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Dark Energy and Large Synoptic Survey Telescope - PowerPoint

VIEWS: 18 PAGES: 40

									Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                Dark Energy and the LSST
                              Christopher Stubbs
                              John Oliver
                              Peter Doherty
                              Nathan Felt
                              Meghna Kundoor
                              Gautham Narayan
                              Amali Vaz

               Harvard University Laboratory for Particle Physics and Cosmology

                                                DOE Site Visit
                                                Sept 20, 2010

                                                 2010 DOE Site Visit              1
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




Introduction to the Dark Energy Crisis, and LSST
LSST Camera electronics development
LSST Detector testing and optimization
Improved Precision for Dark Energy Characterization
Addressing the Challenges of LSST Exploitation



                                                  2010 DOE Site Visit   2
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




Introduction to the Dark Energy Crisis, and LSST




                                                  2010 DOE Site Visit   3
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology



          Emergence of a Standard Cosmology
Our geometrically flat Universe started in a hot big bang
13.7 billion yrs ago. It has been expanding ever since.

The evolution of the Universe is increasingly dominated by
the phenomenology of the vacuum, the “Dark Energy”.


                                                                 “Dark matter”: what is it?

                                                                 Ordinary matter is a minor component.

                                                                 Luminous matter comprises a very
                                                                 small fraction of the mass of the
                                                                 Universe.

                                                  2010 DOE Site Visit                                    4
 Harvard University
 Department of Physics
 Laboratory for Particle Physics and Cosmology




   Large Synoptic Survey Telescope
Top ranked ground-based project in 2010 Decadal Survey
Optimized for time domain
     scan mode
     deep mode
10 square degree field
6.5m effective aperture
24th mag in 20 sec
>20 Tbyte/night
Real-time analysis
                       Engineered to minimize systematics for Dark Energy
                                                 2010 DOE Site Visit        5
   Harvard University
   Department of Physics
   Laboratory for Particle Physics and Cosmology




                                    Our efforts on LSST…
  • Stubbs has long-standing engagement and leadership role in
    LSST:
         –    Past member of LSST Board of Directors
         –    Original LSST Project Scientist
         –    Current member of LSST Science Council
         –    Coordinator for DOE efforts on SN cosmology
         –    Likely head of system commissioning team
         –    Co-author on LSST Science Book
         –    Laid intellectual foundation for calibration scheme
                          – Adopted by LSST, by Dark Energy Survey… and others



And the 12 ft diameter LSST secondary mirror is sitting in our lab…

                                                   2010 DOE Site Visit           6
    Harvard University
    Department of Physics
    Laboratory for Particle Physics and Cosmology



LSST Camera system:
    –        electronics development,
    –        back end modules

LSST Detector Test and Characterization:
    –        Detector test system is here
    –        Responsibility for device testing and optimization

LSST Calibration system:
    –        Conceptual development and refinement
    –        Laboratory development of projector system
    –        Same philosophy being adopted for DES.

Preparing for LSST Data Analysis:
    –        Optimal data reduction techniques and analysis
    –        Supernova observations as a probe of dark energy
    –        Minimizing system uncertainty budget for supernova cosmo.


                                                    2010 DOE Site Visit   7
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




LSST Camera electronics development




                                                  2010 DOE Site Visit   8
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                        LSST Focal Plane Overview
            21 “Science Rafts”
             4 special purpose                                           Cryostat Assembly
            “Corner Rafts” for
                guiding and                      16 Mpixel CCD
            wavefront sensing                    image sensors




                                                ~3.2 Gpixels total



                                                   2010 DOE Site Visit                       9
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology
                                                Requirements

           Large focal plane ~ 3.2 GPixels
           Rapid exposures  back to back 15 second (cosmic
          ray rejection)
           Low dead time  2 second readout
           Low read noise  6 e rms (limited by sky shot noise)
           Read time and noise specs can only be met by highly
          segmented sensors and highly parallel readout.
               1 readout channel per megapixel
               3,200 readout channels
           High density ASIC based readout system “a la hep”.




