RE: SAOCOM-1A Falcon-9 RTLS launch plots

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Mon, 8 Oct 2018 12:36:22 -0400
Björn Gimle asked:

> Should the RA of asc node fit launch site at ĺùķnthe launch time - or on
> that later time ?

Where no better information can be found, setting the epoch, mean anomaly and RAAN of the initial orbit to pass over the launch site 4-6 minutes after launch should be adequate to find the object. The initial orbit of payloads launched by the same vehicle to roughly similar orbits can provide useful guidance.

In this case, the intended mean local time of ascending node (MLTAN) was published: 06:00 AM. I used the MLTAN spreadsheet that I posted previously (see URL below) to determine that RAAN of 106.7 deg corresponded to 06:00 MLTAN for the epoch of my TLE.

http://satobs.org/seesat/Sep-2015/0178.html

The actual initial RAAN was just 0.7 deg less.

For the eventual launch of SAOCOM-1B, we should be able to accurately estimate its elements by using the initial elements of SAOCOM-1A as a proxy. Marco Langbroek published a handy program for that purpose:

http://satobs.org/seesat/Nov-2017/0058.html

Ted Molczan



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Received on Mon Oct 08 2018 - 11:37:23 UTC

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