Statement of Work Request for Proposal: Date: 07/03/08 Rev: 0 Optical Coating Design and Demonstration for the Large Synoptic Survey Telescope Camera 1.0 Summary The Stanford Linear Accelerator Center (SLAC) requests that proposals be submitted by interested vendors for Optical Coating Design and Demonstration for the Large Synoptic Survey Telescope (LSST) Camera. LSST aims to perform the most comprehensive astronomical survey in history by imaging most of visible sky in a continuous series of short exposures. LSST is currently in the exploratory R&D phase. LSST would be funded from both Federal (NSF, DOE) and private sources. SLAC would lead the collaboration focused on the development of the camera for LSST, a major instrument development effort. Working in collaboration with SLAC, Lawrence Livermore National Laboratory (LLNL) has the lead responsibility for the camera optics. This request for proposals seeks to identify qualified vendors for the development and fabrication of the optical coatings required for the LSST camera optics. 2.0 Introduction The Large Synoptic Survey Telescope (LSST) aims to perform the most comprehensive astronomical survey in history by imaging most of visible sky in a continuous series of short exposures. This will result in an astronomical catalog thousands of times larger than ever previously compiled. During the ten years required for the baseline survey, ~2000 separate images will be obtained for each position on the sky, opening a revolutionary time window on our universe. This survey will catalog billions of galaxies and discover hundreds of thousands of Type Ia supernovae. Specific measurements will include spatial correlations in the shapes of galaxies due to weak gravitational lensing, and spatial correlations in the positions of galaxies as a result of acoustic oscillations in the primordial plasma. Combined with studies of supernovae detected by LSST, these measurements will determine fundamental cosmological parameters and constrain the nature of dark energy and dark matter. The scientific programs planned to be performed with the LSST in a decade would require centuries to complete with existing telescopes because the LSST system optical throughput will be two orders of magnitude greater than any existing facility. To achieve these unprecedented capabilities, the LSST makes use of a novel three-mirror design, with an 8.4-meter primary mirror, resulting in a field of view of 9.6 square degrees with seeing-limited image quality across a wide wavelength band. All three mirrors will be actively supported to control wavefront distortions introduced by gravity and environmental stresses on the telescope. The LSST camera provides a 3.2 Gigapixel focal plane array. The entrance window to the focal plane cryostat is one of three refractive lenses in the camera. The other two lenses are mounted in an optics structure at the front of the camera body, which also contains a mechanical shutter, and a carrousel assembly that holds five of the six large optical filters at any given time. The LSST Observatory will be located on Cerro Pachon in Chile next to the Gemini South Telescope. 3.0 Camera Optics Figure 1 shows the optical schematic of the telescope, including the camera optics. Camera optical element prescriptions are established by V3.1 of the observatory optical design (available on request). Optical design of camera lenses and filters is integrated with optical design of telescope mirrors to optimize performance. There are 3 refractive lenses with clear aperture diameters of 1.55m, 1.10m and 0.70m and 6 interchangeable, broad-band, filters with clear aperture diameters of 0.75m. Figure 1. Baseline LSST optical design schematic Derived parameters for the camera optical elements from the prescriptions are shown in Table 1. Table 1. Derived Camera Optical Element Parameters The optical design provides excellent image quality across a flat, 3.5 degree field. The image quality is < 0.20 arcsec FWHM in the six optical bands whose wavelength range is specified in Table 2. Table 2. Baseline LSST filter band-pass FWHM points in nm Filter ?1 ? 2 u 330 400 g 402 552 r 552 691 i 691 818 z 818 922 y4 930 1070 The need for L1 and L2 derives from the requirement to correct the chromatic aberration introduced by L3 and the filters. The baseline design meets this requirement using a single glass type, fused silica, for all the camera optics. The chromatic characteristics of this design are illustrated in Figure 2. This design introduces no net power - rays entering and leaving corrector are nearly parallel, and the focal length of telescope including corrector is nearly constant over the bandwidth of any given filter. The F/# of the beam through the camera is f/1.23. The beam also has a 61.5% linear obscuration due to the secondary/tertiary mirrors. The camera optics are nominally concentric about the chief ray, so all portions of the optics see the same angle of incidence range, 14.2 to 23.6. At the filter, the unvignetted beam illuminating a single field point is ~100 mm in diameter. Figure 2. Illustration of camera optics chromatic correction. Figure 3 shows a schematic view of the assembled camera. Five filters are resident in the camera; the active filter can be changed in less than 90 seconds. One of the six filters will be stored at off-camera at any given time and can be exchanged with any of the five on-camera filters during a daytime servicing operation. Figure 3. Baseline LSST camera design schematic 3.1 Optical Coatings LSST camera optics require two distinct types of optical coatings: 1. Anti-reflection (AR) coatings, 2. Band-pass coatings. The filters require both types of coatings while the lenses require only AR coatings. Optical Coatings Proposal Schedule: July 09, 2008 RFP Issued July 18, 2008 Clarification Conference call for all vendors July 25, 2008 All questions due Aug 08, 2008 Proposal Submittal date Aug 15, 2008 Anticipated Award date
