HUNTSVILLE, Ala. – The U.S. Air Force said Aug. 18 it sent one of its high-orbiting space surveillance satellites to check on a Navy communications satellite that ran into propulsion problems about halfway to geosynchronous orbit.

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 been expected to reach geosynchronous orbit and a test location about 35,400 kilometers above Hawaii by July 3.

But 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.

To better understand why the satellite was struggling, the Joint Functional Component Command for Space at Vandenberg Air Force Base in California tasked the Geosynchronous Space Situational Awareness Program, or GSSAP, satellites for an image of MUOS-5. Satellite operators from Schriever Air Force Base in Colorado Springs, Colorado then used rendezvous and proximity maneuvers to get the once-classified vehicle into position to capture the best images of the Navy satellite, the Air Force said in a press release.

It is unclear how, or if, the information the GSSAP satellite provided will help the Navy. A Navy spokesman did not immediately respond to questions.

Air Force officials disclosed the previously classified GSSAP program in February 2014. Since then, they have acknowledged that the satellites would perform rendezvous and proximity maneuvers to allow close-up looks at spacecraft in geosynchronous orbits, some 36,000 kilometers above Earth’s surface. In the Aug. 18 press release, the Air Force also said GSSAP can provide the location, orbit and size of satellites and space objects.

Last year, Gen. John Hyten, the head of Air Force Space Command, said that the Defense Department had used the satellites to capture “truly eye-watering” images for unspecified users while they were in test mode. The Air Force declared the program operational in October 2015.

The GSSAP program, with a price tag thought to be about $700 million, operates in a “near-geosynchrous orbit regime” to provide accurate tracking and characterization of man-made orbiting objects. Two satellites, built by Orbital ATK of Dulles, Virginia, are already on orbit. The third and fourth satellites in the constellation are expected to launch Aug. 19 from Cape Canaveral Air Force Station in Florida aboard a Delta 4 rocket.

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.