Even multiple spacecraft in orbit around the Moon can generate dozens of collision warnings and require multiple maneuvers, suggesting the need for more robust coordination mechanisms.

Soyun Chung, a senior scientist in the Strategy and Planning Department of the Korea Aerospace Research Institute (KARI), said in a presentation at the Safe World Foundation’s Space Resilience Summit on July 11 that her agency has received 40 “red alerts” about possible spacecraft collisions that have orbited the moon over the past 18 months.

The alerts primarily concern a close approach involving KARI’s Korean Pathfinder Lunar Orbiter (KPLO), NASA’s Lunar Reconnaissance Orbiter (LRO) and India’s ISRO space agency’s Chandrayaan-2, all of which are in similar low orbits around the moon. The three agencies voluntarily share information about the spacecraft’s orbits using a NASA platform called MADCAP, which generates collision alerts.

Since KPLO entered lunar orbit in December 2022, the system has generated 40 alerts, called red alerts, of possible connections. Some have “resolved naturally” because improved orbital data shows no risk of collision, he said. Others could be relayed if one of the spacecraft performs a routine maneuver to maintain its orbit.

“But in some of them, you have to do some maneuvering to avoid a potential collision,” he said. KPLO has performed three such maneuvers so far: one to avoid a close approach to LRO, another to avoid Chandrayaan-2, and a third to avoid Japan’s Smart Landing Vehicle for Exploring the Moon (SLIM) spacecraft shortly before its landing in January. The SLIM link requires a decision on the maneuver to be made within 24 hours to avoid a conflict with the landing, he said.

Maneuvers to avoid collisions around the Moon are not unprecedented. In 2021, Chandrayaan-2 maneuvered to avoid a close approach with LRO after coordination between ISRO and NASA. At the time, neither agency disclosed the frequency of these potential contacts.

The scale of potential collisions between spacecraft in lunar orbit is not currently widely discussed in public. “It’s a real thing that we don’t talk about much,” Chang said.

He said the problem highlights the lack of formal processes and procedures for coordinating spacecraft around the Moon, a problem that will worsen as more companies and countries send missions there.

“There is currently no mutually agreed international consultative mechanism or protocol to address such conflict risks,” he said. Coordination between ISRO, KARI and NASA is a voluntary system in which others like China do not participate. “Not all participants are involved in this process.”

There is no formal mechanism to determine which spacecraft will perform a collision avoidance maneuver when necessary. Such maneuvers can disrupt the spacecraft’s operation and shorten the spacecraft’s life by consuming fuel. He later said that KARI agreed to perform these three KPLO maneuvers because it had more fuel.

“Through our experience with KPLO, we understand the need for an information-sharing platform and mutually agreed international protocols to identify and manage collision risk between missions around the Moon, as we do on Earth,” he said.

One mechanism could be the UN Committee on the Peaceful Uses of Outer Space (COPUOS). At its meeting last month, the committee decided to establish the Consultative Action Group on Lunar Activities, following a proposal from the Republic of Korea and Romania. Coordination mechanisms for lunar spacecraft would be one of the issues the task force would consider, Chung said.