Re: Galaxy 7

Date: Thu Mar 17 2005 - 08:37:19 EST

  • Next message: Greg Roberts: "Rosetta positions 4 March 2005"

    Ed has certainly got the hang of it, and I admit I also find difficult to
    visualize the geometry of a rotating satellite with a panel, and the 
    changing (apparent) solar position.
    A small addition: (very generally) the flashes occur near the same
    RA and decl. on consecutive days, mainly displaced by the apparent
    solar motion. How early or late this happens to be depends partly
    on the siderial period of the satellite. 
    Even the majority of non-operational GEOs have their panels
    pointing near the celestial equator and (thus) the rotation axis
    near the celestial poles (SuperbirdA is the most notable exception). 
    This means that the path of the flashes is roughly E-W.
    As Ed noted, as Sun gains about 0.4 degrees declination daily now,
    so does the position of the best flashes. 
    Galaxy 7 moves very nearly on constant declination where you saw
    flashes, which can make the visibility period very long. But the unfortunate
    side effect is that the intersection track/flash path can move tens of 
    sideways per day, and after five days the flashes will pass "your" RA two 
    above your obs, and be very difficult to spot. You need to move -12 degrees
    in latitude to see "your" flashes then.
    ----- Original Message ----- 
    From: "Ed Cannon" 
    > Thomas Dorman wrote:
    > > > Galaxy 7 flashing. ... when out this coming morning at 
    > > around the same time would I be able to see Galaxy 7 flash again.
    > In general (very general), the ones that drift to the west 
    > (the great majority of drifters) flash some minutes later 
    > from one night to the next.  ... It's all very technical, and I don't 
    get a lot of it.
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