FGS catalog creation not quite robust

[kjbrooks]

The currently implemented FGS catalog creation does not appear to be robust. The following are the two known issues with mirage.catalogs.create_catalog.get_all_catalogs for FGS:

• Bug: mirage.catalogs.create_catalog.get_all_catalogs documentation says to use "Guider" for FGS but, the code actually expects "FGS"
• According to @KevinVolkSTScI (from an email I received from him): "The code in Mirage interpolates from the input catalogue photon weighted mean flux density values as a function of pivot wavelength to the pivot wavelength of the filter under consideration. This is the best general method because if there is extinction then the magnitudes are affected but interpolation should generally give a reasonable result. However, this actually only works if the JWST filter is of a similar wavelength width as the input 2MASS/WISE/GAIA filters. For the Guider this is not going to work because the response is so wide that it is dominated by the short wavelength part of the stellar spectrum but the pivot wavelength is around 2.3 microns. So in essence the “proper” magnitude is roughly similar to a V or NIRISS F090W filter magnitude, while the interpolation will give you something like the K magnitude. For cooler objects, the magnitude will be too bright when the Guider filters are used."

For the second point above, there are two alternatives to figuring out the FGS countrates/magnitudes: using jwst-magnitude-conversion or jwst-fgs-countrate. These two modules will give FGS count rates/magnitude but they arrive at these values in different ways:

• jwst-magnitude-conversion uses stellar atmosphere model spectra to simulate the different magnitudes

• jwst-fgs-countrate uses stellar energy distributions that are derived from the observed GSC2, 2MASS, and SDSS magnitudes to compute the FGS count rate or magnitude

Both tools use the characteristics of the science instrument detectors (e.g., throughput, gain) to compute the instrument magnitudes.

Since I have some experience with the jwst-fgs-countrate tool, I have written a way to use it to create FGS catalogs for the use of the JWST OTE team for OTE commissioning. It can be found here: https://grit.stsci.edu/wfsc/tools/-/blob/master/mirage-ote-utils/mirage_ote_utils.py#L475

I am not sure what is in the best interest of mirage as a whole which is why I made this issue and didn't just submit a PR. There is the option to use the bit of code I have written up when trying to create an FGS catalog if it is believed to be complete enough.