The James Webb Space Telescope (JWST) will be an incredible addition to the scientific community once it is launched and operational but the relative short planned mission time will make this a time critical operation.

The planned minimal mission time is 5 years with a projected 10 year life span of the spacecraft. Those 5 years seam quite short if you consider that the telescope is now delayed for longer than it supposed to be working. Those 5 years are also outshined by the 29 years Hubble has been operational (disregarding the optician consultation Hubble needed).

JWST may be in a considerably more "complicated" orbit than Hubble but launch cost as dropped significantly in the last few years. Therefore the price of a launcher for a planned refueling mission would only be a fraction of the whole JWST project.

Taking all this into account and the fact that Hubble was serviced every few years:

Why are there no plans to refuel JWST and is it even possible?

(Not asking about service mission such as the question: 1, 2, 3)

On the German Wikipedia article about the JWST I found a mention of the possibility of docking to the JWST for refueling.

Während der vorgesehenen Nutzungsdauer sind bisher keine Reparatur- und Wartungsmissionen vorgesehen; es gibt jedoch eine Vorrichtung, die eine nachträgliche Ergänzung der Treibstoffvorräte durch eine Robotermission ermöglichen würde.

Roughly translating to:

In the intended service life no repair and maintenance missions are planned; However, there is a mechanism that would allow for a subsequent supplementation of the fuel supplies by a robot mission.

There is no source for this information so it may well be outdated or outright false, but this gives me the hope that JWST may be refuel-able and will be if the necessary budget gets allocated.

Bottom (sun-facing side) of JWST Bottom (sun-facing side) of JWST; Wikipedia

Is the payload adapter for the Ariane 5 maybe useable as a docking mechanism for refueling or could a probe just dock with JWST and be used for station keeping without any fuel transfer?

I know there've been multiple question on the serviceability of JWST for example using Orion as a shuttle replacement, but I do not ask about changing instruments how it was done with Hubble but rather a "simple" reboost/refuel for station keeping.

This question ask about how the JWST will be serviced with the answer saying that it will not be serviced because:

There is currently no servicing capability that can be used for missions orbiting L2, and therefore the Webb mission design does not rely upon a servicing option.

This answers the other question about servicing but not mine about the refueling capabilities as it is something completely different to send a shuttle-like mission to JWST for servicing compared to sending something like an ATV launched from a Falcon 9/Ariane 6 for a refuel/reboost.

I just can't imagine that another 200 million USD for a launcher and automated probe wouldn't be justifiable if a spending of 2% of the overall project cost could mean a doubling of the life span.

  • $\begingroup$ @Hobbes I've already read your answer at the linked question but the quote with which you answer states:"There is currently no servicing capability that can be used for missions orbiting L2". But I do think that there is refueling capabilities for missions orbiting L2. $\endgroup$
    – GittingGud
    Commented Aug 27, 2019 at 10:30
  • $\begingroup$ @Hobbes see the quote in the update at the beginning of Besides HST, JWST and stations, are there any examples of satellites designed for service in space?, though I see you have an answer there as well negating the idea, so maybe it's not so relevant. $\endgroup$
    – uhoh
    Commented Aug 27, 2019 at 11:04
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    $\begingroup$ This question asks if it is possible. I think it really is a different question, especially after the revision, so voting to re-open. $\endgroup$
    – uhoh
    Commented Aug 27, 2019 at 15:07
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    $\begingroup$ Especially because the question/answer this is supposed to be a duplicate of discusses servicing JWST which is considerably different to just refueling. $\endgroup$
    – GittingGud
    Commented Aug 27, 2019 at 15:45
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    $\begingroup$ I'm going to guess this answer here is not technical enough for you. "In-space refueling of #JWST? Logically possible but difficult. It would require robots!" It was from a public-forum twitter Q&A, but kind of gives the impression that, no, we don't have a plan; but they said it's logistically possible ;). That was John Mather who said that. $\endgroup$ Commented Aug 27, 2019 at 20:54

2 Answers 2


Theoretically possible, but not planned.

Refuelling in the sense of replacing expended fuel in the propulsion system is possible in theory. This answer provides a nice schematic of the propulsion system, and according to the legend at least there is a valve for filling up the propellant tanks. Presumably, you could "top it off" again once the fuels is depleted.

JWST propulsion system

However, this would be extremely difficult and dangerous: I doubt that the risks of an astronaut handling hydrazine in space would be acceptable, so a robot needs to do this. This would require a very advanced robot and I don't think we have this technology yet. I doubt undertaking such a mission would be feasible with technology and budgets available.

At some point in time it was apparently decided to add a dedicated docking ring to JWST for this exact purpose, but I'm unable to confirm if this docking ring still exists:

NASA is adding a docking ring to the James Webb Space Telescope (JWST) just in case a visit by astronauts aboard a future Orion Crew Exploration Vehicle is needed to complete deployment of the multibillion-dollar orbiting observatory.

