|  Dave | ||||| Sunday, March 03, 2002 - 01:32 am
There is some atmosphere at HST's altitude -- very little, but some. All satellites in low earth orbit will re-enter eventually due to atmospheric drag, if not reboosted. ISS, for example, has a built-in reboost engine for this purpose. The effect is particularly pronounced during times of high solar activity -- the increased solar wind heats the outer atmosphere and causes it to expand, raising the atmospheric density in low earth orbit. |
