I strongly suspect that Russell Eberst's unknown of 4 April 2000 is the rocket body 99057C, or an as yet uncatalogued fragment. Here is my analysis: On 6 April, Mike Waterman observed Russell Eberst's unknown of 4 April, and produced elements which he posted here earlier today. Here is the 2-line version: 1 99999U 00095.88774000 .00000000 00000-0 00000-0 0 06 2 99999 98.5120 172.5000 0138900 132.7500 228.4271 14.48925972 03 I obtained a very similar result, with low residuals, using Elcor: 1 99999U 00095.88774000 .00000000 00000-0 00000-0 0 06 2 99999 98.5455 172.5439 0128796 135.7744 225.4205 14.48930416 08 The orbit is very similar to that of the rocket body 99057C, which for some reason, NORAD has not updated for more than 10 days. In reviewing its recent history (below), I noticed a hiccup in the mean motion after day 71. A lower mean motion was reported on day 76, and a much higher one was reported on day 87, and since then, nothing. Looks like something has confused NORAD. 1 25942U 99057C 00087.75147262 .00001539 00000-0 43601-3 0 784 2 25942 98.5194 164.2157 0012053 259.2102 100.8219 14.46902945 23941 1 25942U 99057C 00076.13359437 .00001386 00000-0 39570-3 0 761 2 25942 98.5354 152.5501 0012289 295.8827 58.2073 14.46692961 22276 1 25942U 99057C 00071.63855104 .00001400 00000-0 39810-3 0 745 2 25942 98.5348 148.0201 0012205 309.5032 50.4759 14.46871864 21629 1 25942U 99057C 00069.14898026 .00001603 00000-0 45410-3 0 803 2 25942 98.5373 145.5131 0012467 316.9224 43.0989 14.46866365 21269 1 25942U 99057C 00068.24996416 .00001640 00000-0 46420-3 0 730 2 25942 98.5374 144.6076 0012496 319.5945 40.4314 14.46863701 21139 1 25942U 99057C 00062.23343328 .00001573 00000-0 44581-3 0 776 2 25942 98.5375 138.5437 0013460 337.8453 22.2158 14.46841607 20260 1 25942U 99057C 00060.22790712 .00001125 00000-0 32249-3 0 700 2 25942 98.5385 136.5233 0013876 343.1420 16.9315 14.46831727 19971 If the unknown is 99057C, then its mean motion now is too high, relative to the last reliable 99057C elements, of epoch day 71. Allowing for decay since then, the unknown's orbital period is about 8 s lower than would have been expected of 99057C. As a result, they are pulling away from one another at the rate of about 2 min/d. On 6 April, they were 38 min apart in time, which means they were last near each other about 19 days earlier, on day 78, close to the date of the hiccup in NORAD's elements. Since NORAD lost 99057C soon after, I speculate that it may have been due to a small, but sudden change in its orbital period. Another possibility is that the unknown is a fragment of 99057C that may have been shed around day 78. In that case, where is 99057C? Also, it is interesting that Russell and Mike have observed other fragments in nearly same the orbit as the unknown. This leads me to suspect that 99057C may have broken up. Another fact that tends to support a break-up, is that 99057C's RCS (radar cross-section) has gone from 14.1 m^2 (as given in Mike McCants latest RCS file, dated 20 Mar 2000), to only 0.0125 m^2. Mike's RCS was based on 3 values issued in the past by GSFC. Assuming the values Mike used pre-dated epoch day 71, then the tiny RCS that is now given by GSFC may be because NORAD's last elset of 99057C was really a fragment. If 99057C has broken up, then I would think that NORAD would have released some elements of fragments by now. The absence of such, argues against a break-up. 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 : Fri Apr 07 2000 - 12:53:35 PDT