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JWST launched recently.

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Orbit

JWST needs to use propellant to maintain its halo orbit around L2, which provides an upper limit to its designed lifetime, and it is being designed to carry enough for ten years.

Since L2 is just an equilibrium point with no gravitational pull, a halo orbit is not an orbit in the usual sense: the spacecraft is actually in orbit around the Sun, and the halo orbit can be thought of as controlled drifting to remain in the vicinity of the L2 point. This requires some station-keeping: around 2–4 m/s per year from the total ∆v budget of 150 m/s.

$\frac{150ms^{-1}}{3ms^{-1}y^{-1}}=50y$ so I'm not sure where they're getting 10 years from, but I digress.

My main question is: what happens to JWST after that? It will drift from L2.. but where will it end up? I assume we can choose which direction to let it ultimately drift away to. Can we not put it into some sort of useful orbit around the Earth and/or Moon? Will it still be operational? I would expect it to be fine more or less anywhere. Will it still be mechanically operational and in communication for a long time?

Basically, what happens after its 10 year mission ends?

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    $\begingroup$ 10 years is the government's requirement. To practically guarantee they meet that, the contractor actually builds something that will probably last considerably longer, so as to reduce the risk of failing to meet the requirement and thus losing out on award fee payments. $\endgroup$
    – Ryan C
    Dec 28, 2021 at 20:55
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    $\begingroup$ There are many questions about JWST end-of-life here. I think that this answer answers your question the best, but have a look around. $\endgroup$
    – uhoh
    Dec 28, 2021 at 22:11
  • $\begingroup$ The 150 m/s $\Delta\text V$ budget also includes propellant needed for three mid-course corrections, for insertion into a pseudo-orbit about the L2 point, for attitude control, and for end of mission decommissioning. $\endgroup$ Dec 29, 2021 at 15:51
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    $\begingroup$ @RyanC Ten years is a goal, not a requirement. The requirement is five years of operational time. $\endgroup$ Dec 29, 2021 at 15:53
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    $\begingroup$ The wording in the Mission Requirements document (JWST-RQMT-000634) is very clear: [MR-48] "Propellant shall be sized for 10 years of operation after launch". Normal engineering practice dictates that there will be propellant left after 10 years. What to do next will depend on many factors: state of the scientific instruments, scientific results, state of platform bus, follow-on missions (LUVOIR?). international competition(?), budget/man-power ... However, navigating it to demo an ITN feasibility would be cool, IMO. $\endgroup$
    – Ng Ph
    Dec 30, 2021 at 10:40

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It will continue to be used until it cannot be used anymore. Consider other NASA missions

Mission Planned Lifetime Actual Use
Hubble Space Telescope 15 years Still in use (31+)
Sojourner Mars Rover 7-30 sols 83 sols
Spirit Mars Rover 90 sols 2208 sols
Opportunity Mars Rover 90 sols 5110 sols
Curiousity Mars Rover 2 years Still in use (9+)
International Space Station 10 years (per module) Still in use (23+ for Zarya and Unity)
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    $\begingroup$ I think of ISS as a bit different from all the others listed. Hubble had some significant repairs/maintenance done, but none since the retirement of the shuttles, and the rovers have not had any hands-on maintenance at all. But ISS has had, and continues to have, replacement parts sent up from Earth and installed by crew, frequent 6-hour spacewalks for repairs/maintenance and several modules added or replaced. JWST will (currently planned at least) be like the rovers - no on-site maintenance available. $\endgroup$ Dec 29, 2021 at 17:01
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    $\begingroup$ @manassehkatz-Moving2Codidact That's all true. I merely added it for completeness, since the modules had to (according to spec) last 10 years. Hubble got a service mission as well. $\endgroup$
    – Machavity
    Dec 29, 2021 at 17:03
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    $\begingroup$ I disagree with the "planned lifetime" column. That was the minimum lifetime that NASA guaranteed and would precluded a Spanish Inquisition level inquiry. $\endgroup$ Dec 29, 2021 at 18:52
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    $\begingroup$ Moreover, I strongly disagree with "It will continue to be used until it cannot be used anymore." The JWST will be decommissioned by using the last bits of propellant to place it into an Earth-trailing heliocentric orbit. The second to last thing anyone wants is an uncontrollable spacecraft that is chaotically orbiting in the vicinity of the Sun-Earth L2 point for a few years. The last thing anyone wants is an uncontrollable spacecraft that chaotically orbits the Earth for a several years, and this is a real possibility. $\endgroup$ Dec 29, 2021 at 18:58
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    $\begingroup$ Perhaps, what you meant to say is that planned obsolescence does not exist in US space missions (and Space in general), and I am inclined to agree with that: as long as something is still of some (residual) use, there will be corresponding budget extension(s) to use it, with or without in-space servicing. $\endgroup$
    – Ng Ph
    Dec 30, 2021 at 11:33
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This might look like a joke, but it will happen, you'll see!

5 years from now when the formal science mission ends, and of course the telescope has gotten funding to continue, the principal investigator of JWST will have a casual lunch with the politically appointed NASA Administrator, who says:

"-Too bad that this JWST thingy is running out of fuel in a couple of years. After all, it did see the moment when God said: Let there be light! My constituency kind of liked that."

"- Mr. Administrator. As if by chance, I just so happen have here in my pocket a memory stick with the complete design and production plan for a probe that could dock with the JWST, which for some reason happens to have a docking port suitable for precisely this purpose. And that probe would use its fuel and thrusters to maneuver the JWST mirror for another 20 years.

"- Hmm. I've got an idea!"

"- You're a genius, Mr. Administrator!"

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  • $\begingroup$ The docking ring was added due to some significant political pressure; there are serious unknowns in its actual use. No one's quite sure if we can manage to get an actual spacecraft to dock with it without the craft's thrusters damaging the sunshield. $\endgroup$
    – ceejayoz
    Dec 30, 2021 at 16:40

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