  While the spectrum of the light emitted by a star can be calculated by
simulating the flow of radiation through each layer of the star's atmosphere,
this process is computationally expensive. Therefore, it is often far more
efficient to pre-calculate spectra over a grid of photospheric parameters, and
then interpolate within this grid. MSG (short for Multidimensional Spectral
Grids) is a software package that implements this interpolation capability.
