ISS, Prowler, and a flashing Vortex 1 rocket

Apart from a  glimpse through clouds of the ISS on January 2nd (video posted here earlier), I managed to do my first observations of 2012 this weekend, in the evening of January 7 from Leiden and (using a remote telescope in the USA) on January 9.

Conditions were not ideal on January 7th: a lot of moonlight and intermittent clouds. I observed the HEO object USA 200 (08-010A), but due to the moonlight interference the trails were weak (but good enough to get a few positions) and the pictures not pretty.

For the night of January 8-9, I scheduled a few observations on a "remote" telescope, the 61-cm F10 Cassegrain of SSON in California. Target was Prowler (90-097E), an enigmatic object discussed here earlier.

click image to enlarge

The image series on Prowler (I always take a series of at least three images at minute intervals, in case the object is a bit off from predictions) contained a flashing stray.

This turned out to be a classified object as well: Vortex 1r, the r/b from the Vortex 1 launch (78-058B). This rocket stage is clearly tumbling or spinning, as attested by a quite regular flash pattern:

click image and diagram to enlarge

The main flashes are 2.96 seconds apart, and flanked on each side by slow secondary flashes about 0.47s before and after the sharp main flashes, giving the trail on the image a dash-dotted appearance.