The mission's primary payload was the Atmospheric Laboratory for Science and Applications-2 (ATLAS-2), the second in a series of investigations designed to assess the impact on the earth's ozone layer of annual variations in solar activity and atmospheric composition. The ATLAS series is a vital part of NASA's Mission to Planet Earth project, a long-term effort to study the earth as a global environmental system.
The primary life sciences payloads on STS-56 included the Physiological and Anatomical Rodent Experiment.03 (PARE.03). Experiments in this payload were designed to study changes that occur in rapidly growing bone after exposure to microgravity by comparing them to changes occurring after exposure to simulated microgravity.
Additional life sciences experiments performed during the STS-56 mission were those classified as Detailed Supplementary Objectives (DSOs). A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who serve as the test subjects. These studies are designed to require 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 the Commercial Materials Dispersion Apparatus Instrumentation Technology Associates Experiment designed to aid research in drug development and delivery, biotechnology, basic cell biology, protein and inorganic crystal growth, bone and invertebrate development, immune deficiencies, manufacturing processes, and fluid sciences; Space Tissue Loss; Solar Ultraviolet Experiment; Cosmic Radiation Effects and Activation Monitor experiment; Hand-held, Earth-oriented, Real-time, Cooperative, User-friendly, Location-targeting and Environmental System (HERCULES); Radiation Monitoring Equipment III; and Air Force Maui Optical Site (AMOS) calibration test.
On April 11, the crew used the remote manipulator arm to deploy the Shuttle Point Autonomous Research Tool for Astronomy-201 (SPARTAN-201), a free-flying science instrument platform designed to study velocity and acceleration of solar wind and observe sun's corona. SPARTAN-201 was retrieved on April 13.
The crew also made numerous radio contacts to schools around world using Shuttle Amateur Radio Experiment II (SAREX II), including a brief radio contact with Russian Mir space station, the first such contact between Shuttle and Mir using amateur radio equipment.
After orbiting Earth for eight days, the Shuttle landed at Kennedy Space Center on April 17, 1993.