The primary objective of the STS-70 mission was the launch and deployment of the seventh Tracking Data and Relay Satellite (TDRS), the sixth placed in operational use. The TDRS system is a space-based network that provides communications, tracking, telemetry, data acquisition and command services essential to the Space Shuttle and other low-earth orbital spacecraft, such as the Hubble Space Telescope (HST).
Life sciences payloads aboard STS-70 included National Institutes of Health Rodents payload (NIH-R2), and the Space Tissue Loss payload (STL-B). NIH.R2 continued the National Institutes of Health investigations into behavioral changes and the development of muscle, bone, nervous, and circadian timing systems in rats exposed to microgravity in utero. This project emphasized features of the rat's behavior and physiology that are known to contribute to successful pregnancy, labor, delivery and the onset of postnatal care, especially lactation. In addition, examination of the offspring after birth is expected to provide information about the earliest development of the vestibular system under gravity as compared to microgravity conditions.
STL-B was a collaborative research project between NASA and the Walter Reed Army Institute of Research in Washington, D.C. STL-B was designed to study the effects of microgravity on embryogenesis in the Medaka fish egg at the molecular level. Of particular interest was the digital image capture of the gastrulation development phase; images were captured via the STL-B on board video microscope and telemetered to investigators on the ground. This follow-up experiment helped validate previous findings, as well as provided additional definition to the model for future space biology experimentation.
STS-70 carried two Biological Research in a Canister (BRIC) payloads, BRIC-4 and BRIC-5. BRIC payloads consisted of passive experiments contained within a metal canister placed in a middeck locker with foam padding for vibration dampening. BRIC-04 experiments were specifically designed to examine how the hormone system and muscle formation processes of the tobacco hornworm are affected an altered gravitational field. BRIC-05 experiments tested whether the cell division changes observed in the daylily were caused by the direct effects of microgravity or indirect effects like water availability. BRIC experiment specimens were exposed to the temperatures, carbon dioxide, oxygen, atmospheric pressure and humidity conditions of the middeck; there was little to no crew interaction with the payload.
Other life sciences experiments performed during the STS-70 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.
Additional payloads flown included the Bioreactor Demonstration System; Commercial Protein Crystal Growth; Shuttle Amateur Radio Experiment-II; Visual Function Tester-4; Hand-held, Earth Oriented, Real-time, Cooperative, User-friendly, Location-targeting and Environmental System (HERCULES); Microcapsules in Space-B; Windows Experiment; Radiation Monitoring Equipment-III; and the Military Applications of Ship Tracks.
STS-70 landed on July 22, 1995, at Kennedy Space Center (KSC) after a mission duration of almost nine days.