Björn Gimle wrote: > Since it has not been found on any of Ted's search elsets, I > would propose that the large raise was made, probably on the > evening of Dec.19, when USA 161 perigee was on the equator. > You can make search elsets by just adding small +- increments > to MM, eg 14.719 14.739 and 14.733 14.753 > > USA 129 +19 m/s > 1 24680U 96072A 3353.75010000 .00027406 00000-0 28356-3 0 11 > 2 24680 97.7982 53.4604 0545501 117.4163 359.3733 14.72878899 207 > USA 161 +14 m/s > 1 26934U 01044A 03353.84324512 .00002200 00000-0 90000-4 0 28 > 2 26934 97.9250 105.5870 0354827 0.1152 0.0078 14.74316830 15 We should keep in mind that planar searches are difficult to perform and not always immediately successful. It could have passed just outside Tony's binocular FOV, or been fainter than predicted when he used his unaided eye. Having said that, another possible manoeuvre would be to raise the perigee to 411 km, which would result in these orbits: Earliest arrival 1 71008U 03355.77065979 .00003000 00000-0 18672-3 0 05 2 71008 97.7982 55.4465 0393000 110.5013 0.0000 14.62800000 06 Latest arrival 1 70008U 03352.53751164 .00003000 00000-0 18672-3 0 03 2 70008 97.7982 52.2685 0393000 121.1405 0.0000 14.62800000 07 Three KH's have manoeuvred to the 411 km perigee at some point in their lives, two of which remain in orbit. USA 86 (92083A / 22251) did so in the spring of 1996, about 6 months after the launch of its replacement, USA 116 (95066A / 23728). It was de-orbited in June 2000. USA 161 (01044A / 26934) was launched in 2001 Oct, to replace USA 116. It entered the standard approx 270 x 1030 km orbit, but in January 2002, it manoeuvred twice, once to lower its apogee and once to raise its perigee, resulting in a 411 x 867 km orbit. The result is a very low drag orbit, but probably several years worth of normal reboost propellant was consumed to get there. All this is totally without precedent for a modern KH, so early in its mission. USA 116 was in approximately a 322 x 950 km in the fall of 2001, when it was replaced by USA 161. It was permitted to decay slowly from this orbit until the fall of 2002, when it apogee had decayed to about 850 km - about the same as USA 161's - whereupon its raised it perigee to 411 km. It has not manoeuvred since. All three of the 411 km perigee pioneers had been launched into the eastern KH plane, so for the western plane USA 129 to adopt it would be a first, but not shocking at this point. Performing the manoeuvre while still in a standard plane might have been shocking at one time, but USA 161 did it - and near the start of its mission, not the end. If USA 129 did raise its perigee to 411 km, it will be interesting to see whether or not the apogee was changed too. I could imagine a small decrease, to bring the mean motion to about 14.65 rev/d. This was done late in USA 86's life, apparently to make the ground-track nearly repeat every three days. To conserve propellant the operators could elect to wait for drag to trim the apogee. 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
This archive was generated by hypermail 2b29 : Fri Dec 26 2003 - 10:39:30 EST