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The Large Synoptic Survey Telescope (LSST)

The Large Synoptic Survey Telescope (LSST). Presentation to the Experimental Program Advisory Committee at SLAC November 14, 2003. The Large Synoptic Survey Telescope. The LSST will be a large, wide-field ground-based telescope designed to survey the entire visible sky every few nights.

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The Large Synoptic Survey Telescope (LSST)

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  1. The Large Synoptic Survey Telescope (LSST) Presentation to the Experimental Program Advisory Committee at SLAC November 14, 2003 SLAC EPAC Meeting Nov. 14-15, 2003

  2. The Large Synoptic Survey Telescope • The LSST will be a large, wide-field ground-based telescope designed to survey the entire visible sky every few nights. • This project concept has been strongly endorsed by three separate National Academy committee reports: Astronomy and Astrophysics in the New Millennium, New Frontiers in the Solar System, and Connecting Quarks with the Cosmos. • LSST will enable a wide variety of complementary scientific investigations, utilizing a common database. These range from searches for small bodies in the solar system to precision astrometry of the outer regions of the galaxy to systematic monitoring for transient phenomena in the optical sky. • Of particular interest to HEP, LSST will constrain models of dark energy vs. cosmic time by measuring the dark matter power spectral density via weak lensing. SLAC EPAC Meeting Nov. 14-15, 2003

  3. SLAC Involvement in LSST • The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) has chosen to emphasize dark matter and dark energy as key focus areas for its experimental program at SLAC. • We believe it is essential to probe the standard cosmological model on multiple “fronts”, i.e. not only constraining parameters, but testing for internal consistency via disparate measurement techniques. • LSST is an excellent complement to SNAP. By participating in BOTH projects, we believe that SLAC will be ideally positioned to play a key role in the next wave of cosmological discovery. SLAC EPAC Meeting Nov. 14-15, 2003

  4. Outline of Presentations • Probing Dark Energy with LSST – A. Tyson • The Design and Development of the LSST Camera – W. Althouse • LSST Project Organization – S. Kahn SLAC EPAC Meeting Nov. 14-15, 2003

  5. LSST probes of DE 1. Number counts vs. redshift:N(M,z) *Comoving Volume element dV/dzd *Growth rate of density perturbations (z) Counts of mass clusters: 3-D tomography 2. Shear Tomography:<g(z1)g(z2)> 3. Sachs-Wolfe effect:<CMB g(z)> SLAC EPAC Meeting Nov. 14-15, 2003

  6. mass structure vs time 3 billion lyr 7 billion lyr SLAC EPAC Meeting Nov. 14-15, 2003

  7. Weak Gravitational Lensing • Over 250,000 resolved hi-redshift galaxies per square degree • Each is moved on the sky and distorted SLAC EPAC Meeting Nov. 14-15, 2003

  8. Strong lensing SLAC EPAC Meeting Nov. 14-15, 2003

  9. Cosmic Mirage SLAC EPAC Meeting Nov. 14-15, 2003

  10. Cluster Tomography Source Redshift Distribution Distant Source Galaxies Mass Cluster @ z = 0.5 P(z) Foreground Source zsource Lens Strength Dsource Dlens zlens = 0.5 Lens Strength 1 - Dlens/Dsource The blue galaxyis sheared more than the red galaxy. Thegreen galaxyis not sheared. zsource

  11. Tomographic mass slices in z SLAC EPAC Meeting Nov. 14-15, 2003

  12. Observed mass: 2x2 degree field z = .7 SLAC EPAC Meeting Nov. 14-15, 2003

  13. DLS 1055-05 SLAC EPAC Meeting Nov. 14-15, 2003

  14. mass – baryon correlation? DLS mass map CXO .5-4 keV SLAC EPAC Meeting Nov. 14-15, 2003

  15. Mass Cluster Counting • The mass function is steep and exponentially sensitive to errors in Mlimit (z) and uncertainty in M(observables,z). • Measure mass function, determine Mlimit (z) from LSST cluster survey, devise a test that is insensitive to the limiting mass. SLAC EPAC Meeting Nov. 14-15, 2003

  16. Cluster Counting • Goal:Determine cosmological parameters by comparing the observed distribution of clusters to predictions from theory/N-body simulations • However cluster mass is not an observable. Instead we measure: • SZ decrement • X-rays (LX or TX) • Optical Richness • Galaxy v • Shear  • To interpret the observations we must know • M(observables,z) • Completeness(observables,z) No baryon bias SLAC EPAC Meeting Nov. 14-15, 2003

