download PDF - KICP - University of Chicago

Outline●●●●●●ScienceMissionTelescope●●Mechanical StructuresMirrors, etc…Spacecraft / OrbitInstrumentsGigaCAMCCD TechnologyNIR TechnologySpectrographStatus

The Accelerating Universe: Science’sBreakthrough 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:

How Can We Address These New Questions?• 3 rd generation experiment• Need 1000’s of SNe to improvestatistical/systematic accuracy.• The most demanding SNAPrequirements are devoted toeliminating and controlling allsystematic uncertainties.— All data taken with singlededicated, instrument.— Above atmospheric interference— Imaging for discovery &photometry— Spectroscopy to classify Type Iasupernovae and for redshift

What makes the SN measurement special?Control of systematic uncertaintiesAt every moment in the explosion event, each individual supernova is “sending” us a rich streamof information about its internal physical state.Lightcurve & Peak BrightnessImagesRedshift & SN PropertiesΩ M and Ω ΛDark Energy Propertiespectradata analysis physics

Supernova SystematicsModels are used to indicate which observables are sensitive to physicalconditions. These can be used to create subsets:Observables•Ni 56 mass from spectral ratios•Metallicity from UV continuum•Kinetic energy from Line RatiosLight CurveObservableStretchRise TimePeak to tail ratioRequirement form < 0.021%0.3 days0.05 mag

From Science Goalsto Project DesignScience• Measure Ω M and Λ• Measure w and w (z)Statistical Requirements• Sufficient (~2000) numbers of SNe Ia• …distributed in redshift• …out to z < 1.7Systematics RequirementsIdentified and proposed systematics:• Measurements to eliminate / boundeach one to +/–0.02 magData Set Requirements• Discoveries 3.8 mag before max• Spectroscopy with S/N=10 at 15 Å bins• Near-IR spectroscopy to 1.7 µm•Satellite / Instrumentation Requirements• ~2-meter mirror• 1-square degree imager• Spectrograph(0.35 µm to 1.7 µm)Derived requirements:• High Earth orbit• ~50 Mb/sec bandwidth•

Mission Requirements●Minimum data set criteria:— Discovery within 2 days (rest frame) of explosion (peak + 3.8magnitude),— 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 multiplexadvantage -- *******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.

Advantages of Space

Mission DesignSNAP 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 1°x 1° billion pixel mosaic camera, high-resistivity, radtolerantp-type CCDs and, HgCdTe arrays. (0.35-1.7 µm)— Integral field optical and IR spectroscopy: 0.35-1.7 µm, 2”x2” FOV

Observatory ParametersPrimary Mirrordiameter= 200 cmSecondary Mirrordiameter= 42 cmTertiary Mirrordiameter=64 cmAperture~ 2.0 meterField-of-view 1° x 1°Optical resolution diffraction-limited at I-bandWavelength 350nm - 1700nmSolar avoidance 70°Temperature Telescope 270-290K (below thermalbackground)Fields of study North and South Ecliptic CapsImage Stabilization Focal Plane Feedback to ACSPlate Scale ~ 0.1 arcsec/pixelOptical Solution:Edge Ray Spot Diagram(box = 1 pixel):

Optical Train

Telescope AssemblyMovie courtesy of Hytec

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 cellsDesign with locally thicker web platesStandard web thickness = 5 mm (orange)Thickened plates = 10 mm (red)Initial design for primary mirrorFundamental mode: 360 Hz1g front face ripple on perfectback-side supportP-P Z deflection = 0.018 µmDeformations of mirror top face underpseudo-static launch loads: peak

Spacecraft from Goddard/Integrated MissionDesign Center Study

SNAP Assembly

Launch Vehicle Study

Launch Vehicle StudyAtlas-EPF Delta-III Sea Launch

Orbit Trade-StudyFeasibility & Trade-StudyOrbit Radiation Thermal Telemetry Launch Stray Light RankHEO/Very Good Passive Med. BW Fair Dark 1Lunar/AXAFHEO / L2 Very Good Passive Low BW Fair Dark 2HEO / GEO Poor Passive 24 hr Fair Dark 3LEO / Equator Lowest Dose Mechanical High BW Fair Earth Shine 4LEO / Polar High at Poles Mechanical High BW Excellent Earth Shine 5LEO / 28.5 Lowest Dose Mechanical High BW Excellent Earth Shine 6

