JWST will be in a 6 month halo orbit around the Sun/Earth L2 point, which is located at the anti-solar point. Internet graphics give conflicting information on whether the skypath is clockwise or counterclockwise around this moving point.

This post Will the James Webb Space Telescope be visible from earth? says JWST, in halo orbit, will be observable from earth by dedicated amateurs and provides a link for generating an ephemeris.

Will the skypath be clockwise or counterclockwise with respect to the antisolar point? Will JWST display apparent retrograde motion, or just “slow down”?

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    $\begingroup$ Not sure this is (accurately) predictable yet until after the MidCourse Correction 2 (MCC-2) burns takes place around Jan 25. The JPL ephemeris used for the ephemeris generation in the linked post says the trajectory file is NOBURN_2021363-2022017_01U.OEM.V0.1 which suggests it doesn't incorporate MCC-2 and allows predictions up to 2022-Feb-14 00:01. So it seems until the results of MCC-2 burn are known, an accurate ephemeris won't be possible. There is some info here on JWST orbit but says these are "representative" $\endgroup$ Jan 18, 2022 at 23:30
  • $\begingroup$ @astrosnapper ---- thanks for the comment. The publicly available information is contradictory to point where I can't even tell if the halo orbit is prograde or retrograde. A general description with orbital direction would satisfy me. The diagram in the link you provided is from 2017 and is offered as "representative", but it contradicts other, later information. $\endgroup$
    – Woody
    Jan 19, 2022 at 0:12
  • $\begingroup$ Agreed. I suspect that diagram was prepared for the JWST Cycle 1 call for proposals but hasn't been updated after the launch (and the call) was postponed. I also suspect it's a representative diagram to satisfy the small subset of proposers who were curious about the orbit but the details of the orbit are not needed to propose observations. Obviously (several) people know the details but suspect this is internal to the project until an updated trajectory is delivered to JPL. $\endgroup$ Jan 19, 2022 at 16:37
  • $\begingroup$ HORIZONS (ssd.jpl.nasa.gov/horizons/app.html) recognizes JWST, have you tried there? $\endgroup$ Jan 20, 2022 at 12:44
  • $\begingroup$ @barrycarter ---- search returns "No ephemeris for target "James Webb Space Telescope (spacecraft)" after A.D. 2022-FEB-14" $\endgroup$
    – Woody
    Jan 20, 2022 at 16:55


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