Supernova data shows an acceleration of the expansion, implying that the universe is dominated by a new Dark Energy!

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SNAP Introduction

• Supernova data shows an acceleration of the
  expansion, implying that the universe is
  dominated by a new Dark Energy!
• Remarkable agreement between Supernovae recent
  CMB.

Credit STScI
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Theoretical Questions
Would be number one on my list of things to
figure out - Edward Witten Right now, not
only for cosmology but for elementary particle
theory this is the bone in the throat - Steven
Weinberg

• What is the Nature of the dark energy?
• Largest component of our universe
• Theory proposes a number of alternatives each
  with different properties we can measure.
• What is the evolution and fate of the universe?

• Our main achievement in understanding dark
  energy is to give it a name Michael Turner
• In string theory, to get ? gt 0 but extremely
  small is impossible - Ed Witten

Maybe the most fundamentally mysterious thing
in basic science - Frank Wilczek This is the
biggest embarrassment in theoretical physics -
Michael Turner
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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. (0.4-1.7 mm)
• Integral field optical and IR spectroscopy
  0.4-1.7 mm, 2x2 FOV

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Simulated SNAP data
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Ground-based measurements will reach systematic
limits
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The Time Series of Spectra is a CAT Scan of the
Supernova
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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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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 High bandwidth (0.4 ?m to
  1.7 ?m)

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SAGENAP (2000)

• Science review by SAGENAP of 260-page proposal,
  March 2000.
• DOE support commenced after SAGENAP
• Study phase (effort to develop CDR, cost,
  schedule, key technologies).

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RD Review

• Recent DOE/Science RD Review (Jan 2001)
• SNAP is a science-driven project with compelling
  scientific goals.
• SNAP will have a unique ability to measure the
  variation in the equation of state of the
  universe.
• We believe that it is not an overstatement to
  say that the Type Ia supernova measurements will
  uniquely address issues at the very heart of the
  field Implications for string theory
• Issues Raised at RD Review
• Look at greatly increasing the near-infrared
  capabilities
• Is the proposed IR spectrograph throughput
  adequate?
• Look at a descoped instrument complement Can the
  spectroscopy be done by ground-based facilities?
• Develop a calibration strategy and plan.
• Address NASA relationship

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Todays Talk Status of RD

• Science Requirements Definition
• Monte Carlo Event Generator
• Lightcurve generator and fitter
• Cosmology fitter
• SNe Modeling
• Optical Telescope
• Optical Design/Layout
• Optical Quality
• Technology
• Stray Light
• Thermal Design

• NASA IMDC/ISAL Studies
• Spacecraft Packaging
• Mass Power
• Attitude Control/Pointing
• Launch Vehicle
• Orbit
• Instrumentation
• Camera
• Survey Strategy
• CCD Detectors
• Radiation Damage
• NIR Detectors
• Spectrograph

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Tools for Requirements Definition
Monte Carlo implements detailed list of
systematics Event generator - Create an object
list with fluxes. Ingredients Supernova types,
Type Ia subclasses Galactic, host, and gray
dust Gravitational lensing Host galaxy
properties Image simulator and SN extraction -
Measure photometry, spectra from images Data
simulator - Generated calibrated light curves and
spectra S/N calculated based on observatory
parameters Calibration errors Detection
efficiency - Measure contamination of non SNe Ia
and Malmquist bias Light curve and spectrum
fitter - Simultaneously fit key parameters of SN
and dust Cosmology fitter - Determine best fit
cosmological and dark energy parameters
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Simulation Studies Suite
Modeling Theory ? To probe dark energy,
follow SN to z ? 1.5 -- optimal redshift range,
SN distribution, priors Refinement of
observational requirements space from -- SN
observations/templates rise time, line
widths/shifts, UV -- SN explosion modeling
progenitor, C/O, kinetic energy,
metallicity Study of deep, wide field surveys
-- advanced exposure time calculations --
dithering, sampling, pixel strategies Gravitationa
l lensing corrections in data analysis -- cross
correlate SNAP weak lensing map with SN
amplification -- direct fit of microlensing
amplification distribution peak and tail
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Supernova Data Sheet
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Supernova Requirements
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Advantages of Space
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Primary Science Mission Includes
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Current Optical Configuration
Annular Field TMA Prolate ellipsoid concave
primary mirror, 2 meter diameter Hyperbolic
convex secondary mirror Flat oval 45degree
folding mirror feeds transverse rear axis Prolate
ellipsoid concave tertiary mirror Flat focal
plane Delivers lt 0.04 arcsecond FWHM geometrical
blur over annular field 1.37 sqdeg Effective
focal length 21.66m f/10.8 final focus Provides
side-mounted detector location for best detector
cooling
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OTA geometrical ray traceTMA62 configuration
Compare Airy disk 26 microns FWZ diameter at 1
micron
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OTA Technologies

