Luna 25

Background and program history

Luna 25 traces its origins to the Luna-Glob project, a post-Soviet concept that evolved through multiple configurations over more than two decades — initially involving orbiters, impact penetrators, and combined orbiter/lander designs before settling on a lander-only mission focused on polar landing technology and surface science. Russia had not attempted a lunar mission since Luna 24 returned samples from the Moon in 1976, a gap of 47 years.

The project suffered repeated delays. Early plans targeted a launch in 2018–2019; the baseline later shifted to 2022, then to October 2021, and finally to August 2023, with software issues cited among the reasons for the last postponement. The mission was explicitly positioned as the opening step of a new three-mission Russian lunar roadmap: Luna 25 for site characterization and technology demonstration, Luna 27 for more advanced drilling and analysis, and Luna 28 for sample return.

A notable late change was the removal of ESA's Pilot-D navigation camera, which had been integrated into the payload. Following Russia's 2022 invasion of Ukraine, international sanctions led to the instrument's exclusion from the mission.

Spacecraft design

Luna 25 was an uncrewed polar lander built around two main sections: a landing platform housing the propulsion system and four-legged landing gear, and a non-pressurized instrument container carrying the solar panels, radiators, antennas, TV cameras, power systems, and scientific instruments. Reuters described the spacecraft as comparable in size to a small automobile. The scientific payload totalled approximately 30 kg spread across nine instruments.

Power was provided by solar panels mounted on the instrument container, supplemented by onboard batteries and supported by a thermal control system using radiators. The descent and landing system included velocity and range meters for autonomous guidance during the final approach.

A robotic arm approximately 1.6 m in length formed a central element of the science operations concept. Equipped with a scoop and sample acquisition tool, it was designed to excavate regolith to depths of 20–30 cm and collect small samples for delivery to an internal laser spectrometer.

Failure analysis

On 3 October 2023, Roscosmos announced the results of its preliminary investigation into the Luna 25 crash. The most likely cause identified was the failure of the accelerometer unit within the BIUS-L (Lunar Angular Velocity Measurement Unit) device to activate. Because the unit sent zero signals to the onboard flight control system (BKU) during the orbit-lowering burn, the control system had no velocity data with which to detect when the required change in velocity had been reached.

Unable to trigger a velocity-based engine cutoff, the control system allowed the propulsion system to continue firing until a pre-set time limit was reached. The engine ran for 127 seconds rather than the planned 84 seconds — an overrun of roughly 51 percent. This excess delta-v drove the spacecraft's perilune below the lunar surface, placing Luna 25 on what Roscosmos described as an 'undesigned open orbit' that intersected the Moon. Contact was lost moments later.

Roscosmos characterised the finding as the 'most likely' cause rather than a fully closed root-cause determination, and stated that recommendations had been prepared for application to future lunar missions. One suggested contributing factor was a possible command-stream issue in which commands with differing implementation priorities interfered with the activation of the BIUS-L unit.

Likely crash site

Using impact coordinates estimated by Roscosmos, NASA's Lunar Reconnaissance Orbiter (LRO) imaged the target region on 24 August 2023 and compared the result with earlier LRO imagery from June 2022. The comparison revealed a new, bright crater approximately 10 m wide on the inner rim of the Pontécoulant G crater, at approximately 57.865°S, 61.360°E — a location that did not exist in the 2022 imagery.

NASA's LRO team concluded that the new crater was likely formed by Luna 25 rather than a natural impactor, given its proximity to the estimated impact point and the absence of any other known artificial impact in the area during the relevant period. The site lies approximately 400 km short of the intended landing area near Boguslawsky crater at 69.545°S, 43.544°E. As of the available reporting, the association with Luna 25 is described as 'likely' rather than formally confirmed by a joint Roscosmos–NASA statement.