Two spacewalking astronauts, one standing attached to the space shuttle's robotic arm, work on the Hubble Space Telescope in the shuttle's cargo bay.

Astronauts working on Hubble’s Reaction Wheels

During Servicing Mission 3B in March 2002, astronauts Michael Massimino (left) and James Newman (right) replaced one of Hubble’s four Reaction Wheel Assemblies, which help turn the spacecraft.

Credits: NASA