[Lewis Thomson (OP)]

Listener Francis is interested in finding answers to this question.

"During the planning process for Japan's round-trip to the asteroid Ryugu was there any discussion of leaving any sort of instrument on the asteroid to take photos and collect data as it continued on it's journey? Does anyone have plans to use an asteroid or comet as a vehicle to survey the farther reaches of our solar system?) If we have enough time to locate an astronomical vehicle, build a probe and intercept, why not hitchhike?"

What do you think? Leave your answers in the comments below...

[chris]

Would there be any advantage to this? After all, a spacecraft capable of reaching an asteroid is, by definition, already travelling through space at that speed and capable of powering itself, so what would be the purpose of the added risk and complexity of landing on an asteroid or comet, other than to study that body itself?

[Janus]

Here's the thing, to "hitch a ride" with an asteroid, you first have to match velocity with it.  But once you do that, your probe is already traveling on the same path the asteroid is on, and would remain so, whether the asteroid was there or not.
So, unless you needed the physical body of the asteroid for some reason (as a platform to build a large structure?), there is no point. 

[evan_au]

The Rosetta mission to a comet did leave a probe on the surface: Philae.
- And the Rosetta spacecraft was left in orbit to monitor the comet as it continued in its orbit around the Sun
- But in line with the policy that we shouldn't leave space junk floating around in unknown orbits to cause later problems, the Rosetta spacecraft was intentionally crashed on the comet before it went outside communications range and became an uncontrollable object in an unknown orbit.

https://en.wikipedia.org/wiki/Rosetta_(spacecraft)