The National Aeronautics and Space Administration marks its 40th anniversary in October, the same month NASA is scheduled to return to space one of the country's original astronauts.

Mercury Project astronaut John Glenn became the first American to orbit Earth on Feb. 20, 1962. He will again make history when he returns to orbit 36 years later on STS-95 and becomes the oldest human to fly in space.

More than 80 experiments probing mysteries ranging from the inner universe of the human body to studies of our Sun will be conducted during the nine-day mission. The main objectives of the 92nd Space Shuttle flight are to perform microgravity research in a SPACEHAB single module, deploy and retrieve the Spartan-201 solar-observing spacecraft, and conduct operations with the Hubble Space Telescope Orbital Systems Test platform and the International Extreme Ultraviolet Hitchhiker.

A four-term Democratic senator from Ohio, the 77-year-old Glenn will be one of the chief subjects and operators of a series of experiments that will study the physiological correlation between the aging process on Earth and the effects of space flight on the human body. Bone and muscle loss, balance disorders, a depressed immune system and sleep disturbances are among the physiological responses shared by the elderly on Earth and space travelers.

Gerontologists hope that the research will help older people live more productive and active lives, and reduce the number of elderly requiring long-term medical care. In turn, space biomedical researchers believe that data collected from these will aid in planning for long-duration space flight on the International Space Station.

On its 25th flight, the Space Shuttle Discovery will lift off from Launch Pad 39B and ascend at a 28.5-degree inclination to the equator for direct insertion to a 345-statute-mile (300-nautical-mile/556-kilometer) orbit. Landing is planned at KSC's Shuttle Landing Facility.

Leading the seven-member flight crew as mission commander will be four-time space flier Curt Brown, an Air Force lieutenant colonel. He was an instructor pilot and a test pilot in the Air Force before being selected for the astronaut program in 1987. He was the pilot on STS-47 in 1992, STS-66 in 1994 and STS-77 in 1996, and the commander of STS-85 in 1997.

Steven W. Lindsey, also a lieutenant colonel in the Air Force, will be the pilot. Lindsey had a varied career with the Air Force as a pilot, academic instructor and integrated product team leader responsible for weapons certification. He was chosen as an astronaut candidate in 1994 and flew once, as the pilot on STS-87 in 1997.

One of three mission specialists, Stephen K. Robinson (Ph.D.) also will serve as the payload commander. Robinson earned his doctorate in mechanical engineering from Stanford University while working as a research scientist at NASA's Ames Research Center in California. He was a scientist at NASA's Langley Research Center before being chosen for the astronaut program in 1994. He first flew as a mission specialist under Brown's command on STS-85.

Mission Specialist Scott E. Parazynski (M.D.) also will serve as the flight engineer. Parazynski earned his medical degree from Stanford Medical School and was in a residency program in emergency medicine when chosen as an astronaut candidate in 1992. He conducted physiology research at Ames Research Center, and flew twice as a mission specialist, on STS-66 with Brown and on STS-86 in 1997.

Mission Specialist Pedro Duque of Spain will make his first space flight. Duque was selected to join the astronaut corps of the European Space Agency (ESA) in 1992. He then qualified as a research astronaut for joint ESA-Russian missions. After serving as alternate payload specialist for STS-78 in 1996, he was chosen by ESA to attend NASA astronaut candidate training.

Payload specialists making their second space flight are Chiaki Mukai (M.D., Ph.D.), representing the National Space Development Agency of Japan (NASDA); and Sen. John Herschel Glenn Jr. (Col., USMC, retired).

Mukai, a cardiovascular surgeon, received a medical degree and a doctorate in physiology from Keio University in Tokyo. She was selected by NASDA as a payload specialist candidate in 1985, and was the first Japanese female to fly in space on STS-65 in 1994. Mukai is a research instructor at Baylor College of Medicine in Texas and a visiting associate professor at the Keio University School of Medicine.

At 77, Glenn will be the oldest person to fly in space by 16 years. The Marine combat pilot and test pilot flew the Mercury-Atlas 6 "Friendship 7" spacecraft, circling Earth three times on the first manned U.S. orbital mission. He later was a business executive until his election to the Senate in 1974. He has nine honorary doctoral degrees. Glenn still flies his own plane and in 1996 set his second flight speed record. This will be his first Shuttle flight.

