WASHINGTON — A planned October launch of the U.S. Air Force’s Space-Based Space Surveillance (SBSS) satellite aboard a Minotaur 4 rocket has been delayed indefinitely due to technical concerns with the launch vehicle, the service said.

“The Air Force is investigating an issue with the Minotaur 4 launch vehicle, which affects the entire M4 fleet,” the Air Force Force Space and Missile Systems Center in El Segundo, Calif., said in a statement. “There is a problem with the [government-furnished equipment] hardware that supports the third stage of the launch vehicle.”

 Air Force officials are eyeing several corrective actions, though a final design solution has not been identified, resulting in “an indefinite delay of the SBSS launch,” the statement said. “At this time we do not have a projected resolution date or total cost of a corrective action plan and launch slip.”

The SBSS spacecraft, built by Chicago-based Boeing Co., is intended to keep tabs on objects in space, particularly in geosynchronous orbit 36,000 kilometers above the equator — the operating location of most communications satellites. SBSS has encountered numerous delays due to technical issues during its development; the program was restructured in 2007.

The satellite previously was slated to launch in April but was delayed following the February failure of a Taurus rocket carrying NASA’s Orbiting Carbon Observatory satellite. That failure was attributed to a problem with the Taurus fairing, which is similar to the Minotaur 4 fairing.

SBSS was the Air Force’s first planned launch atop the Minotaur 4, currently in development by Dulles, Va.-based Orbital Sciences Corp. The first three stages of the Minotaur 4 are based on excess U.S. Peacekeeper missile hardware, with commercial solid-rocket motor serving as the fourth stage.

Barron Beneski, a spokesman for Orbital, deferred to the Air Force for comment.

The SBSS launch is slated to take place from Vandenberg Air Force Base, Calif.

Air Force Col. Ed Wilson, commander of the Space Development and Test Wing at Kirtland Air Force Base, N.M., part of Space and Missile Systems Center, said the delay is not expected to affect Air Force plans to launch a second Minotaur 4 in May 2010. That rocket, slated to carry multiple experimental payloads, is slated to launch from Kodiak Island, Alaska.

“We should be able to hold the launch schedule for May,” Wilson said.