Luna-25 probe crash caused by onboard control system abnormal operation — Roscosmos
MOSCOW, October 3. /TASS/. Russia’s Luna-25 automatic lunar probe crashed due to the abnormal operation of its onboard control system, the State Space Corporation Roscosmos said on Tuesday.
"The interagency commission is wrapping up its work to find the reasons for the abnormal operation of the Luna-25 automatic station in the lunar orbit. It has been established that Luna-25 most likely crashed due to the abnormal operation of the onboard control system resulting from a failure of the accelerometer unit in the BIUS-L device (the angle velocity measuring instrument) after commands with different priorities of their fulfilment possibly entered into one array of data," Roscosmos said in a statement.
The distribution of commands in arrays of data is random (probabilistic) in nature. Due to this, the onboard control system received zero signals from accelerometers, it said.
"This made it impossible to record the moment the required velocity was reached in issuing the corrective impulse and timely switch off the spacecraft’s propulsion unit, as a result of which it was turned off using a temporary command," Roscosmos explained.
Following the results of its work, the commission will issue recommendations on additional measures for subsequent lunar missions to rule out a repeat of such incidents, it said.
A Soyuz-2.1b carrier rocket with the Luna-25 automatic station blasted off from the Vostochny spaceport in the Russian Far East at 2:10 a.m. Moscow time on August 11. The lunar probe carried out two orbit adjustments on August 12 and 14. On August 16, the Luna-25 automatic station entered its lunar orbit. On August 19, the spacecraft received an impulse to move into a pre-landing elliptical orbit and at about 2:57 p.m. Moscow time contact with the lunar probe was lost.
According to preliminary data, Luna-25 ceased to exist after crashing into the Moon’s surface.