JWST will orbit at the Earth-Sun L2 point, about 1.5M km outside the Earth’s orbit. (By contrast, the Earth is about 100 times as far or about 150M km from the Sun.) It is much too far away for the Shuttle to reach it and unlike Hubble, isn’t designed for in-orbit servicing or repairs. The Orion could get there by using an Earth Departure Stage launched by an Ares 5. like a Moon mission, but I don’t think there are any plans for that, even as a contingency. No grapple fixtures, for example. I think it would make a good rehearsal mission before a moon landing (testing out everything in deep space, much quicker and easier than an asteroid rendezvous, and you don’t get stuck if the LSAM fails.)

Someone in the other thread wondered if it would make more sense to put the Hubble on (or near?) the ISS to make servicing easier. I think it would make sense to put observatories and other large, serviceable satellites in orbits in the same plane but somewhat higher than the ISS. Raising or lowering the orbit of a satellite requires a relatively small amount of fuel. (By contrast, orbital plane changes (such as changing from the Hubble’s 28 degree orbit to the ISS’s 50 degree orbit, or changing between two misaligned 50 degree orbits requires *HUGE* quantities of fuel. ) They could park the observatory in a co-planar orbit a few hundred miles about the ISS, and when they needed to service it, they could send a small space tug-type vehicle (a Soyuz, Progess, Orion, Dragon or ATV could all do the job it it was equipped with a small robot arm with a grappling adapter) that
would rendezvous with it, grab it and pull it back to the ISS. Then ISS-based astronauts could then repair it, replace instruments, etc. using parts sent up on a Progress, ATV or other ISS supply flight. They could take as long as necessary (wouldn’t be restricted to a 14-day shuttle mission) and could check it out before using the tug to send it back to its parking orbit. (By placing it in a higher orbit, it would remove any danger of it colliding with the ISS or lost cameras, tools, etc. or arriving or departing supply or crew flights, it would be exposed to less contamination from rocket exhaust, waste water, etc. than in the immediate vicinity of the ISS, and there would be less air friction to cause its orbit to decay at a higher altitude. (The shuttle servicing missions always boost the Hubble to the highest possible altitude before they leave for this reason.)

(They wouldn’t want to just leave the observatory permanently attached to the ISS because then it would be subject to all the bumps of dockings, reboosts, people moving around inside, pumps moving water and fuel and thus changing the center of mass, the solar wings rotating, etc. For many payloads (e.g. the AMS) this wouldn’t matter but it would wreak havoc with a high-resolution telescope. (Remember the Skylab astronauts running around the inside of it, creating artificial gravity for themselves? I saw what that did to the solar telescope data. Not pretty! Well, actually, it was kind of interesting, but scientifically worthless.)

However, to move the Hubble to such an orbit would require retrieving it and bringing it back to Earth on one shuttle flight, and then re-launching it into the ISS’s orbit on a 2nd flight. For the same cost, they could do 2 servicing missions. And the shuttle may not be powerful enough to launch it to the ISS orbit… Hubble is currently in a 28 degree orbit which provides the maximum payload for a rocket launched from Cape Canaveral. Launching to a higher (or lower) inclination orbit reduces the maximum payload significantly. The ISS is in a 50 degree orbit to maximize the payload from Baikonur. I don’t think Soyuz’s could reach it if it were in a lower inclination orbit, though that would increase the maximum payload for American and European launches to it. That’s one of the things that many people think is wrong with the ISS.

Maybe the next space observatory will take advantage.