SNAP

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SNAP
Physics Discoveries
Launch
Assembly
Configuration
Development
Supernova Acceleration Probe
2010
2001
Integration
Technology
Physics
Engineering
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Outline

• Science
• Mission
• Telescope
• Mechanical Structures
• Mirrors, etc
• Spacecraft / Orbit
• Instruments
• GigaCAM
• CCD Technology
• NIR Technology
• Spectrograph
• Status

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The Accelerating Universe Sciences Breakthrough
of the Year

• Redshift of spectral features measures the
  expansion of the universe.
• A magnitude vs. redshift plot provide a Hubble
  diagram measuring the expansion rate
• Ground-based work thus far has uncovered a major
  surprise

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How Can We Address These New Questions?

• 3rd generation experiment
• Need 1000s of SNe to improve statistical/systemat
  ic accuracy.
• The most demanding SNAP requirements are devoted
  to eliminating and controlling all systematic
  uncertainties.
• All data taken with single dedicated, instrument.
• Above atmospheric interference
• Imaging for discovery photometry
• Spectroscopy to classify Type Ia supernovae and
  for redshift

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What makes the SN measurement special?Control of
systematic uncertainties

• At every moment in the explosion event, each
  individual supernova is sending us a rich
  stream of information about its internal physical
  state.

Lightcurve Peak Brightness
Images
?M and ?L Dark Energy Properties
Redshift SN Properties
Spectra
data
analysis
physics
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Supernova Systematics

• Models are used to indicate which observables are
  sensitive to physical conditions. These can be
  used to create subsets
• Observables
• Ni56 mass from spectral ratios
• Metallicity from UV continuum
• Kinetic energy from Line Ratios

Light Curve Observable Requirement for m lt 0.02
Stretch 1
Rise Time 0.3 days
Peak to tail ratio 0.05 mag
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Supernova Requirements
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From Science Goalsto Project Design
Science

• Measure ?M and ?
• Measure w and w (z)

Systematics Requirements
Statistical Requirements

• Identified and proposed systematics
• Measurements to eliminate / bound each one to
  /0.02 mag

• Sufficient (2000) numbers of SNe Ia
• distributed in redshift
• out to z lt 1.7

Data Set Requirements

• Discoveries 3.8 mag before max
• Spectroscopy with S/N10 at 15 Å bins
• Near-IR spectroscopy to 1.7 ?m

Satellite / Instrumentation Requirements

• 2-meter mirror Derived requirements
• 1-square degree imager High Earth orbit
• Spectrograph 50 Mb/sec bandwidth (0.35 ?m
  to 1.7 ?m)

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Mission Requirements

• Minimum data set criteria
• Discovery within 2 days (rest frame) of explosion
  (peak 3.8 magnitude),
• Ten high S/N photometry points on lightcurve,
• Lightcurve out to plateau (2.5 magnitude from
  peak),
• High quality peak spectrophotometry
• How to obtain both data quantity AND data
  quality?
• Batch processing techniques with wide field --
  large multiplex advantage -- key to
  SNAP 1 SNe/CCD/Field/yr
• Wide field imager designed to repeatedly observe
  an area of sky
• Infrared observations
• Mostly preprogrammed observations, fixed fields
• Very simple experiment, passive expt.

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Advantages of Space
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Mission Design

• SNAP a simple dedicated experiment to study the
  dark energy
• Dedicated instrument, essentially no moving parts
• Mirror 2 meter aperture sensitive to light from
  distant SN
• Photometry with 1x 1 billion pixel mosaic
  camera, high-resistivity, rad-tolerant p-type
  CCDs and, HgCdTe arrays. (0.35-1.7 mm)
• Integral field optical and IR spectroscopy
  0.35-1.7 mm, 2x2 FOV

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Imaging Strategy
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Observatory Parameters
Primary Mirror diameter 200 cm Secondary
Mirror diameter 42 cm Tertiary
Mirror diameter64 cm
Optical Solution
Edge Ray Spot Diagram (box 1 pixel)
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Optical Train
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Telescope Assembly
Movie courtesy of Hytec
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Primary Mirror Substrate

• Key requirements and issues
• Dimensional stability
• High specific stiffness (1g sag, acoustic
  response)
• Stresses during launch
• Design of supports
• Baseline technology
• Multi-piece, fusion bonded, with egg-crate core
• Meniscus shaped
• Triangular core cells

