As taken from the Fit2D homepage
FIT2D is both a general purpose and specialist 1 and 2 dimensional data analysis program, used on most of the European Synchrotron Research Facility beam-lines and by many other crystallography groups throughout the world. FIT2D is used for both interactive and “batch” data processing, and is used by many different user communities for different purposes.
Calibration and correction of detector distortions is one of the important uses of FIT2D. Difficult data analysis problems may be tackled using fitting of user specified models. To enable model fitting to be performed on a wide variety of input data, many other more basic data analysis operations are also available. A wide variety of performant graphical display methods are available.
The program is available free to academic users and is available by Internet for a wide range of computer systems.