SNAP OCU ProjectSLAC EPAC Meeting Nov , The Supernova / Acceleration Probe (SNAP) Presentation to the Experimental Program Advisory Committee at SLAC. November 14, 2003

SNAP OCU ProjectSLAC EPAC Meeting Nov , SLAC Involvement in SNAP With the creation of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), experiments addressing issues at the interface between particle physics and astrophysics will play an increasingly prominent role in the SLAC research program. Of particular interest will be the “dark sector”, the nature of dark energy and dark matter, and the roles they play in the evolution of the Universe. Technology development in connection with the SNAP mission has been a cornerstone of the DOE-OS program addressing the mystery of dark energy. We believe that SLAC can and should play a prominent and important role in this mission if it goes forward as currently planned.

SNAP OCU ProjectSLAC EPAC Meeting Nov , SLAC Involvement in SNAP The first discussions about SLAC involvement with the leadership of the SNAP collaboration (S. Perlmutter, M. Levi) were held in February At that time, a potential hardware role in the mission associated with the design and development of the Observatory Control Unit (OCU) was identified. We also highlighted our science interest in the use of SNAP data for strong lensing investigations. A letter of application for institutional membership in the SNAP collaboration on behalf of Stanford and SLAC was submitted in August That application is currently still under discussion, but the preliminary responses have been very positive.

SNAP OCU ProjectSLAC EPAC Meeting Nov , Outline of Presentations The Science of Dark Energy and the Design of the SNAP Mission – E. Linder Strong Lensing Investigations with SNAP – R. Blandford The Observatory Control Unit – M. Huffer Concluding Comments – S. Kahn

SNAP OCU ProjectSLAC EPAC Meeting Nov , National priorities HEPAP: Scientic potential and facility need – absolutely central Secretary of Energy (11/10/03) – SNAP has very high priority (#3 on list)

SNAP OCU ProjectSLAC EPAC Meeting Nov , SLAC and SNAP SLAC/Stanford major strengths include: Strong Gravitational Lensing – Blandford Dark matter / dark energy / cosmology

SNAP OCU ProjectSLAC EPAC Meeting Nov , SLAC and SNAP Observatory control unit expertise – Huffer Technical experience and development resources

SNAP OCU ProjectSLAC EPAC Meeting Nov , SLAC and SNAP SLAC/Stanford major strengths include: Space mission experience – Kahn Extensive design and implementation Knowledge of NASA culture Experience with joint NASA-DOE projects from GLAST Collaborative agency working relationships Dark Energy and High Energy Physics – Existing and ongoing SNAP theory collaboration by Kallosh & Linde

SNAP OCU ProjectSLAC EPAC Meeting Nov , Revolutions in Physics Lord Kelvin (1900): Two clouds on the horizon The horizon is 95% cloudy!

SNAP OCU ProjectSLAC EPAC Meeting Nov , Mapping our history The subtle slowing down and speeding up of the expansion, of distances with time: a(t), maps out cosmic history like tree rings map out the Earth’s climate history.

SNAP OCU ProjectSLAC EPAC Meeting Nov , Accelerating universe

SNAP OCU ProjectSLAC EPAC Meeting Nov , What is dark energy? 70-75% of the energy density of the universe Accelerating the expansion, like inflation Determining the fate of the universe But what is it? Einstein’s cosmological constant  ? Problems: fine tuning and coincidence Matter Dark energy Today Size=2 Size=4Size=1/2Size=1/4

SNAP OCU ProjectSLAC EPAC Meeting Nov , Dark energy – discovery! accelerating decelerating  > 0 at 99% confidence

SNAP OCU ProjectSLAC EPAC Meeting Nov , Next generation Supernova/Acceleration Probe: SNAP Dedicated dark energy probe

SNAP OCU ProjectSLAC EPAC Meeting Nov , Mission design ~2 m aperture telescope Reach very distant SNe. 1 degree mosaic camera, ½ billion pixels Efficiently study large numbers of SNe – 1.7  m spectrograph Analyze in detail each SN. Dedicated instrument designed to repeatedly observe an area of sky. Essentially no moving parts. 3+ year operation for experiment (lifetime open ended).

SNAP OCU ProjectSLAC EPAC Meeting Nov , Mission design Spectrograph Guider CCD’s HgCdTe BITE Photometry: half-billion pixel mosaic camera, high- resistivity, rad-tolerant p- type CCDs (  m) and, HgCdTe arrays (  m). Field of View Optical ( 36 CCD’s) = 0.34 sq. deg. Four filters on each 10.5  m pixel CCD detector Field of View IR (36 HgCdTe’s) = 0.34 sq. deg. One filter on each 18  m pixel HgCdTe detector

SNAP OCU ProjectSLAC EPAC Meeting Nov , Mission design Input port Slicer Prism BK7 Prism CaF 2 NIR detector Vis Detector Integral field optical and IR spectroscopy:  m, 3”x6” FOV, low resolution, high throughput.

