I have written on the enigmatic Prowler satellite (1990-097E) before. I periodically observe it using a 'remote' telescope (usually the 0.61-meter Cassegrain of SSON, MPC G68).
On 2014 June 10 I captured it briefly flaring - I had not observed that before, though other observers had. The brief flare can be seen near the edge of the image (the trail runs out of the FOV) in the lowermost of the two images above.
Approximate positions of this flare:
- begin RA 17 25 24.73 DEC -20 49 41.7
- maximum RA 17 25 26.15 DEC -20 49 45.2
- end RA 17 25 27.36 DEC -20 49 45.6
Extrapolation from the measured timed positions above, gives the following approximate times for the flare:
- begin 09:25:23.9 (UT, 10 June)
- maximum 09:25:25.3 (UT, 10 June)
- end 09:25:26.5 (UT, 10 June)
Apart from these short flashes, observers report a much slower brightness variation. Indeed, I had suspected such from my own observations, as the trail brightness widely varies (between bright and completely invisible) between different image sessions. On May 27 for example, I also tried to image Prowler using the same 0.61-meter telescope, but it was invisible.
As Allen Thomson remarked, part of this brightness behaviour might be due to Prowler's former stealth characteristics.