The Air Force has reclaimed and will soon launch a communications satellite that had been hanging in the Smithsonian Institution's Air and Space Museum for 15 years.

Using the old satellite instead of building a new one will save more than $2 million, according to Air Force officials.

The refurbished, 270-pound satellite, renamed Polar BEAR, for Polar Beacon Experiment and Auroral Research, is to carry Defense Department-sponsored experiments into a polar orbit Oct. 8 from Vandenberg Air Force Base in California. The experiments are aimed at helping other communications and meteorological satellites over the North Pole to overcome radio interference caused by the aurora borealis, or northern lights.

The Air Force said it will also save another $6 million to $8 million by using flight-qualified spare parts for the satellite's launch vehicle, a Scout, which has been spared the technical problems that have grounded the nation's other rocket boosters.

"Nothing is ever permanently retired," said Walter Boyne, director of the museum. The Air Force "had some need for the hardware and will use it."

Boyne said this is not the first time that space or defense agencies have borrowed for testing or reuse some of the aircraft and other equipment on display at the museum. "We have a lot of things which would be capable of launch."

The retooled Polar BEAR is an Oscar 17 satellite that was built in the mid-1960s by the Navy as a spare but never launched.

Researchers at Johns Hopkins University Applied Physics Laboratory in Laurel, where the satellite is undergoing prelaunch testing for the Air Force, persuaded the museum to trade its Oscar 17 for a Transit 5A, an earlier and almost identical model of the first operational navigation satellite used by the Navy.

Allan Needell, a curator at the Air and Space Museum, said the trade was made about a year ago and that the Transit 5A was what the museum had wanted all along. The museum's original Satellite Gallery has been replaced with a new exhibit, however, he said, so the Transit 5A is now in storage.

The electronics for the Oscar 17 were also stored while the satellite was on display at the museum, according to an Air Force spokeswoman. She said that when Johns Hopkins researchers later tested them, most of the equipment was usable and only one solar cell out of thousands on the solar panel was rated marginal and had to be replaced.