SNAP OCU ProjectSLAC EPAC Meeting Nov , Mission design 15 sq.deg. Deep Survey ~300 sq.deg. Wide Survey 9 filters m AB =27.7 every 4 days 120 epochs coadd AB=30.3 (31) GOODS HDF 9 filters m AB =28.1

SNAP OCU ProjectSLAC EPAC Meeting Nov , SN control of systematics Images Spectra Redshift & SN Properties Lightcurve & Peak Brightness dataanalysisphysics  M and   Dark Energy Properties Each supernova sends a rich stream of information about its physical state.

SNAP OCU ProjectSLAC EPAC Meeting Nov , High energy physics

SNAP OCU ProjectSLAC EPAC Meeting Nov , Complementarity Next generation data will map the acceleration of the universe so precisely that it can probe: The nature of dark energy w(z) Structure of the vacuum w´(z)  V´ / V(  ) High energy physics

SNAP OCU ProjectSLAC EPAC Meeting Nov , Fate of the universe a t w a =2w´ w0w0 t doom =  (  ) t doom > 29 Gyr [95% SNAP] t doom > 35 Gyr [95%SNAP+CMB] t doom > 40 Gyr [95% SN+CMB+WL] Kallosh, Kratochvil, Linde, Linder, & Shmakova JCAP 2003; astro-ph/ First and simplest DE model: linear potential (Linde 1986) leads to collapsing universe. Such models look like  in the past, but develop a strong w´.

SNAP OCU ProjectSLAC EPAC Meeting Nov , SNAP Cosmology and Physics SN Ia Weak Lensing SN II Strong Lensing Wide, Deep and Colorful 9000 times the area of Hubble Deep Field 10 billion years of detailed history 10 8 galaxies, 10 5 lenses, 9 wavelength bands

SNAP OCU ProjectSLAC EPAC Meeting Nov , Strong Lensing Program Multiple imaging by galaxies, groups and clusters Ancillary program - complementary to: –Supernova cosmography –Weak lensing study of large scale structure –Galaxy-galaxy lensing study of galaxy halos Telescope nearly ideal for strong lensing because of –9 filters –0.1(0.05)” pixels –4 day cadence –Deep (15 sq deg) and Wide (300 sq deg) surveys Lensing rate => ~300,000 “events” –Quantitative, identification pipeline (cf CLASS) –Emphasize standard elliptical galaxy “scattering” with 0.5<z<1 Complementary to LSST and Square Kilometer Array

SNAP OCU ProjectSLAC EPAC Meeting Nov , Scientific Goals Source Population –Study the faintest galaxies – building blocks of normal galaxies redshift distribution luminosities star formation rates etc –AGN microlensing –Rare high magnification events Lens Population –Galaxy substructure out to R ~ 10kpc –Cluster substructure Cosmography Propagation Effects –Time delays Þ small scale dark matter distribution –Quasar absorption lines etc

SNAP OCU ProjectSLAC EPAC Meeting Nov , Source Population Understand empirically where when and how small galaxies merge to form larger galaxies –~2 x 10 5 isolated elliptical galaxy lenses on deep field –total cross section ~ 0.02 sq deg –10000 (30000) clean lenses on deep field to I AB ~ 28 (30) –Use lens colors to measure lens distance –Use color maps to separate source from lens, remove dust –Use Einstein ring radius to measure source distance 100 times too faint for spectroscopy –Infer source properties statistically and test CDM theory

SNAP OCU ProjectSLAC EPAC Meeting Nov , Simulation Massive elliptical lens, I=21.5, at z d =0.7 Faint blue galaxy, B=29, at higher redshift Fit 9 images with two “spectral” models to reconstruct lensed source Infer z s from Einstein ring radius Input images (true color, different intensity scales!):

SNAP OCU ProjectSLAC EPAC Meeting Nov , Simulation Simulated SNAP images: 0.12” pixels, 0.14” FWHM PSF, no dither Deep survey, 1.5 mag fainter than HDF B, V and I-bands shown for illustration: B (440nm) V (582nm) I (770nm)

SNAP OCU ProjectSLAC EPAC Meeting Nov , Simulation Optimal weighting of 9 filters' images allows lens and source components to be separated

SNAP OCU ProjectSLAC EPAC Meeting Nov , Simulation Measuring source redshift with: Einstein ring radius to ±1/4 pixel Lens photo-z to ±0.02 Lens velocity dispersion to ±10 km s -1 => Find 1.2 < z s < 1.5 (1  ) (true value = 1.3) Lensing provides vital additional information to photo-z at high redshift

SNAP OCU ProjectSLAC EPAC Meeting Nov , Scientific Goals Source Population –Study the faintest galaxies – building blocks of normal galaxies redshift distribution luminosities star formation rates etc –AGN microlensing –Rare high magnification events Lens Population –Galaxy substructure out to R ~ 10kpc –Cluster substructure Cosmography Propagation Effects –Time delays => small scale dark matter distribution –Quasar absorption lines etc

SNAP OCU ProjectSLAC EPAC Meeting Nov , Cluster Arc Images Multi-colour, high resolution surveying and imaging: RCS0224 (CFHT): Cl0024 (HST):

