1. 1 K. Gilmore - SDW2005

2. 2 The Large Synoptic Survey Telescope (LSST) Status Summary Kirk Gilmore SLAC/KIPAC

3. 3 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 200 detectors 30 Second Cadence –Highly Dynamic Structure –Two 15 second Exposures Data Storage and Pipelines Included in Project

4. 4 LSST is designed to go wide – deep – fast ~10 deg 2 per field ~6.5m effective collecting aperture m~24 AB mag per 15 sec. exposure (2 per pointing) wide coverage > 20,000 square degrees multiple filters (e.g. grizy - maybe u) accumulated depth of 27 AB magnitude in each filter LSST System Summary

5. 5 The Science of KIPAC Particle Astrophysics –Black Holes, Neutron Stars, White Dwarfs… –GRBs, magnetars, supernovae… –Accretion disks and jets… –Relativistic shocks, particle acceleration, UHECR… Cosmology –Dark energy, dark matter –Gravitational lenses –Clusters of galaxies and intergalactic medium –Microwave background observations –First stars, galaxy formation

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 Optical Design 0.6”

8. 8 Science Objectives Drive System Requirements Image Quality Is the Key f/1.25 beam Large focal Plane Construction Techniques

9. 9 From LSST 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)  small pixel size (0.2” = 10 µm) 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 output ports)  150 I/O connections per sensor Low read noise  < ~ 5 rms electrons

10. 10 Camera Challenges Detector requirements: –10  m pixel size –Pixel full-well > 90,000 e – –Low noise (< 5 e – rms), fast (< 2 sec) readout (  < –30 C) –High QE 400 – 1000 nm –All of above exist, but not simultaneously in one detector Focal plane (75cm 2) position precision of order 3 mm, flat to 5 u rms Package large number of detectors, with integrated readout electronics, with high fill factor and serviceable design Large diameter filter coatings Constrained volume (camera in beam) –Makes shutter, filter exchange mechanisms challenging Constrained power dissipation to ambient –To limit thermal gradients in optical beam –Requires conductive cooling with low vibration ________________________________

11. 11 Strawman CCD layout under Study 4k x 4k, 10 µ m pixels, 32 output ports; Pixel full-well >90,000 e; Noise < 5 rms e Segmented readout to achieve the required readout time (2 seconds required, 1 second target) with moderate clock frequency (to minimize read noise and crosstalk), (e.g., 0.5 Mpixels/output read out at 250-500kHz).

12. 12 LSST Sensor Design

13. 13 A hybrid Si-PIN-CMOS detector, analogous to near-infrared (NIR) array detectors. Separation of photon detection from readout facilitates separate optimization of - CMOS readout electronics (multiplexer) - Si PIN detector array Thickness, QE, PSF, operating voltage considerations are the same as for CCDs. Bump bonding technology on 10 µ scale required. Si PIN array bump-bonded to CMOS readout

14. 14 Raft Assembly

15. 15 Integrating structure Raft structure AlN UP

16. 16 3.5° FOV  64 cm  4096x4096 pixels; 10 µm pixels 1678 mm 2 active 41.7 mm x 41.7 mm Si 42 mm pitch (0.3 mm gaps)  95% fill factor  25 x 3x3 = 225 chips If allow dummies outside 64cm, then:  21 rafts with 9 live; +4 corners with 3 live ea = 201 live chips total wea 8/6/04 8/5/04 workshop CCDs: 3x3 4° FOV  74 cm  XXX XX X X XX XXX X XX XXX XXX XX X WFS Tiling of the Focal Plane

17. 17 Effect of displacement of the focal plane : (a) position of best focus for short-wavelength light; (b) focal plane displaced 10µm in direction of incoming rays (best for long wavelength-light). Refraction causes position of focal point to move about 5 times farther than sensor displacement.

18. 18 PSF Simulations Monte-Carlo simulation of long-wavelength light absorption in silicon sensor.

19. 19 FPA Flatness Allocations Established 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

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22. 22 Camera layout 1.6m L1L2L3 FilterFocal plane array Shutter

23. 23 Spin Casting of large optics at the U of Arizona LSST is in the queue

24. 24 LSST Filter Development at SLAC CHALLENGE CHALLENGE Fabricate large curved filters (76cm) with uniform coating to do accurate photometry do accurate photometry STATUS STATUS Discussions with multiple vendors ongoing –Preliminary feedback from vendors – no show-stoppers Study 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. ______________________________

25. 25 Science Simulator Overview

26. 26 LSST Data Rates LSST Data Rates 3.2 billion pixels read out in 2 sec (15 second integration) 1 pixel = 2 Bytes (raw) Over 3 GBytes/sec peak raw data from camera Real-time processing and transient detection: < 10 sec Dynamic range: 4 Bytes / pixel > 0.6 GB/sec average in pipeline 5000 floating point operations per pixel 2 TFlop/s average, 9 TFlop/s peak ~ 20-30 Tbytes/night ________________________________

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