jwst-fgstoj-tools

This repository serves as a central place for maintaining tools related to the JWST FGS-toJ frame calibration. Below are the high-level descriptions on what each tool does and how to use them.

• fgstoj_calibration.py This code includes tools for solving the matrix equation to obtain the FGSics to J-frame matrix.

  (1) The method provided by NGAS in their matlab tool FGStoJ_Calibration.m. This tool does NOT solve the full matrix equation. Instead, it calculates the angular difference between the (x_FGSidl, y_FGSidl) coordinates predicted using the old FGS-to-J matrix and the observed positions. This angular difference is applied to the old matrix to come up with a new matrix. For this reason, the tool works with any number of calibration sources.

  (2) This tool is for solving the matrix equation in its full form - see the accompanying PDF file for details on how the matrix equation is set up and how to solve it. The solution requires at least 3 calibration sources.

• vtoj_siaf.py This tool was written to calculate the V2Ref, V3Ref, V3IdlYAngle SIAF parameters for the psudo-aperture J-FRAME for FGS1. Everytime the FGS-to-J matrix is updated, this tool must be run to update these SIAF parameters for the J-FRAME aperture. The vtoj_siaf.ipynb Jupyter notebook provides examples on how to run the tool.

• fgs2tofgs1_calibration.py This tool is for calculating the FGS2 to FGS1 matrix. Required inputs are SIAF alignment parameters [V2Ref, V3Ref, V3IdlYAngle] (must be in this order) for FGS2 and FGS1.