(from: NASA Adds Docking Capability For Next Space Observatory, space.com, 2007)

However, the launch vehicle interface ring, which mates the JWST with the Ariane 5 launcher, can potentially be used as alternative to dock an autonomous spacecraft for providing attitude and orbit control:

There are, however, modest efforts being made to make JWST “serviceable” like Hubble, according to Scott Willoughby, JWST’s program manager at Northrop Grumman Aerospace Systems in Redondo Beach, California. The aerospace firm is NASA’s prime contractor to develop and integrate JWST, and has been tasked with provisioning for a “launch vehicle interface ring” on the telescope that could be “grasped by something,” whether astronaut or remotely operated robot, Willoughby says. If a spacecraft were sent out to L2 to dock with JWST, it could then attempt repairs—or, if the observatory is well-functioning, simply top off its fuel tank to extend its life.

(from: Is the James Webb Space Telescope "Too Big to Fail?", Scientific American, 2017)

In any case, if a spacecraft docks with JWST, this would require some reconfiguring of the JWST control software, since it would need to delegate the attitude control to the docked spacecraft. Depending on how the control software is designed, this may be trivial or very complicated.

  • 1
    $\begingroup$ "This would require a very advanced robot and I don't think we have this technology yet. " Well we have cartoons of one at least! Is Landsat-7's propellant resupply port “robot-ready”? (Restore-L mission) $\endgroup$
    – uhoh
    Commented Aug 28, 2019 at 11:37
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    $\begingroup$ I did my Ph.D. in robotics in the area of physical interaction: it's hard. Not at all a solved problem. Even if you did it with some remote control, you'd need some haptic feedback, which at those distances is really tricky. $\endgroup$
    – Ludo
    Commented Aug 28, 2019 at 11:47
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    $\begingroup$ @Ludo It wouldn't be that bad--just take it extremely slowly. To make a robot reach over and grab something is hard. To move it a millimeter at a time and observe the result might require days but isn't hard. It's an unmanned mission, so what if it takes days? $\endgroup$ Commented Aug 30, 2019 at 15:30
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    $\begingroup$ @LorenPechtel the problem is in the contact: at the moment you go from free-moving to in-contact, the dynamics of the system change dramatically and you need to account for this in the control loops, which is not trivial. Moving slowly has nothing to do with it. If you add haptics to it, the time delay comes into the equation which makes it even harder. A fellow PhD student in my lab spent his Ph.D. trying to implement stable haptic feedback over a link from Netherlands to Australia, imagine doing it at distance to L2. $\endgroup$
    – Ludo
    Commented Aug 30, 2019 at 15:57
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    $\begingroup$ Ars Technica's All hail the Ariane 5 rocket, which doubled the Webb telescope’s lifetime "Because ten years seemed like a fairly short operational period for such an expensive and capable space telescope, NASA had already been contemplating a costly and risky robotic refueling mission. But now that should not be necessary, as Webb has at least two decades of life." $\endgroup$
    – uhoh
    Commented Jan 11, 2022 at 22:48

Partial, sort of-answer, in addition to the above:

Q: Is it possible to refuel the James Webb Space Telescope?

A: That depends on the JWST having its tanks/plumbing/ports accessible to a robot. (not had time to look for this yet, but from what I have seen, I think it is a no..)

(The bus seems to have a conical rocket base, is the base also comprising of a Marman ring, used for grabbing on to by future robot arms?)

IF it does then...yes-ish:

Northrop Grumman's MEV - Mission Extension Vehicles - have demonstrated the ability to physically grab and make a hard dock with a vehicle that was not previously designed to dock with..anything. And with that, the MEV is able to provide station keeping, attitude control and manoeuvring if required.


April 2021:

Successful docking paves the way for future on-orbit and life-extension services through robotics


The Mission Extension Vehicle-1 (MEV-1), the industry’s first satellite life extension vehicle, completed its first docking to a client satellite, Intelsat IS-901 on February 25, 2020. MEV is designed to dock to geostationary satellites whose fuel is nearly depleted. Once connected to its client satellite, MEV uses its own thrusters and fuel supply to extend the satellite’s lifetime. When the customer no longer desires MEV’s service, the spacecraft will undock and move on to the next client satellite.


The Northrop Grumman-built spacecraft called MEV-2 docked successfully with the nearly 18-year-old Intelsat IS-10-02 satellite, in a move that is expected to add another five years of life to the satellite.

mev ( Intelsat’s IS-10-02 satellite as MEV-2 approached for docking )

Current versions of MEV and its peers is that they are geared for LEO or EO operation. Full time control over a distance like L2 for JWST would require a slightly different and a more autonomous approach given the time delays over that distance.

