I wrote: > 91082A's orbit is sun-synchronous, so its visibility window > is seasonal - during the Northern and Southern hemispheres' > respective winters. > > Weather permitting, it would be worthwhile performing a > planar search for debris. And minutes later, Greg Roberts reported three positions observed last night: http://satobs.org/seesat/May-2004/0345.html Here they are, along with Paul Gabriel's of May 03: 21798 91 082A 8305 G 20040503015037570 27 35 0734628-284686 26 21798 91 082A 0433 P 20040526175532000 56 15 1214399+033436 39 R+071 05 21798 91 082A 0433 P 20040526175631400 56 15 1150235+200649 39 R+073 05 21798 91 082A 0433 P 20040526175746600 56 15 1128303+332954 39 R+076 05 What these numbers mean: http://www.satobs.org/position/IODformat.html It was 57 s early and within 0.1 deg of the predicted track of 42 d old elements, after compensating for Earth's rotation. In my earlier post, I mistakenly stated that Paul observed it 0.22 deg off track after compensating for its 24 s early arrival. That was the actual cross-track difference; compensating for Earth's rotation reduces it to 0.08 deg. Assuming Paul and Greg observed the same object, which I suspect they did, the change in its orbit was fairly small. Here are updated elements, based upon the above observations: DMSP B5D2-6 6.4 1.7 0.0 6.6 v 5.43 1 21798U 91082A 04147.68193666 .00000150 00000-0 76795-4 0 05 2 21798 98.6774 169.0941 0011441 256.3294 103.6607 14.15552118 08 WRMS residuals = 0.029 deg. Description of 2-line elements: http://www.satobs.org/element.html I propagated the 42 day old elset to the ascending node prior to Greg's observation, and adjusted only the RAAN, mean anomaly and mean motion. The fragmentation had only a small effect on 91082A's orbit, and Greg observed it to be about as bright as usual, so I now believe that the fragmentation was relatively minor; perhaps the rupture of a hydrazine tank, or the explosion of a battery, as suggested by one correspondent. Most of the resulting debris would likely be too small to observe. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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