RE: X-37B OTV 4 search elements

From: Ted Molczan via Seesat-l <>
Date: Wed, 20 May 2015 08:44:11 -0400
ULA reports that there are two windows for today's launch, both of 10 min. duration, beginning at 15:05 UTC and 16:42

Note also, that the NOTAM for launch tomorrow (May 21 UTC) reveals that the first window opens 13 min. later. Something
similar occurred on the launch of OTV 2 in March 2011. Bob Christy and I discussed this at length, mostly off list. We
speculated that one of the KH-11's had a role in observing the spacecraft once it reached orbit, possibly to verify the
condition of the heat shield. Here are a couple of our comments to the list:

I do not recall that we ever reached a firm conclusion, but I have yet to thoroughly review our correspondence.

On Sunday, I posted various search elements based on the opening of today's first window at 15:05 UTC:

I have since selected one OTV TLE and one Centaur TLE, based on comparison with the ground station radio monitoring
windows in the LightSail day one mission timeline:

I have concluded that if the Centaur will manoeuvre to the orbit of the secondary payloads at a node, then this will be
at the first descending node after launch, near T+00:38, with the perigee more likely to be ~390 km than ~350 km. My
corresponding Centaur search TLE is:

Centaur                                                  387 X 700 km
1 75997U 75997A   15140.65512731  .00000000  00000-0  00000-0 0    08
2 75997  57.0000 342.1175 0226000 180.0000   0.0000 15.07600000    02

The X-37B most likely would be in the following circular ~390 km orbit:

OTV 4                                                    390 X 391 km
1 75996U 75996A   15140.64236111  .00000000  00000-0  00000-0 0    00
2 75996  39.0000 342.1980 0001000   0.0853 107.9999 15.60000000    00

The Centaur will de-orbit into the southern Indian Ocean; time of impact is shortly after T+02:30.

Ted Molczan

Seesat-l mailing list
Received on Wed May 20 2015 - 07:44:42 UTC

This archive was generated by hypermail 2.3.0 : Wed May 20 2015 - 12:44:42 UTC