An astronaut on the end of the robotic arm opens an equipment door on Hubble. The solar array and the blue earth are in the background.

Astronaut John M. Grunsfeld

John M. Grunsfeld, positioned on a foot restraint on the end of Discovery's Remote Manipulator System (RMS), prepares to replace a radio transmitter in one of the Hubble Space Telescope (HST) electronics bays. Steven L. Smith, STS-103 payload commander, was working to Grunsfeld's left.

Credits: NASA