<p>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.</p>
<p>This post <a href="https://astronomy.stackexchange.com/questions/46744/will-the-james-webb-space-telescope-be-visible-from-earth">Will the James Webb Space Telescope be visible from earth?</a> says JWST, in halo orbit, will be observable from earth by dedicated amateurs and provides a link for generating an ephemeris.</p>
<p>Will the skypath be clockwise or counterclockwise with respect to the antisolar point? Will JWST display apparent retrograde motion, or just “slow down”?</p>

CC BY-SA 4.0
2022-01-18T23:30:57.003Z
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](https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit) but says these are "representative"
astrosnapper
CC BY-SA 4.0
2022-01-19T00:12:40.340Z
@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.
Woody
CC BY-SA 4.0
2022-01-19T16:37:56.917Z
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.
astrosnapper
CC BY-SA 4.0
2022-01-20T12:44:13.753Z
HORIZONS (https://ssd.jpl.nasa.gov/horizons/app.html) recognizes JWST, have you tried there?
Barry Carter
CC BY-SA 4.0
2022-01-20T16:55:44.217Z
@barrycarter ---- search returns "No ephemeris for target "James Webb Space Telescope (spacecraft)" after A.D. 2022-FEB-14"
Woody
CC BY-SA 4.0
2022-01-20T17:50:11.307Z
I got that too-- it only gives you through 2022-FEB-14 for now, so the default settings need to be adjusted. I'm assuming they'll add more data when available
Barry Carter
CC BY-SA 4.0
2022-01-26T15:13:48.857Z
FWIW, I've just posted some interactive 3D plots of the trajectory of the JWST relative to the Sun-(Earth-Moon barycentre) L2 point https://space.stackexchange.com/a/57832/38535
PM 2Ring
CC BY-SA 4.0
2022-01-26T15:15:34.197Z
@barrycarter Horizons now has JWST data upto 2024-JAN-22
PM 2Ring
<orbit><james-webb-space-telescope>
What is the skypath of JWST?
Woody
# What is the skypath of JWST?

(Asked by: username_0 on 2022-01-18)

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?](https://astronomy.stackexchange.com/questions/46744/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”?

**Tags:** orbit, james-webb-space-telescope

> **Comments:**
> **username_1**: 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](https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit) but says these are "representative"  
> **username_0**: @username_1 ---- 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.  
> **username_1**: 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.  
> **username_2**: HORIZONS (https://ssd.jpl.nasa.gov/horizons/app.html) recognizes JWST, have you tried there?  
> **username_0**: @barrycarter ---- search returns "No ephemeris for target "James Webb Space Telescope (spacecraft)" after A.D. 2022-FEB-14"  
> **username_2**: I got that too-- it only gives you through 2022-FEB-14 for now, so the default settings need to be adjusted. I'm assuming they'll add more data when available  
> **username_3**: FWIW, I've just posted some interactive 3D plots of the trajectory of the JWST relative to the Sun-(Earth-Moon barycentre) L2 point https://space.stackexchange.com/a/57832/38535  
> **username_3**: @barrycarter Horizons now has JWST data upto 2024-JAN-22  

---

## 0 answers

