New Methods for Compressing FITS Binary Tables

Pence, William

Modern astronomical observatories are generating greater and greater volumes of FITS binary tables, for example, in the form of X-ray photon event lists and in Mega- and Giga-sized source catalogs. In this paper we examine some promising file compression techniques which provide much higher compression of FITS binary tables than is possible with the commonly used technique of externally compressing the whole FITS file with the GZIP compression utility. These new table compression techniques build on our previous success in developing the FPACK and FUNPACK FITS image compression tools, which store the compressed image using the FITS tiled image compression convention. In this paper we propose an analogous FITS convention for compressing FITS binary tables. We present the results of compression tests using a prototype implementation of this new FITS convention which demonstrate that significantly higher compression ratios can be obtained than by simply gzipping the FITS file, at no additional CPU cost.

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