MOSCOW, Oct. 3 The most likely cause of the Luna-25 station accident is an error in the operation of the on-board control unit, which was unable to determine which commands to execute first, the Roscosmos press service reported following the results of the work of the interdepartmental commission.
“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 into one data array of commands with different priorities for their execution by the device «, says the press release.
The distribution of commands in such data sets is random. Thus, the on-board control complex received zero signals from the accelerometers. This did not allow us to accurately determine the moment of gaining sufficient speed and turn off the engines in time.
As a result, the installation worked for 127 seconds instead of the planned 84, the station entered an undesigned orbit and collided with the Moon.
Based on the results of the investigation, the state corporation will formulate recommendations to avoid a repetition of the incident in future missions.
The Soyuz 2.1b rocket with the first domestic lunar station in almost 50 years launched from the Vostochny Cosmodrome on August 11. On August 16, the device entered lunar orbit. The transfer to the pre-landing orbit was expected on August 19, and a soft landing on the south pole of the Moon was expected on August 21.
However, on August 19, Roscosmos announced that an emergency situation had occurred on board the station, which did not allow the transition to the pre-landing orbit. The next day, the state corporation reported that Luna-25 switched to an off-design orbit and collided with the Moon.
Later, the head of Roscosmos, Yuri Borisov, named the cause of the emergency: the engine of Luna-25, when trying to go into a pre-drop orbit, worked for 127 seconds instead of 84, and the device crashed into the Earth satellite.