Saturday, September 12, 2009

Molniya orbits and a Keyhole flare again

The evening of September 10 saw more than a nice Space Shuttle pass (see previous post) and the ISS.

In fact, it was a prolific evening which yielded data on the Lacrosse 2 SAR (91-017A), the USA 186 KH-12 Keyhole (05-042A) and two objects in Molniya orbits: the ELINT and SBIRS satellite USA 184 (06-027A) and the SDS-3 communication satellite USA 198 (07-060A).

USA 184 was imaged in two sessions 1h 45m apart. It is interesting to see the effect of it moving towards its apogeum (see below: in these images, which are on the same scale and at full pixel resolution, 1 pixel equals 10" (arcseconds)): while during the first session the satellite still creates a recognizable trail in the 10 second exposures (taken with the EF100/2.8 Macro USM), it appears as an almost static stellar object in the exposures taken 1h 45m later:

click image to enlarge

The Keyhole USA 186 flared brightly to -1 at about 20:25:43 UTC, just before the start of an exposure. I captured the descending branch of the flare. As I had mispointed the camera in haste, the satellite unfortunately runs out of the FOV (the sat is moving from right to left on the image):

click images to enlarge

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