The primary objective for this mission was the use of the Atmospheric Laboratory for Applications and Sciences-3 (ATLAS-03). ATLAS-3 will continue to collect information on the sun's energy and its effects on the Earth's climate and environment. ATLAS-03 will also be the first payload to make detailed measurements of the Northern Hemisphere's middle atmosphere in late fall. Correct timing of the flight was critical as its projected orbit permitted scientists to observe the effects of the ozone hole in mid-latitudes.
In addition to the experiments performed on ATLAS-03, life sciences payloads included the National Institutes of Health Rodent Experiment (NIH-R1) and the National Institutes of Health Cells Experiment (NIH-C2). These experiments included investigators from the United States, Russia and France. NIH-R1 was designed to collect data on a wide range of topics, including the effects of spaceflight on muscles, nerves, and vestibular development, the development of sensory receptors in skeletal muscles, the development of the brain, choroid plexus, and heart natriuretic peptide in space, the effect of microgravity on the epidermis of a rat, the effect of gravity on the tendon-bone attachment and in the optic nerve, the effect of microgravity on the immune system, and placental development in microgravity.
NIH-C2 was designed to study the effects of microgravity on mineral, bone and muscle fibers. Primary cultures of each type of cell were loaded into cartridges and placed into the Space Tissue Loss-A (STL-A) module, which fits inside a Shuttle middeck locker. The automated STL-A module collected and fixed samples from the cultures during flight for analysis upon return to Earth.
Other life sciences experiments performed during the STS-66 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 on this mission was the deployment and retrieval of the Cryogenic Infrared Spectrometer Telescope for Atmosphere (CRISTA). The payload was designed to explore the variability of the atmosphere and obtain measurements which will complement those provided by the Upper Atmosphere Research Satellite launched aboard Discovery in 1991. CRISTA was released from orbiter's Remote Manipulator System arm on the second day of the mission. The payload collected data for over eight days before its retrieval and return to the cargo bay. The samples obtained can lead to better models of the Earth's energy balance and atmosphere. A new approach method to the spacecraft was successfully tested to retrieve CRISTA. This new attachment method called the R-bar approach was expected for use in the Mir docking system as it saves propellant while reducing the risk of Mir contamination.
STS-66's other payloads included Protein Crystal Growth Experiments, Space Acceleration Measurement System and the Heat Pipe Performance Experiment.
On November 14, 1994, the crew consisting of Donald McMonagle, Mission Commander; Curtis L. Brown, Jr., Pilot; Ellen Ochoa, Payload Commander; Joseph R. Tanner, Mission Specialist; Scott E. Parazynski, Mission Specialist; and Jean-Francois Clervoy, Mission Specialist touched down at Edwards Air Force Base in California. This landing was a diversion from the Florida site due to high winds, rain, and clouds caused by a tropical storm. This was the fourth diverted landing in 1994.