> This mystery has grabbed me, it begs solving. It seems to me there are 2 likely explanations for this phenomenon (Lacrosse 5 dimmings). 1) None or little of the satellite is white and instead it is made of mirror reflective surfaces such as gold foil. In this case the right shape can cause dimmings. One example might be a cylinder capped not with half spheres but capped with cones in turn capped with 1/3 spheres. 2) There is a large flat surface that can put most of the rest of the satellite into shadow and this surface is either dark (like solar panel) or is flat and shiny (reflecting light back towards the sun or at least away from the earth). Kind of like self-eclipse. I like possibility 2 as it seems more likely to me. There is a big observable difference between these 2 possiblities: #1 will result in the object going dark at different times for observers in different locations along the path because this is determined not just by the orientation of the satellite, but also by the observer-sat-sun angle. The dimming would move mostly along the ground path similar to a huge shadow (but not at the exact same speed because the satellite is probably rotating as it orbits). #2 will result in the object going dark for everyone at the same instant because it only depends on the orientation of the satellite with respect to the sun and not the location of the observer. So if you can get 2 observers to observe the "faint" on the same pass with accurate timings (1 second should be fine for observers 20 miles apart, 10 second accuracy for observers 200 miles apart) then we can possibly elminate one of the above 2 possibilities that I can think of. If it really does happen simultaneusly then the next step would be to try to figure out if there is some obvious axis of the satellite pointing to the sun at these times and try to be able to predict these dimmings based on sun position and guestimate satellite orientation. - George Roberts http://gr5.org ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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