: An average difference image is computed and subtracted from all difference images, resulting in "residual" images that are easier to compress.
: Detector reads are converted into difference images (the first read plus difference images) to reduce dynamic range. : An average difference image is computed and
: Compressed files generated by APZIP are saved with the .apz extension. : An average difference image is computed and
The theoretical maximum compression for APOGEE's noise levels and bit depth is approximately 2.6. In practice, APZIP’s compression of ~2.0 is considered as good as can be expected for the specific astrophysical data it handles. : An average difference image is computed and
: The resulting multi-extension FITS files are compressed using the FPACK utility and the lossless Rice compression algorithm . 3. Usage and Accessibility