SNAP OCU ProjectSLAC EPAC Meeting Nov , Scientific Goals Source Population –Study the faintest galaxies – building blocks of normal galaxies redshift distribution luminosities star formation rates etc –AGN microlensing –Rare high magnification events Lens Population –Galaxy substructure out to R ~ 10kpc –Cluster substructure Cosmography Propagation Effects –Time delays => small scale dark matter distribution –Quasar absorption lines etc

SNAP OCU ProjectSLAC EPAC Meeting Nov , Time delays Lens time delays measure the Hubble constant, age of universe –Accuracy limited by lens model Currently lens determinations are competitive with traditional astronomical methods By the time SNAP is launched this will probably be settled Small scale structure along the line of sight causes deviation from apparent pure Hubble expansion Can measure statistically and check CDM predictions

SNAP OCU ProjectSLAC EPAC Meeting Nov , B delays Time delays of 1-2 months, measured to precision of 1-2 days... H 0 = 75±6 km s -1 Mpc

SNAP OCU ProjectSLAC EPAC Meeting Nov , Research underway and planned Simulations using Hubble images and projected SNAP resolution (including dithering) and sky/detector noise (Marshall) –Establish procedure for data analysis pipeline to find clean and dirty lenses –Establish procedure for refining elliptical potentials –Use Hubble Ultradeep Field to describe source population –Estimate accuracy for determining source properties Work with weak lensing group to develop strategy to combine strong and weak lensing studies of galaxy structure (Koopmans) Study rare, higher order catastrophes as (Baltz): –highly magnifying telescopes –probes of granularity of dark matter –surveying instruments

SNAP OCU ProjectSLAC EPAC Meeting Nov , What instrument deliverable does SLAC propose? The Observatory Control Unit (OCU) Both a hardware (electronics) and software system Supervises and manages (on-station) observatory operation

SNAP OCU ProjectSLAC EPAC Meeting Nov , Electrical Block Diagram Filter Wheel Mass store Primary OCU Redundant Mass store Redundant K a xmt Primary K a xmt Redundant Power CD&H ACS S-band Transponder Primary S-band Transponder Redundant Focal Plane Assembly OCU Primary Shutter Focus Thermal Power 1553 Bus After H. Heetderks 200 GBytes Spectrograph

SNAP OCU ProjectSLAC EPAC Meeting Nov , Functional requirements Executes instrument’s observation plan –Transfer pointing requests to ACS –Controls CCD array parameterization and readout Science data management –Manage mass store –Route real-time and stored data to downlink transmitters Mechanism management, control, and operation –Telescope cover, optical shutter, stepper coils, etc… Power distribution and management

SNAP OCU ProjectSLAC EPAC Meeting Nov , Functional requirements… Thermal management –Manage heater elements Primary, Secondary mirrors, telescope structure, etc… –Survival heaters –Monitor and trend temperatures –Housekeeping »Monitor instrument environment »Packetize and route as telemetry Data (Event) readout and acquisition Command processing and distribution –Command database definition and maintenance –Decoding, distribution, and execution

SNAP OCU ProjectSLAC EPAC Meeting Nov , What is the scope of the OCU within the observatory? OCU performs electronic supervision of entire instrument Encompasses design, specification and implementation of… –The bulk of instrument’s digital electronics –A modest amount of analog electronics –The entire Flight Software System Executes the science mission … Natural consequence is significant role in defining…. –instrument architecture –translation of science objectives to operational program

SNAP OCU ProjectSLAC EPAC Meeting Nov , How does it fit within SLAC’s current program? OCU development requires a unique blend of skills… –Data Acquisition –Detector Monitoring and Control SLAC has extensive experience in these areas… –Successful, lead role within 2 major HEP experiments: SLD BaBar SLAC has space heritage… –Lead role in both Electronics and Flight Software for GLAST –Demonstrated collaboration with NASA based labs SLAC has long history of successful collaboration with LBL –We enjoy a physical proximity… Phases well with GLAST and BaBar program –BaBar no longer in development –GLAST moving out of design/development stage

SNAP OCU ProjectSLAC EPAC Meeting Nov , Concluding Comments In October 2003, NASA and DOE announced the results of a year-long discussion regarding the possibility for cooperation in a space-based mission devoted to exploring the nature of dark energy. The plan involves the development of a Joint Dark Energy Mission (JDEM). NASA/DOE will issue a single AO soliciting a dark energy science investigation requiring a space-based observatory. The science investigation will be PI-led and will be selected via open competition. The present schedule shows selection of the science investigation one year after the onset of new funding, leading to launch of the mission eight years later.

SNAP OCU ProjectSLAC EPAC Meeting Nov , Organization of JDEM

SNAP OCU ProjectSLAC EPAC Meeting Nov , Concluding Comments The proposed plan is for the SLAC team to participate in an LBNL-led proposal for a JDEM science investigation based on the SNAP concept. SLAC and LBNL have a long history of close cooperation in high energy physics experiments. The differences in culture between the NASA and DOE communities will introduce some challenges in making the JDEM concept work. SLAC’s extensive experience working with both agencies in the GLAST program should prove to be a key asset to the SNAP collaboration.