LRO in orbit
NASA's only current lunar mission is Lunar Reconnaissance Orbiter, developed as part of the Vision for Space Exploration and launched in 2009. Credit: NASA

WASHINGTON — India’s Chandrayaan-2 lunar orbiter maneuvered in October to avoid a close approach to NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft, a conjunction both agencies have acknowledged but have said little more about.

In a Nov. 15 statement, the Indian Space Research Organisation (ISRO) said Chandrayaan-2 performed a maneuver Oct. 18 to avoid a predicted close approach to LRO two days later. According to the statement, Chandrayaan-2 was predicted to come within three kilometers of LRO had it not maneuvered.

According to the statement, ISRO and NASA worked together starting a week before the predicted conjunction. “Both the agencies deemed that the situation warranted a collision avoidance maneuver (CAM) to mitigate the close approach risk, and it was mutually agreed that CH2O would undergo the CAM,” ISRO said in the statement, referring to the Chandrayaan-2 orbiter as CH2O.

The statement, though, did not explain why Chandrayaan-2 was the spacecraft selected to perform the maneuver. ISRO did not respond to questions about the maneuver submitted Nov. 27.

The ISRO statement — overlooked by many at the time since it was issued the same day as a Russian antisatellite test in low Earth orbit that created thousands of pieces of debris — was the first time either agency discussed the potential conjunction. NASA did not issue its own statement about the close approach.

“NASA and Indian Space Research Organisation fully coordinated the collision avoidance maneuver conducted by ISRO’s Chandrayaan-2 spacecraft Oct. 18,” NASA spokesperson Nancy Jones said in a Nov. 30 statement offered in response to questions about the conjunction submitted Nov. 19. “Such coordination between space agencies is an ongoing part of ensuring safe operation of satellites around the moon. At no time was NASA’s Lunar Reconnaissance Orbiter or Chandrayaan-2 in danger.”

That statement is the only comment NASA provided about the close approach. NASA did not answer questions about how the agencies determined Chandrayaan-2 should be the spacecraft to maneuver, or how many times LRO has had close approaches to other spacecraft in lunar orbit.

ISRO, in its statement, said that it regularly performs collision avoidance maneuvers for satellites in Earth orbit, but that this event “is the first time such a critically close conjunction was experienced for a space exploration mission of ISRO which necessitated an evasive maneuver.”

Chandrayaan-2 entered lunar orbit in August 2019 and, at the time, ISRO officials said the spacecraft would have enough propellant to operate for seven and a half years. LRO, by contrast, has been in lunar orbit since 2009. In a presentation at the annual meeting of the Lunar Exploration Analysis group in August, project officials said they had enough fuel on board for at least six more years of operations.

Collision avoidance is traditionally associated with satellites in Earth orbit, particularly low Earth orbit, but may increasingly become an issue both at the moon and Mars with more missions by more organizations. In March, NASA confirmed it was exchanging data with the China National Space Administration about the orbits of their spacecraft orbiting Mars, after some initial frustrations among those in NASA’s Mars program regarding the lack of data about the orbit of Tianwen-1, China’s first Mars orbiter, which arrived at Mars in February.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...