1. 1 Large Synoptic Survey Telescope Review Kirk Gilmore - SLAC DOE Review June 15, 2005

2. 2 LSST Technical Concept 8.4 Meter Primary Aperture –3.4 M Secondary –5.0 M Tertiary 3.5 degree Field Of View 3 Gigapixel Camera –4k x 4k CCD Baseline –65 cm Diameter 30 Second Cadence –Highly Dynamic Structure –Two 15 second Exposures Data Storage and Pipelines Included in Project

3. 3 Science Objectives Drive System Requirements Image Quality Is the Key f/1.25 beam High Etendue Large focal Plane Construction Techniques

4. 4 From Science Reqts to Sensor Reqts High QE to 1000nm  thick silicon (> 75 µm) PSF << 0.7” (0.2”)  high internal field in the sensor  high resistivity substrate (> 5 kohm∙cm)  high applied voltages (30 - 50 V) Fast f/1.2 focal ratio  sensor flatness < 5µm  package with piston, tip, tilt adj. to ~1µm Wide FOV  ~ 3200 cm 2 focal plane  > 200-CCD mosaic (~16 cm 2 each)  industrialized production process required High throughput  > 90% fill factor  4-side buttable package, sub-mm gaps Fast readout (1 - 2 s)  segmented sensors ~6400 TOTAL PORTS

5. 5 Optical Design 0.6” Optical Design

6. 6 Why is the LSST unique? Primary mirror diameter Field of view (full moon is 0.5 degrees) Keck Telescope 0.2 degrees 10 m 3.5 degrees LSST

7. 7 Meeting the FPA Requirements SLAC personnel will provide major technical and management effort to meet camera goals: Focal Plane Motion Control Focal Plane Metrology (warm/cold) Thermal Analysis & Control Focal Plane Assembly ~25 people at SLAC Vacuum Control working on LSST Cryostat Integration & Testing (FEE & BEE) Camera Controls Data Acquisition _______________________________________________

8. 8 Focal plane array 3.5° FOV  64 cm  Raft = 9 CCDs + 1cm x 1cm reserved for wavefront sensors 201 CCDs total Strawman CCD layout 4K x 4K, 10 µm pixels 32 output ports

9. 9 FPA Flatness = Image Quality Sensor Module 5  m p-v flatness over entire sensor surface Raft Assembly 6.5  m p-v flatness over entire surfaces of sensors Focal Plane Assembly 10  m p-v flatness over entire surfaces of sensors

10. 10 Monte-Carlo simulation of long-wavelength light absorption in silicon sensor. PSF Simulations

11. 11 Why good image quality (PSF) is essential for LSST science

12. 12 Raft Assembly

13. 13 The LSST FPA Assembled and tested at SLAC 25 Rafts with nine 4 Mpixel x 4 Mpixel CCDs each –except corners: 3 CCDs each Total of 201 CCDs, 3.3 Gpixel Active area diameter 640 mm Lens L3 25 mm above FPA Inner diameter of support for L3 680 mm. Space between support and active area 20 mm.

14. 14 Spot Measurement and Accuracy Measure the location of spots using standard centroiding methods. Even in low S/N environment can obtain accuracy of better than 1/30 of a pixel size. With LSST pixel size of 10 microns, accuracy should be of order 0.3 microns. Metrology at SLAC

15. 15 Integrating structure Raft structure AlN UP

16. 16 Camera Assembly at SLAC

17. 17 Camera layout 1.6m L1L2L3 FilterFocal plane array Shutter

18. 18 Camera Electronics External services FPA FEMs Back End Electronics Timing/control crate

19. 19 LSST Filter Development at SLAC CHALLENGE CHALLENGE Fabricate large curved filters with uniform coatingFabricate large curved filters with uniform coating STATUS STATUS Discussions with multiple vendors ongoingDiscussions with multiple vendors ongoing –Preliminary feedback from vendors – no show-stoppers Study RFQ’s going out to vendors in FY06Study RFQ’s going out to vendors in FY06 –Will include solicitation for design and development funding needed to qualify vendors for fixed price contract Current LSST baseline uses filter set comprised of g, r, i, z, and Y bands. Approximate FWHM transmission points are shown below.Current LSST baseline uses filter set comprised of g, r, i, z, and Y bands. Approximate FWHM transmission points are shown below. Final specifications being driven by simulations modeling.Final specifications being driven by simulations modeling.

20. 20 Science Simulator Overview Simulations

21. 21 Cerro Pachon Atmosphere Experiment DIMM – Integrated Measurement MASS – Structure above 500m Cerro Pachon Facilities SOAR 4.2m Telescope Gemini 8m Telescope MASS DIMM Weather All-sky Camera

22. 22 Data Management Base Camp Center Mirror Sites Archive Computing Center Telescope Site Portal User 10 1 to 2 kM 1.25 GB/s Rate = Rate AVG * 2 for redundancy/ reliability 10 3 to 4 kM.35 GB/s 30 TB/night* 1/8.64*10 4 full days/sec 10 3 to 4 kM.35 GB/s 10 -1 kM,.625 GB/s Rate RO = 3.0 * 10 9 pixels/read-out * (16 image + 4 eng, ops, control, etc.) bits/pixel * 0.5 read-outs/second = 30 Gb/s Rate AVG = Rate RO * 2 /12 read-out time/(exposure time + read-out time) = 5 Gb/s =.625 GB/s Focal plane Portal Users 150 TB disk 10 TFLOP 6.0 GB/image*5 images/minute* 500 minutes observing/night* 5 nights = 75 TB raw images + 75 TB processed images 2 PB disk (6 mo) 120 PB archival 20+ (?) TFLOP 30 TB/night * 200 nights observing/yr* 10 years = 60 PB images + 60 PB catalogs Portal Users GRID, Internet 2 GRID, Internet 2 45 TB disk, 1 TFLOP 6.0 GB/image*5 images/minute* 500 minutes observing/night* 3 nights = 45 TB raw images Notes: B = bytes, b = bits Raw image data is transferred/stored compressed (assume 75% reduction), uncompressed to 64 bit words locally for processing