International Launch Services (ILS) says the Dec. 8, 2012 failure of a Proton rocket equipped with a Briz M upper stage has been traced to “adverse conditions” that caused damage to a bearing in the Briz M main engine turbo pump.

The mishap led to the premature shutdown of the Briz M upper stage and the subsequent release of the Russian Yamal 402 satellite into the wrong orbit.

According to ILS, “the most probable root cause of the failure was due to a combination of adverse conditions which affected the operation of the Briz M main engine during the startup of the third burn causing damage to a bearing on the oxidizer side of the turbo pump,” ILS said today. “This ultimately resulted in the failure of the bearing during the fourth burn and caused the fourth burn of the Briz M to end about four minutes early, with subsequent separation of the spacecraft.”

The launch failure was the Russian rocket’s third in 16 months. ILS said its own failure review board agreed Feb. 7 with the findings of a launch mishap investigation led by the Russian government.

Built by Thales Alenia Space for Russian fleet operator Gazprom Space Systems, Yamal 402 was eventually maneuvered to its intended orbital position Jan. 8, though the effort depleted onboard fuel reserves and reduced the spacecraft’s planned 15-year design life by four years.

ILS says Proton will return to flight in March with the launch of the Satmex 8 satellite for Mexico.

“Scheduling of this mission and of the remainder of the ILS Proton near-term manifest for 2013 is currently being determined,” the company said.