Design with locally thicker web plates Standard
web thickness 5 mm (orange) Thickened plates
10 mm (red)
Initial design for primary mirror
1g front face ripple on perfect back-side
support P-P Z deflection 0.018 ?m
Deformations of mirror top face under
pseudo-static launch loads peak deflection 20
?m
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Spacecraft from Goddard/Integrated Mission Design
Center Study
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SNAP Assembly
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Launch Vehicle Study
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Launch Vehicle Study
Atlas-EPF Delta-III Sea Launch
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Orbit Trade-Study

• Feasibility Trade-Study

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Orbit Optimization

• High Earth Orbit
• Good Overall Optimization of Mission Trade-offs
• Low Earth Albedo Provides Multiple Advantages
• Minimum Thermal Change on Structure Reduces
  Demand on Attitude Control
• Excellent Coverage from Berkeley Groundstation
• Outside Outer Radiation Belt 80 of orbit
• Passive Cooling of Detectors
• Minimizes Stray Light

Chandra type highly elliptical orbit
Lunar Assist orbit
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Ground Station Coverage
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Mission Operations/Space Sciences Laboratory

• Mission Operations Center (MOC) at Space Sciences
  Using Berkeley Ground Station
• Fully Automated System Tracks Multiple Spacecraft
• 11 meter dish at Space Sciences Laboratory
• Science Operations Center (SOC) closely tied to
  MOC
• Science Operations at LBNL NERSC
• Operations are Based on a Orbital Period
• Autonomous Operation of the Spacecraft
• Coincident Science Operations Center Review of
  Data with Build of Target List
• Upload Instrument Configuration for Next Period

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Camera Assembly
GigaCam
Shield
Heat radiator
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GigaCAM

• GigaCAM, a one billion pixel array
• Approximately 1 billion pixels
• 140 Large format CCD detectors required, 30
  HgCdTe Detectors
• Larger than SDSS camera, smaller than H.E.P.
  Vertex Detector (1 m2)
• Approx. 5 times size of FAME (MiDEX)

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IR Enhanced Camerawith Fixed Filter Set
3 IR Filters 8 Visible Filters
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Step and Stare
Drag star through multiple fixed length exposures
in multiple filters
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3-month rotation
1O X 10O SNAP FIELD
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Focal Plane Layout with Fixed Filters
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Number of SNe per 0.03 z after two years.
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High-Resistivity CCDs

• New kind of CCD developed at LBNL
• Better overall response than more costly
  thinned devices in use
• High-purity silicon has better radiation
  tolerance for space applications
• The CCDs can be abutted on all four sides
  enabling very large mosaic arrays
• Measured Quantum Efficiency at Lick Observatory
  (R. Stover)

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LBNL/CCD 2k x 4k
USAF test pattern. 2K x 4K
1294 x 4186 12 ?m
2k x 4k 15 ?m
1478 x 4784 10.5 ?m
Industrialized wafer
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LBNL/CCD 2k x 2k results
Image 200 x 200 15 ?m LBNL CCD in Lick Nickel
1m. Spectrum 800 x 1980 15 ?m LBNL CCD in NOAO
KPNO spectrograph. Instrument at NOAO KPNO 2nd
semester 2001 (http//www.noao.edu)
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LBNL CCDs at NOAO
Science studies to date at NOAO using LBNL CCDs

1. Near-earth asteroids
2. Seyfert galaxy black holes
3. LNBL Supernova cosmology

Cover picture taken at WIYN 3.5m with LBNL 2048 x
2048 CCD (Dumbbell Nebula, NGC 6853)
Blue is H-alpha Green is SIII 9532Å Red is HeII
10124Å.
See September 2001 newsletter at
http//www.noao.edu
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10.5 ?m Well Depth
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CCD Noise Performance Breakthrough
Noise vs Sample Time for LBNL CCDs
Readout Noise (electrons)
Sample time (msec)
New design
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Radiation Damage Comparison to Conventional CCDs
CTE is measured using the 55Fe X-ray method at
128 K. 13 MeV proton irradiation at LBNL 88
Cyclotron Degradation is about 1?10-13
g/MeV. SNAP will be exposed to about 1.5?106
MeV/g.
1L.Cawley, C.Hanley, WFC3 Detector
Characterization Report 1 CCD44 Radiation Test
Results, Space Telescope Science Institute
Instrument Science Report WFC3 2000-05,
Oct.2000 2 T. Hardy, R. Murowinski, M.J. Deen,
Charge transfer efficiency in proton damaged
CCDs, IEEE Trans. Nucl. Sci., 45(2), pp.
154-163, April 1998
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Packaging prototypes
2k x 2k back-illuminated mount. 2k x 4k mount
similar, extending along wire-bond edge.
First back-illuminated image with new mount. CCD
is engineering grade used for assembly practice.
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Mosaic Packaging
With precision CCD modules, precision baseplate,
and adequate clearances designed in, the focal
plane assemble is plug and play.
140 K plate attached to space radiator.
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GigaCAM Vertex Detector

