Add support for MIRI FND for simulating coron TA images

[mperrin]

I don't understand how/why this wasn't already implemented. It's in the data files. May have just been an oversight accidentally .

[Skyhawk172]

I stumbled upon this issue and decided to take a closer look at it.

It appears the only change that needs to be done is add a line for FND in the MIRI filters.tsv file, which lives under webbpsf-data/MIRI/. Given the large bandpass of this filter, the minimum number of wavelengths to use should be larger than the other filters, probably ~20.

I ran a quick test by simply adding a line to the MIRI filters.tsv file and a PSF is generated without any apparent problem.
I get the following, assuming a flat spectrum covering 8-26 microns:

The current transmission curve looks like as follow:

I don't know if the FND.fits needs to be updated, but it looks a bit noisy at larger wavelengths.

[Skyhawk172]

Github won't let me attach a .tsv file, so I'll just paste the content here since it's short. To be absolutely clear, this is to replace the filters.tsv file under webbpsf-data/MIRI/. The only difference is the last line for the neutral density filter (FND):

filter nlambda
F1000W 9
F1065C 9
F1130W 9
F1140C 9
F1280W 9
F1500W 9
F1550C 9
F1800W 9
F2100W 9
F2300C 9
F2550W 9
F560W 9
F770W 9
FND 20

[Skyhawk172]

Marcio gave me the link to where the new webbpsf data reside until the next release (on STScI central store), so I just dropped the updated file there.