Timeline for How frequent are (or will be) JWST station keeping burns at L2?
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| Feb 27, 2022 at 1:07 | comment | added | uhoh | @TLW "Why 21 days & 12cm/s thresholds for station keeping decisions?" would also be an excellent new question! Again I'm no expert, but my hunch is that "diminishing returns" and "risk minimization" would be parts of the answer. Shutting down the observatory and turning on rocket engines, then turning them off and starting up the observatory again every three weeks steals observing time and costs time and money on the ground, and each one is an opportunity for something to go wrong; miscalculation, stuck valve, cosmic ray event in the navigation computer... | |
| Feb 27, 2022 at 0:59 | comment | added | uhoh | @Sheldon ...they need to measure several times and fit those measurement to orbit propagation calculations to get the full picture. But I'm no expert in this, I think that "Has JWST done its first station keeping yet?" is a great new question to post, that way folks who do know or at least know how to find out will see it and be able to see it. | |
| Feb 27, 2022 at 0:58 | comment | added | uhoh | @Sheldon I don't know and that's a great new question! My feeling is that the 21/42 day cadence is for the steady state situation after it's settled down and there's sufficient tracking history to accurately project its orbit in 3D. The delay-doppler and vlbi measurements by the DSN don't necessarily give the position and velocity to sub-meter and sub mm/sec accuracy from a single measurement... | |
| Feb 26, 2022 at 17:51 | comment | added | Sheldon | Has JWST done its first station keeping yet? The last burn I know about was the MCC2 burn on Jan24; more than 21 days ago; and that was a pretty long burn with a $\Delta_V$ of 1.6 m/sec or 160 cm/sec, which is much larger than the 12cm/sec so I would assume they would want another burn at 21 days just because JWST must always stay on the Earth side of the halo orbit, and there had to be some reasonable margin in the MCC2 burn. | |
| Feb 26, 2022 at 2:47 | comment | added | TLW | It would be interesting to see why they chose 21d & 12cm/s as the threshold and not something smaller. Is the limiting factor % of time spent not doing science? Accuracy of the rocket engine? Fixed costs of starting of the rocket engine? Accuracy of measurement? Other? | |
| Feb 25, 2022 at 16:57 | vote | accept | BradV | ||
| Feb 25, 2022 at 2:38 | history | edited | uhoh | CC BY-SA 4.0 |
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| Feb 25, 2022 at 1:21 | history | edited | uhoh | CC BY-SA 4.0 |
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| Feb 25, 2022 at 0:22 | history | answered | uhoh | CC BY-SA 4.0 |