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.

Tracking MiTEx 1

MiTEx 1, 18 May 2015 (click to enlarge)

Over the years, the USA has been experimenting with satellites intended for close-range inspection of other satellites at geostationary altitudes.

The first one was the highly secret Prowler (1990-097E), clandestinely launched on Space Shuttle mission STS-38 in 1990. Two other ones were launched less covertly, though their orbits were and are classified: the experimental MiTEx satellites, MiTEx 1 and MiTEx 2 (2006-024A and B), brainchilds of DARPA, launched from Cape Canaveral in June 2006.

Speculation on the reason for their development can be found here. What we do know is that early 2009, two-and-a-half years after their launch, both MiTEx satellites were used to inspect the malfunctioned DSP-23 satellite. This was actually observed by amateur trackers Greg Roberts and Peter Wakelin.

MiTEx is an acronym that stands for Micro-satellite Technology Experiment.They are small objects, each weighing about 225 kg. While some sources (similar statements also here) have tauted that "ground-based detection via visual observation or radar is extremely difficult if not impossible" for these small objects at such a large distance, matter of fact is that amateurs (including me) actually track these objects, albeit infrequently.

The image in the top of this post shows MiTEx 1 (2006-024A) imaged on May 18, 2015, using the 0.51-m telescope of Warrumbungle Obs. in Australia. The satellite was at a low sky elevation.

I also imaged it two days earlier, on May 16, and captured it briefly flaring at that time (the trail is leaving the FOV of the CCD camera at left in this image):

MiTEx 1 is currently located in a disposal orbit at an orbital altitude just above that of operational geostationary satellites. It is drifting Westwards at a rate of about 5-6 degrees per day. During my May 16 and May 18 observations, it was moving westwards over the mid-Pacific south of Hawaii, as shown on the map below. The map also shows the drift path over the next two weeks, until the satellite's approximate position for June 1. The "wobble" in the path is the daily analema it makes due to the slight inclination of its orbit. Footprint shown is for May 18.

(click map to enlarge)

Where the MiTEx 1 sistership  MiTEx 2 (2006-024B) currently is, is less certain: my attempts to recover it near its expected position on May 16 and May 18 based on a 20-day old elset failed so far.

MiTEx 1, AEHF 1 and Prowler

Weather conditions have not been too well lately. In the evening of March 14, I could do some imaging from Leiden, albeit under hazy skies. The relatively bright geostationary SIGINT Mentor 2 (98-029A) was the target.

In addition, I used a "remote" telescope, the 37-cm F14 Rigel Cassegrain of Winer Observatory (MPC 587) to image a few geostationary objects over US longitudes. Targets were (below images from top to bottom) the communication satellite AEHF 1 (10-039A), and the enigmatic objects MiTEx 1 (06-024A) and Prowler (90-097A).

click image to enlarge

AEHF 1 (aka USA 214) is the first of the Advanced Extremely High Frequency communication satellites that should replace the Milstar system. Because one of its onboard rocket boosters failed, the satellite had to be brought from GTO to its geostationary destination using smaller thrusters designed for station keeping, a procedure which took over a year.

This was the first time I imaged AEHF 1.

Prowler and MiTEx 1 are both enigmatic objects. Prowler's unique story has been discussed here before. MiTEx 1 (USA 187)  is an enigmatic object that has some connection to the Prowler legacy. Like Prowler presumably was, it was designed to inspect other satellites. Two MiTEx satellites were launched (in the same launch in 2006), MiTEx 1 and 2. They were used to inspect, amongst others, the failed DSP satellite DSP-23 in 2009. I imaged MiTEx 2 before, this was the first time I also imaged MiTEx 1.