REX (Radiation Experiment) or ISES (Integrated Space Experiment System) was an Air Force Rome Laboratory ionospheric research satellite which tested the effects of the atmosphere on radio transmissions, and employed GPS for on-board navigation and attitude control.
Polar OrbitSTS-40 was the eleventh launch of Columbia and carried the Spacelab module for Spacelab Life Sciences 1 (SLS-1), the fifth Spacelab mission and the first dedicated to biology. It was also the first mission to carry three women crew members.
Low Earth Orbit