NIRISS AMI contrast simulator

The Aperture Masking Interferometry (AMI) mode of NIRISS aboard the James Webb Space Telescope is designed to perform Non-Redundant Aperture Masking (NRM) Interferometry with a 7 hole mask, providing high angular resolution (from less than 0.1 up to 0.4 arcsecond) and moderate contrast (from 3 to 9) in the infrared. Four filters will be available at 2.77, 3.8, 4.3, and 4.8 microns.

AMI observations were simulated for the four filters, target magnitude between 3 and 15 with a 0.5mag sampling, and exposure times between ten minutes up to three hours. The simulated datacubes were then analyzed to derive the contrast curves for each combination of parameters. In this tool, for a given filter, integration time, and target magnitude, the instrument configuration, observing time including overheads and calibrators, and the predicted contrast performances (either extact from the grid or interpolated) are provided to the user.

Usage notes:

• Because of the pre-computed grid, the user cannot choose himself Ngroup and Nint for the simulations, these numbers are optimized as a function of the well depth. A future function will be made available to enable arbitrary instrument parameters, with the generation of a new simulation (time consuming).
• The contrast performance evolves as sqrt(t), except for long exposure (>1h) and bright targets (<6mag) for which it saturates due to instrumental noise.
• The contrast also nearly saturates as a function of magnitude for stars brighter than 5 mag because of instrumental error domination in the noise budget.
• For more accurate estimates of the overheads, please use the last version of the APT.
• For comments and questions, contact julien.rameau@astro.umontreal.ca