MUOS 4 recovered at 75 E

MUOS 4 at 74.8 E on 8 March 2016
image (c) by Greg Roberts, South Africa
(click to enlarge)

In a recent post I wrote that MUOS 4 (2015-044A) had left it's check-out position at 172 W near Hawaii late January, drifting westwards. I presumed that it was being moved to its assigned operational spot at 75 E, over the Indian Ocean just south of India.

This is now confirmed. On 8 March 2016, Greg Roberts from Cape Town, South Africa, recovered MUOS 4 at 74.8 E. Greg's recovery image (used with his permission) is above. As I wrote before, it probably arrived there on 29 February 2016, after a 37-day drift westwards at a rate of ~3 degrees/day.

With four satellites at their operational positions, the MUOS constellation is now complete.

MUOS 1   2012-09A       177 W  Pacific
MUOS 2   2013-036A      100 W  CONUS
MUOS 3   2015-002A     15.8 W  Atlantic
MUOS 4   2015-044A       75 E  Indian

However, one more MUOS satellite will be launched. This fifth satellite will be parked at 72 E and will function as an on-orbit spare, in case one of the other four MUOS satellites malfunctions on-orbit.

(click to enlarge)

As can be seen in the illustrations above, the MUOS satellites are separated by ~90 degrees in longitude, but with a slightly bigger gap (~108 degrees) between MUOS 1 and MUOS 4, a gap representing the Pacific. The latter is probably in order to assure access to/from at least two ground facilities, with Hawaii and California serving MUOS 1. The latter would not have been possible with MUOS 1 at ~90 rather than 108 degrees from MUOS 4. MUOS ground facilities are indicated by yellow squares in the map above.

[UPDATED] MUOS 4 has been moved to its operational position at 75 E

MUOS 4 imaged while still in its check-out position at 172 W on 27 September 2015

Since September 2015, I have been periodically covering MUOS 4 (2015-044A), a newly launched military communications satellite in geostationary orbit. It was launched on 2 September 2015 and initially placed at 172 W, just west of Hawaii. This position was temporary: it is the "check-out position" where the satellite is initially placed, well situated with regard to key monitoring stations, to check if it is working okay. It stays there for a few months until this check-out is complete: then it is moved to its operational position. In the case of MUOS 4, it is known (see my earlier post and this unclassified publication) that the operational position assigned to MUOS 4 is at 75 E, south of India.

At the start of December 2015, it was announced that check-out had been completed and that the satellite would be moved to its operational position in the spring of 2016.

When I checked upon MUOS 4 on 4 December 2015 using the 0.51-m telescope of Warrumbungle obs in Australia, it was still at 172 W. For various reasons I did not get to check that position again until a few days ago. When I imaged that location on March 1, 2016, using the same Warrumbungle telescope, MUOS 4 was no longer there. It had been moved somewhere between December 4 and March 1.

This is confirmed by observations of the Russian ISON network. I received two of their MUOS 4 elsets for mid February 2016, which show the satellite drifting westwards at a rate of about 3 degrees/day. From the drift rate I reconstruct from these elsets, I find that the move from 172 W to 75 E started near 23.0 January 2016. At this drift rate, it should have reached its designated operational slot at 75 E 37 days later, on 29.0 February 2016.

[UPDATE 11 March 2016:  On March 8, Greg Roberts in South Africa recovered MUOS 4 at 74.8 E, very close to the expected position]

Imaging Geostationary satellites, and PAN's past relocations

Last week saw some clear evenings, and I used one of them to image some geostationary satellites. It concerned "the usual suspects": MENTOR's, MERCURY's and the enigmatic, probably SIGINT satellite PAN (2009-047A). The latter satellite has not been moved for quite a while now: since the end of 2013 it is at longitude 47.7 E, parked close to a number of commercial comsats. In the past it was frequently relocated, taking positions next to various commercial COMSATS. In four years time between 2009-2013, it moved at least 9 times (which is a lot) to various longitudes between 33 E and 52.5 E.

