Mission Overview

1. Mission Overview Talk Outline: • Introduction • Mission Overview & Requirements • Observing Plan • Orbit/Telemetry • Launch Vehicle • R&D Strategy • Prelim. Project Organization • Prelim. Project Schedule & Costs • Summary • SuperNova /Acceleration Probe • R&D Plan Presented by: Michael Levi July 9, 2002

2. Project History and Status • Project conceived of in March 1999. • Sizable active collaboration now exists. • Project is being developed as a multi-agency partnership: • Team that produced current results was supported by DOE and NASA. • Science review by SAGENAP of 260 page proposal March 2000: strong endorsement of science and recommendation for study funding. • DOE support commenced after SAGENAP • Endorsement by HEPAP subpanel for development of cost, schedule, R&D • Call by NAS Turner panel for “a wide-field telescope in space” • NASA/SEU Roadmap now has a SNAP-like mission • Currently in pre-conceptual design phase (equivalent to NASA pre-phase A) to develop key technologies. • Cost to be determined by study phase in FY03 & 04

3. Active Members of SNAP Collaboration G. Aldering, C. Bebek, J. Bercovitz, W. Carithers, C. Day, S. Deustua*, D. Groom, S. Holland, D. Huterer*, A. Karcher, A. Kim, W. Kolbe, R. Lafever, M. Levi, E. Linder, S. Loken, P. Nugent, H. Oluseyi, S. Perlmutter, K. Robinson, A. Spadafora (Lawrence Berkeley National Laboratory) E. Commins, G. Goldhaber, S. Harris, P. Harvey, H. Heetderks, M. Lampton, J. Lamoureux, D. Pankow, C. Pennypacker, R. Pratt, M. Sholl, G. F. Smoot (UC Berkeley) C. Akerlof, G. Bernstein*, D. Levin, T. McKay, S. McKee, M. Schubnell, G. Tarle , A. Tomasch (U. Michigan) R. Ellis, R. Massey*, J. Rhodes, A. Refregier* (CalTech) N. Mostek, J. Musser, S. Mufson (Indiana) A. Fruchter (STScI) P. Astier, E. Barrelet, A. Bonnissent, A. Ealet, J-F. Genat, R. Malina, R.Pain, E. Prieto, G. Smadja, D. Vincent (France: IN2P3/INSU/LAM) R. Amanullah, L. Bergström, M. Eriksson, A. Goobar, E. Mörtsell (U. Stockholm) A. Mourao (Inst. Superior Tecnico,Lisbon)

4. Mission Requirements • Observe over 2000 type Ia Supernova • Quantity: Field-of-View one degree • Quality: 2% cross-wavelength calibration, from 400 - 1700 nm • Distribution: Ability to accurately study supernovae as far away as z<1.7 • Need consistent uniform data set where selection criteria can be applied and systematic sources can be analyzed and factored. • Minimum data set criteria: 1) discovery within 2 days (rest frame) of explosion, 2) 10 high S/N photometry points on lightcurve, 3) high quality peak spectrophotometry

5. Mission Design • How to obtain both data quantity AND data quality? • Batch processing techniques with wide field -- large multiplex advantage, • Wide field imager sensitive to 30th magnitude • No trigger • Mostly preprogrammed observations, fixed fields • Very simple experiment, passive, almost like an accelerator expt. • Follow-up observations with spectrograph

6. Mission Design • SNAP design meets these objectives • Satellite: Dedicated instrument, few moving parts

7. Mission Design • SNAP design meets these scientific objectives • Satellite: Dedicated instrument, few moving parts • Telescope: 2 meter aperture sensitive to light from distant SNe

8. Mission Design • SNAP design meets these scientific objectives • Satellite: Dedicated instrument, few moving parts • Telescope: 2 meter aperture sensitive to light from distant SNe • Photometry: 1° FOV half-billion pixel mosaic camera, high-resistivity, rad-tolerant p-type CCDs (0.4-1.0 mm) and, HgCdTe arrays (0.9-1.7 mm).

