AEHF On Orbit After 14 Months

Corporate Staff
posted November 02, 2011

In an achievement that showcased The Aerospace Corporation’s technical excellence, the U.S. Air Force’s first Advanced Extremely High Frequency military communications satellite has reached its intended operational position in geosynchronous orbit following a painstaking 14-month orbit-raising operation.

Shortly after launch on Aug. 14, 2010, the AEHF-1 experienced a failure in its bi-propellant propulsion system, which was intended to place the spacecraft near its operational orbit.

A joint team of engineers from The Aerospace Corporation, the Air Force, Lockheed Martin, and Aerojet immediately swung into action to devise an orbit-raising plan using the spacecraft’s two other propulsion systems — a hydrazine system with five-pound thrusters and a Hall Current Thruster electric propulsion system consisting of four HCTs, the most powerful ever flown in space.

The original mission plan would have used the HCTs firing continuously for approximately three months to complete the orbit transfer. But without the bi-propellant system, the engineering team had to devise a more efficient use of the HCTs, using discrete apogee and perigee burns.

Over 14 months, the team executed a sophisticated campaign of approximately 500 burns using the hydrazine thrusters and the HCTs. The revised orbit-raising plan safely delivered AEHF-1 to its intended orbit on Oct. 24, while maintaining its required 14 years of mission life.

“I’m extremely proud of the Aerospace team’s contributions to this accomplishment,” said Andrew Dawdy, principal director of EHF Systems. “They have been with this from the early days of the anomaly investigation and creation of the recovery plan. The mixed team of SSG and ETG personnel worked tirelessly in efforts to continuously optimize burn profiles, avoid collision risks, and monitor the health and safety of the satellite.”

AEHF is a joint service satellite communications system that will provide survivable, global, secure, protected, and jam-resistant communications for high-priority military ground, sea, and air assets. The AEHF system is the follow-on to the Milstar system, augmenting, improving, and expanding the MILSATCOM architecture.

The AEHF team has now begun an approximately four-month detailed test and checkout phase of all spacecraft systems before the Space and Missile Systems Center transfers satellite command authority to Air Force Space Command’s 14th Air Force in early 2012.