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geosynchronous orbit. The other two returned to Earth with Challenger after nearly a week of testing and experimentation in space. One of these, the Shuttle Pallet Satellite, or SPAS, is a re-usable platform for mounting many types of science instruments and equipment, and was operated during STS-7 both inside the cargo bay and-another shuttle first-outside as a free-flying spacecraft. The fourth payload in the cargo bay, named OSTA-2 for NASA's Office of Space and Terrestrial Applications, remained fixed inside the bay, where four instrument packages ran materials processing experiments-mixing, melting or crystalizing such substances as metal alloys and glass in the weightless vacuum of space. The OSTA-2 experiments were developed by the United States and the Federal Republic of Germany.

Also out in the cargo bay, attached to its walls, were seven Getaway Special canisters with 22 experiments sponsored by high school and university students, a private company, and two government agencies. Inside Challenger, two more experiments were carried in the mid-deck cabin. Both of these had flown on previous shuttle missions: the Continuous Flow Electrophoresis System (CFES) for separating large quantities of pure pharmaceutical fluids in low gravity, and the Monodisperse Latex Reactor, which manufactures small rubber spheres of identical size to be used for precise calibrations and measurements. 

The total payload weight for Challenger's second trip into space, both inside and out in the cargo bay, was 14,449 kg., or 31,985 lbs.

After a smooth and trouble-free countdown, Challenger was launched on time from the Kennedy Space Center's Pad 39A at 7:33 a.m. EDT on June 18 into a circular orbit at 256 km. (160 nautical mi.) altitude. The accuracy of the vehicle's ascent trajectory was the best yet for a space shuttle.

Mission Objectives

The first order of business after setting up station in orbit was to release the Anik C-2 communications satellite, sponsored and paid for by Telesat of Canada. Approximately 9 1/2 hours into the mission and shortly before the end of their first workday in space, the crew spring-ejected Anik from its spinning platform in the cargo bay and fired Challenger's engines to back the shuttle away from the satellite. A Payload Assist Module (PAM-D) rocket motor attached to Anik then fired to begin raising it to its 36,000 km. (22,300 mi.)-high geosynchronous orbit over the equator, where it will initially be used for North America's first direct satellite-to-home pay TV service.

Challenger's second day in orbit featured a nearly identical deployment of the Indonesian Palapa B-1 satellite, which also was boosted by a PAM-D rocket to its geosynchronous station over the islands of Indonesia. This first in a new series of Indonesian satellites will be used for many of that nation's telecommunications needs, including video, telephone and data transmission.

By the fourth day of the STS-7 mission, both of these communications satellites had reached their desired high orbits, on time and on target.

With the two commercial satellites successfully delivered, the crew turned to other equipment and tasks, including the activation of seven Getaway Special canisters, more than any other shuttle had carried. These varied experiments were designed to test, among other things, the effects of space on the social behavior of an ant colony, on radish seeds, germinating snowflowers, liquid mercury, and soldering operations. Two of the canisters featured new Getaway Special technologies, including the first fully automatic experiment (turned on by a barometric switch rather than by the crew) and the first canister with an opening door.

Also on this second day of the mission were the first checkouts of the Ku-band antenna which will be used for ground communications through the Tracking and Data Relay satellites in geosynchronous orbit. The antenna's motion and signal acquisition were successfully proven, and it was pronounced ready for operation.

The crew began their third workday with a test that proved that the cabin air pressure could successfully be reduced from 14.7 pounds/square inch to 10.2 psi by controlling the mix of oxygen and nitrogen in the air. This technique is being considered as an alternative to the 3-hour pre-breath of pure oxygen that is now required before astronauts leave the controlled environment of the shuttle for space-suited extra-vehicular activity. Cabin pressure would be dropped while the crew was sleeping to allow a shorter pre-breath time for purging nitrogen from an astronauts bloodstream prior to a spacewalk, all to avoid the body's painful reaction to fast changes in atmospheric pressure, commonly known as the "bends."

During this 30-hour test, the crew also lowered Challenger's orbit slightly to begin a run of experiments with the Shuttle Pallet Satellite (SPAS-01) mounted in the cargo bay. SPAS is the first shuttle cargo financed as a private commercial venture by a European company, Messerschmitt-Bolkow-Blohm of Munich. The SPAS concept is to sell space on the platform-a supporting pallet that provides power and computer processing to attached instruments-to several different customers on future shuttle flights. The SPAS itself is used over again.

For STS-7, ten American and European experiments were fixed to the pallet. Seven of these operated while SPAS remained in the cargo bay: microgravity experiments with metal alloys, heat pipes, and pneumatic conveyors; a new instrument to control a spacecraft's position by observing the Earth below; a remote sensing scanner that was pointed at different kinds of terrain and land/water boundaries; a mass