Post a Comment On: SatTrackCam Leiden (b)log

The evening of Saturday-Sunday 20-21 February saw a very dynamic weather situation. Fields of clouds came and went very rapidly: the sky could go from clear to clouded to clear to clouded again in a matter of minutes. It made it a big gamble whether a particular object would eb visible or not.

As it came to be, I hauled a nice batch of positions on several objects: Lacrosse 5 (05-016A), the Lacrosse 5 r/b (05-016B), the STSS Demo 2 (09-052B) and the NOSS 3-2 (03-054A & C) duo. I also photographed the NOSS 3-4 duo but the image was too much hampered by cliuds tp reliably measure it. I lost amongst others Lacrosse 4 and the STSS Demo 1 to clouds (the latter a pitty, as it was predicted to pass right through the Pleiades).

Most of the images have some clouds on them: some extensively. Below are a few pictures: from top to bottom they show the Lacrosse 5 r/b amidst clouds; The NOSS 3-2 duo passing between the Pleiades and the Hyades; and the STSS Demo 2 passing near capella and the three Goats:

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The STSS Demo 2 appears to show an unusual brightness variation in the first 2 seconds of the trail (the left part of the trail in below negative image), consisting of what appear to be a series of even spaced modest glints. Note the dashed appearance of the first part of the trail:

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Below is the brightness profile over the trail (grey small crossmarks are individual pixel values, the solid line is a 3 point average), and below that is a graph of the time between brightness maxima visible in the profile.

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Note in the second diagram how the time between maxima is very constant, at about 0.13 seconds, during roughly the first 2 seconds . After that, it begins to wildly vary. As the first diagram shows, the amplitude of the brightness variations is larger in those first 2 seconds too. In fact, after those first two seconds the variation is largely or completely random pixel variation.

The first 2 seconds of the trail are quite different in character from the rest of the trail though: a clear constant, larger amplitude pulsing behaviour. This is very interesting. A second image obtained on the STSS Demo 2 during the same pass showed a quite constant brightness.