Import data from pygdsm

[mkolopanis]

pygdsm is one of the only python wrappers for GSM data (both 2008 and 2016). Due to licensing we cannot import this module directly (depends on healpy/GPL license) but we could construct a function which coerces maps created by this module into a sky object.

[mkolopanis]

This is basically what I came up with in a jupyter notebook. Not sure how much more we would need? Here Galactic is an astropy coordinates object that you can just import from the module.

gsm2008_coords = HEALPix(ahp.npix_to_nside(gsm2008_cube.shape[1]), frame=Galactic())
coords = gsm2008_coords.healpix_to_skycoord(np.arange(gsm2008_coords.npix))
coords_icrs = coords.transform_to("icrs")
ra, dec = coords_icrs.ra, coords_icrs.dec
skymod_freqs  = freqs * units.Hz
stokes = units.Quantity(np.zeros((4, freqs.size, gsm2008_coords.npix)), unit=units.K)
stokes[0] = gsm2008_cube << units.K

[aelanman]

I think this is a specific case of issue #119 . We've discussed adding frame transformations to our setup.

[mkolopanis]

yeah this very well could be. It just came up again today and felt at least different enough to me at the time 🤔

[bhazelton]

@mkolopanis now that we've implemented the frame support, is this still something we should do?