Hi Russ, > Awhile back, a comment was made that nadir pointing reflecting surfaces > could not generate visible flares. It was stated that this had been > discussed sometime ago in this discussion list. Can anyone point me > in the general direction of that discussion? I'm not sure I agree > with the general statement and want to find out what I'm missing in > my analysis of the geometry. It's easier for me to answer than to dig up references to prior Seesat discussions on the subject. Draw yourself a circle to represent the earth, and above it (say one earth-radius above) draw a horizontal dash to represent a satellite reflective surface pointing to the earth's center. Now draw two lines from the center of this dash to the earth limb: one tangent to the earth on the upper left, one on the upper right. Let the left line represent the direction to the sun. The right line then represents the reflection direction of a solar glint. You see the problem: in order to get the glint to intersect the earth (the right line angling inward), the sun line must also angle inward. But if it does, then the earth blocks the sun, and the satellite is no longer illuminated. Now, due to atmospheric refraction and scattering by the satellite mirror, the geometry can be off several degrees and still produce a bright reflection, but this can only happen when the satellite is within a few degrees of the horizon at the same azimuth as the (set) sun, and it must occur very close to satellite sunrise or sunset. Best, Rob ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
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