Re: Upcoming Dragon CRS-19 launch: elset and Falcon 9 trajectory oddities

From: Patrick Schmeer via Seesat-l <seesat-l_at_satobs.org>
Date: Wed, 4 Dec 2019 18:14:47 +0000 (UTC)
 "SpaceX has called off today's Falcon 9 launch attempt
due to out-of-limits upper level winds."
Next attempt tomorrow (5 December 2019) at 17:29:23 UT:
https://spaceflightnow.com/2019/12/04/spacex-crs-19-mission-status-center/

Clear skies,
Patrick
-------
     Am Dienstag, 3. Dezember 2019, 13:40:11 MEZ hat Marco Langbroek via Seesat-l <seesat-l_at_satobs.org> Folgendes geschrieben:  
 
 
Hi all,

If weather cooperates, SpaceX will launch the DRAGON CRS-19 cargo supply mission
to the ISS tomorrow 4 December 2019 at 17:51 UT.

This estimated elset should be valid for the first revolution:


DRAGON CRS-19                  for launch at 4 Dec 2019, 17:51:00 UT
1 70000U 19999A  19338.76053366 -.00003589  11345-4  00000+0 0    00
2 70000  51.6437 236.5410 0114760  48.6187  62.8495 15.97921108    06


(it is for launch at 17:51:00 UT: I haven't seen a more precisely defined launch
time yet, so this is +- 1 minute).

Ireland and the western UK and westernmost coastal France have on-orbit sighting
opportunities 20 minutes after launch. For mainland Europe sighting
opportunities aren't great: for my location in the western Netherlands for
example, CRS-19 will disappear into earth shadow at only 10 deg elevation in the
west.


** ODDITIES:

There is something odd with the Falcon 9 upper stage deorbit. Normally with CRS
flights, these are brought down in the 2nd part of the first revolution, and
normally the location of this area along the orbit ground path shows no
significant deviation from a 51.6 degree orbital inclination.

For CRS-19, the deorbit area indicates a much later deorbit, 6 hours/3.5
revolutions after launch.

Moreover, the hazard zone does not fit well with a 51.6 degree inclined orbit
but rather suggests a 57-58 degrees inclined orbit. See the map here, where the
CRS-17 deorbit area is also shown in comparison:

https://sattrackcam.blogspot.com/2019/12/an-interesting-crs-19-falcon-upper.html

So it is clear that they are doing something with the Falcon 9 upper stage that
includes a prolonged time on-orbit and, it seems, an inclination change by some
5 degrees.

The prolonged on-orbit time might be a coasting test with an eye on future
missions that require coasting over several revolutions. The indicated
inclination change might likewise be a test for a future mission requirement.

I have been entertaining the possibility of an undisclosed cubesat rideshare, to
a ~58 degree inclination orbit. But that is pure speculation and is perhaps not
very likely.


- Marco


-----
Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
e-mail: sattrackcam_at_langbroek.org

Station (b)log: http://sattrackcam.blogspot.com
Twitter: _at_Marco_Langbroek
-----
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Received on Wed Dec 04 2019 - 12:15:47 UTC

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