• Lots of silicon
• Lots of pixels
• Custom ASICs
• Radiation tolerance, cooling, mechanical stability

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Shortwave HdCdTe Development

• Hubble Space Telescope Wide Field Camera 3
• WFC-3 replaces WFPC-2
• CCDs IR HgCdTe array
• Ready for flight July 2003
• 1.7 mm cut off
• 18 mm pixel
• 1024 x 1024 format
• Hawaii-1R MUX
• Dark current consistent with thermoelectric
  cooling
• lt 0.5 e/s at 150 K
• 0.02 e-/s at 140 K
• Expected QE 60 0.9-1.7 mm
• Individual diodes show good QE

NIC-2
WFC-3 IR
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Integral Field Unit Spectrograph Design
SNAP Design
Camera
Detector
Prism
Collimator
Slit Plane
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Mirror Slicer Stack
E. Prieto, (LAM)
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Diffraction Analysis
Throughput better than 90.6 (reflectance
diffractionedge)
E. Prieto, (LAM)
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Throughput
Fore optics 3 mirrors 0.983
0.941 Slicer unit 3 mirrors ...
0.90 Spectrograph 2 Mirrors
0.982 0.96 Folding Mirrors 2
0.982 0.96 Prism (2
interface internal) 0.962 x 0.9
0.83 Telescope 4 Mirrors
0.984 0.92 Detector better than
0.60
0.64
0.60
Worst Case
0.36
E. Prieto, (LAM)
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Technology readiness and issues

• NIR sensors
•        HgCdTe stripped devices are begin
  developed for NGST and are ideal in our
  spectrograph.
•        "Conventional" devices with appropriate
  wavelength cutoff are being developed for WFC3
  and ESO.
•  
• CCDs
•        We have demonstrated radiation hardiness
  that is sufficient for the SNAP mission
•        Extrapolation of earlier measurements of
  diffusion's effect on PSF indicates we can get to
  the sub 4 micron level. Needs demonstration.
•        Industrialization of CCD fabrication has
  produced useful devices need to demonstrate
  volume
•        ASIC development is required.
•  
• Filters we are investigating three strategies
  for fixed filters.
•         Suspending filters above sensors
•         Gluing filters to sensors
•         Direct deposition of filters onto
  sensors.
•  

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Technology readiness and issues

• On-board data handling
•        We have opted to send all data to ground
  to simplify the flight hardware and to minimize
  the development of flight-worthy software.
•        50 Mbs telemetry, and continuous ground
  contact are required. Goddard has validated this
  approach.
• Calibration
•        There is an active group investigating
  all aspects of calibration.
•  
• Pointing
•        Feedback from the focal plane plus
  current generation attitude control systems may
  have sufficient pointing accuracy so that nothing
  special needs be done with the sensors.
•  
• Telescope
•        Thermal, stray light, mechanical
  control/alignment
• Software
•        Data analysis pipeline architecture

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A Resource for the Science Community
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Wide field survey in space

• Key Cosmological Studies
• Type Ia supernova calibrated candle Main goal
• Type II supernova expanding photosphere
• Hubble diagram to z1 and beyond
• Weak lensing
• Direct measurements of density vs z
• Mass selected cluster survey vs z
• Constraints on SNe magnification
• Strong lensing statistics W?
• 10x gains over ground based optical
• resolution, IR channels depth
• Galaxy clustering

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Ultra-deep multi-band imaging survey

• Galaxy populations and morphology to co-added m
  32
• Low surface brightness galaxies in H band
• Quasars to redshift 10
• Epoch of reionization through Gunn-Peterson
  effect
• Galaxy evolution studies, merger rate
• Evolution of stellar populations
• Ultraluminous infrared galaxies
• Globular clusters around galaxies
• Extragalactic stars (in clusters or otherwise)
• Intracluster objects (globulars, dwarf
  galaxies, etc.)
• Lensing projects
• Mass selected cluster catalogs
• Evolution of galaxy-mass correlation function
• and its scaling relations
• Maps of mass in filaments

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Wide-field Survey

• Potential One Year Wide Field Survey
• Band 30,000 deg2 3,000 deg2 300 deg2
• H' 26.4 27.85 29.25
• J 26.6 28.1 29.4
• Z 27.35 28.85 30.2
• I 27.4 28.9 30.25
• R 27.55 29.1 30.4
• V 27.25 28.85 30.25
• B 27.65 29.3 30.65
• Magnitudes given are for S/Ngt5 detections for
  95 of point sources. (Assumes filter wheel)
• All magnitudes are AB system. (G. Bernstein)

