Wavelength calibration

[StevenTomczyk]

Description: For the CoMP instrument, we used spectral absorption features in the flat sequences to determine the wavelength of CoMP tunings. This was done by fitting the absorption features with a smoothed out spectrum from the Kitt Peak spectral atlas. This was very tricky because of the poor spectral resolution afforded by CoMP (and UCoMP). It would be very valuable to extend this flat spectrum fitting to UCoMP, especially since we are experiencing a systematic drift in the UCoMP Lyot filter transmission wavelengths. This may not be possible at all UCoMP wavelength regions depending on the availability of solar and telluric absorption features in a particular wavelength region.

Method: Apply Steve's code to all the wavelength regions.

[detoma]

It seems UCOMP stopped taking flats with multiple-points (13-points, 11-points, etc.) in February 2022. Thus, this technique cannot be applied for most of 2022.

For the existing flat spectra, the shorter wavelengths do not have a lot of counts, but in principle the technique could be tried on the existing spectra. To extend the CoMP code to other wavelength regions requires significant work. Steve gave us some references for solar spectra but we will probably need help from somebody with experience in spectroscopy to properly implement it. The code that Steve wrote for the CoMP 1074nm and 1079nm is quite complex, with nearly no comments, and ad-hoc assumptions for these particular lines.

[detoma]

Solar spectra can be found here: https://nso.edu/data/historical-archive/

This is include the Kitt Peak atlas used by Steve that is in: /hao/corona3/Data/Backups/alfven/Atlas

The Kitt Peak is a normalized flux spectrum at high spectral resolution. Care must be taken to deconvolve it down to UCOMP spectral resolution. To compare the two, the continuum must be subtracted out by the UCOMP spectra which does not seem easy to do accurately given the very low resolution of UCOMP.