HSTCAL is a C-based package which is comprised of the science calibration software in support of the Advanced Camera for Surveys (ACS), Space Telescope Imaging Spectrograph (STIS), and Wide Field Camera 3 pipelines. Initially, the pipelines were written using C, but were encapsulated within the IRAF/STSDAS environment, relying on IRAF to perform I/O and other basic interface functions. HSTCAL replaces all the IRAF-based functionality with routines based on the third-party package CFITSIO. This allows all the pipeline software to be compiled and run without any dependence on IRAF. Not only can HST data be processed using the C code directly via the C executables, but the pipelines can also run by using a high-level Python interface. The Python interface scripts are thin wrappers for the C executables.

Detailed documentation for each instrument’s calibration processing code can currently be found in the following locations: