The Dash (Density And Scale Height) satellites were
2.5-m-diameter balloons used to measure air densities at
altitudes of approximately 3500 km. The area-to-mass ratio for
the spacecraft was 40 sq ... cm/g. The orbit, originally circular,
increased in eccentricity rapidly under the action of solar
radiation pressure. This experiment used the variations in orbit
characteristics of the Dash balloon satellite to deduce neutral
air densities and to study the effect of solar radiation
pressure. Other effects, such as terrestrial radiation pressure,
lunar gravity, and solar gravity were also observable.
Dash 2 reentered the earth's atmosphere on April 12, 1971.
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