Thursday, April 07, 2011

Bright and fast KH-12 USA 129 zapping through perigee

Yesterday evening was clear, and I observed the KH-12 Keyholes USA 129 (96-072A) , USA 186 (05-042A) as well as the SAR satellite Lacrosse 3 (97-064A).

USA 129 was making a pass at 40 degree altitude in the east, at an altitude of only 303 km only minutes from passing through perigee. As a result, it was bright and very fast, zipping through the sky at notable speed: very cool to watch. It resulted in two long bright trails on the images. Two strays were captured as well: a very faint Russian rocket stage (84-067B) in one image, and a brighter Russian rocket stage (Kosmos 1484 r, 83-075B) in the second. The latter cruised up parallel to USA 129, being overtaken by it when both were passing through the tail of the Big Dipper. See the image below, where the longer brighter trail (the lower one of the two) is USA 129, the other the Russian rocket stage:

click image to enlarge

KH-12 USA 186 passed through the same sky area 20 minutes later, but at a much different altitude (830 km, against only 303 km for USA 129). The clear difference in trail length this generates, is shown by the image below, which is a stack of the two images of 19:41 and 20:03 UTC:

click image to enlarge

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