9. Mission Design • SNAP design meets these scientific objectives • Satellite: Dedicated instrument, few moving parts • Telescope: 2 meter aperture sensitive to light from distant SNe • Photometry: 1° FOV half-billion pixel mosaic camera, high-resistivity, rad-tolerant p-type CCDs (0.4-1.0 mm) and, HgCdTe arrays (0.9-1.7 mm). • Integral field optical and IR spectroscopy: 0.35-1.7 mm, 3”x3” FOV Guiders Cold plate Radiator Cables Thermal links Shield Spectrograph CCDs/ HgCdTe Shutter Filters

10. SNAP Instrumentation Key Instruments: 1) GigaCAM Imager 1 degree FOV 36 CCD’s + 36 HgCdTe 2) Spectrograph low resolution high throughput 350 nm – 1700 nm These instruments coexist on a common focal plane, passively cooled to 140K.

11. Mission Overview • Simple Observatory consists of : • 1) 3 mirror telescope w/ separable kinematic mount • 2) Baffled Sun Shade w/ body mounted solar panel and instrument radiator on opposing side • 3) Instrument Suite • 4) Spacecraft bus supporting telemetry (multiple antennae), propulsion, instrument electronics, etc • No moving parts (ex. Shutters, reaction wheels), rigid simple structure.

12. What’s New Since Last Review

13. Questions from Last Review • Determine observing requirements. • what is the optimal red-shift distribution • can we use a wider distribution of fields to test assumption of isotropy? • can photometric redshifts be determined in advance? • Determine photo-z requirement for the trigger. • Non-Ia triggering. • Weak lensing cost/benefit analysis. • Based on current observing requirements the photometric observing capabilities of Subaru, PRIME, LSST, HST,, NGST, ... • Based on current observing requirements the spectroscopic observing capabilites of Keck, VLT, NGST, SNAP with AO, OH-suppression. • Some cursory look into coordinated ground or planned space alternative or complementary missions. • Determine SNAP exposure-time requirements for the faintest spectroscopy. • Shown no need for initial photo-z survey. • Analysis of K-correction, Malmquist-bias errors. • Redshift range justification. • Anisotropy possibilities for the dark energy. • Theoretical analysis of dithering. • SCP experience with subtractions. • The evil produced by not having a shutter. • How to do standard star calibrations. • Can simple cuts provide an efficient trigger. Answers are online

14. Questions from Last Review In progress: • Error budget. Not enough people are working on this. Gravitational lensing, gray dust, and host-galaxy dust are problematic. SN evolution errors are based on observing requirements. • Justification of calibration requirements. • Summarizing results for observing capabilities of different observatories to construct viable alternatives, possiblities for descoping SNAP, shifting work to the ground, and prioritizing the instrumentation suite. Note that the capabilites have been determined. • Make the matrix the committee wanted. • Rerun all the different telescope capabilities based on new observing requirements. • Alternative methods for reducing sources of systematic error. • Software that demonstrates ability to sucessfully subtract galaxies with substructure with dithered images. • More looking into future telescope/detector/AO developments.

15. Observation Concept Imager • Step the focal plane through the observation field. • Fixed length exposures determined by a shutter. • Multiple exposures per filter. • To implement dithering pattern. • To eliminate cosmic ray pollution. • All stars see all filters (modulo field edge effects). • Fields revisited every four days. Spectrograph • SNe candidates are scheduled for spectrographic measurement near peak luminosity. • Analysis done on ground to identify Type Ia and roughly determine z. • Note peak luminosity is 18 days to 45 days after discovery for z = 0 and 1.7 respectively.

16. How Mission Operations map onto the Instrument Concept Reliability • Shutter is the only major moving part, • Minimal onboard data processing. Satellite • Body mounted radiator and solar panels provide a stable platform for long exposures, • Passive, radiative cooling, • But, quantizes orientation of the focal plane relative to observation fields. Orbit and telemetry • 3 day orbit period a good match to data generation, • Generated data volume per orbit compatible with available solid state recorders, • Telemetry band width and dwell time over ground station compatible with down-linking an orbit’s data buffer.

