CALPRODUCT-NS-012: NISP-S Grism Centers of Rotation¶
Parent requirement¶
Scheduling¶
Once, during PV phase.
Time-critical¶
No
Objective¶
The NISP grism wheel positions a grism within 0.5 degrees or better of the commanded value. The jitter angle can be determined from the orientation of the spectra traces, and must be used to appropriately transform the calibrations (potentially taken with a slightly different jitter angle) to match the science spectra exposures.
Note that, due to optics chromaticity, the dispersion pattern (i.e. spectral trace and wavelength solution) does not purely rotate with rotation of the dispersing grism, but includes higher-order distortion terms. However, to first order in small jitter angle, the dispersion pattern can locally be derived from reference calibration solution as a simple rotation with respect to an ad-hoc position.
To derive these first-order rotation elements, NISP shall observe an arbitrary stellar field 5 times for each grism setup with independent random realizations of the jitter angle. The GWA must therefore execute a full rotation between exposures.
Observations¶
Fulfilled by¶
Data volume¶
30*NP = 2640 MB
Processing input¶
Data Description: 30 NISP science images
Processing method¶
TBD
Processing output¶
For each grism, determine the location and uncertainty of the center of rotation as a function of position in the field of view.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
NISP-S calibration scientist