MUOS-5 is getting close to its orbit

After problems with main propulsion, American military communication satellite seems to have had speed up and is reaching end of its orbital journey to designated orbit.

MUOS-5 was launched on June 24, 2016 on atop of Atlas V (551) from Cape Canaveral SLC-41. Satellite was last, backup unit, from series of five communication satellites developed as part of the new communication system for U.S. Navy. MUOS-5 was developed and manufactured by Lockheed Martin with participation of Boeing and Harris. Satellite after being delivered to GTO, should initialize propulsion system - IHI BT-4 bi-fueled (N2H4/MON-3) thruster. Next, using 450 N of thrust generated by BT-4, satellite should change orbit from 35750 km x 3827 km and inclination of 19.1° to GEO with altitude of 35398 km. Unfortunately, main thruster failed on July 29, 2016 and satellite failed to finish orbit raise maneuver. Specialists from Lockheed and U.S. Navy decided, after analyzing data and pictures taken by on from GSSAP satellites, to continue maneuver with reduced speed using only attitude control thrusters. This procedure was only hope to move worth $340 million MUOS-5 into designated orbit. Using additional thrusters determines, that satellite will move with limited speed and, what is more important, it will burn most of hydrazine, fuel for attitude control system. This fact will give an effect of shortening operational life - satellite will have less fuel to keep correct orbit and will not be able to remain in space for 15 years, as it was originally planned.

Basing on previous data provided by satellite spotters, it was even possible to predict, that MUOS-5 will not manage to reach correct orbit before December 2016. Luckily for U.S. Navy, satellite increased pace and almost reached designated GEO orbit. Since September, when MUOS-5 was on 16100 km x 36680 km orbit, it moved for 14000 km and was spotted on October 6 on orbit of 30000 km by 36680 km with inclination of 9.7°. Until today orbit changed to 34810 km x 36764 km with inclination: 9.6745° - satellite is on 104.8° W position. It seems that it will reach correct orbit in the end of October and probably it will start test and calibration period on November. After three months of trials satellite will enter service. Next step should be moving to position of 72° E to get closer to MUOS-4 remaining on 75° E position over Indian Ocean. It was planned, that MUOS-5 will serve on this position as support and backup spacecraft for MUOS-4. But for the moment only thing which is sure is fact, that another position change will decrease amount of hydrazine and will again limit operational life of satellite. U.S. Navy and Lockheed Martin have not announced about future of MUOS-5 and its alternative position after trail period. Also it was not confirmed how long satellite will able to remain in space. It seems quite possible, that MUOS-5 could be good candidate for refueling mission in future - loss of expensive and crucial for national security satellite surely puts it high on the list of spacecrafts waiting for in-orbit refueling.

On picture above: MUOS-5 encapsulated waits for launch on atop of Atlas V.