Flaring Keyhole USA 161

Yesterday evening/early night was a night with intermittent very clear skies, and large cumulus fields roving the skies. I was lucky though with the selected targets, although some narrowly escaped the roving cloud fields only. I observed 3 Keyholes (USA 129, USA 161 and USA 186) and Lacrosse 3.

USA 129 (96-072A) was imaged low in the sky in a small gap between clouds. USA 186 (05-042A) was imaged in twilight and the trails were rather faint. It briefly flared to mag. -1, before the camera was open, at roughly 22:59:50 UTC.

USA 161 ((01-044A, a Keyhole high-resolution optical reconnaissance satellite, like the other two USA objects mentioned) also briefly flared to -1 a few times. It did so twice while the camera was open, at 23:28:13.40 UTC and 23:30:17.15 UTC, resulting in the pictures below:

(click images to enlarge)

The second image yielded this brightness profile, with the flare saturating at the peak:

(click diagram to enlarge)

Lacrosse 3

Phil Masding provided me with a number of potential flare time predictions for Lacrosse 3 (97-064A). The aim is to determine at what angle flares will be no longer visible.

Two of these predictions were for yesterday evening and as the sky was very clear again, I covered both.

At 21:30:38 UTC (2 seconds after the nominal prediction) and almost right in the zenith for me, Lacrosse 3 indeed "flared", albeit very modestly. The short increase in brightness was no more than say 0.5 magnitudes but discernable. Below is the image (visually, the "flare" was somewhat better discernable).

On the other hand, during the second predicted time (23:12:38) Lacrosse 3 did nothing, it was steady as usual.

(click image to enlarge)