The SNAP near infrared system will be an integral component of the focal plane.
In the baseline concept thirty-six 2k x 2k HgCdTe imaging sensors covering a total of 0.34 square degrees will be placed in four 3x3 arrangements symmetric to the CCD placement. The HgCdTe devices have a cell pitch of 18 m, resulting in a total of 150 Megapixel for the NIR system. These devices exhibit low read-out noise and dark current while providing excellent quantum efficiency (typically 50%-80% over the wavelength interval 1-1.7 m). The cutoff at a wavelength of 1.7 m is a good match to the SNAP working concept; the sensors are blind to the thermal background from the warm telescope.
NGST field of view (comp to 1 NIR ) Hubble WFPC (comp to 1 CCD filter) ; outer circle 28 ½ cm ; inner circle ~ 13 cm
plate scale: 0.17 arcsec/ pixel (IR)