  17. QCDM or LCDM? • Redshift distributions differ at a high statistical significance • Lensing kernel is broader for LCDM and probes a broader range of z and M than QCDM • w precision 2% • Unlike other cluster counting surveys, this test is ROBUST against uncertainties in mass limit. Normalized Cluster Redshift Distribution QCDM LCDM 3% of LSST sample SLAC EPAC Meeting Nov. 14-15, 2003

  18. Cosmic shear vs redshift SLAC EPAC Meeting Nov. 14-15, 2003

  19. LSST shear tomography + SLAC EPAC Meeting Nov. 14-15, 2003

  20. Precision on DE P/r SUGRA LCDM LSST WL + WMAP SNAP SN + Planck SNAP WL + Planck P/r = w0 + wa (1-a) a = (1+z)-1 SLAC EPAC Meeting Nov. 14-15, 2003

  21. LSST Weak Lensing survey Low z WL SLAC EPAC Meeting Nov. 14-15, 2003

  22. Weak Lensing with LSSTSummary • An incisive probe of new physics: 3-D tomography / Dark Energy • Multiple probes break degeneracies • Probes dark energy in multiple ways: w and dw/dz from shear-shear and cluster dN/dz. Wm , Wx curves. • Comparison with CMB and with SN1a tests fundamental assumptions SLAC EPAC Meeting Nov. 14-15, 2003

  23. Controlling Systematics • Need baryon unbiased estimates of cluster mass shear survey • Minimize delivered PSF shear • Chop shear signal multiple ways • Large sample of mass clusters • Explore mass function SLAC EPAC Meeting Nov. 14-15, 2003

  24. Figure of Merit Apparatus & Eff. Science goals site & optics Volume surveyed (number of objects found) to some S/N at some magnitude limit, per unit time: A – aperture W – camera FOV QE – det. Eff. e – observing eff. Fsky – sky flux dW – seeing footprint SLAC EPAC Meeting Nov. 14-15, 2003

  25. Optical Throughput Required LSST SLAC EPAC Meeting Nov. 14-15, 2003

  26. Unexplained optical bursts Deep Lens Survey SLAC EPAC Meeting Nov. 14-15, 2003

  27. Massively Parallel Astrophysics LSST DATA PUBLICSimultaneously address: • Dark matter/dark energy via weak lensing • Dark matter/dark energy via supernovae • Galactic Structure encompassing local group • Dense astrometry over 30000 sq.deg: rare moving objects • Gamma Ray Bursts and transients to high redshift • Gravitational micro-lensing • Strong galaxy & cluster lensing: physics of dark matter • Multi-image lensed SN time delays: separate test of cosmology • Variable stars/galaxies: black hole accretion • QSO time delays vs z: independent test of dark energy • Optical bursters to 25 mag: the unknown • 5-band 27 mag photometric survey: unprecedented volume • Solar System Probes: Earth-crossing asteroids, Comets, TNOs SLAC EPAC Meeting Nov. 14-15, 2003

  28. SLAC EPAC Meeting Nov. 14-15, 2003

  29. LSST Optics SLAC EPAC Meeting Nov. 14-15, 2003

  30. Camera Configuration SLAC EPAC Meeting Nov. 14-15, 2003

  31. SLAC EPAC Meeting Nov. 14-15, 2003

  32. Camera Components • Focal plane array • 10 μm pixels  0.2 arcsecond/pixel (~1/3 seeing-limited PSF) • 55 cm diameter  3° FOV  2.3 Gpixels • integrated front-end electronics • 16 bits/pixel, 2 sec readout time  2.3 GB/sec  Parallel readout • Housings (environmental control) • Filters • Optics • Mechanisms • L2 position varies with wavelength (filter) • Filters insertion • mechanical shutter SLAC EPAC Meeting Nov. 14-15, 2003

  33. Camera Challenges • Detector requirements: • 10 μm 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 position precision of order 3 μm • 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 SLAC EPAC Meeting Nov. 14-15, 2003

