Sunday, January 14, 2007

Failed Lacrosse flare

Phillip Masding predicted a potential flare by Lacrosse 5 (05-016A, #28646) for my location for 17:06:59 UTC this evening. This was to be in late twilight, and at a favourable sky elevation of 70 degrees (almost in the zenith).

Streaks of cirrus occupied the sky at that time. About 1 minute before Lacrosse 5, I observed Lacrosse 2 (91-017A, #21147) pass through the zenith at a bright mag. +2. A minute later Lacrosse 5 however turned out to be very faint, mag. +3.5 or fainter. It did not flare, and the trail on the photographic image is very marginal. I only used one position of it, as the other one came out as an obvious anomaly.

Lacrosse 2 is visible in the same image, but in a streak of cirrus, and hence very marginal. I did not get usable positions on it.

During the next pass of Lacrosse 5, at 18:50 UTC and 48 degree maximum sky elevation due North, it was brighter (about mag. +2.5) . It easily registered on the photographic image (see below), and added two positions.

The three positions obtained on Lacrosse 5 in total suggest it was on-track, and about 0.2s late relative to a 4-day-old elset.

(click image to enlarge)


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