Re: Crew Dragon and USA 245 close approach (~125 km) imaged!

From: Michael Robert Thompson via Seesat-l <>
Date: Mon, 1 Jun 2020 05:49:00 +0000
Hi Marco,

That's very interesting.  USA 224 had some close conjunctions as well, but all within shadow.

Looking at the previous launch window on the 27th, USA-245 passed 1600km "behind" the ISS (in an along-track sense) at May 28th, 04:14.

That would have been nearly 8 hours into flight.  If the approach was the same as the one eventually used, Dragon would have been around 400km behind the ISS.  So it wouldn't have been a very close approach with Dragon.  No way to know for sure if the approach trajectory would be the same though.

USA 186 looks very interesting though.  At on May 28, 02:34:20, USA-186 was 450 km behind the ISS, and if Dragon used the same approach it would have been 530 km behind. Definitely an opportunity there.

Doubt it's something that's driving launch windows, but with approaches like that why wouldn't you get an image?

Something to keep an eye out for next time.

From: Seesat-l <> on behalf of Marco Langbroek via Seesat-l <>
Sent: Sunday, May 31, 2020 5:57 AM
To: satelliet lijst (SeeSat) <>
Cc: Ted Molczan <>
Subject: Crew Dragon and USA 245 close approach (~125 km) imaged!

Op 31-5-2020 om 00:56 schreef Marco Langbroek via Seesat-l:
> Op 31-5-2020 om 00:23 schreef Marco Langbroek via Seesat-l:

> On one of my images, I have it together with USA 245!
> - Marco

As it turns out, I was imaging Crew Dragon and USA 245 during an actual close

DATE      UT          SSC   NAME     TARGET                   KM      angle
5/30/2020 21:18:16.99 39232 USA 245  CREW DRAGON              125.3   172.8

Now I am starting to wonder whether this was intentional, and USA 245 was
perhaps imaging the Crew Dragon?

We know that the KH-11 imaged some Space Shuttles, to inspect them for tile
damage, after the Columbia accident. We suspect they also image the X-37B
shortly after launch, to check upon them.

The analysis above is based on the 20151.85044152 elset for Crew Dragon, and the
20146.86101776 elset for USA 245.

The latter elset was 5 days old, but the position of USA 245 on my photograph is
very close to the ephemerids. Crew Dragon is about 3 seconds behind on the used
elset. So there is some leeway of a few seconds in the approach time, and hence
some leeway in the approach distance (but not more than about 25 km). But that
this indeed was a relatively close approach, is clear.

I did not know in advance, it is serendipity that I was imaging it right at that
moment, within (taking into account uncertainties) seconds of the actual close

Image was taken from 52.1420 N, 4.5016 E (Cronesteyn Park, Leiden), with a Canon
EOS 80D + SamYang 1.4/85 mm lens _at_ F2.0, 500 ISO, 0.5 second exposure, at
21:18:19 UT.

- Marco

Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.

Station (b)log:
Twitter: _at_Marco_Langbroek
Seesat-l mailing list
Seesat-l mailing list
Received on Mon Jun 01 2020 - 00:51:10 UTC

This archive was generated by hypermail 2.3.0 : Mon Jun 01 2020 - 05:51:11 UTC