sensor Units (RSUs), each containing two gyros. They also installed Voltage/Temperature Improvement Kits (VIKs) on Hubble's six batteries.

EVA Day 2
Michael Foale, Claude Nicollier
Actual Time: 8 hours, 10 minutes
Actual Start Time: 1:06 p.m. CST, December 23, 1999
Actual Finish Time: 9:16 p.m. CST, December 23, 1999
The second team replaced the telescope's central computer and a Fine Guidance Sensor (FGS). The old computer and fine guidance sensor are now stowed in the orbital replacement carrier for return to Earth.

EVA Day 3
Steven Smith, John Grunsfeld
Actual Time: 8 hours, 8 minutes
Actual Start Time: 1:17 p.m. CST, December 24, 1999
Actual Finish Time: 9:25 p.m. CST, December 24, 1999
The first pair of space walkers installed a transmitter and a solid state recorder (SSR).

EVA Day 4
Due to a shortened flight schedule, a fourth space walk is no longer planned.