Discovery launched from Kennedy Space Center on July 13, 1995 at 9:41 AM EDT and landed at Kennedy on July 22 at 8:02 AM EDT. The shuttle orbited 143 times at an altitude of 160 nautical miles and an inclination of 28.45 degrees and travelled 3.7 million miles. The mission lasted 8 days, 22 hours, 20 minutes, and 5 seconds.

The primary objective of the mission was accomplished when the Tracking and Data Relay Satellite-G was deployed from the orbiter payload bay about six hours after liftoff. Approximately one hour after deployment, Inertial Upper Stage (IUS) booster attached to TDRS-G completed the first of two scheduled burns to place TDRS-G in geosynchronous orbit. Once it completed an on-orbit checkout, TDRS-G became an operational spare, completing the existing TDRS network of advanced tracking and communications satellites.

During the remainder of mission, five crew members completed a variety of experiments. Biological Research in Canister (BRIC) experiments studied effects of microgravity on a wide range of physiological processes in plants, insects and small invertebrate animals. BRIC-4 examined how hormone system and muscle formation of tobacco hornworm were affected by microgravity; BRIC-5 tested whether cell division changes in daylily were due to microgravity or other causes. Also, the Bioreactor Development System (BDS), a device developed at Johnson Space Center, used colon cancer cells to test bioreactor performance in microgravity. This experiment worked extremely well, yielding tissue cultures better than any seen previously.

The National Institutes of Health-R-2 conducted a suite of experiments examining how microgravity affects different aspects of rodent pre- and post-natal development.

The Commercial Protein Crystal Growth (CPCG) experiment featured Protein Crystallization Facility (PCF) on its eighth flight. Five of these flights had yielded space-grown protein crystals of superior X-ray quality. Human insulin crystals grown on SPACEHAB 1 and 2 missions yielded the most detailed analysis ever made of this protein, which led to a key medication used to treat diabetes. The pharmaceutical industry used this structural information to develop new and improved time-release insulin formulations. On STS-70, crystals of alpha interferon protein — used to treat human viral hepatitis B and C — were grown.

Other experiments: Space Tissue Loss-B (STL-B), studying effect of microgravity on embryogenesis; and Hand-Held, Earth-Oriented, Cooperative, Real-Time, User-Friendly, Location Targeting and Environmental System (HERCULES), a space-based geolocating system that featured video cameras and electronic still cameras to document locations on Earth and tag every frame with latitude and longitude to within three nautical miles. Crew had difficulty at first aligning the HERCULES camera, but eventually obtained 95% of planned photographic targets.

Also, Microencapsulation in Space-B (MIS-B), made its second flight aboard the shuttle. MIS-B was designed to produce a better microencapsulated antibiotic. This type of antibiotic has proven extremely effective in treating wound infections, as it releases antibiotics at precise and predictable rates to cure infection. The first flight of MIS-B yielded purer microcapsules than could be obtained on Earth, but only a small quantity was produced. Researchers hoped this second flight of MIS-B on STS-70 would yield greater quantity of antibiotics.

Midcourse Space Experiment (MSX) required no onboard hardware; military MSX satellite used the shuttle during mission as a tracking and calibration target. Military Applications of Ship Tracks (MAST) required the crew to photograph ship tracks as part of an effort to determine how pollutants generated by ships modify the reflective properties of clouds. The Radiation Monitoring Equipment-III (RME-III) was a prototype dosimeter instrument which had been flying on shuttle since STS-31, and measured exposure to ionizing radiation on the shuttle. The data from RME-III is archived and used to update and refine models of space radiation environments in low-Earth orbit.

The Objective of Window Experiment (WINDEX), another military experiment, gained an understanding of chemistry and dynamics of low Earth orbit by collecting variety of data about such phenomena as shuttle thruster plumes, water dumps and atmospheric nightglow.

Visual Function Tester-4 (VFT-4) was designed to gain a better understanding of whether astronauts’ vision is affected by microgravity. VFT-4 instrument measured eyesight at near- and close range to test theories on what happens to the human eye in space. Astronauts since Gemini days in early ’60s had noticed that in space it takes longer to adjust and focus on near objects, and the STS-70 crew confirmed this observation.

The crew also spoke with ground radio operators as part of Shuttle Amateur Radio Experiment (SAREX), with around 50 contacts a day for several days of flight.

No significant problems were experienced with the orbiter. STS-70 marked first flight of new Block I main engine featuring new high-pressure liquid oxidizer turbopump built by Pratt & Whitney. Engine 2036 flew in number one position and the other two main engines were of existing Phase II design.

Discovery was crewed byCommander Terence T. Henricks, Pilot Kevin R. Kregel, and Mission Specialists Nancy Jane Currie, Donald A. Thomas and Mary Ellen Weber.