WASHINGTON — Russia says its first lunar lander mission in nearly half a century crashed in August because of faulty commands in an onboard computer during a maneuver.
The Luna-25 spacecraft crashed Aug. 19 during a maneuver to lower the spacecraft’s orbit around the moon to set up a landing planned for two days later. Roscosmos said the spacecraft suffered an “emergency condition” that caused its main engine to fire for 127 seconds instead of the planned 84.
In an Oct. 3 statement posted on social media, Roscosmos said that the most likely cause of the crash was “abnormal functioning” of the onboard computer. Specifically, the computer failed to turn on an accelerometer in a device called BIUS-L, which measures the angular velocity of the spacecraft.
As a result, “the on-board control complex received zero signals from the accelerometers of the BIUS-L device,” according to a translation of the Roscosmos statement. “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.”
Luna-25 launched Aug. 10 on a Soyuz-2.1b rocket from Russia’s Vostochny Cosmodrome and arrived in lunar orbit six days later. The lander, weighing an estimated 1,750 kilograms at launch, carried a package of Russian scientific instruments weighing 30 kilograms, and had planned to land at Boguslawsky crater at approximately 70 degrees south latitude.
NASA released Aug. 31 an image from its Lunar Reconnaissance Orbiter (LRO) spacecraft showing the likely impact site of Luna-25, on the steep inner rim of Pontécoulant G crater about 400 kilometers from the planned landing site. The impact site, a crater 10 meters across, does not appear in the previous LRO image of the area taken in June 2022. NASA estimated the impact took place at 7:58 a.m. Eastern Aug. 19.
Luna-25 was the first mission to the moon by Russia or the former Soviet Union since the Luna-24 sample return mission in 1976. Luna-25 encountered years of development delays, and the European Space Agency dropped out of participating on the mission after Russia’s invasion of Ukraine in February 2022.
Yuri Borisov, head of Roscosmos, said the agency would continue its lunar exploration efforts. “No one is going to fold their arms, and we are determined to continue the lunar program,” he said in a translated statement. “Moreover, we are considering the possibility of shifting the Luna-26 and Luna-27 missions to the left in order to get the results we need as quickly as possible.” He did not offer a revised schedule for those future missions.