>Looking closer on the BSTAR drag value of the ISS over time, >I noticed that it is varying by around 10% with a period of >about 20 days. What about where its perigee is -- at the equator versus elsewhere, and is the perigee occurring in darkness or daylight? This yields four conditions: near equator in daylight (most drag) near equator in darkness away from equator in daylight away from equator in darkness (least drag) There's at least one other thing, the issue of the southern hemisphere being "fatter" than the northern (pear-shaped Earth), but I don't know if it could produce a noticeable effect. I'm neither equipped nor qualified to do the analysis, but maybe the above might be involved in the 20-day variation. Ed Cannon - ecannon@mail.utexas.edu - Austin, Texas, USA ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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