WASHINGTON — A contingency plan to raise the altitude of the U.S. Air Force’s first Advanced Extremely High Frequency (AEHF) satellite after one of its thruster systems failed on orbit is moving along on schedule, a service official said Oct. 5.

The AEHF-1 secure communications satellite, built by Lockheed Martin Space Systems of Sunnyvale, Calif., was successfully launched Aug. 14 into a highly elliptical orbit ranging from 230 kilometers above Earth at perigee to 50,000 kilometers above Earth at apogee. The satellite was designed to use its hydrazine-fueled liquid apogee engine to raise its perigee to 19,000 kilometers over 30 days, and then use its xenon-ion electric thrusters to circularize its orbit at 36,000 kilometers over 90 days.

Operators first attempted to fire the satellite’s liquid apogee engine Aug. 15, but it failed. The Air Force announced Aug. 30 it had begun to implement a backup plan to raise the satellite’s perigee to 19,000 kilometers using smaller on-board thrusters fueled by the same hydrazine tank as the liquid apogee engine. The plan is expected to take an additional six to seven months to complete but will not reduce the satellite’s operational lifespan.

Five weeks into the contingency plan, the AEHF-1’s perigee has been raised to about 4,700 kilometers and the satellite remains on schedule to reach its final geostationary orbit between June 2011 and August 2011, Air Force Space and Missile Systems Center spokesman Joe Davidson said in an Oct. 5 e-mailed response to questions.