PAN amidst several commercial COMSATS on 9 December 2015 (click to enlarge)

The diagram below charts these frequent movements of PAN. Relocations typically took place about once every 6 months. Late 2013, they stopped. PAN however must still be operational, as active station-keeping is necessary for it to stay at 47.7 E.

relocations of PAN over time, 2009-2015 (click to enlarge)

Four other SIGINT satellites and a military comsat were imaged as well: Mentor 4 (2009-001A) and Mentor 6 (2012-034A), Mercury 1 (1994-054A) and Mercury 2 (1996-026A), and the military comsat Milstar 5 (2002-001A).

Mentor 4, next to commercial comsat Thuraya 2 on 9 Dec 2015 (click to enlarge)

Mentor 6 and a number of commercial satellites, close to the Orion nebula, on 9 Dec 2015

Using the remote telescope at Warrumbungle (MPC Q65) in Australia, I recently (4 December 2015) also checked-up on the recently launched US Navy COMSAT MUOS 4 (2015-044A). It is still at its check-out location over the Pacific at longitude 172 W, but some recent press statements suggest check-out has been successfully completed, and it will be moved to its operational position at longitude 75 E near India in the spring of 2016.

MUOS 4 at its 172 W check-out location

MiTEx 1 on 16 September 2015
(click image to enlarge)

On September 16, I was using the Warrumbungle 0.51-m telescope in Australia to track MiTEx. Indeed, MiTEx 1 (2006-024A) was imaged as a faint object close to the expected location (image above).

But about 5 degrees Northeast of MiTEx 1, I imaged another, very bright object (see image below) at approximately 172 W. It was too bright to be MiTEx 2 and didn't fit any known object. This UNID turned out to be the newly launched classified military COMSAT, MUOS 4 (2015-044A).

MUOS 4 on 16 September 2015
(click image to enlarge)

MUOS 4 was launched from Cape Canaveral with an Atlas V rocket two weeks earlier, on 2 September 2015. It is the fourth satellite in the Mobile User Objective System (MUOS) system of Geosynchronous narrowband communication satellites, the first of which was launched in 2012. This system of military COMSAT is to provide communication facilities to 'mobile users': i.e. military personel in non-fixed positions such as ships, aircraft, tanks and vehicles or on foot. It is a replacement for the aging UFO constellation of COMSAT.

The MUOS system is to consist of four operational satellites and one spare fifth satellite. According to a publication by Oeting et al. in the Johns Hopkins APL Technical Digest 30:2 of 2011, the operational satellites will be placed in slots at longitudes:

15.5 W
100 W
177 W
75 E

...while the spare satellite (MUOS 5, to be launched) will be placed at longitude 72 E. Compare this to the actual locations of the MUOS satellites according to our tracking:

MUOS constellation, from Oeting et al. 2011
(click image to enlarge)

Current locations of MUOS satellites,
based on amateur tracking:
------------------------------------------
MUOS 1   2012-09A       177 W  Pacific
MUOS 2   2013-036A      100 W  CONUS
MUOS 3   2015-002A     15.8 W  Atlantic
MUOS 4   2015-044A      172 W  (check-out)
------------------------------------------

(click map to enlarge)

The map and table above show the current locations of MUOS 1, 2 and 3 (from Mike McCant's INTTLES file). The positions agree well with the slots depicted in the mentioned publication.

(and yeah: if you think it is a tad silly that these orbits are 'classified' while the intended orbit slots have been published in a publicly available publication, you are of course right).

The yellow dots in the map are ground facilities related to the MUOS system. The MUOS constellation is designed such that each satellite has at least two Radio Acces Facilities (RAF) in range.

MUOS 4 imaged on 24 September 2015

My additional observations on September 24 (see image above) show that MUOS 4 is stationary at 172 W, as depicted in the map below. An approximate orbit for the satellite can be found here.

(click map to enlarge)

As MUOS 4 appears intended for an operational slot at longitude 75 E over the Indian Ocean (red dot in the map above), this means the current location at 172 W is not the intended operational longitude. Rather, it is a temporary initial check-out location. Once check-out is completed (and this might take several weeks), it will probably be moved to longitude 75 E.

(click images to enlarge)

This check-out position at 172 W has been used for the MUOS satellites before, according to Ted Molczan (priv.com). It is in range of three MUOS ground facilities: two Radio Acces Facilities (RAF) at Wahiawa in Hawaii and (although barely) Geraldton in Australia, and the primary Satellite Control Facility (SCF) in Pt. Mugu, California.