                                                2010 DOE Site Visit   10
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




             LSST Raft Tower Electronics
                                                                          Electronics must live in
  9 Sensor Raft – 144 Readout channels
                                                                          “shadow” of raft




                                                                        Raft Tower Assembly
                                                                                                 Raft

                                                                                                 FEE
• 6 Back End Boards
     • 24x 18 bit video ADCs/Board
     • “Slo-controls”, thermal control, etc                                                            BEE
• 1 “Raft Control Module”                                                                             Harvard
                                                                                                     Deliverable
     • Readout state machine (sequencer)
     • Data collection + fiber optic to DAQ
     • Slow control processing


                                                  2010 DOE Site Visit                                              11
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                     LSST Electronics Status
   Back End Electronics – Harvard deliverable Status
        • All boards in 2nd or greater version
        • Current version supports 144 readout channels, fiber optics, etc.
        • Under test – ADC performance measured
        • Integration with FEE and DAQ  Ongoing
        • Raft Control Crate fully designed. Multiple copies will be made available for testing in
        collaboration.
        • Firmware development continuing for BEB & RCM

   Full system status
         • 2nd generation ASICs tested
         • 3rd and final generations in design
         • 2nd generation FEB completed. Under test. U. Penn
         • 2nd generation BEB under test in Raft Control Crate – Harvard
         • Vertical Slice testing – In progress, will continue through CD1 and beyond
         • Additional Raft Control Crates under construction for collaboration use




                                                2010 DOE Site Visit                                  12
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




LSST Detector testing and optimization




                                                  2010 DOE Site Visit   13
    Harvard University
    Department of Physics
    Laboratory for Particle Physics and Cosmology




             LSST Detector Test Overview
•      Multiple Test Facilities (BNL, LPPC, etc.)
•      Multiple Detector Vendors (E2V, ITL, others?)
•      Stringent Requirements (flatness, PSF, QE)
•      Comprehensive Testing and Characterization
•      Repeatability, Reproducibility, Consistency
•      189 Sensors in LSST Focal Plane!
•      Led By Paul O‟Connor (BNL)



                                                    2010 DOE Site Visit   14
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




            LSST Detector Testing at LPPC
Current LPPC Efforts :
       –    Detector Test Stand Hardware Management
       –    Preparation and Validation of Test Hardware
       –    Electro-Optical Testing of Candidate Detectors
       –    Development of Test Software
       –    Establishing Detector Test Standards
LPPC Strengths:
  Decades of Experience in CCD Image Sensor Test

A Rapidly Growing Role for LPPC in LSST Detector Test


                                                2010 DOE Site Visit   15
 Harvard University
 Department of Physics
 Laboratory for Particle Physics and Cosmology




Detector Test Stand Hardware Management
Managing the acquisition and distribution of
  detector test electronics to all test sites:
            Brookhaven National Laboratory
            Harvard LPPC
            L'Institut National de Physique Nucléaire
             et de Physique des Particules (IN2P3)
            SLAC/UC Davis
            Purdue University


Managing the Standardization of Test Facilities


                                                 2010 DOE Site Visit   16
 Harvard University
 Department of Physics
 Laboratory for Particle Physics and Cosmology




                         Validation of Test Hardware
Currently finishing assembly and validation
   of BNL cryostat for testing E2V
   candidate sensors in Oct/Nov 2010
   timeframe

Preparing for integration and test of ITL
   candidate sensors at LPPC in Nov/Dec
   2010 timeframe

Working with IN2P3 to finalize detector test
  facility in Paris

Coordinating development of a new test
  facility at Institute of Physics, Academy
  of Sciences, Prague


                                                 2010 DOE Site Visit   17
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




Electro-Optical Testing of Candidate Detectors
 LPPC has a long-established detector test
    facility that has been used on multiple
    projects: PISCO, Pan-STARRS, LSST, etc.

