Charles posted an observation project in the restricted "So you want to see satellites" Facebook group. It relates to possible future breakups of DMSP 15,16,17. He included a map showing one position and a rather dim partial track. Using a recent feature at Heavens-Above I extended it to show full world tracks, with extent of surface darkness, and sunlight and shadow along the tracks. This was made as three images for 02:24 UTC Jan 24 to have surface darkness. I combined them with PaintShop Pro ("Lightest") The tracks are drawn true to the topography. So when F15 passes e.g. South African latitude (moving southbound) some 15 minutes after the predicted position, the distance from F15 to the morning terminator will be about four degrees shorter, and F16 track some 15 minutes before prediction is four degrees (400 km) further away as it passed near Cape Town. F17 will only be in the E during dawn. Chris Peat described the mapping feature : "I also added a time parameter to make it easier for you. If you use this URL, you can modify the "mjd" parameter, which stands for the Modified Julian Day number. Today (2016-03-14 midnight UTC) is 57461.0 http://www.heavens-above.com/orbitdisplay.aspx?icon=iss& width=1200&height=600&satid=25991&mode=M&mjd=57767.10 You could also adjust the size using the width and height parameters. (Use same aspect ratio !) The mode parameter controls the view. Possible values are; A - above satellite (aspect ratio 1:1) M - map (ground track over rectangular Earth map) (1:2) N - above orbital plane (1:1) " _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Tue Jan 24 2017 - 04:00:55 UTC
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