The primary purpose of STS-37 was the deployment of the Gamma Ray Observatory (GRO). The GRO is a space-based observatory designed to study the universe in an invisible, high-energy form of light known as gamma rays. Gamma rays, which cannot penetrate the Earth's atmosphere, are of interest to scientists because these rays provide a reliable record of cosmic change and evolution. Their study will yield unprecedented answers about the structure and dynamics of the Milky Way Galaxy, the nature of pulsars, quasars, black holes and neutron stars, as well as clues about the origin and history of the universe itself.
Life Sciences experiments on this mission included multiple Detailed Supplementary Objectives (DSOs). A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who serve as the test subjects. These studies required minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns, including space motion sickness, cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry.
Other payloads included Crew and Equipment Translation Aids, an Ascent Particle Monitor, the Shuttle Amateur Radio Experiment II, a Protein Crystal Growth Experiment, the Bioserve/Instrumentation Technology Associates Materials Dispersion Apparatus, Radiation Monitoring Equipment III, and the Air Force Maui Optical Site (AMOS) experiment.
The landing was originally scheduled for April 10, but was delayed one day due to adverse weather conditions at Edwards Air Force Base in California and Kennedy Space Center. The Space Shuttle Atlantis touched down at Edwards Air Force Base on April 11, 1991.