I took advantage of a second consecutive, mostly clear morning, (rare here, at this time of year) to observe USA 193. Temperature was -18 C; wind chill -30 C, but I was outdoors for less than 10 min, so it was quite tolerable. The object exited eclipse at about 9 deg elevation, and was setting. I observed a single point, at just 7.9 deg elevation, before losing it to atmospheric extinction. Once again, the 25x100 binoculars proved indispensible, enabling me to just see the fainter of my two reference stars, which is mag 8.1. The use of those stars was pre-planned, so I simply waited for the object to appear; had I been tracking, I could not have spotted the fainter star. 29651 06 057A 2701 G 20080211105953450 17 25 1446548-382779 18 S+070 05 IOD format: http://www.satobs.org/position/IODformat.html Site 2701: 43.68764 N, 79.39243 W, 230 m The object was 3.4 s early relative my 24 h old elements, due to increased drag, resulting from increased geomagnetic activity in the interim: http://www.swpc.noaa.gov/rt_plots/kp_3d.html The kp index reached 5 during one three hour period, which is considered storm level; kp was 4 during three other periods. To more fully capture the effects of the spike on drag, I reduced the arc to one day, and adjusted only rate of decay, mean anomaly and mean motion: USA 193 5.0 2.5 0.0 4.3 v 255 X 268 km 1 29651U 06057A 08042.43411818 .00214910 00000-0 31472-3 0 05 2 29651 58.4821 69.5983 0009338 66.1500 294.0578 16.04437931 07 Arc 2008 Feb 10.46 - 11.46, WRMS residuals = 0.019 deg Definition of 2-line elements format: http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/SSOP_Help/tle_def.html The altitude decreased by 1.2 km over 24 h. In the unlikely event that geomagnetic activity was to remain at the levels of the past 24 h, then the date of decay would be quite a bit earlier than recent estimates. Using the above elements and a 10.7 cm solar flux of 72, Satevo v0.51 estimates decay from orbit on 2008 March 10. However, it is more likely that geomagnetic activity will soon subside, so my guess is that rate of decay will return to nearly its previous level, per the following approximate elements: 1 70000U 08042.43411819 .00170715 00000-0 25000-3 0 06 2 70000 58.4821 69.5983 0009338 66.1500 294.0578 16.04437931 01 Using these elements and a 10.7 cm solar flux of 72, Satevo v0.51's estimate of the date of decay from orbit is 2008 March 18, one day earlier than recent estimates. The uncertainty is at least one week. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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