The 2MASS Second Incremental Data release includes 1,897,017 FITS images in the three survey bands constructed from the scans of 8.5´ × 6° long Survey Tiles. The image data from each Tile are divided into twenty-three separate Atlas Images in each band. Twenty-two of these are 512×1024 (1"/pix) in size, and one is 512×698 (1"/pixel). Thus, there are 1,814,538 512×1024 images and 82,479, 512×698 Atlas Images in the Release. 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.
[Last Updated: 2000 February 16, by R. Cutri]