The next step is refueling:

Robotic Satellite-Refueling Test Resumes on Space Station, 2013

enter image description here

Robotic Refueling Mission calls for Dextre, which sits at the end of the orbiting lab's huge Canadarm2 robotic arm, to perform simulated refueling and repair tasks on a washing-machine-size platform affixed to the station's exterior.

The experiment's goal is to demonstrate technology that could someday fix and refuel orbiting satellites robotically, thereby extending their lives and potentially saving satellite operators billions of dollars over the long haul. Such work can be challenging, since current satellites were generally not designed to be serviced.

The first RRM experiments began last year (2012), when controllers on the ground used the two-armed Dextre to snip some wires with minimal clearance. The latest round of activities will be more complex and involved, as Dextre will snip more wires, unscrew caps and pump simulated fuel, NASA officials have said.


Orbit Fab Demonstrates Satellite Refueling Technology on Space Station, 2019

Orbit Fab announced June 18 it completed tests of an experiment called Furphy on the ISS, demonstrating the ability to transfer water between two satellite testbeds. At the end of the tests, the water was transferred into the station's own water supply, the first time a private payload supplied the station with water in that manner.


The company has acknowledged that it is getting ahead of the market, since no satellite refueling systems yet exist and most satellites are not designed to be refuelable in orbit.



More on RRM:


Robotic Refueling Mission 3 Can’t Perform Cryogenic Fuel Transfer


enter image description here

RRM has established a firm legacy in demonstrating satellite servicing capabilities and that on-orbit servicing is technologically ready for implementation. RRM launched in July 2011 aboard the final space shuttle flight and was the last payload to be removed from the shuttle cargo bay by an astronaut. It was subsequently mounted outside onto a Express Logistics Carrier built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. RRM demonstrated and tested the tools, technologies and techniques needed to robotically refuel and repair satellites in space that were not designed to be serviced.



About a decade ago, the Space Servicing Capabilities Office was established for:

  • Advancing the state of robotic servicing technology to the point where America can routinely service satellites never designed to be serviced,
  • Positioning America to be a global leader· in on-orbit repair, maintenance and satellite clisposal, and
  • Supporting the development of a U.S. industry for spacecraft servicing

RRM as seen here was one project, Argon was another:

The Argon system was composed of a feature recognition camera and software designed to allow a future spacecraft to robotically dock with an non-cooperative spacecraft, thereafter be able to repair, refuel or otherwise service it.

In tests, Argon sensors record images of the spacecraft target as it moves through some pre-determined motion.

The Argon Project completed integration in November 2011 and began a ground test campaign that will culminate in an end-to-end simulation of proximity operations, approach, and capture of a non-cooperative spacecraft target in· the Fall of 2012. The Argon team will conduct a series of increasingly sophisticated demonstrations leading up to the end-to-end test. Two different models for the GOES-12 spacecraft; a geostationary satellite that is a potential candidate for a refueling mission, have been used.

Tests were conducted in late 2011 that simulated separation distances between approximately 90 meters and 1 meter, with the targets positioned statically or with relative motion simulated by an overhead crane. Current testing underway in the ssco facility at GSFC where the relative motion between Argon and the target is simulated using robotic motion platforms.

In parallel with the Argon test campaign, the ssco is conducting a development and test program to integrate robot arm technology with a maiman ring capture tool that can be used to reach out and grab on to the target spacecraft at the point of capture. This development is ongoing in the ssco facility and will come together with the Argon system in late 2012 to conduct the end~to-end non-cooperative proximity operations and capture demonstration for a potential servicing mission.

  • Examples of features of a cooperative spacecraft for servicing include: docking mechanism and grapple fixtures.

  • Examples of features of a non-cooperative spacecraft for servicing include: Marman rings, bolt holes and nozzles.

  • Argon's feature recognition included looking for visual fiducials (reference points), silhouettes, edges, image correlation from a database, corners, and points on the non-cooperative spacecraft.

In summary though, it is possible, and if not now then in the near future, but it depends on the will and the cost.

In that time JWST could well be superseded.

Also, I am aware of Ludo's assertion about it being very hard to do, especially at that distance and with or without haptic feedback. I knew someone who was trying to do that with robots performing human surgery across continents (USA to Australia IIRC) - very hard.

End note:

This image suggests that there is no Marman ring that a robotic spacecraft could grab hold of without damaging something.


Update, Jan 2022, regarding in space refueling service provider service Orbit Fab mentioned above:


Orbit Fab, the Gas Stations in Space™ refueling service provider and Astroscale U.S. Inc., the U.S. subsidiary of Astroscale Holdings Inc. and market leader in securing long-term orbital sustainability, today announced a commercial agreement to refuel Astroscale’s Life Extension In-Orbit (LEXI™) Servicer in geostationary orbit (GEO); LEXI is the first satellite designed to be refueled.

Under the terms of this initial agreement, Orbit Fab’s GEO fuel shuttle will resupply Astroscale’s fleet of LEXI Servicers with up to 1,000 kilograms of Xenon propellant.


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