Re: A Preliminary Analysis of StarLink #85 Flare Captured by Kevin Fetter on 04-19-2020 @ 01:02:01

From: Andreas Hornig via Seesat-l <>
Date: Tue, 21 Apr 2020 11:51:00 +0200
Hi Robert,

do you need more measurements for your geometric model?

I did photos of yesterday's StarLink pass over Jena, Germany. (the video is still uploading and will be
finished in 20 minutes).

I saw several flares (not so many and not so regularly as that day before,
but still)
Because I saw several "parallel flyers" (left and right) that blinked
instead of the main train, I think it is a wider range where they can blink
and I assume the flat bottoms are orientated differently.

If these are interesting, I will upload the relevant photos that also
contain the gps location and time. I only used a 10 seconds exposure time).

Best regards,


On Tue, Apr 21, 2020 at 8:58 AM Robert Herrick via Seesat-l <> wrote:

> Kevin Fetter provided a great video with an embedded clock timer running to
> the millisecond along with the satellite ID info on SeaSat-L, Vol. 74 Issue
> 23, Message #17 . This along with Kevin's location I was able to
> reconstruct all of the geometries at the time of the flare, see attachment.
> Because the satellite sub-point was sufficiently close to Keven's
> location I used a flat earth for purposes of the attached diagram but a
> full spherical earth was used to derive all of the geometries.
> Although the sun had set at Keven's location, it almost came directly over
> his location to illuminate the satellite at the time of the flare.
> Therefore there had to be a surface orientated so as to reflect the sun
> downwards to Keven's location. Furthermore, the surface could not have been
> static as the flare lasted only about 1 second (as many of them are
> observed to do). For a fixed surface on a satellite at the altitude of this
> StarLink satellite, it takes 8 to 9 seconds for a secular reflection of the
> sun to move across a point on the earth's surface. What is the cause of
> this disparity in flare duration? Does this imply that the satellite, or
> portion of it, is moving or rotating?
> Two other observations. First, there was a second satellite in Kevin's
> video above #85 and moving along with it, but was less bright and did not
> exhibit any flaring. Second, the sun set on StarLink #85 at 01:06:06, just
> 4 minutes 5 seconds after the flare.
> Any comments or corrections are welcome.
> Regards,
> Bruce
> Link to Kevin's video:
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