“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,” an Isro statement reads.
It added that both the agencies deemed that the situation warranted a CAM to mitigate the close approach risk, and it was mutually agreed that Isro’s orbiter would undergo the same.
“The manoeuvre was scheduled on October 18, 2021. It was designed to ensure a sufficiently large radial separation at the next closest conjunction between the spacecraft. The CAM was executed nominally at 8.22pm (IST). After orbit determination 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,” Isro said.
Chandrayaan-2 and LRO orbit 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 CAMs to mitigate collision risk due to space objects including space debris and operational spacecraft. Isro monitors such critical close approaches and execute CAMs for its operational satellites whenever risk is assessed to be critical. However, this is the first time such a critically close conjunction was experienced for a space exploration mission of Isro,” the space agency said.
It added that the event highlights the importance of continual assessment of close approach situations for lunar and martian missions, and the fact that effective mitigation of close approach risk involves close coordination and synergy among different space agencies.