Astronauts Steve Smith and John Grunsfeld on Friday installed a transmitter that sends scientific data from Hubble to the ground. The transmitter replaced one that failed in 1998. A second transmitter had successfully carried the load without any disruption to Hubble scientific operations. Since the transmitters are considered very reliable, they were not designed to be replaced in orbit and special tools were developed to make the job easier.
Smith and Grunsfeld also installed a solid state digital recorder, replacing an older mechanical reel-to-reel recorder version. The digital Solid State Recorder provides more than 10 times the storage capacity of the old unit. They also applied new insulation on two equipment bay doors.
Both the transmitter and the recorder checked out normally on early tests by telescope controllers.
Two previous space walks on Wednesday and Thursday had completed the highest priority tasks of the mission. Those tasks included installation of six new gyroscopes and six Voltage/Temperature Improvement Kits, giving Hubble a new computer 20 times faster and with six times the memory of the old computer, and replacement of one of Hubble's three Fine Guidance Sensors.
Friday's space walk lasted 8 hours and 8 minutes, ending at 9:25 p.m., making it the fourth longest in history. Part of the reason for the length of the space walk was difficulty in hooking Grunsfeld's suit up to orbiter power after he had returned to Discovery's airlock. Friday's space walk brings the total time of STS-103 extravehicular activity to 24 hours, 33 minutes. This mission's three space walks bring the total amount of time spent servicing Hubble to 93 hours, 13 minutes. Space Shuttle Program space walks now total 317 hours, 3 minutes. And Steve Smith now is the astronaut with the second longest combined space walk time, with 35 hours, 33 minutes behind only Jerry Ross, with 44 hours, 11 minutes.
Discovery is in an orbit with a high point of 380 miles and a low point of 363 miles. All of the orbiter's systems continued to function normally.