Spaceflight Insider

MUOS-5 satellite starts pre-operational testing

The MUOS-5 satellite lifts off from Cape Canaveral's SLC-41 on June 24, 2016. Photo Credit: Mike Deep / SpaceFlight Insider

The MUOS-5 satellite lifts off from Cape Canaveral’s SLC-41 on June 24, 2016. Photo Credit: Mike Deep / SpaceFlight Insider

The fifth, and final, Mobile User Objective System (MUOS) satellite has reached its intended orbit and has started pre-operational testing. With the spacecraft’s solar array and antennas now deployed, it marks a turning point for the satellite which encountered a problem with its propulsion system. 

That system, which was used to raise MUOS-5, experienced this anomaly as it made its way to geosynchronous orbit on June 29 of this year (2016). Launched five days earlier on June 24, MUOS-5 flew atop a United Launch Alliance Atlas V 551 (the seventh launch of this configuration of the rocket).

“In the end, the Navy and Lockheed Martin engineering team were able to isolate the issue and develop a work-around using alternative propulsion,” Mark Woempner, director of Narrowband Communications Systems at Lockheed Martin (the satellite’s manufacturer) said via a release issued by the company. “Once we had a plan together, in early October we carefully re-started orbit raising maneuvers.”

The satellite was placed into safe mode in a transfer orbit as mission managers worked to determine what the problem was. According to the U.S. Navy: “The transfer maneuver was designed to take the satellite from its initial elliptical launch orbit to its final circular geosynchronous orbit [GEO].”

MUOS-5 was supposed to reach GEO and enter the orbital test site 22,000 miles (35,406 kilometers) above Hawaii by July 3.

Once the investigation was concluded, MUOS-5 completed the journey to its intended orbit on Oct. 22, deploying its array and antennas eight days later on the 30th.

The spacecraft will now undergo on-orbit testing before its operations are handed over to the U.S. Navy. They will, in turn, continue testing and then bringing it into service. MUOS-5 will serve as an on-orbit spare.

MUOS has been fielded so as to provide beyond line-of-sight communications and other services across the globe. audio, video, and other data will be transmitted across the fleet and via ground stations.



Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

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