Design and Development of the 3.2 Gigapixel Camera for the Large Synoptic Survey Telescope

The Large Synoptic Survey Telescope (LSST) is a large aperture, wide-field facility designed to provide deep images of half the sky every few nights. There is only a single instrument on the telescope, a 9.6 square degree visible-band camera, which is mounted close to the secondary mirror, and points down toward the tertiary. The requirements of the LSST camera present substantial technical design challenges. To cover the entire 0.35 to 1 mu m visible band, the camera incorporates an array of 189 over-depleted bulk silicon CCDs with 10 mu m pixels. The CCDs are assembled into 3 x 3 "rafts", which are then mounted to a silicon carbide grid to achieve a total focal plane flatness of 15 mu m p-v. The CCDs have 16 amplifiers per chip, enabling the entire 3.2 Gigapixel image to be read out in 2 seconds. Unlike previous astronomical cameras, a vast majority of the focal plane electronics are housed in the cryostat, which uses a mixed refrigerant Joule-Thompson system to maintain a -100 degrees C sensor temperature. The shutter mechanism uses a 3 blade stack design and a hall-effect sensor to achieve high resolution and uniformity. There are 5 filters stored in a carousel around the cryostat and the auto changer requires a dual guide system to control its position due to severe space constraints. This paper presents an overview of the current state of the camera design and development plan.