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 LightChandra type highly elliptical orbitLunar Assist orbit

Ground Station Coverage

Mission Operations/Space Sciences LaboratoryMission Operations Center (MOC) at SpaceSciences Using Berkeley Ground Station• Fully Automated System TracksMultiple Spacecraft• 11 meter dish at Space SciencesOperationsLaboratoryComponents• Mission Science Operations Center (SOC)• Science closely Operations tied to MOCCenter• 11-meter S-Band Antenna withX-band capabilityScience Operations at LBNL NERSC• High Speed Communications to NASAGround NetworkOperations • Network are Based Security on a Orbital Period• Autonomous Operationsof theSpacecraft Pass SupportsOrbit Determination & Tracking• Coincident Science Operations CenterEmergency Response SystemReview of Data with Build of Target List• Upload Instrument Configuration forNext PeriodSelf Checking

Camera AssemblyShieldGigaCamHeat radiator

GigaCAMGigaCAM, 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 m 2 )●Approx. 5 times size of FAME (MiDEX)

IR Enhanced Camerawith Fixed Filter Set3 IR Filters8 Visible Filters

Step and StareDrag star through multiple fixed length exposures in multiple filters

3-month rotation1 O X 10 OAP FIELDUNITCELLFPAGROWTHQ1Q2Q4Q3

Focal Plane Layout with Fixed Filters

Number of SNe per 0.03 z after two years.# SNe/0.0311010090807060504030201000.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00z

LBNL/CCD 2k x 4k94 x 418612 µmUSAF test pattern.2K x 4Kx 4kµm78 x 478410.5 µmIndustrialized wafer

LBNL/CCD 2k x 2k resultsImage: 200 x 200 15 µm LBNL CCD in Lick Nickel 1m.Spectrum: 800 x 1980 15 µm LBNL CCD in NOAO KPNO spectrograph.Instrument at NOAO KPNO 2 nd semester 2001 (http://www.noao.edu)

LBNL CCD’s at NOAOScience studies to date at NOAO usingLBNL CCD’s:1) Near-earth asteroids2) Seyfert galaxy black holes3) LNBL Supernova cosmologyCover picture taken at WIYN 3.5mwith LBNL 2048 x 2048 CCD(Dumbbell Nebula, NGC 6853)Blue is H-alphaGreen is SIII 9532ÅRed is HeII 10124Å.See September 2001 newsletter at http://www.noao.edu

CCD Noise Performance BreakthroughNoise vs Sample Timefor LBNL CCD’sReadout Noise (electrons)Sample time (µsec)New design

Radiation Damage: Comparison to Conventional CCDs[2] T. Hardy, R. Murowinski, M.J. Deen, “Charge transfer efficiency in protonCTE is measured using the 55 Fe X-ray method at 128 K.13 MeV proton irradiation at LBNL 88” CyclotronDegradation is about 1×10 -13 g/MeV.SNAP will be exposed to about 1.5×10 6 MeV/g.CTE1.000000.999900.999800.999700.999600.999500.999400.999300.999200.999100.99900LBNL CCDLBNL Notch CCDMarconi [1]Tektronix [2]0 200 400 600 800 1000 1200 1400 1600Dose (10 6 MeV/g)[1]L.Cawley, C.Hanley, “WFC3 Detector Characterization Report #1: CCD44Radiation Test Results,” Space Telescope Science Institute Instrument ScienceReport WFC3 2000-05, Oct.2000

Mosaic PackagingWith precision CCD modules, precision baseplate, andadequate clearances designed in, the focal plane assembleis “plug and play.”140 K plate attachedto space radiator.