 LPPC is constructing a new detector test
    facility specifically for LSST image
    sensors (lab space courtesy of Dr. Franklin)
                                                                        STA/ITL Prototype Imager
 LPPC has more experience in the testing of
    CCD image sensors than any other
    institution in the LSST collaboration

 Working in close collaboration with LSST
   partner institutions to support device
   testing at multiple locations
                                                                         E2V Prototype Imager

                                                  2010 DOE Site Visit                              18
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




    Development of Detector Test Software
   Multiple test facilities require the ability to reduce image data with consistent
     results

   Currently multiple sites use diverse software toolsets
       – Good for development phase (diverse ideas, techniques, etc)
       – Bad for the long term (consistency, coherence, etc)

   LPPC will assist existing developers to standardize on a set of software tools
      for use across the collaboration

   LPPC will draw on tools in use both at LSST partner sites, industry standard
      tools, and its own extensive library of CCD test data reduction code




                                                2010 DOE Site Visit                    19
 Harvard University
 Department of Physics
 Laboratory for Particle Physics and Cosmology




          Establishing Detector Test Standards
LPPC is
• Leading the effort to standardize the image data set required
  for device characterization
• Working to formalize image header keywords for consistency
  across facilities
• Coordinating the effort to standardize the software tools used
  to reduce detector test data
• Helping create a standard detector test report for use at all
  facilities engaged in LSST image sensor testing




                                                 2010 DOE Site Visit   20
 Harvard University
 Department of Physics
 Laboratory for Particle Physics and Cosmology




 Near-Term LPPC Detector Test Goals
• Delivery of detector test cryostat to BNL for E2V detector test (10/2010)
• Characterization and optimization of ITL detector prior to NSF PDR and
  DOE CD-1 (11-12/2010)
• Completion of new test facility (12/2010)
• Definition of standardized image file header keywords (12/2010)
• Preparing to integrate detector test and Raft Tower Electronics for „Vertical
  Slice Test‟




                                                 2010 DOE Site Visit              21
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




Improved Precision for Dark Energy Characterization




                                                  2010 DOE Site Visit   22
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




        Passbands and System Sensitivity




                                                2010 DOE Site Visit   23
      Harvard University
      Department of Physics
      Laboratory for Particle Physics and Cosmology




                     Pushing to Better Precision
• LSST promises considerable advances over current capabilities

• The requisite flux precision for pushing to the next level of characterization of the
  Dark Energy is < 1%
            • Supernova distance measurements
            • Photometric redshifts for weak lensing measurements, and BAO analysis.

• Inadequate corrections for variable atmospheric transmission will be a leading
  source of systematic error.

• SDSS achieved few-percent precision all-sky, while
  differential measurements in single frames reach part per thousand levels

• We are nowhere close to the Poisson limits for objects with SNR > 100.

                  Why?
                                                      2010 DOE Site Visit                 24
      Harvard University
      Department of Physics
      Laboratory for Particle Physics and Cosmology




     Broadband photometry                                               Galactic scattering


                              (i, j)                   S( )A( )G( )T( ) d
                                                      sources
                                                          Source         Atmosphere Instrumental transmission

Four aspects to the photometry calibration challenge:

1.    Relative instrumental throughput calibration (i.e. get the flux ratios right)
2.    Absolute instrumental calibration (This is far less important)
3.    Determination of atmospheric transmission
4.    Determination of Galactic extinction (most stars lie behind the extinction layers).

Historical approach has been to use spectrophotometric sources (known S()) to deduce the
       instrumental and atmospheric transmission, but this (on its own) is problematic: integral
       constraints are inadequate, plus we don‟t know the sources well enough.

                                                                2010 DOE Site Visit                             25
     Harvard University
     Department of Physics
     Laboratory for Particle Physics and Cosmology




Our Basic Philosophy for LSST Calibration
1.    Use precisely calibrated NIST photodiodes as the fundamental
      metrology basis for flux measurements.
2.    Measure instrumental throughput relative to known photodiode.
3.    Measure atmospheric transmission function directly.
4.    Deliver, for each photometric measurement, the effective passband
      through which it was obtained.




