LSST Telescope: Unveiling the Cosmic Marvels

1. K. Gilmore - SDW2005

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

3. LSSTTechnical 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. LSST is designed to go wide – deep – fast ~10 deg2 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. 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 The Science ofKIPAC

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

7. Optical Design 0.6”

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

9. 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 cm2 focal plane  > 200-CCD mosaic (~16 cm2 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 From LSST Science Reqts to Sensor Reqts

10. Detector requirements: 10 mm 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 (75cm2) 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 Camera Challenges ________________________________

11. Strawman CCD layout under Study 4k x 4k, 10 µm 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. LSST Sensor Design

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. Raft Assembly

15. Integrating structure Raft structure AlN UP

16. Tiling of the Focal Plane 4° FOV  74 cm  WFS 8/5/04 workshop CCDs: 3x3 3.5° FOV  64 cm  X X X X X X X X X X X 4096x4096 pixels; 10 µm pixels 1678 mm2 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 X X X X X X X X X X X X X wea 8/6/04

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

19. FPA Flatness Allocations Established Sensor Module 5mm p-v flatness over entire sensor surface Raft Assembly 6.5mm p-v flatness over entire surfaces of sensors Focal Plane Assembly 10mm p-v flatness over entire surfaces of sensors

22. L1 L2 Shutter L3 1.6m Filter Focal plane array Camera layout

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

24. LSST Filter Development at SLAC ______________________________ • CHALLENGE • Fabricate large curved filters (76cm) with uniform coating to • do accurate photometry • 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. • Final specifications beingdriven by simulations modeling.

25. Science Simulator Overview

26. 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 LSST Data Rates ________________________________