Spacewalk. Astronaut Steven L. Smith performing an extravehicular activity (EVA or spacewalk). He is tethered to the end of the space shuttle's robotic arm or remote manipulator system (RMS). Smith is retrieving a power tool which has been specially made for the servicing of the Hubble Space Telescope (HST). The photograph was taken from the space shuttle Discovery during mission STS-103 (19-27 December 1999). During this mission the HST's computer, gyroscopes and tape recorder were all replaced. Also replaced was one of the HST's Fine Guidance Systems (FGSs) which allows the telescope to locate and view its targets.