The primary objectives of STS-95 included conducting a variety of science experiments in the pressurized SPACEHAB module, the deployment and retrieval of the Spartan free-flyer payload, and operations with the Hubble Space Telescope Orbiting Systems Test (HOST) and the International Extreme Ultraviolet Hitchhiker payloads being carried in the payload bay. The scientific research mission also returned space pioneer John Glenn to orbit – 36 years, eight months and nine days after he became the first American to orbit the Earth.
A slate of more than 80 experiments filled the nearly nine days in space. In addition to a variety of medical and material research, the crew released the Petite Amateur Naval Satellite, or PANSAT, to test innovative technologies to capture and transmit radio signals that normally would be lost because the original signals were too weak or contained too much interference. The crew also released the Spartan free-flying satellite to study the sun and the solar wind in a research effort to help scientists better understand a phenomenon that sometimes can cause widespread disruptions of communications and power supplies on Earth.
Medical research during the mission included a battery of tests on Payload Specialist Glenn and Mission Specialist Pedro Duque to further research how the absence of gravity affects balance and perception, immune system response, bone and muscle density, metabolism and blood flow, and sleep.
The Hubble Space Telescope Orbital Systems Test provided an on-orbit test bed for hardware that will be used during the third Hubble servicing mission.