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 20:46:43 +0200

okay I was asked for the photos, so I uploaded them here (because I did not
want to spam the list

Basic Data:
The photos there keep the EXIF metadata, so the location of the shots and
also the creation time is inside. The local time was started 21:27 until
23:26 CEST, so 19:27 until 21:36 UTC for all photos. keep this in mind when
checking the single photos' creation time (properties).

All sats are flying from right image edge to the left.
The image creation time is at the end of the 10 seconds exposure time. So
to get the time of the flare, the left streak edge is on the creation time,
the respective right side is -10 seconds earlier. maybe it
is +-0pointSomething seconds jitter. This is why I was outside to get a
feeling for my new camera :).

I do not know how to determine which of the many starlinks was which
satellite (id). So I don't know how to easily name each streak.
How do you do this? :)

Have fun with the images. I Have a few more photos with flares, but they
were at the starting or ending edge of the streaks, so I did not upload
all. But I would if you want.

So, happy modelling. I am looking forward to see what we will gain here :).


On Tue, Apr 21, 2020 at 11:51 AM Andreas Hornig <> wrote:

> 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,
> Andreas
> 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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Received on Tue Apr 21 2020 - 13:48:26 UTC

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