|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.