Mark Whorton wrote: > Let me emphasize this -- if we are to learn that Cosmos 1 > actually is in orbit, you may very well be the ones to > determine that and let us know. Since the object would be expected to be readily visible to the unaided eye, it would be fairly easy to conduct a planar search. Think of an orbit as an imaginary ring around the Earth. A lost satellite is moving rapidly along the ring, at an unknown location. If we can stare at the ring for as long as it takes the satellite to circle the Earth, then we must eventually see it. Since the Earth rotates under the orbit, the imaginary ring appears to move across the sky, so we cannot just stare in one place and expect to see the object - we must frequently adjust our aim to follow the ring. Of course, for the method to work we need to have a pretty good idea of the location of the ring, i.e. the orientation of the orbital plane with respect to the Earth. Radio signals that may have come from Cosmos 1 were received at several locations soon after launch, at about the expected times. For Cosmos 1 to have been the source, it would have to have entered at least very roughly the planned orbit. Therefore, it seems reasonable to use the planned orbit as the basis for a planar search. Appended are 18 element sets that differ from the planned orbit only in their mean anomaly. The mean anomaly is the angle that states a satellite's position within its orbit. Its range is from zero to 360 degrees. The appended elsets cover the mean anomaly at 20 deg intervals. Since the orbital period is 101 min, 20 deg of travel within the orbit is equivalent to 101 / 360 * 20 = 5.6 minutes. So the time difference between passes predicted by successive elsets below is about 5.6 min, which is a reasonably fine net for searching. To plan a planar search, start by feeding all 18 elsets to your favourite prediction program. Next, organize the output in chronological order from the earliest pass to the latest. This method works equally well for text and graphical programs. In the case of a graphical program, print the portion of the predicted track near culmination. In the case of a text program, I suggest summarizing the results by tabulating the circumstances of the culmination of each prediction. For example, Time Azimuth Elevation 02:05 95 30 02:11 97 34 02:17 100 39 etcetera This sample table means that if the satellite is in the planned orbital plane, and passes at time 02:05, then it will culminate in the east at azimuth 95 deg, elevation 30 deg. Since the Earth rotates toward the East, later passes will be higher in the east, and the very latest will be in the west. Since there was a problem during its ascent, it is likely that even if Cosmos 1 reached orbit, it is somewhat different than planned; therefore, use the search plane only as a guide. If you see a reasonably bright satellite travelling in the expected direction, but quite a bit lower or higher in the sky than predicted, make note of it anyway. Since Cosmos 1 is expected to be bright (if its solar sail deployed), it is best to search with your unaided eyes, so that you can scan a wide area either side of the predicted path. Do not quit observing after spotting the first bright candidate to come along. Note the observational details, then resume your watch. Ideally, each observation you report will consist of one or more timed positions of a satellite with respect to the stars. For example, passed 2 deg below Vega at 02:12:15 UTC. Or passed between two stars, 30 percent from star A to B. If you happen to know the names of Star A and B, note them down; otherwise, sketch them along with other nearby known stars, sufficient to be able to identify them later. Note each object's approximate magnitude and whether or not the object was steady or varying in brightness. if varying, note its approximate period of variation. Upon completing your search, use Heavens-Above or CalSky to predict all bright satellites expected to pass during your search, to help identify the objects you saw. Those that you cannot identify should be reported to SeeSat-L, since one of them might be Cosmos 1. More likely, they will prove to be objects normally too faint to be included in Heavens-Above's or CalSky's standard predictions, but which can be identified using other methods. Cosmos 1 was programmed to deploy its sail on 2005 Jun 26 during the period 04:41:59 to 04:46:58 UTC, so it probably is not worth searching before then. If I have forgotten any important or useful observing tips, please correct me. Time permitting, I may cook up some additional search elsets, based on lower and/or more eccentric orbits than planned. Happy hunting! Ted Molczan 1 70901U 70901A 05172.83732212 .00000000 00000-0 00000-0 0 00 2 70901 80.0406 213.0716 0058440 136.4904 0.0000 14.25860033 18 1 70902U 70902A 05172.83732213 .00000000 00000-0 00000-0 0 03 2 70902 80.0406 213.0716 0058440 136.4904 20.0000 14.25860033 11 1 70903U 70903A 05172.83732214 .00000000 00000-0 00000-0 0 06 2 70903 80.0406 213.0716 0058440 136.4904 40.0000 14.25860033 14 1 70904U 70904A 05172.83732215 .00000000 00000-0 00000-0 0 09 2 70904 80.0406 213.0716 0058440 136.4904 60.0000 14.25860033 17 1 70905U 70905A 05172.83732216 .00000000 00000-0 00000-0 0 02 2 70905 80.0406 213.0716 0058440 136.4904 80.0000 14.25860033 10 1 70906U 70906A 05172.83732217 .00000000 00000-0 00000-0 0 05 2 70906 80.0406 213.0716 0058440 136.4904 100.0000 14.25860033 14 1 70907U 70907A 05172.83732218 .00000000 00000-0 00000-0 0 08 2 70907 80.0406 213.0716 0058440 136.4904 120.0000 14.25860033 17 1 70908U 70908A 05172.83732219 .00000000 00000-0 00000-0 0 01 2 70908 80.0406 213.0716 0058440 136.4904 140.0000 14.25860033 10 1 70909U 70909A 05172.83732220 .00000000 00000-0 00000-0 0 05 2 70909 80.0406 213.0716 0058440 136.4904 160.0000 14.25860033 13 1 70910U 70910A 05172.83732221 .00000000 00000-0 00000-0 0 00 2 70910 80.0406 213.0716 0058440 136.4904 180.0000 14.25860033 17 1 70911U 70911A 05172.83732222 .00000000 00000-0 00000-0 0 03 2 70911 80.0406 213.0716 0058440 136.4904 200.0000 14.25860033 11 1 70912U 70912A 05172.83732223 .00000000 00000-0 00000-0 0 06 2 70912 80.0406 213.0716 0058440 136.4904 220.0000 14.25860033 14 1 70913U 70913A 05172.83732224 .00000000 00000-0 00000-0 0 09 2 70913 80.0406 213.0716 0058440 136.4904 240.0000 14.25860033 17 1 70914U 70914A 05172.83732225 .00000000 00000-0 00000-0 0 02 2 70914 80.0406 213.0716 0058440 136.4904 260.0000 14.25860033 10 1 70915U 70915A 05172.83732226 .00000000 00000-0 00000-0 0 05 2 70915 80.0406 213.0716 0058440 136.4904 280.0000 14.25860033 13 1 70916U 70916A 05172.83732227 .00000000 00000-0 00000-0 0 08 2 70916 80.0406 213.0716 0058440 136.4904 300.0000 14.25860033 17 1 70917U 70917A 05172.83732228 .00000000 00000-0 00000-0 0 01 2 70917 80.0406 213.0716 0058440 136.4904 320.0000 14.25860033 10 1 70918U 70918A 05172.83732229 .00000000 00000-0 00000-0 0 04 2 70918 80.0406 213.0716 0058440 136.4904 340.0000 14.25860033 13 ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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