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Has there ever been probability of conjunction between spacecrafts in Lunar orbit? describes a recent maneuver of two spacecraft in orbit around the moon to avoid a potential collision:

Apparently ISRO's Chandrayaan-2 orbiter and NASA's LRO narrowly avoided a possible conjunction event in Lunar orbit due to timely assessment and action of both agencies.

https://www.isro.gov.in/update/15-nov-2021/chandrayaan-2-orbiter-ch2o-performs-evasive-manoeuvre-to-mitigate-critically

which made me wonder where Chandrayaan-1 is, if anybody knows, if it's been tracked or at least spotted again since 2016, and if it poses any threat.

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    $\begingroup$ Space is big... $\endgroup$
    – GdD
    Nov 15, 2021 at 13:28
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    $\begingroup$ @GdD but not so much low lunar orbit $\endgroup$
    – uhoh
    Feb 26, 2022 at 2:36

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It was not "spotted just once". Rather, it was tracked until its orbital motion became predictable:

On 2 July 2016, NASA used ground-based radar systems to relocate Chandrayaan-1 in its lunar orbit, more than seven years after it shut down.[1][2] Repeated observations over the next three months allowed a precise determination of its orbit which varies between 150 and 270 km (93 and 168 mi) in altitude every two years.[3]

Cited references

  1. Karimi, Faith (10 March 2017). "NASA finds lunar spacecraft that vanished 8 years ago". CNN. Retrieved 10 March 2017.

  2. Agle, D. C. (9 March 2017). "New NASA Radar Technique Finds Lost Lunar Spacecraft". NASA. Retrieved 10 March 2017.

  3. Udhayakumar, M.; Singh, Jitendra (2 August 2017). "Question No. 2783: Chandrayaan-1" (PDF). Lok Sabha. Archived from the original (PDF) on 2 August 2017. Retrieved 2 August 2017.

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    $\begingroup$ and to "is someone still keeping an eye on it from time to time?" the answer is probably something like "no, not necessary because the Moon's irregular gravity field has been mapped to great precision"? $\endgroup$
    – uhoh
    May 31, 2022 at 18:28

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