S2: Functions on the sphere

The S2 code provides functionality to support functions defined on the sky and was developed primarily for astrophysical applications. More generally, however, any arbitrary function defined on the sphere may be represented. Both real space map and harmonic space spherical harmonic representations are supported.

Basic sky representations have been extended to simulate full sky noise distributions and Gaussian cosmic microwave background realisations. Support for the representation and convolution of beams is also provided.

Currently a HEALPix spherical pixelisation scheme is adopted, although this may be extended in the future to support other spherical pixelisations. The spherical harmonic transforms applied are all based on the routines provided by HEALPix.