CALPRODUCT-NS-011: NISP-S Dichroic Ghost Model¶
Parent requirement¶
Not yet in the CalCD-B
Scheduling¶
Once, during PV phase.
Time-critical¶
No.
Dependencies¶
None
Objective¶
Dichroic ghosts above a certain intensity level must be masked, as they bias the spectrophotometry measurements. The on-ground ghost model is based on Zemax simulations. Its in-orbit validation must confirm (1) the location and (2) amplitude of the ghosts. Size, shape and wavelength dependence of the ghosts are expected to be correctly characterized by the simulations and are not a formal part of the in-flight validation. However, should the simulations be inaccurate for these parameters, then this will be evident in the masked pixel data and the models can be updated.
Dichroic ghosts in NISP-S data must be masked for sources brighter than 11 (TBC) AB mag. The required amplitude ratio between brightest point in the ghost and peak flux of the star is 8e-8, for NISP-P; for NISP-S, the ratio is TBD. Optical ghosts from the NISP internal optics are considered negligible.
Fulfilled by¶
In-orbit duration¶
Data volume¶
6*60*NS = 52560 MB for NISP-S
Processing input¶
Ground Processing Input Data: TBD
Data Description: 6*60 NISP-S observations
Processing method¶
With the astrometric solution / 0th order position in the FPA known, determine the size, location and shape of the ghost images, as well as the ratio of the ghost irradiance with respect to the 1st order irradiance, and compare them to the ghost model predictions. Update the masking parameters if necessary.
Processing output¶
Ghost image maps, comparison with model predictions, updated ghost model (if necessary)
Required accuracy, constraints¶
Images successfully acquired, achieving sufficient S/N in the ghosts
Processing tools¶
TBD
Validation¶
The ghosts must fall within the predicted areas of the ghost model. The masks should cover all light from the ghosts while minimizing the overall masked area. The ghosts must not fall on top of other bright stars, otherwise the ghosts’ centroids cannot be measured accurately. The Self-cal data will provide sufficiently many clean ghost images.
Recovery¶
Update the ghost model.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
NISP-S calibration scientist