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Status

• Dark Energy a subject of the recent National
  Academies of Science Committee on the Physics of
  the Universe (looking at the intersection of
  physics and astronomy). One of eleven compelling
  questions What is the Nature of the Dark
  Energy?
• HEPAP subpanel strong endorsement for continued
  development of SNAP
• APS/DPF held Snowmass meeting part of 20 year
  planning process for field
• resource book on SNAP science back from press
• Goddard/Integrated Mission Design Center study in
  June 2001 no mission tallpoles
• Goddard/Instrument Synthesis and Analysis Lab.
  study in Nov. 2001 no technology tallpoles
• Have removed most moving parts, unneeded
  subsystems, and high tech. Single integrated
  focal plane for CCD, HgCdTe, Spectrograph.
  Room Temp Telescope.
• International collaboration is growing, currently
  15 institutions.
• 18 talk 7 posters at upcoming AAS meeting

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Roadmap for Particle Physics

• Timelines for Selected Roadmap Projects.
  Approximate decision points
• are marked in black.RD is marked in
  yellow,construction in green,and
• operation in blue.

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SNAP Collaboration
G. Aldering, C. Bebek, W. Carithers, S. Deustua,
W. Edwards, J. Frogel, D. Groom, S. Holland, D.
Huterer, D. Kasen, R. Knop, R. Lafever, M. Levi,
S. Loken, P. Nugent, S. Perlmutter, K. Robinson
(Lawrence Berkeley National Laboratory) E.
Commins, D. Curtis, G. Goldhaber, J. R. Graham,
S. Harris, P. Harvey, H. Heetderks, A. Kim, M.
Lampton, R. Lin, D. Pankow, C. Pennypacker, A.
Spadafora, G. F. Smoot (UC Berkeley) C. Akerlof,
D. Amidei, G. Bernstein, M. Campbell, D. Levin,
T. McKay, S. McKee, M. Schubnell, G. Tarle , A.
Tomasch (U. Michigan) P. Astier, J.F. Genat, D.
Hardin, J.- M. Levy, R. Pain, K. Schamahneche
(IN2P3) A. Baden, J. Goodman, G. Sullivan
(U.Maryland) R. Ellis, A. Refregier (CalTech) A.
Fruchter (STScI) L. Bergstrom, A. Goobar (U.
Stockholm) C. Lidman (ESO) J. Rich
(CEA/DAPNIA) A. Mourao (Inst. Superior
Tecnico,Lisbon)
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SNAP at the American Astronomical Society
Meeting, Jan. 2002

• Oral Session 111. Science with Wide Field Imaging
  in Space
• The Astronomical Potential of Wide-field Imaging
  from Space S. Beckwith (Space Telescope Science
  Institute)
• Galaxy Evolution HST ACS Surveys and Beyond to
  SNAP G. Illingworth (UCO/Lick, University of
  California)
• Studying Active Galactic Nuclei with SNAP P.S.
  Osmer (OSU), P.B. Hall (Princeton/Catolica)
• Distant Galaxies with Wide-Field Imagers K. M.
  Lanzetta (State University of NY at Stony Brook)
• Angular Clustering and the Role of Photometric
  Redshifts A. Conti, A. Connolly (University of
  Pittsburgh)
• SNAP and Galactic Structure I. N. Reid (STScI)
• Star Formation and Starburst Galaxies in the
  Infrared D. Calzetti (STScI)
• Wide Field Imagers in Space and the Cluster
  Forbidden Zone M. E. Donahue (STScI)
• An Outer Solar System Survey Using SNAP H.F.
  Levison, J.W. Parker (SwRI), B.G. Marsden (CfA)
• Oral Session 116. Cosmology with SNAP
• Dark Energy or Worse S. Carroll (University of
  Chicago)
• The Primary Science Mission of SNAP S.
  Perlmutter (Lawrence Berkeley National
  Laboratory)
• The Supernova Acceleration Probe mission design
  and core survey T. A. McKay (University of
  Michigan
• Sensitivities for Future Space- and Ground-based
  Surveys G. M. Bernstein (Univ. of Michigan)
• Constraining the Properties of Dark Energy using
  SNAP D. Huterer (Case Western Reserve
  University)
• Type Ia Supernovae as Distance Indicators for
  Cosmology D. Branch (U. of Oklahoma)
• Weak Gravitational Lensing with SNAP A.
  Refregier (IoA, Cambridge), Richard Ellis
  (Caltech)

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Conclusion

• SNAP
• Space observations of thousands of supernovae
  will provide the vital breakthrough in precision
  cosmology to characterize the dark energy