Arcturus Traffic Jam

Craig MacDougal wrote:
"John Whisenhunt" wrote in message
...
Sure enough, this mag 2 orbiter lights up another whole magnitude,
and then passes off to the east and fades into shadow.

I fire up Starry Night Pro, and call up this region. Wow - what I thought
was an Iridium was the Hubble! I guess he has fairly large solar arrays.
Anyone else seen a Hubble flare?

Yes. Quite often, when I've watched a pass that occurred not too long past
sunset, and when more or less straight overhead, it will flare like that as
it sets in the east. I suppose that make sense. The solar panels will be
facing the sun, and at that point the observer is close to the Hubble-sun
line.

HST varies more in brightness from one pass to the next than any
other satellite I know of. Similar passes can have steady brightness
of -2 one night and barely manage +5 the next. The illuminated
portion can change vastly depending on which way it points with
respect to the sun and the line of sight. It does occasionally
manage very nice flares - -2 isn't all that rare and I've seen
-4. I tend to wave back after one of those.

The most likely sources of HST's flares are the flat back surface and
some smaller surfaces around the tube - since the solar arrays
ideally give only the Sun a specular reflection! However, the
solar arrays do (from Shuttle video) have a fairly broad
back-reflection range, which would make sense for seeing it
flare just before passing into shadow if it was nearly opposite
the sun from your point of view.


Bill Keel