Re: ISS saturn transit

From: John Locker (
Date: Sun Jan 18 2004 - 02:21:52 EST

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    ----- Original Message ----- 
    Subject: Re: ISS saturn transit
    Hi Tom,
    > The main problem is that, without a high-speed camera a la Roland
    Stalder's 16
    > August '03 solar transit, it'll just be pot luck as to how close you can
    > actually catch it to Saturn.
    Yes , I agreee , maximim speed I might be able to run would be about 30 fps.
    > Technically speaking, it appears that the angular diameter of the ISS will
    > greater than that of Saturn, so if you do get it, it'll be an occultation
    > maybe an eclipse?) rather than a transit.
    True , but that only applies if I actually caught the station "full on" , I
    suspect if anything , I might just see a solar panel clip the rings.
    > ISS Transit is almost ready to go back on the air. My mother had a knee
    > replacement just before Christmas, so most of the "spare time" I thought
    > have for program changes went up in smoke. Something I'd hoped to add- and
    > still get around to it- are ISS Jupiter & Saturn encounters.
    Great stuff ( hope your mum is feeling better !)
    > One thing I've implemented is ray-tracing through the atmosphere.
    Actually, it
    > appears that such presumed precision only makes a difference of a few
    minutes of
    > arc, even at an elevation angle as low as about 1.5 degrees (and
    essentially no
    > difference at high elevations). And, likely as not, the imprecision in the
    > state vector is generally likely to be much greater than the precision
    added by
    > carefully accounting for atmospheric refraction.
    Yes , we found this with the Mars encounter a couple of months ago.
    > I understand from Arnold Barmettler that he seems to be of the opinion
    that MCC
    > TLEs aren't very reliable after a day or so (from my limited experience,
    > come to the opposite conclusion), so he only uses them for long-range
    > predictions; instead using fresh OIG TLEs for near-term predictions. (Just
    > today, I made a request to OIG for a "historic TLE" for the 16 August
    > transit, to compare with my MCC TLE prediction.)
    That would be interesting to do with my two consecutive transits of August
    14 as it would provide quite a high degree of accuracy , having two full
    disk passes on video.
    > I'd suggest that, if possible, you also set up a camera with a time-lapse
    > exposure, so that it'll be possible to determine the prediction accuracy.
    Problem with that is that ISS will be in shadow , so a time lapse will show
    nothing but a very bright track , showing the movement of saturn.....the
    station will be invisible.
    I think the weather may well turn against me , but I was going to  use
    Arnold's predictions to pinpoint location ,  simply sit on Saturn   at  hi
    magnification / 30 fps , and just hope something turned up  :O)
    ( Odds conservatively estimated at one million to one ....he he  )
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