Context: JWST is considered un-repairable in its current L2 location for a number of reasons:

  • Diagnosis is difficult since JWSR has no “selfie” capability. This makes planning for any repair mission (crewed or robotic) problematic.
  • Distance and radiation exposure are vastly beyond the experience of crewed missions
  • JWST was not designed to be serviceable so repair would likely be complex and require the flexible talents of a crewed mission, perhaps multiple missions.
  • Rocket exhaust could damage optical surfaces.
  • JWST cannot transfer itself closer to Earth for repair since this would mean pointing its optics towards the sun for the burn.

Proposal: The key to this proposal is the very low delta-v using inter-manifold transfers between Sun-Earth and Earth-Moon manifolds.

Built a robotic “tugboat” with thrusters which are designed to be safe for the JWST optics. Have the tugboat dock with JWST using the existing docking ring. The tugboat would then transfer JWST to an Earth/Moon L1 orbit. The Gateway/Artemis resources would be available for diagnosis and repair. This would avoid the expense and radiation exposure of a dedicated crewed repair mission to L2. It would also avoid the delta-v of transfer to LEO.

Once repaired, the “tugboat” could reposition JWST at Sun/Earth L2, and remain with JWST in case a repeat mission is needed. The tugboat could also be used for end-of-life decommissioning, extending JWST service life.

This proposal depends on the availability of a low-energy transfer orbit between Sun/Earth L2 and Earth/Moon L1. One unsubstantiated internet source claimed this heteroclinic transfer could be achieved by “near zero delta-V”. https://engineering.purdue.edu/people/kathleen.howell.1/Publications/Journals/2006_AA_HowKak.pdf discusses system-to-system transfers between Sun-Earth manifolds and Earth-Moon manifolds.

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Question: Is the inter-manifold transfer of JWST from Sun-Earth L2 to Earth-Moon L1 within the capability of existing propulsion systems?


1 Answer 1


Answer: Yes.

This paper discusses transfer orbits between Sun/Earth L2 and Earth/Moon L1/L2 halo orbits as well as Near Rectilinear Halo orbit (“Gateway Orbit”) https://ntrs.nasa.gov/api/citations/20190028906/downloads/20190028906.pdf

An analysis of transfers between the Earth-Moon region … EML2 Halo and … SEL2, was completed. These particular orbits are candidates for possible servicing locations for future science missions at SEL2…
The calculated ΔVs from this study… are still within the realm of a minimal ΔV cost. The transfer trajectory correction ΔVs, … are near single m/s level ... the maneuvers and total ΔV cost are within the typical ΔV budget for missions to the Sun-Earth libration orbits. The ΔVs found in this study are assumed to be feasible designs.

  • 2
    $\begingroup$ The part you cite is only about correction maneuvers due to trajectory errors, not about cost of the orbit transfer itself! In addition, transfer to EML1 (as asked) is not part of this study. $\endgroup$
    – asdfex
    Commented Jan 22, 2022 at 18:09
  • $\begingroup$ @asdfex ---- the majority of the analysis in the paper is about the correction delta-v budget, but the conclusion paragraph makes separate statements about total mission delta-v and estimated correction delta-v $\endgroup$
    – Woody
    Commented Jan 22, 2022 at 18:14
  • 1
    $\begingroup$ @Woody the words you've typed in your answer post do not actually answer the question as asked. "It's in this paper" is called a link-only answer and that's strongly discouraged in Stack Exchange. The block quote you have " The ΔVs found in this study are assumed to be feasible designs." does not factually support your "Yes". -1 for now, but happy to reverse once this actually answers the question and supports the answer. Thanks! $\endgroup$
    – uhoh
    Commented Jan 23, 2022 at 0:08

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