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  • $\begingroup$ Remember Tiangong-1? Even the day before they changed the predicted time of impact to serval hours later because of lack of expected solar activity. So it sounds like there is a pretty significant amount of variation, though I don't have any numbers. $\endgroup$
    – Nathanael Vetters
    Commented Apr 10, 2018 at 12:25
  • $\begingroup$ @NathanaelVetters the strong feedback in atmospheric reentry makes the problem much more unpredictable. At 400 km the ISS only looses about 10 meters or less per orbit, so that kind of exponential behavior isn't really a good model here. $\endgroup$
    – uhoh
    Commented Apr 10, 2018 at 12:52
  • 1
    $\begingroup$ Not enough for a true Answer, but perhaps it’ll help somebody: there’s a significant difference in atmospheric density (at 100’s of km altitude) with latitude. That would be a twice-per-orbit effect. It also has a day-night difference. The only non-pay walled paper I have handy is Newton&Pelz: agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/JA074i016p04169 $\endgroup$
    – Bob Jacobsen
    Commented Apr 10, 2018 at 13:47
  • $\begingroup$ Oops, sorry, looks like that paper actually is paywalled. My mistake. I’ll see what I can find... $\endgroup$
    – Bob Jacobsen
    Commented Apr 10, 2018 at 13:52
  • $\begingroup$ @BobJacobsen it's available from NASA. Although data from Explorer in 1966 may not be the final word on the subject, it certainly is interesting to read about! $\endgroup$
    – uhoh
    Commented Apr 10, 2018 at 14:43