An amplitude of +/-10% due to the moon in the drag value is unlikely for LEO. More likely it would be noticed as a change in node orientation. The change is sinus-like, so I do not believe it is the result of orientation changes of the ISS between two modes of operation. BSTAR includes the atmosphere density at the mean height of a satellite at the epoch of the TLE. To be more exactly, it contains a factor that resembles the relation of the real atmospheric density at the epoch (measured through the acceleration of the satellite) and the fourth degree polynom used to model the atmospheric density in SGP4 (see my paper http://people.freenet.de/morheg/englisch.txt). So atmosphere density has an influence on the BSTAR value. Most likely it seems to me now that the change of the perigee being in sunlight, the line of nodes lying in line or perpendicular to the sun, or similar effects have an influence on BSTAR, which could explain the variation. This is where I will look further. Thank you to all who made suggestions! Moritz Heger ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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