NIRISS AMI Calibration Status
The overall calibration status and estimated accuracy of NIRISS aperture masking interferometry are described in this article; please also see the article on known issues affecting NIRISS AMI data.
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Astrometric calibration
Date:
This is the same as for imaging; see NIRISS Imaging Calibration Status.
Photometric calibration
Date:
A range of about 5% in the scaling factors from different standard stars is observed in the F277W/F380M/F430M filters, and the range is 8% for F480M. The uncertainty in the relative calibration of the normal imaging and AMI imaging modes is under 1%.
Calibration of charge migration (CM)
Date:
Analysis from in-flight data shows that charge migration has a ~1% effect on the brightest pixel at an accumulated charge of 26,000 e- in the F480M filter. A charge migration mitigation step has been implemented in the operational JWST pipeline for NIRISS data (v10.0, released Dec 5, 2023). As of CRDS context jwst_1254.pmap, the above signal limit is used by default for all filters in AMI observations. Investigation into filter-dependent signal limits is underway.
Target placement
Date:
An approximately 0.03 pixel standard deviation per axis random error in AMI target placement was measured in the AMI medium band filters during commissioning.
Commissioning data revealed systematic filter-specific offsets from commanded positions (20 mas for F380M, 12 mas for F430M, and 14 mas for F480M). Updated Science Instrument Aperture File (SIAF) definitions were installed onboard to remove these systematic target placement errors. These updates have not been tested yet.