17. Requirements Development 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 < 1.7 Data Set Requirements • Discoveries 3.8 mag before max • Spectroscopy with dl/l~100 • Near-IR spectroscopy to 1.7 m • • • Satellite / Instrumentation Requirements • 2-meter mirror Derived requirements: • 1-degree imager • High Earth orbit • Low resolution spectrograph • ~250 Mb/sec bandwidth (0.35 m to 1.7 m) • • •

18. Requirements Development Four Key Level 1 Science Requirements: • Quantity • Quality • Spectroscopy • Surveys

19. SNAP Level 1&2 Science Requirements

20. Supernova Survey SNe survey takes 1.3 years to obtain 2000 SNe Requirement

21. SNAP Level 1&2 Science Requirements

22. Ten Points on Lightcurve Key requirements: 1. Measurement at peak to S/N>30. 2. Measurement within average 2 days after explosion to S/N>3. 3. Minimum 10 points on lightcurve.

23. Focal Plane/Filter Photometry Field of View Optical ( 36 CCD’s) = 0.34 sq. deg. Four filters on each 10.5mmpixel CCD detector Field of View IR (36 HgCdTe’s) = 0.34 sq. deg. One filter on each 18mmpixel HgCdTe detector Focal plane is rotationally symmetric Pixel size of detectors matched to Airy disk.

24. Supernova Survey • SNe survey takes 1.3 years to obtain 2000 SNe • Survey size is 7.5 square degrees observed in 9 filters. • 22 fields scanned with a 4 day cadence. • Each exposure is 300 seconds long. • Four exposures per position with a small dither pattern • Then the satellite moves by one-half a detector interval (~175 arcsec)

25. Derived Requirements for the Imager

26. SNAP Level 1&2 Science Requirements

27. Spectroscopy • 40% of the time the spectrograph is turned on and the satellite points to the supernovae • During spectroscopy the exposure time increases to 1000 seconds. Both spectrograph and imager are active. • Total integrated exposure time for spectroscopy is ~ 8 hours at z=1.7; varies as 6th power of 1+z. • Would use NGST for some highest redshift SNe if available and in viewing zone. • Host galaxy redshifts from SNAP and ground assets. S SiII

28. Derived Requirements for the Spectrograph

29. SNAP Level 1&2 Science Requirements

30. Weak Lensing Survey • Weak Lensing survey takes 8 months • Survey size is 500 square degrees. • Each field is observed in 9 filters. • ~1500 fields observed • Each field is scanned across with the satellite moving by one-half a detector interval each time (175 arcsec). • Each exposure is 500 seconds long. • Four exposures per position with a small dither pattern

31. Observation Program After launch: • Correct initial orbit for injection errors, station-keeping • One month check out of spacecraft systems • 16 month survey of the North Field • 12 month Weak Lensing Survey, GO program, clean-up of SNe survey • 16 month survey of the South Field • GO program as appropriate, clean-up of SNe survey • At end of mission, lift orbit into 7 day perturbed orbit, eventually ejected

32. Tools for Requirements Definition SNAPfast 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 Image simulator and SN extraction - Measure photometry, spectra from images Data simulator - Generate 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 SNe Cosmology fitter - Determine best fit cosmological and dark energy parameters

33. Example SNAPfast Simulation Full SNAP model simulation of SNe lightcurve and fit. Simulates complete observation strategy. 2% average requirement

34. Studies Undertaken Completed • Focal Plane Layout (LBNL) • Spacecraft Accommodation (GSFC & SSL) • Orbit (SSL & LBNL) • Launch vehicle (Boeing) • Telemetry (SSL) • Telescope Optics (SSL) • Telescope Stray Light (GSFC, SSL & LBNL) • Thermal Study (SSL) • Mechanical Structure (SSL) • Focal Plane Guider (SSL, published) In progress: • Primary Mirror (RESOC/SAGEM) • Data Pipeline (STScI & LBNL) • Calibration Requirements (w/ simulation grp, STScI, Indiana, SSL, LBNL) • Independent Cost Study (Aerospace Corp.) • Instrumentation R&D

35. NASA GSFC/IMDC Spacecraft Study Two independent multi-week studies at GSFC: 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

36. SNAP Spacecraft ACS 40 Ah Battery Star Tracker 0.5m antenna CD&H SSR OCU Reaction Wheels Propulsion Tanks PSE

37. 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 - 86% of orbit) • Passive Cooling of Detectors • Minimizes Stray Light Chandra type highly elliptical orbit

