Cassini at Saturn has sampled geysers although it wasn't designed to do it. The orbiter NEAR Shoemaker was soft landed on its asteroid. Two examples of how interplanetary probes have been partly repurposed while in flight, there are certainly many more subtle ones.

What could be done to make for example the proposed Europa clipper so flexible that it could reconfigure itself in order to follow up on unexpected discoveries instead of having to wait for a completely new probe? Do we still need to keep it simple in order to achieve reliability?

What about reusable orbiter platforms? Somewhat like a space station or a Mars cycler. A platform which once put in orbit then is gradually upgraded and redesigned during many decades. The simplest might be to just launch a radiation shielded platform to Jupiter orbit once and for all, to which several probes could dock one after the other during many decades. The extreme would be to have a probe factory in orbit of an outer planet which only needs the low-weight high tech instrument components and fuel sent to it from Earth, in order to be redesigned to whatever kind of probe is desired next.


3 Answers 3


I see this as really unlikely. There has only really been one un-manned spacecraft that this was successful, and that was the Hubble Space Telescope. Even as such, it required a team of astronauts to upgrade the telescope. Why was it cheaper to upgrade Hubble?

  1. The mirror was a very large expense, along with the pointing, power, and communications.
  2. The structure was unchanged, so the instruments just had to be included in the box.
  3. The satellite is in low earth orbit, easy to reach by astronauts.
  4. The position is really well known, because it is so close to Earth.

How is that different from, say, a Jupiter orbiter?

  1. The position of Cassini isn't that well known. I don't have a great estimate, but I'm sure the position can't be know to more accurate than the few mile range, and likely isn't even that well know. This makes docking difficult, you have to do some kind of active updates on site to find the spacecraft.
  2. The distance makes it so the time required to send out an upgrade package takes a significant amount of time. There would be no guarantee that the far spacecraft would still work after such a long period of time.
  3. Not being in LEO, it would not allow for an astronaut to install the new instruments. The most technology would really allow for right now is a docking maneuver, sharing power, data, and pointing, but not things like a mirror.
  4. An unmanned mission would require constant Earth communication. The same system could presumably send data from the instrument.

Bottom line is, there doesn't seem to be a whole lot of gain to make with this kind of an upgrade, at least not with technology anticipated in the near term future, except for perhaps another instrument like Hubble.

  • $\begingroup$ I'd think the position of Cassini would have to be very well known, in order to make its orbit changing by gravitational assist maneuvers possible. Not to mention figuring out where to point the cameras &c. $\endgroup$
    – jamesqf
    Commented Jun 17, 2015 at 18:18
  • 1
    $\begingroup$ According to space.com/28240-saturn-position-measurement-cassini-vlba.html , we don't even know the position of the center of mass of Saturn to better than 2 miles. I'm sure it's within a few miles, but the position isn't known exactly of Cassini. Might make a good question to track down just how well known it is... $\endgroup$
    – PearsonArtPhoto
    Commented Jun 17, 2015 at 18:27

There is a big difference between making the most of the equipment you have on board, and fabricating new sensors on demand. The first has already been done.

The second is much more complex. "Following up on unexpected discoveries" means you'd have to create new sensors. These instruments take a fully-equipped lab (plus its massive infrastructure in the shape of parts suppliers) on Earth months, if not years to build. We're many years away from being able to build such a factory within the space constraints of a space probe.

In the comments, you've suggested an in-between solution: send new instruments as a package to rendezvous with the original probe, link the two together and use them as one platform. That could have some interesting uses.

Your package is going to need engines, a power system and a radio for the rendezvous at Jupiter, so you're already halfway to building a full probe. But there could be some benefit to reusing things like the high-gain antenna (which is large) and the RTG (which is expensive).

But the most expensive parts of a probe are the instruments. The rest (apart from the RTG) is a piece of cake by comparison, so I doubt you'd save much money in the end.

  • $\begingroup$ The instruments make up a small fraction of an interplanetary probe's mass. It should be possible to launch those components cheaply as dead cargo for docking with a Jupiter orbiter. The big mass systems, like power and communication and thermal control and structure, could maybe be more easily reconfigurable. $\endgroup$
    – LocalFluff
    Commented Jun 17, 2015 at 11:45
  • $\begingroup$ @LocalFluff: Unless you're thinking of high-closing-speed docking, the instruments would at least need orbital insertion, so either some rather dicey and perhaps hard-to-generalize gravity sling maneuvers around various moons, or conventional thrust. $\endgroup$ Commented Jun 17, 2015 at 17:15

An orbiter platform, minus its instruments, would consist mainly of power, attitude control, and communication systems.

A secondary mission to deliver new instruments to that orbiter would also require power, attitude control, and communication systems, in order to reach the destination.

So there's no real savings from re-using parts of the first platform, so there's no incentive to tackle the complexity of a modular upgradable system.


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