MOSCOW, Dec. 8 (Xinhua) -- The failed launch of the Proton-M carrier rocket with three Glonass-M satellites might be caused by over-fueling of the upper stage, Interfax news agency said Wednesday.
"The refueling equipment at the (Kazakh) Baikonur launch pad, which automatically pumps liquid oxygen into the tanks of the DM-03 upper stage, was not operating properly. As a result, it was accidentally overfilled with one or two tons of liquid oxygen than was necessary," Interfax quoted a source as saying.
Therefore, the increased weight of the spacecraft head section prevented the rocket from developing the required speed by the end of the flight and delivering the payload to orbit, the source added.
According to the source, this was the first flight of the DM-03 upper stage which has an increased tank capacity compared to its predecessor, DM-2, thus there was no need to completely fill up the DM-03 tanks.
The three satellites, which were launched Sunday from Kazakh Baikonur space center, failed to enter their designated orbit and crashed in the Pacific Ocean off Hawaii Islands after falling off course.
On Monday, Russian deputy prime minister Sergei Ivanov said the failure of rocket booster may be behind the failed launch, and "the satellites themselves have nothing to do with this failure."
The Sunday launch was the 11th Proton launch of this year. The previous ten launches, including two that positioned Glonass navigation satellites, were successful.