  34. Camera Challenges (con’d) • Key challenge: Detector technology • Main choices: CCD, hybrid CMOS • CCDs: • Monolithic Si array • Routinely used for visible astronomical applications • Have been made in high-resistivity, thick format (to achieve sensitivity at 1 μm wavelength) with 15 μm pixel density • Slow readout: need ~10 μs per pixel to achieve noise level • Hybrid CMOS: • Hybrid array uses thin planar detector with pixelated back contact “bump bonded” to CMOS readout multiplexer • Routinely used for infrared astronomy (with different photo-conversion material) • Avoids need for mechanical shutter • Can integrate substantial electronics on-chip • Low power (< 1/100 of CCD) & Fast readout SLAC EPAC Meeting Nov. 14-15, 2003

  35. Camera Challenges (con’d) • Control of systematics • Lensing studies exploit subtle, systematic image distortions caused by dark matter • Time dependent or environmentally induced distortion in the measuring system (telescope + camera) could mask the lensing signature • May place unusual demands on camera development, particularly testing to ensure acceptable control/knowledge of end-to-end transfer function SLAC EPAC Meeting Nov. 14-15, 2003

  36. LSST Management Plan • In March 2003, four organizations (U. of Washington, U. of Arizona, the Research Corporation, and NOAO) formed the LSST Corporation (LSSTC), a non-profit 501C3 Arizona corporation. • The purpose of LSSTC is to pursue a shared vision for the nature of the LSST endeavor, and a commitment to advance the project through technical, scientific, and/or financial contributions. LSSTC plans to expand its institutional membership as the project progresses. • As presently envisioned, funding for the construction of the LSST will come from NSF, DOE, and private donors. Significant commitments of private funding are already in hand. A proposal to NSF for design & development phase funding will be submitted in December 2003. • While LSST is a distributed project, there is a single management plan. All participating organizations will be coordinated and accountable to the LSST Director and Project Manager, who are appointed by the LSSTC Board of Directors. SLAC EPAC Meeting Nov. 14-15, 2003

  37. DOE Participation in LSST • A collaboration of DOE-funded institutions has been formed to pursue participation in LSST. This collaboration has been working closely with other LSST participants under the coordination of the LSST Director and Project Manager. • The DOE “deliverable” will be the LSST camera system. • SLAC will lead the development of the camera, with significant contributions coming from BNL, LLNL, and DOE-funded university groups (e.g. Harvard, UIUC). • Scientists and engineers at these institutions will also participate in the data acquisition system, the development of pipeline software, and the scientific interpretation of the results. SLAC EPAC Meeting Nov. 14-15, 2003

  38. LSST Project Organization Science Working Groups LSST Corporation Board of Directors John Schaefer, President Research Corporation, University of Washington, National Optical Astronomical Observatory, University of Arizona Executive Advisory Committee Arthur Bienenstock External Review Board LSST Director Anthony Tyson Science Advisory Board Zeljko Ivezic, Philip Pinto Science Assurance System Scientist Christopher Stubbs Data: Kem Cook Camera: Steve Kahn Tel/Site: Chuck Claver Project Manager Donald Sweeney System Engineering Jacques Sebag • Project Support • Change Control Board • Risk Management • Project Controls • Performance Assurance • Administration Array Technology Don Figer, Mike Lesser Public Outreach Michael Shara, Doug Isbell SW Architecture Jim Gray, Robert Lupton Data Management Kem Cook, Sci. tbd , Mgr. Camera Steve Kahn, Sci. Bill Althouse, Mgr. Telescope/Site Charles Claver, Sci. Larry Daggert, Mgr. SLAC EPAC Meeting Nov. 14-15, 2003

  39. LSST Camera Project Organization System Engineering T. Thurston Lead Mech. Engr T. Decker, LLNL Lead Elect. Engr J. Oliver, Harvard Data Bus W. Althouse (act.) Optics J. Taylor, LLNL S. Olivier, LLNL Mechanisms L. Hale, LLNL Housing & Structure T. Thurston Camera I&T W. Craig Array, FE Elex V. Radeka, BNL Opto-Mech Assy T. Decker, LLNL Camera S. Kahn, Sci Lead W. Althouse, Proj Mgr • Camera Project Support • Project Controls & Risk Mgmt • Performance & Safety Assur. • Administration Focal Plane Assy M. May, BNL Array Testing D. Figer, STScI M. Lesser, Steward Obs. All SLAC unless otherwise noted SLAC EPAC Meeting Nov. 14-15, 2003

  40. LSST Design Phase Schedule SLAC EPAC Meeting Nov. 14-15, 2003

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