JWST Focal Plane

The relationships between the JWST focal plane, observatory (V2, V3) coordinates, and field of view (FOV) are covered in this article. An example script to retrieve precise aperture vertices locations is provided.

On this page

See also: JWST Field of View, JWST Target Observability and Observatory Coordinate System, JWST Position Angles, Ranges, and Offsets, JWST Instrument Ideal Coordinate Systems 

JWST observatory coordinates in the context of the focal plane 

Figure 1 shows the connection between the V axes and the JWST focal plane. The V3 axis is the primary observatory reference axis used in APT and in operations to connect the individual instrument reference axes (blue arrows) in the planning and scheduling system to the celestial sphere. This is especially important for any observations where the positioning of the instrument fields of view on the sky is important. See the JWST Position Angles, Ranges, and Offsets article for more information. This figure can also help users understand the output from the JWST Target Visibility Tools, which typically report both V3PA and individual instrument reference position angles. Note that NIRCam and NIRISS are very nearly aligned with V3PA, while MIRI is offset slightly. Only the NIRSpec reference axis is offset by a large amount relative to V3PA.

Figure 1. The JWST observatory coordinates in the context of the focal plane
This figure shows the JWST observatory coordinates in the context of the focal plane. The +V1 (boresight) points into the screen. The blue arrows indicate the reference axes of the individual instruments and the observatory V3 position angle is shown at the top..



The JWST Field of View page gives the coordinates that bound the area on the sky for observations with each JWST instrument. Examples of the types of data that can be obtained with many (not all) JWST observing modes and the locations of apertures in the focal plane are also discussed.





Notable updates

 
Replaced information also contained on the page JWST Field of View with links to that page

Originally published