Hi Kevin, Thanks for posting this video. I've determined the following positions from it: 28537 05 004A 1775 G 20130309085150221 17 25 1828698+374966 37 S 28537 05 004A 1775 G 20130309085159635 17 25 1841140+390367 37 S 28537 05 004A 1775 G 20130309085206453 17 25 1850163+395237 37 S 28541 05 004C 1775 G 20130309085154321 17 25 1825904+365984 37 S 28541 05 004C 1775 G 20130309085159635 17 25 1832830+374398 37 S 28541 05 004C 1775 G 20130309085209636 17 25 1845867+390010 37 S The NOSS 3-3 pair has not been seen for 22 days, yet they are only 40s early. This is interesting because the whole NOSS 3-X constellation has been reorganized after the launch of NOSS 3-6 on 13 September 2012. NOSS 3-5 went into a higher orbit at the end of October and returned to a mean motion of 13.4062 around the end of January 2013. NOSS 3-3 went into a higher orbit around the 20th of October 2012. The higher orbit of NOSS 3-3 could mean two things. It could have been decomissioned. This is what happened to the NOSS 3-1 pair, which was were into lower orbits, with the reorganization after the arrival of NOSS 3-5. However, since the NOSS 3-3 pair is still intact, the observations seem to suggest that it is still in the higher orbit and has not arrived at the required spacing relative to the other operational NOSS 3-X pairs. It is interesting to predict what the required spacing would be. I haven't had a chance to do this in much detail, but a quick look suggests the following. The RA of the ascending nodes of the first four pairs (3-1 to 3-4) are approximately offset by succesive offsets of 90 degrees. NOSS 3-5 was launched in a plane with an RA of about 25 degrees lower than NOSS 3-1 and NOSS 3-6 with an RA about 25 degrees lower than NOSS 3-2. Prior to the arrival of NOSS 3-6, NOSS 3-2 and 3-3 were at about the same relative place in their orbits (with respect to their own ascending nodes); at a node passage of NOSS 3-2, NOSS 3-4 had about 20 degrees to travel in its orbit to reach its ascending node. At the same time NOSS 3-3 and 3-5 were about half an orbit offset, with NOSS 3-5 being about 40 degrees from its node when NOSS 3-3 went through the ascending node of its orbit. This table shows the RA of the ascending nodes (ASCN) as well as the orbital longitudes (with respect to the ascending node) before (PRE) and after (POST) the arrival of NOSS 3-6. All angles are in degrees. NOSS ASCN PRE POST 3-1 90 3-2 195 340 340 3-3 65 160 ?? 3-4 320 320 320 3-5 250 120 70 3-6 170 180 Now where will NOSS 3-3 end up? Since both NOSS 3-3 and NOSS 3-5 repositioned after the arrival of NOSS 3-6, I can only assume that some sort of symmetry needs to be reached. My guess is that NOSS 3-3 will stay in its orbit until it reaches a point where it will be offset from NOSS 3-5 by about 20 degrees, i.e. at an orbital longitude of 50 degrees. In its present orbit it would reach that near the end of May. If I can find the time I'll try to back this up with a simulation of how often and how regular NOSS pairs pass certain latitudes at a given longitude. However, I wouldn't be surprised if all of these guesses are wrong. Regards, Cees _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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