re: Pinpoint flashes

Walter Nissen (dk058@cleveland.Freenet.Edu)
Wed, 17 Jul 1996 10:49:08 -0400

> Subject: Re: Pinpoint flashes 
This isn't really a specific response to the questions which have been 
asked, but a comment reflecting a few decades of observing experience. 
I've seen a few pinpoint flashes coming from otherwise unremarkable places 
in the sky.  At first I might have confused them with the momentary 
reflections of lights, familiar to every wearer of glasses, when moving 
the head.  But over time I saw a few which definitely had no explanation 
other than a momentary light from the sky.  I thought perhaps there was an 
exceptionally rapid variety of nova, which would necessarily be little 
understood, because it is inherently difficult to study something which 
disappears as soon as you see it. 
Then I took up satellite observing, and occasionally saw very bright, 
sudden, momentary flashes from satellites like Tiros N (then) and NOAA 7 
(now).  Now I think it likely that most of the "unattached" flashes I've 
seen have been from satellites, otherwise unseen.  It would be interesting 
to know if anyone has data from before the space age. 
This is an unsetlling thought.  How many false novae are recorded on 
survey and patrol images? 
Walter Nissen          
Footnote on Tiros N: 
>From its line in my list of bright objects: 
Tiros N         11060   78- 96A    mag 4 or 5   glint to mag 2 
I guess I wasn't yet reporting to the BWGS when Tiros N was in its heyday, 
but the OBS in the PPAS database reflect a record very similar to what I 
remember.  One of the earliest OBS, from Kurt Jonckheere, has the comment 
"wrong sat?".  This is a clear message to observers that if you see 
something unusual, it is probably worth checking into and reporting.  If 
you have the wrong sat, you'll want to know that.  If you have the right 
sat, you may have uncovered a whole new phase of flashing behavior and 
every hour which passes before you post your suspicions to SeeSat-L is an 
hour lost when it is dark somewhere and further confirmatory or 
discriminatory OBS might be made.  "wrong sat?" is also a suggestion that 
something unusaul was seen by Kurt Jonckheere.  A later OBS from Tristan 
Cools reports a flash as bright as mag -2.  A later one reports a 
magnitude range from 0 to 7.  Many of the reports are of very complex 
light curves.  I recall seeing very wild flashing behavior, but the part 
that caught my attention was an isolated, very bright, very brief, 
"strobe-like" flash.  Presumably, the brightest flashes are generated by 
specular reflection from solar panels.  A rapid flash can occur if the 
object is rotating rapidly, and especially if this is assisted by a 
peculiar geometry. 
Footnote on NOAA 7: 
>From its line in my forthcoming update: 
NOAA 7          12553   81- 59A    mag 0 or 1   glint to -1 or 0