WASHINGTON — A problem with the power regulator on the Advanced Extremely High Frequency (AEHF)-4 satellite is forcing the U.S. Air Force to slip the launch of the satellite until the coming calendar year but the service says the delay will not result in a major mission impact.

The target date for the for the satellite was Oct. 17, Capt. AnnMarie Annicelli, an Air Force spokeswoman, said.

“The AEHF-4 launch is delayed due to an issue with a power regulator unit that was discovered in January 2017 and confirmed via testing in Apr 2017,” she said.

Satellite contractor Lockheed Martin declined to comment.

“The Air Force determined that the issue with the power regulator unit could affect AEHF’s ability to meet operational requirements, so on 9 June 17 the program executive officer directed a hardware modification to fix the issue,” she said.

“The schedule impact is still under evaluation, but the program office is projecting a launch in calendar year 2018,” she said. “The launch delay has minimal impact on the operational mission as the current on-orbit constellation of AEHF and MILSTAR satellites continue to meet requirements.”

AEHF is a follow-on to MILSTAR. The AEHF program will feature six satellites in geosynchronous Earth orbit that provides 10 times the throughput of the 1990s-era MILSTAR satellites with an increase in coverage, the Air Force says.

AEHF-1 was launched on August 14, 2010 and AEHF-2 was launched on May 4, 2012, AEHF-3 was launched Sept. 18, 2013.

AEHF provides continuous 24-hour coverage between 65 degrees north and 65 degrees south latitude, the Air Force notes.

The AEHF system includes satellites, ground mission control and associated communications links and terminals, which combined will provide communications in a specified set of data rates from 75 bps to approximately 8 Mbps.

Speaking to reporters about the proposed Air Force budget for space in May, Maj. Gen. Roger Teague, space programs director, noted fiscal year 2017 funding of about $645 million included the money needed to produce AEHF-5 and -6.

In a report released earlier this year, the U.S. Government Accountability Office (GAO) noted AEHF is being underused in part because one of the programs meant to benefit from the constellation, Advanced Beyond Line-of-Sight Terminals Command Post Terminals (FAB-T), is not fielded yet.

“FAB-T is designed to communicate through the Advanced Extremely High Frequency (AEHF) network of satellites,” GAO reported. “Since FAB-T is not yet fielded while three of these satellites have already been launched, the lack of synchronization between the two programs has resulted in the underutilization of these costly satellite capabilities. By the time FAB-T achieves initial operational capability in 2019, one of the AEHF satellites will have been operating for nine years.”

Mike Fabey is SpaceNews' senior staff writer covering military and national security space matters. Mike previously covered as Defense News’ air and space warfare reporter in 2005 and 2006. Mike was an Aviation Week...