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I looked around a little bit online but did not find anything discussing how well JWST is doing with managing its orbit. I was wondering if there were any surprises or issues.

It's been out there almost 2 years now and the flight folks should have a good idea if their planning was on target and if fuel will last even longer than originally calculated. (Of course, the great launch and L2 insertion were a large help to fuel conservation.)

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    $\begingroup$ I’m pretty sure it’s actually been out there 2 years now, launch was in late 2021. A year ago they mentioned 20 rather than 10 years of fuel, but I also don’t see anything more recent $\endgroup$ Jan 18 at 4:56
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    $\begingroup$ You can view the orbit in 3D using my scripts here: space.stackexchange.com/a/57832/38535 The JWST trajectory data on Horizons was last updated 2024-Jan-17 ssd.jpl.nasa.gov/api/… $\endgroup$
    – PM 2Ring
    Jan 18 at 9:55
  • $\begingroup$ @fyrepenguin oops... seems I cannot count! $\endgroup$
    – BradV
    Jan 18 at 15:48
  • $\begingroup$ @fyrepenguin I'm pretty sure I heard something a couple of months ago saying things are going much better than originally expected and now they expect a longer operational lifetime. $\endgroup$
    – Barmar
    Jan 18 at 15:56
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    $\begingroup$ @Barmar Yes, that’s what I referred to about 20 rather than 10 of fuel, but there were articles about that within a month or two of launch. Didn’t see updates after that $\endgroup$ Jan 18 at 19:53

1 Answer 1

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Only partial:

Not directly answering since it seems ok:

Can only find up to 2022:

Orbit around L2 is maintained through regular station-keeping burns, which are scheduled every three weeks. As of July 12, 2022, there have been four station-keeping burns, with typical durations of tens of seconds. During commissioning, three station-keeping burns were skipped because the computed correction was negligibly small.

Predicted lifetime of consumables

There are no consumable cryogens onboard JWST; the telescope and the science instruments are passively cooled by the sunshield and radiators, and MIRI’s active cryocooler recycles its helium. The only onboard consumables are propellant: fuel and oxidizer. Before launch, JWST was required to carry propellant for at least 10.5 years of mission lifetime. Now that JWST is in orbit around L2, it is clear that the remaining propellant will last for more than 20 years of mission lifetime. This fortunate surfeit has multiple causes: an accurate launch; launch on a day that required relatively less energy to get to L2 than most other possible launch dates; three timely and accurate mid-course corrections that sent JWST to L2 with the minimum possible propellant usage; and finally, careful stewardship of mass margins by the engineering team over the years, such that the remaining mass margin was used to add more propellant than required, until the tanks were full. For the remainder of the mission, propellant will be used for two purposes: stationkeeping burns (using fuel and oxidizer) to maintain the orbit around L2, and momentum dumps (using only fuel) to remove momentum from the reaction wheels. Momentum accumulates as solar photons hit the sunshield and impart a net torque, which the reaction wheels resist by spinning up. The actual rate at which the observatory builds up momentum is within specifications and is well below worst-case allocations, which further contributes to propellant lifetime. While the detailed propellant usage depends on orientation, which is set by the observing schedule, the big picture is that JWST has sufficient propellant onboard to support science operations for more than 20 years.

Projected observatory lifetime

At this point, it is not clear what will determine the duration of JWST’s mission. The mirrors and sunshield are expected to slowly degrade from micrometeoroid impacts; the detectors are expected to experience cumulative slow damage from charged particles; the sunshield and multilayer insulation will degrade from space weathering; the spacecraft was designed for a five year mission (as is standard for NASA science missions); and the science instruments include many moving parts at cryogenic temperatures. These sources of degradation were all taken into account in the design of JWST, with performance margins set so that JWST will still perform after many years of operation. At present, the largest source of uncertainty is long term effects of micrometeoroid impacts that slowly degrade the primary mirror.

The single micrometeorite impact that occurred between 22—24 May 2022 UT exceeded prelaunch expectations of damage for a single micrometeoroid , triggering further investigation and modeling by the JWST Project. The Project is actively working this issue to ensure a long, productive science mission with JWST.

July 12 2022

Characterization of JWST science performance from commissioning

Also, one of the sensors abnormality has to be accounted for:

Mid-Infrared Instrument Operations Update

On Apr. 21, 2023, the James Webb Space Telescope team shared that one of the MIRI (Mid-Infrared Instrument) observing modes, called Medium-Resolution Spectroscopy (MRS), showed a reduction in the amount of light registered by MIRI’s detectors. Initial analysis of MIRI’s imaging mode did not show a similar effect. However, as part of the team’s investigation into the issue, additional monitoring observations were taken with MIRI imaging. Combined with earlier data, these new calibrations have revealed a reduced signal for MIRI imaging at the longer wavelengths.

This change does not substantially impact MIRI’s science capabilities but will have an impact on the exposure times needed for MIRI imaging.

There is no risk to the instrument, and the effect on imaging is less than the effect in MRS. The team is investigating the cause of this issue.

https://blogs.nasa.gov/webb/

Upto 2024 observing schedule:

https://www.stsci.edu/jwst/science-execution/observing-schedules

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