ACIS, the AXAF CCD Imaging Spectrometer, is an instrument being built by a team from the Massachusetts Institute of Technology’s Center for Space Research and the Pennsylvania State University for the Chandra X-ray Observatory (formerly, AXAF), scheduled for launch in 1999.

This is a good paper discussing practical implementation of data compression in a real world project with interesting parameters.

http://acis.mit.edu/huff/