1. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 2003 1 The Supernova / Acceleration Probe (SNAP) Presentation to the Experimental Program Advisory Committee at SLAC. November 14, 2003

2. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20032 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.

3. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20033 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 2003. 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 2003. That application is currently still under discussion, but the preliminary responses have been very positive.

4. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20034 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

5. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20035 National priorities HEPAP: Scientic potential and facility need – absolutely central Secretary of Energy (11/10/03) – SNAP has very high priority (#3 on list)

6. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20036 SLAC and SNAP SLAC/Stanford major strengths include: Strong Gravitational Lensing – Blandford Dark matter / dark energy / cosmology

7. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20037 SLAC and SNAP Observatory control unit expertise – Huffer Technical experience and development resources

8. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20038 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

9. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 20039 Revolutions in Physics Lord Kelvin (1900): Two clouds on the horizon The horizon is 95% cloudy!

10. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200310 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.

11. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200311 Accelerating universe

12. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200312 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

13. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200313 Dark energy – discovery! accelerating decelerating  > 0 at 99% confidence

14. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200314 Next generation Supernova/Acceleration Probe: SNAP Dedicated dark energy probe

15. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200315 Mission design ~2 m aperture telescope Reach very distant SNe. 1 degree mosaic camera, ½ billion pixels Efficiently study large numbers of SNe. 0.35 – 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).

16. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200316 Mission design Spectrograph Guider CCD’s HgCdTe BITE Photometry: half-billion pixel mosaic camera, high- resistivity, rad-tolerant p- type CCDs (0.35-1.0  m) and, HgCdTe arrays (0.9- 1.7  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

17. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200317 Mission design Input port Slicer Prism BK7 Prism CaF 2 NIR detector Vis Detector Integral field optical and IR spectroscopy: 0.35-1.7  m, 3”x6” FOV, low resolution, high throughput.

18. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200318 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

19. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200319 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.

20. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200320 High energy physics

21. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200321 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

22. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200322 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/0307185 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´.

23. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200323 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

24. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200324 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 0.001-0.002 => ~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

25. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200325 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

26. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200326 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

27. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200327 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!):

28. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200328 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)

29. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200329 Simulation Optimal weighting of 9 filters' images allows lens and source components to be separated

30. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200330 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

31. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200331 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

32. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200332 Cluster Arc Images Multi-colour, high resolution surveying and imaging: RCS0224 (CFHT): Cl0024 (HST):

33. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200333 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

34. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200334 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

35. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200335 B1608+656 delays Time delays of 1-2 months, measured to precision of 1-2 days... H 0 = 75±6 km s -1 Mpc

36. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200336 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

37. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200337 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

38. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200338 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

39. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200339 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

40. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200340 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

41. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200341 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

42. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200342 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

43. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200343 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.

44. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200344 Organization of JDEM

45. SNAP OCU ProjectSLAC EPAC Meeting Nov. 14-15, 200345 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.