• Existing technologies are suitable for SNAP
  Optical Telescope Assembly
• New materials, processes, test evaluation
  methods are unnecessary
• Mirror materials
• Corning ULE glass extensive flight history, but
  expensive
• Schott Zerodur glass/ceramic composite lower
  cost, widely used in ground based astronomical
  telescopes, higher mass optic huge industrial
  base
• Astrium/Boostec SiC-100 newcomer unproven in
  space optics higher CTE adopted for
  Herschel/FIRST in infrared
• Structural materials
• M55J carbon fiber cyanate ester resin epoxy
  adhesive bonds
• Mirror finishing technology
• conventional grind/polish/figure using abrasives
• ion-beam figuring available from two vendors
• Mirror surface metrology
• same as other space telescopes, e.g.
  cassegrains
• standard interferometer setups will do the job
  for SNAP
• no unusual accuracy drivers have been encountered

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Lightweight ULE Mirror Fab
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OTA THERMAL

• OPTICS Build,Test, Fly Warm like Hubble !

• KEY DESIGN FEATURES
• High Earth orbit (HEO) to minimize IR Earth-glow
  loads
• GaAs cell - OSR striping of the (hot) solar
  array panels
• Front surface heat rejection OK
• Optical Solar Reflectors are back silvered
  Quartz tiles (a 8, e 80)
• Low emissivity silvered mirrors
• Thermal Isolation mounting and MLI blanketing

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Stray Light Baffle Design
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Optical Telescope Assembly (OTA)
TMA-62 Optical Prescription
TMA-62 LIGHT PATH- primary- secondary-
folding flat- tertiary- Giga-Cam- Spectrometer

• add PASSIVE 140K CAMERA DEWAR

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Optical Telescope Assembly (OTA)

• add SECONDARY STRUCTURE low CTE - GFRP

• add OPTICAL BENCH low CTE - GFRP

• add OPTICS COFFIN BELOW low CTE - GFRP- WITH
  THREE STIFF METERING TUBES

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Optical Telescope Assembly (OTA)

• add STRAY LIGHT SECONDARY LAMPSHADE

• add STRAY LIGHT PRIMARY STOVEPIPE

• add PASSIVE GIGA-CAM RADIATOR

• enclose OPTICS COFFIN

• add CCD FRONT END ELECTRONICS

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Optical Telescope Assembly (OTA)

• add THERMALLY ISOLATED SOLAR ARRAY PANELS

• add STRAY LIGHT BAFFLE(s)

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Optical Telescope Assembly (OTA)

• add EXTERNAL MLI THERMAL BLANKETS

• add GENERIC SPACECRAFT

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NASA GSFC/IMDC Spacecaft Packaging
Secondary Mirror and Active Mount
Optical Bench
Primary Mirror
Solar Array Wrap around, body mounted 50 OSR
50 Cells
Thermal Radiator
Sub-system electronics
Detector/Camera Assembly
Propulsion Tanks
from GSFC - IMDC study
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IMDC Baseline Configuration

• ROM MASS 700 kg (instrument) 500 kg (bus) 250
  kg (hydrazine)
• ROM POWER 250 w (instrument) 250 w (bus)
• MOSTLY GENERIC SUBSYSYEMS
• EPS (electrical), CDH (command data handling),
  Thermal
• MISSION UNIQUE SUBSYSTEMS
• ACS (attitude control), SMS (structure
  mechanisms), Comm
• Evolving Bus Configuration Notes
• 3-axis stabilized, 4 Reaction wheels, tactical
  IRUs, no torquer bars
• Sun side w/ isolated body mounted solar arrays
  anti-sun side radiators
• Standard Hydrazine propulsion system, 100 kg to
  raise perigee, 10 kg/yr for station keeping,
  100 kg for Post Mission Disposal
• 2 Tbits SSR storage for imaging spectroscopy
  data. (Avg. data rate 52 Mbps lossless
  compression plus overhead).
• High speed Ka band down link near perigee _at_ 300
  Mbps to Northern Latitude ground station
  (Berkeley).

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ACS Driving Requirements

• Pointing Accuracy
• Yaw Pitch 1 arc-sec (1?)
• Boresight Roll 100 arc-sec (1?)
• Attitude Knowledge
• Yaw Pitch 0.02 arc-sec (1?)
• Boresight Roll 2 arc-sec (1?)
• Jitter/Stability -Stellar (over 200 sec)
• Yaw Pitch 0.02 arc-sec (1?)
• Boresight Roll 2 arc-sec (1?)
• Sun Avoidance - VERY RELIABLE SAFE HOLD !
• Earth Avoidance (mostly in orbit choice)
• Moon Avoidance (mostly in orbit choice)

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ACS Issues and Concerns from IMDC

