I have derived the following from observations by David Brierley, Russell Eberst and Peter Wakelin received to this moment: Arc 2003 Apr 15 - 17 UTC: IGS 1A 0.0 0.0 0.0 5.6 v 1 27698U 03009A 03107.89039984 .00011248 00000-0 43600-3 0 00 2 27698 97.4220 180.0285 0010755 281.8399 78.1633 15.26126015 07 Arc 2003 Apr 16 - 17 UTC: IGS 1B 0.0 0.0 0.0 3.1 v 1 27699U 03009B 03107.91428222 .00015350 00000-0 67460-3 0 09 2 27699 97.3768 179.9120 0008304 152.0564 208.1118 15.21917873 07 WRMS residuals of both = 0.018 deg IGS 1A's ground track is resonant, repeating every 4 days (61 revolutions). IGS 1B is not currently resonant, but it may not yet be in its final orbit. It is close to a 5 day (76 revolutions) resonance, but this may be a temporary coincidence. At the epoch of the above elements, IGS 1B's node crossing trailed IGS 1A's by 34.4 minutes, increasing by about 4 min/d. My guess is that the time separation of the two will be fixed at some pre-determined value, at which time IGS 1B will match IGS 1A's mean motion. Orbit tweaking of both may go on for some time. Once the design orbits are achieved, periodic, perhaps frequent, maintenance manoeuvres are likely to be required. My guess is that the radar satellite is the brighter of the two, IGS 1B. Ted Molczan ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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