Some orbits from PC Obs August 13, 2016

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 14 Aug 2016 10:58:22 -0400
Paul Camilleri made a number of observations of interest on Aug 13 UTC, from which he posted selected observations:

http://satobs.org/seesat/Aug-2016/0062.html

Cees Bassa has posted a complete set of reduced data: 

http://satobs.org/seesat/Aug-2016/0066.html

Below are updated orbits of greatest current interest:

USA 227                                              35592 X 35723 km
1 37377U 11011A   16226.79814815  .00000000  00000-0  00000-0 0    04
2 37377   4.6702 358.3293 0015513 107.5443 255.6945  1.00738271    05
Arc 20160808.66-0813.8 WRMS resid 0.004 totl 0.003 xtrk

USA 269                                              35578 X 35998 km
1 41724U 16047A   16226.70924769  .00000000  00000-0  00000-0 0    00
2 41724   5.0306 327.4963 0049808 243.1689  98.6968  1.00271671    01
Arc 20160811.67-0813.71 WRMS resid 0.003 totl 0.002 xtrk

Tiantong 1                                           35753 X 35905 km
1 41725U 16048A   16226.71620370  .00000000  00000-0  00000-0 0    04
2 41725   5.0087 325.1644 0018039  39.7750 316.9347  1.00125910    00
Arc 20160811.74-0813.72 WRMS resid 0.005 totl 0.003 xtrk

USA 227 is an SDS 3 satellite that had been parked near 92 E. At the epoch of the above elements, it was at 111.05 E,
drifting east 1.668 deg/d. It apparently manoeuvred into its present drift orbit on or about 2016 Aug 2 UTC. This was
five days after the launch of USA 269 aboard NROL-61, which arrived near 92 E on Aug 8 UTC.

USA 269 is nearly synchronous near 91.5 E. The above orbital solution assumes that the satellite did not manoeuvre
during the span of the data, Aug 11.67 - 13.71 UTC. Additional observations would clarify the result. The nearly 0.05
initial eccentricity would be unusual for an SDS, but is common among the NRO's SIGINT satellites. I have come to
suspect that the 0.05 eccentricity is intended to greatly reduce the duration of any intrusions into the operational
zone of the GEO belt, to reduce the risk of collisions. Such an orbit would be especially beneficial in the event that a
satellite were to become stranded in the operational zone before it could be re-orbited at its end of life. I discussed
the concept in the following paper, in Section 7.4.2:

http://www.satobs.org/seesat_ref/STS_38/Unknown_GEO_Object_2000-653A_-_90007_Identified_as_Prowler.pdf

UNID is Tiantong 1

Based on a suggestion received off-list, it seems that the UNID that Cees discovered on some of Paul's imagery of Aug 11
UTC was China's recently launched communications satellite Tiantong 1. As I write, USSTRATCOM's latest TLE is of epoch
16219.20977920, at which time the object was still in its initial GTO. Tiantong 1 reportedly is intended for mobile
communications, which does not necessarily require the use of a stationary orbit, and would explain why it is inclined 5
deg. Paul found the object on Aug 13 UTC, close in time and track to the orbit that Cees has determined from his
observations of Aug 11 UTC. The above orbit fits the Aug 11-13 UTC data. The object was at 101.6 E, drifting west, 0.53
deg/d.

Ted Molczan


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Received on Sun Aug 14 2016 - 09:58:59 UTC

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