                                                     Stubbs & Tonry, ApJ 646, 1436 (2006)
                                                        2010 DOE Site Visit                 26
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                                                2010 DOE Site Visit   27
   Harvard University
   Department of Physics
   Laboratory for Particle Physics and Cosmology




Stubbs et al., ApJ in press                        2010 DOE Site Visit   28
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




LSST Calibration Screen Optics - Ms. Amali Vaz




                                                2010 DOE Site Visit   29
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




       Accelerometers on LSST
        calibration telescope




                                                2010 DOE Site Visit   30
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                Atmospheric Transmission




    Stubbs et al., PASP 119, 1163, 2007.
                                                2010 DOE Site Visit   31
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




  So we need to measure (or determine)
 1.         Extinction due to clouds, and transparency variations: This can be
            bootstrapped if a given field is observed many times, some in cloud-free
            conditions. Tougher if only a few visits per band.
 2.         Aerosols: time variable and tough to measure well.
 3.         Water vapor: differential photometry or spectroscopy, or precise dual-
            band GPS?
 4.         Barometric pressure, for MODTRAN input.



Similar challenges for cosmic ray experiments: Auger, Veritas, et


                                                  2010 DOE Site Visit                  32
Harvard University
Department of Physics
Laboratory for Particle Physics and Cosmology




                                                2010 DOE Site Visit   33
    Harvard University
    Department of Physics
    Laboratory for Particle Physics and Cosmology




        Differential Narrowband Water Monitor
• Simultaneous measurements on-band (940 nm) and off-band (880
  nm) using stars to back-light atmosphere.
• Proof-of-principle data shows promising results



                                         300 mm f/2.8                     1K x 1K deep
                                                                          depletion CCD
             940 nm

             880 nm


                                                    2010 DOE Site Visit                   34
      Harvard University
      Department of Physics
      Laboratory for Particle Physics and Cosmology




              Dual-band Geodetic-Quality GPS
 Water vapor in
  atmosphere produces
  difference in arrival
  times for GPS signals
  at two different
  wavelengths
(1.575 and
 1.228 GHz).




                                                      http://www.gpsworld.com/files/gpsworld/nodes/2002/721/chart3.jpg

                                                            2010 DOE Site Visit                                      35
   Harvard University
   Department of Physics
   Laboratory for Particle Physics and Cosmology




           A universal observed stellar locus
 • Disk M dwarfs with metallicity [Fe/H] > 0.7
   all from closer than ~1 kpc
   so minimal sensitivity to
   metallicity gradients

 • Main sequence disk stars
   and evolved halo stars




High et al., AJ 138, 110, 2009
                                                   2010 DOE Site Visit   36
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




Addressing the Challenges of LSST Exploitation


                                                  2010 DOE Site Visit   37
   Harvard University
   Department of Physics
   Laboratory for Particle Physics and Cosmology




Refining
supernova light
curve analysis:

LSST won‟t have
supernova
spectroscopy

Host extinction
redshift extraction
Ib, Ic contamination
…

                                                   2010 DOE Site Visit   38
   Harvard University
   Department of Physics
   Laboratory for Particle Physics and Cosmology




Is the accelerating expansion the same in different directions?
   A. Diercks‟ PhD thesis, UCSB, 1999
   Cook & Lynden-Bell, MNRAS 401, 1409 (2009), and references therein




                                                   2010 DOE Site Visit   39
  Harvard University
  Department of Physics
  Laboratory for Particle Physics and Cosmology




                     LSST: Plans for FY2011
• Camera electronics engineering
• Detector device testing and characterization
• Continue to refine and test innovative calibration
  methods
• Establish SN dark energy working group, with
  LBL and Fermilab, refine light curve fitting
• Develop instrument calibration and atmospheric
  monitoring apparatus.

                                                  2010 DOE Site Visit   40

								
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