GigaCAM = Vertex Detector●●●●Lots of siliconLots of pixelsCustom ASIC’sRadiation tolerance, cooling, mechanical stability

Shortwave HdCdTe Development• Hubble Space Telescope Wide FieldCamera 3• WFC-3 replaces WFPC-2• CCDs & IR HgCdTe array• Ready for flight July 2003• 1.7 µm cut off• 18 µm pixel• 1024 x 1024 format• Hawaii-1R MUX• Dark current consistent withthermoelectric cooling• < 0.5 e/s at 150 K• ~0.02 e-/s at 140 K• Expected QE ~60% 0.9-1.7 µm• Individual diodes show good QENIC-2WFC-3 IRTemperature detector bias variance method modified standard methode/s e/s e/s140K -0.02 0.04+/--- 0.019+/-0.003 0.017+/-0.00004140K -0.25 0.045+/-0.01 0.1+/-0.2 0.02+/-0.012140K -0.5 0.039+/-0.007 0.045+/-0.01 0.043+/-0.008reference pixel mtehod150K -0.02 0.19+/-0.05 0.2+/-0.02 0.22+/-0.037150K -0.25 0.24+/-0.05 0.29+/-0.06 0.31+/-0.0077150K -0.5 0.30+/-0.02 0.53+/-0.03 0.47+/-0.0012

Integral Field Unit Spectrograph DesignSpectrograph architecture Integral field spectrographWavelength coverage 350-1700nmSpatial resolution of slicer 0.12 arcsecField-of-View 2” x 2”Detector Architecture 1k x 1k, HgCdTeDetector Array Temperature 130 - 140 KThroughput 35%Read Noise4 e- (multiple samples)Dark Current1 e-/min/pixelelescope focal plane imaged by theore-optics on the slicer mirror1x2 proportionedimageSlices imaged by the pupilmirrors on the slit mirrorsSNAP Design:CameraDetectorSLIT MIRRORSEntrance of thespectrographImaged thereICER MIRRORPUPIL MIRRORSPrismTelescope exit pupilCollimatorSquare fieldIn the telescopefocal planeFore-optics(anamorphosis)Slit Plane

Mirror Slicer StackE. Prieto, (LAM)

Diffraction Analysisλ = 0.4 µm λ = 0.8 µm λ = 1.4 µm λ = 1.7 µm% energy of the PSF on one centered 89 % 80 % 59 % 55 %slice% energy at the pupil mirror 99.8 % 99.7 % 99.2 % 98.7 %% energy on the 2 attributed CCD lines 98.2 % 96 % 93 % 91 %% energy crosstalk 0 % 0 % 0 % 0 %λ = 0.8 µm% energy of the PSF on one centered 80 %slice% energy at the pupil mirror 99.7 %% energy on the 2 attributed CCD lines 96 %% energy crosstalk 0 %PSF sampling with a sliceAt pupil mirrorThroughput: better than 90.6%(reflectance + diffraction+edge)At slit mirrorDetector sampling

ThroughputFore optics: 3 mirrors 0.98 3 = 0.941Slicer unit: 3 mirrors + ... 0.90Spectrograph: 2 Mirrors 0.98 2 = 0.96Folding Mirrors : 2 0.98 2 = 0.96Prism (2 interface + internal) 0.96 2 x 0.9 = 0.83Telescope: 4 Mirrors 0.98 4 = 0.92Detector: better than 0.600.640.600.36Worst CaseE. Prieto, (LAM)

Technology readiness and issuesNIR sensors• HgCdTe stripped devices are begin developed for NGST and are idealin our spectrograph.• "Conventional" devices with appropriate wavelength cutoff are beingdeveloped for WFC3 and ESO.CCDs• We have demonstrated radiation hardiness that is sufficient for theSNAP mission• Extrapolation of earlier measurements of diffusion's effect on PSFindicates we can get to the sub 4 micron level. Needs demonstration.• Industrialization of CCD fabrication has produced useful devices needto 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.

