Two astronauts work on changing out Rate Sensor Units - boxes that hold two gyroscopes - in the aft shroud (bottom) of Hubble.

STS-125 MS4 Massimino and MS1 Good during EVA2

STS-125 Mission Specialist 4 (MS4) Mike Massimino (left, inside Hubble) and MS1 Michael Good (center) work to remove and replace Rate Sensor Units (RSUs), which contain gyroscopes, on the Hubble Space Telescope during the mission's second session of extravehicular activity (EVA2). MS1 Good is standing on the Manipulator Foot Restraint (MFR), which is connected to the Shuttle Remote Manipulator System (SRMS)/Canadarm Latching End Effector (LEE).

Credits: NASA