Luna-25’s Engines Fired Longer Than Planned

The head of the Russian space agency said today that Luna-25 crashed into the Moon because the spacecraft’s engine fired longer than planned. The trouble began on Saturday when Luna-25 was commanded to lower its orbit in preparation for landing, which was scheduled for today. Instead it crashed into the surface.

According to Russia’s state news agency TASS, Yuri Borisov, Director General of Roscosmos, said the engine fired for 127 seconds instead of 84 seconds.

“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.”

Contact was lost less than an hour later at 2:57 pm Moscow Time.

Launched from the Vostochny Cosmodrome in Siberia on August 10 EDT (August 11 Moscow Time), Luna-25 made two course correction engine firings enroute to the Moon without incident. A special commission is investigating what went wrong this time. TASS reported that the command was “numerously tested on a ground-based simulator before it was uploaded” to the spacecraft.

Luna-25 was Russia’s first lunar spacecraft since Luna-24 robotically returned samples from the Moon in 1976. Loss of the spacecraft is not only a disappointment to the Russian space science community, but to space scientists around the world who continue to wait for a successful landing in this new era of lunar exploration. Luna-25 was the fifth lunar lander in a row to fail since 2019.

India will make the next attempt. Its Chandrayaan-3 lander is already in lunar orbit with landing scheduled for 8:34 am EDT (18:04 India Standard Time) on Wednesday.

India’s Chandrayaan-2 lander was one of the failures in 2019, but the Indian Space Research Organisation is confident this one will succeed. Chandrayaan-2 was a combined orbiter/lander and the orbiter worked well. It is still in lunar orbit and is now communicating with Chandrayann-3, providing backup communications pathways with ISRO’s mission control center, MOX.

Chandrayaan-3 Mission:
‘Welcome, buddy!’
Ch-2 orbiter formally welcomed Ch-3 LM.

Two-way communication between the two is established.

MOX has now more routes to reach the LM.

Update: Live telecast of Landing event begins at 17:20 Hrs. IST.#Chandrayaan_3 #Ch3

— ISRO (@isro) August 21, 2023