I was just learning about 2i/Borosov, which I guess was discovered in August but I only learned of it now. And I thought, if there were any comet we'd want to send a probe to, that would be the one, since it's not coming back and there's no telling when another extrasolar object might appear. But half a year isn't enough for a new mission, there would have to be something ready and waiting. It doesn't have to be ICBM-like, ready to go with seconds of notice. There's still time to arrange for a launch on a Delta or a Falcon or something. But the spacecraft would have to be ready to go, and a launcher would have to be ready to fit it into their schedule on short notice. Is there something like that, or plans for it? Is there a reason we couldn't have a mission ready and waiting?

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    $\begingroup$ There is some relevant information in the answer to the different but related question If a comet-sniffing spacecraft were launched today, could it catch up to newly-discovered ε>3 C/2019 Q4 (Borisov)? $\endgroup$
    – uhoh
    Commented Oct 5, 2019 at 23:56
  • $\begingroup$ Planing, designing and building a space probe for an object usually requires some trajectory information of the object. If the object is too far away or too fast a bigger rocket would be neccessary. But what if a suitable rocket is not built yet? $\endgroup$
    – Uwe
    Commented Oct 6, 2019 at 10:21
  • $\begingroup$ @Uwe If you can't get to it, you shrug and say darn. But 2i/Borisov was known to be extrasolar in September, and it will pass within 2 AU of the sun on 8 December. We could have had about three months. It probably still depends on where the Earth is in its orbit, but if you have a lightweight probe shot up on a heavy lifter as fast as it can go... This is all part of the question, I don't know what we can say about time to intercept versus closest approach. $\endgroup$
    – Greg
    Commented Oct 6, 2019 at 17:06

1 Answer 1


Yes, or at least we will have soon. The ESA Comet Interceptor mission is designed to "lurk" at the Earth-Sun L2 for up to five years until a suitable target comes along. The target will most likely be a "new" comet on its first pass around the Sun, but could be an interstellar visitor. The linked page says:

Although much rarer, another example of a potential target is an interstellar interloper from another star system, like the famed ‘Oumuamua that flew past our Sun on a highly inclined orbit in 2017. Studying an interstellar object would offer the chance to explore how comet-like bodies form and evolve in other star systems.


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