Each CCD chip is read out as a 4144 ×2068 array, including physical and virtual overscans. Two different amplifiers are used to read out each half of the chip. The final images consist of 24 columns of physical overscan, 4096 columns of pixel data, and another 24 columns of physical overscan. Each column consists of 2048 rows of pixel data followed by 20 rows of virtual overscan. The orientation of the chip is such that for the grism spectra, the dispersed images have wavelength increasing from left to right in the positive x-direction.
The HRC CCD is read out as a 1062 ×1044 array, including physical and virtual overscans. There are 19 columns of physical overscan, followed by 1024 columns of pixel data, and then 19 more columns of physical overscan. Each column consists of 1024 rows of pixel data followed by 20 rows of virtual overscan. As with the WFC, the orientation of the chip was chosen so that grism images have wavelength increasing from left to right.
Space Telescope Science Institute http://www.stsci.edu Voice: (410) 338-1082 help@stsci.edu |