The Sept. 17 return to flight of Russia’s Proton rocket was postponed Sept. 11 for technical reasons associated with the Russian launch vehicle.

Marketed by International Launch Services (ILS) of Reston, Va., the commercial mission was slated to loft The EADS-Astrium-built Astra 2E satellite for fleet operator SES of Luxembourg.

“The launch date will be determined at a later time,” ILS said in a Sept. 12 statement.

Engineers at Proton prime contractor Khrunichev State Research and Production Space Center of Moscow received an out-of-tolerance reading in the first stage of the vehicle at its Baikonur launch site in Kazakhstan on Sept. 11, according to ILS.

“It was determined that further investigation is necessary, requiring the launch vehicle be returned to the processing hall for additional testing,” said ILS, which is majority-owned by Khrunichev. “The vehicle and satellite remain in a safe configuration at the launch site.”

The mission would mark the first Proton rocket to launch since a July 2 mishap during a Russian federal mission sent a Proton M/Block DM3 crashing to the ground seconds after launch carrying three Russian Glonass M navigation satellites.

The mishap, attributed to the incorrect placement of angular-rate sensors on the rocket’s first stage, has already delayed the Astra 2E nearly two months from a planned July 20 launch.