Ed Cannon reported an unidentified satellite in this post: http://www2.satellite.eu.org/seesat/Aug-2001/0231.html I believe that this object probably is USA 159 r (26881 / 01033B), the Titan IV 2nd stage of the DSP satellite launched on 2001 Aug 06 at 07:28 UTC. As I write this, U.S. Spacecom has issued only two elsets, both of which have flaws: 1 26881U 0133B 01218.36215998 .00000332 00000-0 00000+0 0 18 2 26881 28.6968 249.1085 0243087 78.4785 282.1509 15.23242448 11 1 26881U 0133B 01226.28993968 .00000349 00000-0 00000+0 0 27 2 26881 28.6968 195.6121 0243087 165.2938 177.1552 15.22595359 1228 The ndot/2 decay terms are about 100 times too low for the stated orbit. The B* decay term required by the SGP4 orbit propagator is set to zero. The international designator is incorrect; it should be 01033B. Note also that second elset's inclination and eccentricity are identical and its mean motion has decreased, despite the passage of 8 days, which is unrealistic. By all appearances, U.S. Spacecom is struggling with this object's orbit, without success. Ed Cannon and Mike McCants have not been able to find the object in the above orbits in circumstances in which it should have been easily visible to the unaided eye. In a recent e-mail, Ed Cannon pointed out that previous Titan IV 2nd stages from DSP launches had been in significantly more eccentric orbits than the ones that U.S. Spacecom issued for this launch. For example, here is an early elset of the Titan IV 2nd stage of DSP 20, launched on 2000 May 08 at 16:01 UTC: 1 26357U 00024B 00131.15084957 .00421046 -54059-5 52085-3 0 94 2 26357 28.6455 279.7515 0402109 90.4083 274.2447 15.34290365 234 Inspired by Ed Cannon, I decided to check whether or not this would have been a more reasonable orbit for the DSP 21 launch, so I changed the Epoch and RAAN to match the circumstances of that launch: 1 77001U 01219.79459954 .00421046 -54059-5 52085-3 0 02 2 77001 28.6455 239.6200 0402109 90.4083 274.2447 15.34290365 232 Next, I tried to use this orbit to predict Ed Cannon's unknown of last night. I found that it was about 13 min too early, but near the correct track. When I allowed for Earth's rotation during 13 min, I found that Ed Cannon's unknown was within 1 min of time and a fraction of 1 deg of the predicted track. Also, eclipse followed by about 15 s, as Ed reported. A 13 min error after 8.3 days amounts to about a 6 s difference in the orbital period, which seems reasonable, given that no two launches are identical. More likely, the difference is due to small differences in all of the elements. I suggest the following search orbit, which is the above orbit, propagated to the time of Ed's observation 1 77002U 01228.12618056 .00439299 00000-0 52085-3 0 00 2 77002 28.6455 181.9913 0373000 183.5141 268.1500 15.41279729 05 Predictions should be accurate to within a few minutes of time for the next few nights. Ted Molczan ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Thu Aug 16 2001 - 06:22:03 PDT