MOSCOW, August 21. /TASS/. The propulsion unit of the Luna-25 automatic lunar probe operated for 127 seconds during its orbit adjustment instead of the planned 84 seconds, which was the main cause of the probe’s crash, Roscosmos Chief Yury Borisov said in a live broadcast on the Rossiya-24 television channel on Monday.
"At 2:10 p.m. Moscow time [on August 19], thrusters intended to adjust the spacecraft and bring it into the pre-landing orbit were switched on. Unfortunately, the thruster shutdown did not occur normally in accordance with the cyclogram but under a time cutoff and it operated for 127 seconds instead of 84. That was the main cause of the probe’s crash," Borisov said.
The Luna-25 orbit adjustment was numerously tested on a ground-based flight simulator before it was uploaded into the automatic station, the Roscosmos chief said.
Roscosmos reported earlier, citing preliminary data that the Luna-25 automatic station had ceased to exist after crashing into the Moon’s surface. Before that, the spacecraft was given an impulse to create its pre-landing elliptical orbit. At about 2:57 p.m. Moscow time on August 19, contact with the Luna-25 lunar probe was lost.
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. The spacecraft’s landing was planned for August 21.