karn@mouton.UUCP (08/13/84)
The comment was made that the US is more "tidy" in keeping spent boosters, etc, out of orbit than is the Soviet Union. This is correct. With all of the objects in orbit being tracked by NORAD, they want to minimize the number as much as possible. On a low orbit mission, the upper stage is maneuvered into an elliptical orbit with a low perigee after the payload is separated, so that the launcher (which has a very large area/mass ratio to start with) will decay within several years. For example, the Delta second stage on the Landsat-5/UoSAT-Oscar-11 launch was dropped into a 500 x 700 km orbit after the payloads were deposited in 700 km circular orbits. On geostationary launches, the initial elliptical transfer orbit generally has a very low perigee (e.g., 200 km for the Ariane). This serves the dual purpose of shortening the lifetime of the launcher upper stage and reducing the energy required to reach transfer orbit. Ariane 3rd stages have been reentering in about 3 years; I don't know about STS PAMs, but they will probably also reenter fairly quickly due to the low starting perigee of 300 km or so (the circular altitude of the shuttle). Phil