WASHINGTON – The U.S. Navy said its newest communications satellite was about halfway to geosynchronous orbit when its orbit raising propulsion system failed during a transfer maneuver June 29.

Following a June 24 launch, the fifth satellite in the Navy’s next-generation narrowband communications constellation, known as the Mobile User Objective System, had expected to reach geosynchronous orbit and a test location about 35,400 kilometers above Hawaii by July 3.

But in an Aug. 2 statement, the Navy said the satellite “experienced a failure of the orbit raising propulsion system,” five days into a 10-day climb, halting the transfer maneuver that would push the satellite from its initial elliptical launch orbit to geosynchronous orbit.

As a result, the Navy is “considering alternate orbit adjustment options, calculating mission impact and investigating all options before proceeding,” said Steven Davis, a spokesman for Space and Naval Warfare Systems Command.

“The MUOS 5 satellite is currently stable, safe and under positive control,” he said.

The Navy said the satellite remains in a stable intermediate orbit, but amateur satellite observers have noted in recent weeks that the satellite appears to have made a series of small maneuvers.

MUOS-5 is an on-orbit spare for a system that provides smartphone-like communications to mobile forces at rates 10 times faster than the Navy’s legacy satellites, the Ultra-High Frequency Follow-on system. United Launch Alliance lifted MUOS-5 June 24 from Cape Canaveral Air Force Station in Florida aboard an Atlas 5 rocket.

In a June 24 press release, the Navy said the satellite was responding to commands from a team at the Naval Satellite Operations Center in Point Mugu, California and that the satellite was in transit toward its location in geosynchrnous orbit, where it would deploy its solar arrays and antennas and begin months of on-orbit testing. On July 8, the Navy first announced an unidentified problem with the satellite.

Davis said the four primary MUOS satellites, which are expected to provide service beyond 2025, are performing as expected on-orbit.

Lockheed Martin is the prime contractor on the $7.7 billion MUOS program.

“We are working closely with Navy on this,” said Chip Eschenfelder, a Lockheed Martin spokesman. “Nothing is more important than mission success.”

In 2010, the Air Force’s highly protected military communications satellite, known as Advanced Extremely High Frequency-1, took more than a year to reach its geostationary operating orbit due to a propulsion glitch.  Then, the Air Force’s Space and Missile Systems Center, Aerospace Corp., and Lockheed Martin, the AEHF prime contractor, developed a backup plan to use one of the satellite’s other propulsion systems to get it to its interim orbit, albeit later than planned.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.