Technology readiness and issuesOn-board data handling• We have opted to send all data to ground to simplify the flight hardwareand 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 controlsystems may have sufficient pointing accuracy so that nothing specialneeds be done with the sensors.Telescope• Thermal, stray light, mechanical control/alignmentSoftware• Data analysis pipeline architecture

Wide field survey in spaceKey Cosmological Studies•Type Ia supernova calibrated candle: Main goal•Type II supernova expanding photosphere:Hubble diagram to z=1 and beyond•Weak lensing:Direct measurements of density vs zMass selected cluster survey vs zConstraints on SNe magnification•Strong lensing statistics: Ω Λ10x gains over ground based opticalresolution, IR channels + depth•Galaxy clustering

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 catalogsEvolution of galaxy-mass correlation functionand its scaling relationsMaps of mass in filaments

Wide-field SurveyPotential One Year Wide Field SurveyBand 30,000 deg 2 3,000 deg 2 300 deg 2H' 26.4 27.85 29.25J 26.6 28.1 29.4Z 27.35 28.85 30.2I 27.4 28.9 30.25R 27.55 29.1 30.4V 27.25 28.85 30.25B 27.65 29.3 30.65Magnitudes given are for S/N>=5 detections for 95% ofpoint sources. (Assumes filter wheel)All magnitudes are AB system.(G. Bernstein)

Status• Dark Energy a subject of the recent National Academies of Science Committee onthe 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 technologytallpoles• Have removed most moving parts, unneeded subsystems, and high tech. Singleintegrated focal plane for CCD, HgCdTe, & Spectrograph. Room Temp Telescope.• International collaboration is growing, currently 15 institutions.• 18 talk & 7 posters at upcoming AAS meeting

Roadmap for Particle PhysicsTimelines for Selected Roadmap Projects. Approximate decision pointsare marked in black.R&D is marked in yellow,construction in green,andoperation in blue.

SNAP at the American AstronomicalSociety Meeting, Jan. 2002Oral Session 111. Science with Wide Field Imaging in Space:The Astronomical Potential of Wide-field Imaging from SpaceGalaxy Evolution: HST ACS Surveys and Beyond to SNAPStudying Active Galactic Nuclei with SNAPDistant Galaxies with Wide-Field ImagersAngular Clustering and the Role of Photometric RedshiftsSNAP and Galactic StructureStar Formation and Starburst Galaxies in the InfraredWide Field Imagers in Space and the Cluster Forbidden ZoneAn Outer Solar System Survey Using SNAPOral Session 116. Cosmology with SNAP:Dark Energy or WorseThe Primary Science Mission of SNAPThe Supernova Acceleration Probe: mission design and core surveySensitivities for Future Space- and Ground-based SurveysConstraining the Properties of Dark Energy using SNAPType Ia Supernovae as Distance Indicators for CosmologyWeak Gravitational Lensing with SNAPStrong Gravitational Lensing with SNAPStrong lensing of supernovaePoster Session 64. Overview of The Supernova/Acceleration Probe:Supernova / Acceleration Probe: An OverviewThe SNAP TelescopeSNAP: An Integral Field Spectrograph for Supernova IdentificationSupernova / Acceleration Probe: GigaCAM - A Billion Pixel ImagerSupernova / Acceleration Probe: Cosmology with Type Ia SupernovaeSupernova / Acceleration Probe: Education and OutreachS. Beckwith (Space Telescope Science Institute)G. Illingworth (UCO/Lick, University of California)P.S. Osmer (OSU), P.B. Hall (Princeton/Catolica)K. M. Lanzetta (State University of NY at Stony Brook)A. Conti, A. Connolly (University of Pittsburgh)I. N. Reid (STScI)D. Calzetti (STScI)M. E. Donahue (STScI)H.F. Levison, J.W. Parker (SwRI), B.G. Marsden (CfA)S. Carroll (University of Chicago)S. Perlmutter (Lawrence Berkeley National Laboratory)T. A. McKay (University of MichiganG. M. Bernstein (Univ. of Michigan)D. Huterer (Case Western Reserve University)D. Branch (U. of Oklahoma)A. Refregier (IoA, Cambridge), Richard Ellis (Caltech)R. D. Blandford, L. V. E. Koopmans, (Caltech)D.E. Holz (ITP, UCSB)M. Levi (LBNL)M. Lampton (UCB)R. Malina (LAMarseille,INSU), A. Ealet (CPPM)C. Bebek (LBNL)A. Kim (LBNL)S. Deustua (LBNL)

ConclusionSNAP:—Space observations of thousands of supernovae will provide the vitalbreakthrough in precision cosmology to characterize the dark energy