The Indian Space Research Organisation (ISRO) said on Monday that it performed a “collision avoidance manoeuvre” (CAM) on October 18 to avoid a “critically close approach” of the orbiter of its moon mission Chandrayaan-2 and NASA’s robotic spacecraft of Lunar Reconnaissance Orbiter (LRO).
The official announcement on the ISRO website on Monday stated that following a discussion with Jet Propulsion Laboratory (JPL, which is the robotic exploration division of NASA) and NASA, it was “deemed that the situation warranted a CAM to mitigate the close approach risk, and it was mutually agreed that CH2O (Chandrayaan-2 orbiter) would undergo the CAM”.
According to ISRO, a “very close conjunction” between Chandrayaan-2 orbiter and LRO of NASA was expected to occur on October 20 at 11.15 am Indian Standard Time near the lunar north pole. A conjunction is an event in which two satellites or spacecrafts or a satellite and a piece of debris are estimated to pass near each other.
In the week ahead of the expected conjunction, “analyses by both ISRO and JPL/NASA consistently showed that the radial separation between the two spacecraft would be less than 100 metre and the closest approach distance would be only about 3 km”.
The CAM, which involves orbital correction, was designed to ensure a “sufficiently large radial separation at the closest conjunction between the two spacecraft” and was executed normally on October 18, with further post-manoeuvre analysis showing that there would be no further close conjunctions with LRO in the near future, according to ISRO.
The ISRO stated that “this is the first time such a critically close conjunction was experienced for a space exploration mission of ISRO which necessitated an evasive manoeuvre”.