Columbia returns home to KSC

satellites and Bill Shepherd monitored a Boeing study called the Crystals by Vapour Transport Experiment (CVTE), which produced large, high-quality, electro-optical cadmium-telluride crystals.

''This experiment is important to the semiconductor industry because the ability of semiconductors to process and store information is dependent on the quality of the crystals used,'' said Boeing's CVTE Project Manager Barbara Heizer before the flight. ''Large, uniform crystals grown during spaceflight may lead to greater speed and capability for computers, sensors and other electronic devices.''

Medical experiments were also conducted during the longer-than-normal, 10-day mission. One, the Physiological Systems Experiment (PSE), studied the effects of hormone therapy on changes in rats in the microgravity environment. ''The goal of this experiment'', said Roy Walker of designer Merck and Company of Pennsylvania, ''is to see if an experiment compound we're developing will prevent or slow osteoporosis from developing in microgravity during spaceflight. If it does, the compound may be a useful treatment for many people on Earth who suffer bone loss from being bedridden for long periods of time due to accidents or paralysis.''

Twelve adolescent male albino rats (Rattus norvegicus), accommodated in a pair of Animal Enclosure Modules (AEMs) in Columbia's middeck, were the test subjects for the PSE experiment. They were matched by body mass into pairs, and one member of each pairing was given subcutaneous injections of an anti-osteoporotic protein two days before launch, followed by a second injection of a bone marker called calcein. The other rats were left untreated. Other medical investigations included a Canadian study of back pain, which had been experienced by several astronauts.

During a Spacelab mission in January 1992, Canadian Payload Specialist Roberta Bondar conducted the first in-depth studies of this back pain and found it to be at its worst during the first few days in orbit. Her research suggested that it may be attributable to spinal increases of up to 7.5 cm, caused by a lengthening of the spinal column and of the normal spinal 'curves'.

This, investigators theorised, may itself have been due to increased water content and thus the height of the discs between the spinal vertibrae. The resulting tension on soft tissues such as muscles, nerves and ligaments might then lead to the occurrence of back pain. Throughout STS-52, MacLean carefully measured his height and used a special diagram to record precise locations and intensities of back pain.

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