The 2MASS Spring 1999 data release includes 233,979 FITS images in the three survey bands constructed from the scans of 8.5´ × 6° long Survey Tiles. 223,806 of the images are 512×1024 (1"/pix) in size, and a small number, 10,173, from the ends of scans are 512×698 (1"/pixel). The J, H and Ks images for each region of sky are resampled to the same scale and registered to facilitate 3-color investigations. Positional and photometric calibration data are carried in the FITS header for each image.
Because of the prohibitive size of image data, currently only ~20:1 lossy-compressed versions of the Atlas Images are accessible on-line. Compression of the images was carried out using the hcompress procedure. It is hoped that it will be possible to serve the full resolution Atlas Images in the future.