SPACEHAB experiments – Investigations focusing on microgravity sciences, advanced technology and life sciences will be conducted inside a pressurized SPACEHAB single module. Besides NASA, the diverse SPACEHAB experiments are sponsored by ESA, NASDA and the Canadian Space Agency. The geriatric studies include an evaluation of bone cell activity in microgravity, a protein turnover experiment on the effects of space flight on whole-body and skeletal muscle protein metabolism, and an investigation of the effectiveness of the pineal hormone melatonin as an hypnotic during space flight.

Spartan-201-5 -- This is a reflight of the Spartan payload which developed problems shortly after deployment on STS-87 last year and was recaptured by astronauts during a spacewalk. Spartan-201 will investigate the physical conditions and processes of the solar corona and the solar winds that influence orbiting satellites and weather conditions on Earth which, in turn, affect television and phone communications. The free-flying platform will be deployed on flight day 4 and retrieved by Discovery's robot arm two days later. Spartan-201 with its two instruments, the Ultraviolet Coronal Spectrometer and the White Light Coronagraph, successfully flew on three previous missions. Secondary investigations include the Technology Experiment Augmenting Spartan (TEXAS) for radio frequency communications; the Video Guidance Sensor to test a key component of the automated rendezvous and capture system; and the Space Experiment Module for educational experiments.

International Extreme Ultraviolet Hitchhiker – IEH-03 is comprised of seven experiments, including a small satellite that will be deployed on flight day 3. The non-recoverable Petite Amateur Navy Satellite (PANSAT) stores and transmits digital communications. Other IEH investigations are the Solar Extreme Ultraviolet Hitchhiker, Spectrograph/Telescope for Astronomical Research, Solar Constant experiment (SOLCON), Ultraviolet Spectrograph Telescope for Astronomical Research (UVSTAR), and two Get-Away Special (GAS) canister experiments. The IEH experiments are mounted on a Hitchhiker bridge in Discovery's payload bay. Two other GAS can experiments which are not part of IEH are attached to the side of the cargo bay.

Cryogenic Thermal Storage Unit Flight Experiment -- The fifth in a series of Hitchhiker cryogenic test bed payloads, CRYOTSU will be housed in a canister attached to the side of Discovery's payload bay. CRYOTSU is designed to demonstrate the functionality of four spacecraft thermal control devices in the weightlessness of space.

Hubble Space Telescope Orbital Systems Test -- HOST will provide an on-orbit test bed for studying the effects of radiation and zero gravity on the performance of components planned for installation during the third Hubble Space Telescope servicing mission, targeted for 2000. HOST also will evaluate new technologies such as an advanced cooling system for science instruments.

The Electronic Nose is an experimental instrument to identify atmospheric compounds for monitoring the air quality on the Space Shuttle and International Space Station. Based on the human nose, its thin polymer sensors can detect both organic and inorganic compounds. Other middeck experiments include the Biological Research in Canisters to investigate the effects of space flight on small arthropod animal and plant specimens, and the Protein Crystal Growth-Single Locker Thermal Enclosure System.

The Mercury-Atlas vehicle which Glenn flew into space had a launch weight of less than 1/18th and a liftoff thrust of about 1/20th of the Space Shuttle – less than the thrust produced by just one of the Shuttle's three main engines. At 72 feet high, the Mercury-Atlas was about 2.5 times shorter than the 184.2-foot-tall Shuttle.

Only one astronaut could fit into the Mercury capsule, while the orbiter can accommodate up to 10 people in an emergency.

Glenn, the oldest of the Mercury astronauts, was 40 when he experienced a maximum of 8 g's on his first flight; he will be subject to no more than 3g's on STS-95. He was strapped in for the nearly five-hour duration of his first space flight; this time, he will be able to float weightless during the nine-day mission.

While Glenn was the first American to orbit Earth in 1962, the first human was Yuri Gagarin of the Soviet Union, who spent 108 minutes making one orbit of Earth in his Vostok 1 spacecraft 10 months earlier.