Roscosmos Planetary Exploration Missions

“Luna-25”: preliminary results of work to determine the reasons for the abnormal functioning of the station

On August 19, when issuing a corrective impulse to transfer the spacecraft from a circular lunar orbit to an elliptical pre-landing orbit, the Luna-25 propulsion system operated for 127 seconds instead of the planned 84 seconds. As a result, the station switched to an undesigned open orbit and collided with the lunar surface.

It was established that the most likely cause of the 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. In this case, the distribution of commands in data arrays is random (probabilistic) in nature.

In this regard, the on-board control complex received zero signals from the accelerometers of the BIUS-L device. This did not allow, when issuing a corrective pulse, to record the moment the required speed was reached and to timely turn off the spacecraft propulsion system, as a result of which its shutdown occurred according to a temporary setting.

Recommendations for additional activities for subsequent lunar missions have been formed.

#Moon25 #MissionMoon25

There will be no shift to the left in the Russian lunar program and the next launch to the Moon will take place only in four years. This became known from the updated plan for upcoming missions, which was presented at the 14th international symposium on solar system research, held at the Space Research Institute of the Russian Academy of Sciences.
The new plan has two differences from the old one.
Firstly, the launch date of the Luna-27 station has been slightly adjusted. Now the launch of this mission is listed as 2028+, and not definitely 2028, as it was before.
Secondly, Luna-27 now has a double. It will be launched into space a few months after the main mission.
No “training” flights are planned to revive our skills in soft landing on the Moon.
Yes, apparently, our celestial neighbor will have to wait a long time for the Russian to leave his traces on its surface.

The head of the state corporation, Yuri Borisov, noted that the landing site for the Luna-27 spacecraft will be determined by the orbital Luna-26.

MOSCOW, December 26. /TASS/. Roscosmos is considering a proposal from the Russian Academy of Sciences to create two Luna-27 spacecraft in order to increase reliability. This was announced by the head of Roscosmos Yuri Borisov.

"The [Russian] Academy of Sciences came up with a proposal to make two satellites - Luna-27a and Luna-27b - for reliability and to ensure the guaranteed completion of this mission. We are now considering their proposal, but nevertheless, 2028 is certainly in the deadlines are worth it,” Borisov said in an interview with Russia-24 .

According to him, the landing site for the Luna-27 spacecraft will be determined by the orbital Luna-26, work on which is already in full swing. “The launch is planned for 2027,” added the head of Roscosmos.

Borisov recalled that the situation with Luna-25 greatly upset all workers in the field, especially the young team of the NPO named after. S. A. Lavochkina. “But we need to put our worries aside and roll up our sleeves to work on a new project,” he emphasized.

The Soyuz-2.1b launch vehicle with the Luna-25 automatic station launched from the Vostochny Cosmodrome on August 11. After sending a pulse to the device to form its pre-landing elliptical orbit, communication with the spacecraft was interrupted. It ceased to exist when it collided with the surface of the Moon.

The interdepartmental commission came to the conclusion that the accident of the Luna-25 automatic station occurred due to abnormal functioning of the on-board control complex associated with the failure to turn on the accelerometer unit in the BIUS-L device (unit for measuring angular velocities).