Web based FITS spectrum analyser

[varenius]

Need FITS spectrum analysis software, in browser, to replace SalsaJ. Likely in javascript/html5. Like https://js9.si.edu/, but for SALSA spectra. Should have similar functionality as Matlab SalsaSpectrum class (see https://github.com/varenius/salsa/blob/master/SalsaSpectrum/Documentation/SalsaSpectrum_documentation.pdf?raw=true). Top functions which a new web-based application should be able to do:

• Open SALSA FITS (and maybe others?) from file on hard drive
• Open FITS from URL
• Open FITS with shortcut (https://salsa.oso.chalmers.se/spectrum_analyser/?fits=http:// ...)
• Plot intensity vs velocity (Optional: vs /chan/freq)
• Fit and subtract polynomial baseline (where one can set which parts of the spectrum to use for fit, and polynomial degree)
• Fit multi-Gauss function to peaks
• DIsplay fit results as table of values (gaussian parameters)
• Choose plot font/ticks/color/limits
• Zoom in plot by mouse
• Trace the plot values when hovering with mouse in figure, and show coordinates in some corner of figure
• Save result as FITS, PNG, PDF, ASCII (by default save all data, but give option in dialog to only save current zoom on screen)

Optional

• For some GLON/GLAT, download spectrum for comparison from https://www.astro.uni-bonn.de/hisurvey/AllSky_profiles/
• Flag RFI, i.e. exclude/flatten parts of spectrum

[varenius]

Robert C suggested during today's SALSA dev meeting that we could have these additional good features:

• For the baseline and gaussian fitting, it could be nice to be able to plot the combined model and residuals, not only step by step. It could also be nice to get the associated uncertainties from the combined fitting and not step by step.
• It could be nice to have "auto-find baseline" button.
• And it could be nice to have tabs where to show the data model, and the residuals (data - model)

Both of these things should be solvable, once we can do the action of actually fitting a baselinse - so interacting with the graph.