On October 20, a close conjunction between Chandrayaan-2 Orbiter (CH2O) and Lunar Reconnaissance Orbiter (LRO) of NASA was expected to take place according to the analyses of both ISRO and NASA. It showed that the radial separation between the two spacecraft would become less than 100 m and the closest approach distance would be 3km.
ISRO has declared that it had to perform a collision avoidance manoeuvre (CAM) in order to avoid a collision with NASA’s Lunar Reconnaissance Orbiter (LRO) in the month of October.
The statement given by ISRO read, “A very close conjunction between the Chandrayaan-2 Orbiter and the LRO was expected to occur on October 20 near the Lunar North pole. Over a span of one week prior to the conjunction, analyses by both Isro and JPL/NASA consistently showed that the radial separation between the spacecraft would be less than 100 m and the closest approach distance would be only about 3 km at the aforementioned time of closest approach,”
The statement said that the agencies considered the situation warranted a collision avoidance manoeuvre (CAM) in order to mitigate the close approach risk adding that it was mutually agreed that CH2O would undergo the CAM. The statement said, “The manoeuvre was scheduled on 18th October 2021, it was designed to ensure a sufficiently large radial separation at the next closest conjunction between the two spacecraft. The CAM was executed nominally at 14:52 UTC (8:22 pm IST), on October 18th. After orbit determination of CH2O with post-manoeuvre tracking data, it was reconfirmed that there would be no further close conjunctions with LRO in the near future with the achieved orbit.”
The statement further noted that it was common for satellites in Earth’s orbit to perform Collision Avoidance Manoeuvres for the mitigation of collision risks with space objects including space debris and operational spacecraft. It said, “…CH2O, LRO orbit the Moon in a nearly polar orbit and hence, both the spacecraft come close to each other over the Lunar poles. It is common for satellites in Earth Orbit to undergo Collision Avoidance Manoeuvres to mitigate collision risk due to space objects including space debris and operational spacecraft.
“ISRO regularly monitors such critical close approaches and execute CAMs for its operational satellites whenever the collision risk is assessed to be critical. However, this is the first time such critically close conjunction was experienced for a space exploration mission of ISRO which necessitated an evasive manoeuvre,” the statement further added.
