This Fortran code makes projected GRXE sky model.

Model parameters are from [Revnivtsev+ 2006](https://ui.adsabs.harvard.edu/abs/2006A%26A...452..169R/abstract) paper.

The final map can be converted to `erg/s/cm2` by multiplying by `Lsun/kpc^2` (Lsun=3.826e+33 ergs/s, kpc=3.08568e+21 cm)
`