• Jitter
• Isolate fundamental wheel frequency through
  detailed analysis from manufacturer
• Must tune wheel isolators - type, size and
  interface
• Flexible Mode Analysis
• Require extensive analysis to avoid
  control/structure resonance
• Solar Wind Tipping, given the Large Baffle Cp-Cg
  offset
• Smaller offset will minimize thruster firing
  frequency and propellant required for daily
  momentum unloading (est. 30 Nms wheels)
• 3? Pointing jitter values
• Use current Star tracker with a very accurate
  Kalman Filter
• Augment Star Tracker data with instrument data
  (on focal plane guider) for fine pointing
• May need to replace gyro with SKIRU-DII
• Use of Instrument guide data
• Possible mitigation by use of more sophisticated
  focal plane-sensors

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Launch Vehicle Study
Atlas-EPF Delta-III Sea Launch
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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 (elliptical 3 day -
  84 of orbit)
• Passive Cooling of Detectors
• Minimizes Stray Light

Chandra type highly elliptical orbit
Lunar Assist orbit
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Ground Station Coverage
Orbit perigee remains over Berkeley for 3 years
without adjustment. 6 hour ground pass over
Berkeley
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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
• Smaller than H.E.P. Vertex Detector (1 m2)

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Imaging Strategy
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Focal Plane Layout with Fixed Filters
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Survey Strategy
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Filter Wheel Concept
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LBNL CCD RD Status

• Goals already met
• Quantum efficiency from 350 nm to 1000 nm.
• Dark current
• Read noise
• CTE for variety of pixel sizes
• Proton radiation tolerance
• 60Co radiation tolerance
• Commercialization of fabrication process
• Active projects
• Intrapixel response
• Device thinning at commercial foundry
• Packaging for ground based observatories
• Multistage outputs
• Readout electronics specification and technology
  assessment

• Future work
• Backup plans for device thinning
• Further rad hardening by defect engineering
• SNAP design optimization
• Number of pixels
• Pixel size
• Thickness
• Output MOSFET structure
• SNAP specific packaging
• Design of integrated electronics running cold
  adjacent to CCDs

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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 SCP Group Supernova Spectrum at NOAO
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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) New
instrument at NOAO available in shared risk mode
using LBNL CCDs Multi-Aperture Red
Spectrometer (MARS) LBNL CCDs scheduled for 37
nights during 2002A (Jan July 2002)
See September 2001 newsletter at
http//www.noao.edu
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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 1.8?107
MeV/g (solar max).
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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Dark Current Degradation
Dark current is measured with one thousand or
more second exposures. The gaussian charge
distribution in the active region of the CCD is
compared with the gaussian change distribution in
the overscan region.
208K
Fit gives expected Si bandgap, so no new dark
current sources are developing. The plateau at
right is not identified yet, but could be surface
leakage currents.
158K
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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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NIR sensors

• HgCdTe
• Working with Rockwell
• Tracking developments within WFC3
• Dark current ok
• Read noise larger than expected
• QE being addressed in a new growth of crystals
• Future activities
• Acquiring our own RSC mux in May
• Acquiring our own RSC sensor in Summer 2002
• Explore alternative technologies there may be
  none.

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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 RD
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Diffraction Analysis
Throughput better than 90.6 (reflectance
diffractionedge)
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Technology readiness and issues

• NIR sensors
•        HgCdTe devices are begin developed for
  WFC3 and ESO with appropriate wavelength cutoff.
•        Read noise and QE not yet demonstrated.
•  
• 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
•         Direct deposition of filters onto
  sensors
•         Filter Wheel

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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.
•        Ka-band telemetry, and long ground
  contacts 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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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 out on CDROM
• International collaboration is growing, currently
  15 institutions.
• 18 talk 7 posters at recent AAS meeting

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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) J.
Musser, S. Mufson (Indiana) 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 Reviews/Studies/Milestones
Mar 2000 SAGENAP-1 Sep 2000 NASA Structure and
Evolution of the Universe (SEU) Dec 2000 NAS/NRC
Committee on Astronomy and Astrophysics Jan
2001 DOE-HEP RD Mar 2001 DOE HEPAP Jun
2001 NASA Integrated Mission Design Center July
2001 NAS/NRC Committee on Physics of the
Universe Nov 2001 CNES (France Space Agency) Dec
2001 NASA/SEU Strategic Planning Panel Dec
2001 NASA Instrument Synthesis Analysis Lab Mar
2002 SAGENAP-2 NOW ------------------------------
------------------------------ July
2002 DOE/SC-CMSD RD (Lehman) Sept 2002 NASA/SEU
Releases Roadmap Oct 2002 CNES Review
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Roadmap for Particle Physics

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

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A Resource for the Science Community
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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 will provide space observations of thousands
of supernovae needed to characterize the dark
energy accelerating the expansion of the
universe and may lead to a fuller understanding
of gravity space-time.