"The most likely cause of the Luna-25 accident was the abnormal functioning of the on-board control complex, associated with the failure to turn on the accelerometer unit in the BIUS-L device (angular velocity measurement unit) due to the possible entry of commands with different priorities for their execution by the device into one data array," Roscosmos said in a statement.
The distribution of commands in such data sets is random, in other words, probabilistic, according to the statement.
"Because of that, the on-board control complex received zero signals from the accelerometers of the BIUS-L device. This did not allow, when issuing a corrective impulse, to identify the moment when the required speed was reached and timely shutdown the spacecraft propulsion system, as a result of which its shutdown occurred according to a temporal setting," Roscosmos said.
The space corporation also said that the interdepartmental commission is concluding its work on the identification of causes of the accident, and recommendations to prevent similar issues in the future have been prepared.
Luna-25, the first Russian lunar mission in almost 50 years and the first one in Russia's post-Soviet history, lifted off atop the Soyuz-2.1b carrier rocket from Russia's Vostochny Cosmodrome on August 11, and entered lunar orbit a week later. On August 20, Roscosmos said that Luna-25 seemingly crashed into the moon's surface after going into an unplanned orbit. Roscosmos head Yuri Borisov said that Luna-25’s engine had not turned off as planned and worked for 127 seconds instead of 84 seconds during a pre-landing maneuver.