GS Paper - 3 (Space Technology)

The Indian Space Research Organisation (Isro) has disclosed that Chandrayaan-2 orbiter had to perform a collision avoidance manoeuvre (CAM) to avoid colliding with NASA's Lunar Reconnaissance Orbiter (LRO), in October. A very close conjunction between the Chandrayaan-2 Orbiter and the LRO was expected to occur on 20 October 2021 near the Lunar North pole.


  1. 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.
  2. The manoeuvre was scheduled on 18 October 2021. It was designed to ensure a sufficiently large radial separation at the next closest conjunction between the spacecraft.
  3. 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.
  4. 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.
  5. Isro monitors such critical close approaches and executes CAMs for its operational satellites whenever risk is assessed to be critical.
  6. However, this is the first time such a critically close conjunction was experienced for a space exploration mission of Isro.