Roscosmos: the crash of Luna-25 occurred due to a block of angular velocities

The most likely cause of the accident of the Russian automatic interplanetary station “Luna-25” was the abnormal functioning of the on-board control complex, reported “Roscosmos”.

The state corporation clarified that the accelerometer unit in the BIUS-L device (unit for measuring angular velocities) was not turned on due to the possible inclusion of commands with different priorities for their execution by the device in one data array. The distribution of commands in data arrays is random (probabilistic) in nature. Because of this, zero signals from the accelerometers arrived at the on-board control complex. When issuing a correction pulse, the moment of reaching the required speed was not recorded and the spacecraft engine could not be turned off in time. The shutdown occurred according to a temporary setting.

Thus, during the issuance of a corrective impulse for the transition of the device from a circular lunar orbit to an elliptical pre-landing orbit, the Luna-25 engine worked for 127 seconds instead of the planned 84 seconds. The station switched to an undesigned open orbit and collided with the surface of the Moon.

Roscosmos has already formulated recommendations for future lunar missions.

Luna 25 was launched on the night of August 11 from the Vostochny Cosmodrome. On August 16, the spacecraft entered lunar orbit. The station was expected to land north of the Boguslavsky crater on August 21. But during the transition of Luna-25 to the pre-landing orbit, the station happened accident. The accelerometer has already malfunctioned called among the possible causes of the crash. Head of Roscosmos Yuri Borisov statedthat Russia can repeat the mission to the South Pole of the Moon by 2026.