Investigators probing last week's failure of a Russian rocket are narrowing their focus on the control system of the vehicle's Breeze M upper stage, which left a Russian Express communications satellite in the wrong orbit.

Footage of the launch of the Proton rocket with the Express AM4 satellite. Credit: Roscosmos
 
Although officials are tracking the Express AM4 spacecraft in orbit, engineers were still trying to contact the satellite more than five days after it launched, according to a statement released by Roscosmos, the Russian space agency.

The communications satellite lifted off Aug. 17 on a Proton rocket from the Baikonur Cosmodrome in Kazakhstan. The three-stage Proton vehicle performed as designed, then the hydrazine-fueled Breeze M rocket engine took over for five planned burns to direct Express AM4 closer to its ultimate station in space.

But something went awry during the third or fourth burn of the upper stage, and the rocket deployed Express AM4 in the wrong orbit. The initial consensus is there was a problem with the upper stage's guidance or control systems.

U.S. and Russian military assets determined Express AM4 is circling Earth in an orbit between 618 miles and 12,610 miles in altitude. Its orbital inclination angle is 51.23 degrees to the equator, according to Roscosmos.

"During the mission of the ascent unit, including the Breeze M upper stage and the spacecraft, an anomaly occurred in the Breeze M control system, and Express AM4 was injected into an off-design orbit," Roscosmos said in a statement Tuesday.

The Russian space agency, the Russian Ministry of Communications, the Russian Satellite Communications Co. and EADS Astrium mounted joint efforts to contact the spacecraft and activate its systems.

"Currently, the specialists continue their attempts to re-establish contact with the satellite," the Roscosmos statement said.

Artist's concept of the Express AM4 satellite in orbit. Credit: EADS Astrium
 
Gregory Gavroy, an EADS Astrium spokesperson, said Tuesday he had no more details other than what was released by Roscosmos and Khrunichev. EADS Astrium constructed the spacecraft to provide communications coverage over Russia and neighboring countries for the next 15 years. The satellite was to be operated by the Russian Satellite Communications Co., the country's state civil satellite operator.

RSCC's satellite fleet beams presidential and government communications services, federal television and radio signals, direct-to-home television, broadband Internet, and facilitates VSAT and corporate networks.

Russia set up a state commission inquiry to find the cause of the problem.

"A number of possible scenarios are analyzed, the main one being an anomaly in the upper stage control system," the Roscosmos statement said.

Officials are still trying to recover the Express AM4 satellite and attempt to bring it into service.

The spacecraft would have to raise its orbit using on-board propellant, likely reducing its useful life if it could be recovered at all.

Khrunichev, the Proton and Breeze M's prime contractor, has suspended preparations for upcoming launches until investigators determine what caused last week's mishap.

Two commercial Proton missions were scheduled by International Launch Services for launch in September. The next flight was supposed to haul the QuetzSat 1 direct broadcasting satellite into orbit for SES and EchoStar Corp. to cover Mexico.