Noise and bias in square-root compression schemes

We investigate data compression schemes for proposed all-sky diffraction-limited visible/NIR sky surveys aimed at the dark energy problem. We show that lossy square-root compression to 1 bit of noise per pixel, followed by standard lossless compression algorithms, reduces the images to 2.5-4 bits per pixel, depending primarily upon the level of cosmic-ray contamination of the images. Compression to this level adds noise equivalent to