On Aug. 20, 2023, the Russian space agency Roscosmos made official the news that the automatic station Luna-25 has been lost.
The official sources were scarce: Until Aug. 21 we had to rely on what was leaked, unofficially, by the people involved in the project. Then, fortunately, Yuri Borisov, CEO of Roscosmos, began to provide some more data.
On August 19, around 12:10 UTC, an impulse was given to transfer the orbit in which Luna-25 was stationed towards the final one which would have allowed, around 11:00 UTC on Aug. 21, 2023, to carry out the ignition that would have brought the probe to land.
Following an unspecified and unidentified error, the ignition lasted 1.5 times longer than expected (127 seconds instead of 84), generating too much abrupt braking. Result: loss of communications with Earth aggravated by the circumstance in which the automatic station would be found, shortly after, on the far side of the Moon.
It was, therefore, necessary to wait until the morning of Aug. 20 to discover, once the moon landing area was back within range of the terrestrial-monitoring stations, that Luna-25 had ended its mission by crashing into the ground of our satellite.
Here is the translation of the text released at 09:44 UTC on Aug. 20 by TASS:
“Communication with the automatic station “Luna-25” has been interrupted, Roscosmos reported. According to preliminary calculations, “Luna-25″ went into an unintended orbit and collided with the surface of the Moon. Roscosmos added that a specially formed interdepartmental commission will be engaged in clarifying the reasons for the loss of Luna-25”.
What went wrong?
According to some rumors, some disturbing readings had been provided by the flight telemetry already during the first orbit correction, when Luna-25 was placed in a polar circular orbit.
However, little prominence was given to these anomalous signals, probably due to a software problem, given that the whole series of onboard scientific equipment, at the same time, had been successfully activated and tested.
Therefore, again according to the internal source reported by the RIA NOVOSTI news agency, it was thought that the software problem had been accidental. But the problem was not a minor one and it was fatal at the most critical moment.
Below is the translation of the excerpt from the article which can be consulted here:
“Ominous signs” at the Luna-25 station were noted even before the attempted transition to pre-landing orbit, but the decision to postpone the maneuver was not made, Nathan Eismont, a scientist, a leading researcher of the Space Research Institute (IKI) of the Russian Academy of Sciences, he told RIA Novosti”.
“There were problems, they weren’t that significant, but the signs were, shall we say, ominous, but everyone hoped that somehow they would be able to deal with it… There were problems, I’ll say it carefully, there are calculated things, but they are not at face value… If we have a slightly higher deviation than we expected, that is a disturbing fact, but it was not disturbing enough to move to a radical solution”, said Eismont”.
So, perhaps, postponing the final maneuver would have been an adequate solution to save the mission. Even if this would have meant landing on the lunar south pole after India’s Chandrayaan-3 Mission, whose moon landing is expected around 12:00 UTC on August 23, 2023.
The most obvious: a programming error. It wouldn’t be the first time this has happened, and it has happened to everyone: from the Soviets to the Americans via Europeans, Indians, and Japanese. Anyone who has come to terms with spaceflight sooner or later makes programming errors, even trivial ones such as the failure to convert between the metric system and the imperial system which led to the failure of the Mars Climate Orbiter mission in September 1999.
Some Telegram channels and the Novosti Kosmonavtikij forum suggest the hypothesis of hacking; considering the security measures adopted, the hypothesis is implausible, but it is one of the scenarios under consideration.
After all, the mission, born to be a joint project with ISRO, then saw the Indian agency, which would have supplied the launcher, slip away, giving way to ESA which, until the embargo caused by the war in Ukraine, supplied part of the software and various scientific instruments. Material that has been disembarked from the spacecraft and replaced with something of internal production.
For this reason, the launch, initially scheduled for 2018, was postponed to 2021 and then to 2023.
In the meantime, the final trajectory of Luna-25 has been calculated by the Keldysh Mathematical Institute. It is estimated that the impact occurred in the area of the Pontecoulant crater at the coordinates 60.1°E – 57.2°S.
What are we left with?
One could say nothing, given the failure of the moon landing, but there is something good to work on.
First, it has been shown that such a mission could be launched from a (relatively) low-cost launcher such as the Soyuz 2.1b. Equipment weighing just 1800 kg can be launched in a direct trajectory and carried in five days to prepare for the moon landing. Considering that, for the same weight and with a decidedly more powerful carrier (the Indian GSLV MkIII), Chandrayaan-3 took more than 20 days to follow a trajectory with very low consumption, the mission profile of the Russian automatic station certainly proved to be more efficient.
Secondly, the excellent quality of the images, unfortunately perhaps the only ones, transmitted by the STS-L camera of the Zeeman Crater region showed an higher resolution than those coming from the LRO satellite, used so far as a touchstone.
It would have been truly a unique show to watch the moon landing live in high definition thanks to STS-L.
The future of the Luna program
Next mission: Luna-26, expected in January 2027; it will not be a lander, this time, but a high-resolution observation satellite, intended for mapping the polar regions for the subsequent missions, Luna-27 (scheduled for January 2028 which is a lander with a small rover) and Luna-28 (scheduled for January 2030 as a sample return mission).
The launch of these additional missions, following the events of Luna-25, according to Borisov, will not be delayed but will be further accelerated.