38. SNAP Orbital Parameters 3 day synchronous orbit Perigee = 2.56 Re (geocentric), eg. 10,000 km altitude Apogee = 24.94 Re (geocentric) This orbit is in the plane of the moon and is stable against lunar perturbations. Also, simultaneously maximizes solar, lunar, and earth avoidance angles. Launch vehicle [Delta IV 4240] is capable of lifting 2020 kg to that orbit significant mass margin held in Perigee, Apogee, SC-propulsion. Can use equivalent Delta III, IV, Atlas, or Sea Launch. Time passage through radiation belts = 11.2 hours During this time SNAP is not observing, rather performing data dump. This corresponds to an 86% operational efficiency. Total proton dose from belts = 8 x 105 p/cm2/year [25 mm Al] Study is online

39. Ground Station Coverage Orbit perigee remains over Berkeley for 3 years without adjustment. 5.2 hour ground pass over Berkeley

40. Launch Vehicle Study Atlas-EPF Delta-III Sea Launch

41. Telemetry 250 Mbit/s downlink requirement 375 Gbytes storage requirement Requires 0.5m 6W Ka-band Xmit, with 10m ground station Study is online.

42. Optical Study • Flat focal plane • Delivers < 0.04 arcsecond FWHM geometrical blur over field 1.37 sq • Effective focal length 21.66m; f/10.8 final focus • Provides side-mounted detector location for best detector cooling • study is online

43. Stray Light – Baffle Design Stray light study is online

44. Thermal Study • KEY DESIGN FEATURES • High Earth orbit (HEO) to minimize IR Earth-glow loads • OSR striping of the (hot) solar array panels • Low emissivity silvered mirrors • Thermal Isolation mounting and MLI blanketing OPTICS: Build,Test, & Fly Warm… Study is Online

45. First vibration mode—62 hertzstudy is online Structural Study

46. R&D Management • Risk Assessment • Schedule • Organization • Funding • ITAR

47. Detector R&D In the past year we have conducted a technical and scientific trade studies covering a range of options for the SNAP instrumentation suite. We have arrived at a coherent instrument working concept and observation strategy constrained by reliability, satellite, orbit, thermal, and telemetry issues and SNe characteristics that optimizes the science reach of SNAP. In developing this concept we have minimized risks by using proven solutions to the greatest extent possible. We have identified risks in three detector technology areas: CCDs, HgCdTe, & custom integrated circuits. The R&D period concentrates on: • Paper studies to eliminate or better understand these risks. • A limited, focused hands-on R&D program to mitigate risk. • Mitigating technical risk by the end of the R&D phase, NASA TRL Level 5- “Component and/or breadboard test in a relevant environment.” • Producing a credible project cost and schedule

48. R&D Risk Assessment and Management • Technology assessment and development • Risks documented with requirements and specification assumptions • Development of all technology to adequate flight readiness level • R&D Phase Controls • Technical Definition • Systems requirements • Objectives/goals • Management • Manpower • WBS • Budget • R&D Phase Performance metrics • Defined deliverables • Defined goals – such as detector deployment (ie. at a telescope) • Goddard/Integrated Mission Design Center study in June 2001: no mission tall poles • Goddard/Instrument Synthesis and Analysis Lab study in November 2001: no technology tall poles

49. Technology Readiness Assessments Assist in Development Plans Goals: Achieve TRL 5 by CDR Achieve TRL 6 by PDR present state Telescope Guider Spacecraft Electronics Software IR Imager IFU Spectrograph Optical Imager = CDR = PDR Technology Readiness Levels 9 Actual system flight proven or operational flight System Test and Operations Actual system completed & "flight qualified" through test demonstration 8 System/Subsystem Development 7 System prototype demonstrated in flight environment 6 System/subsystem model or prototype demonstrated/validated in a relevant environment Technology Demonstration Component and/or breadboard test in a relevant environment 5 Technology Development Component and/or breadboard test in a laboratory environment 4 Analytical and experimental critical function, or characteristic proof-of-concept 3 Research to Prove Feasibility Technology concept and/or application formulated (candidate selected) 2 Basic Technology Research 1 Basic principles observed and reported

50. 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 R&D 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 Jan 2002 Two Special Sessions at AAS Meeting Mar 2002 SAGENAP-2 Apr 2002 NRC/CPU Report NOW DOE/SC-CMSD R&D (Lehman) Sept 2002 NASA/SEU Releases Roadmap Oct 2002 CNES Review