The InstrumentThe focal plane is like an HEP detector, larger than any present astronomical camera, but smaller than a vertex detector. ½ Billion pixels.

Contains both optical and near infrared devices, covering a wavelength range of 0.35 -1.7 m. The total number of pixels is ~600 million.

The detectors are low noise, high QE.

Spectrograph covers both optical and near infrared

LBNL, UC Berkeley, CalTech, FNAL, Indiana U, IN2P3/INSU (France), JPL, LAM (France), U Michigan, U Penn, U Stockholm, STScI, Yale

The Science Return:Premier measurement of the dark energy density DE, its equation of state w, and dynamical physics of w´ = dw/dz.

Complementary cosmological properties measurements.

Map the expansion history a(t), probing dark energy, higher dimensions, or alternative gravity.

The SNAP Mission OutlineA 2 M space telescope with visible light CCDs, NIR detectors, and a spectrograph.

Complementary Measurements Study Dark Energy and Dark Matter

Supernovae Survey to explore dark energy

• 15 sq. deg. to AB magnitude ~30 (28/scan)

• 9000 times the area of Hubble Deep Field, same resolution, ~1.5 magnitudes deeper.

Lensing Survey to explore dark energy and dark matter

• 1000 sq. deg. to AB magnitude ~28.

2000 Type 1a Supernovae:Identify Type 1a SN with CCD and NIR detectors in redshift range 0.3 < z < 1.7.

Fit peak of SN1a lightcurve with <S/N> of 50:1.

Obtain spectrographic observations near peak intensity with a resolution R~100 over = 0.35 to 1.7 microns.

Tightest Control of Systematics in individual supernovae measurements.

Light Curve & Spectrum

Gravitational Weak Lensing:A 1000 sq-deg survey.

Direct measurement of P(k) vs z.

Mass selected cluster survey vs z.

Shutter

Shield

Filters

Sensors

Cold plate

Front-end electronics

Calibration lamps

Spectrograph

Radiator

Shutter

Shield

Filters

Sensors

Cold plate

Front-end electronics

Calibration lamps

Spectrograph

Radiator

Strong Lensing Photo

Ca II HK

G band

H

H Mg?

Recent Fermilab Contributions

ELECTRONICS–Our physics interests require the instrument has the ability to store and manage large data samples in between transmission periods.

–Mass Memory & Data Manager• Research radiation tolerance of Flash Memory & FPGA’s and attain familiarity

with a space qualified FPGA device in a radiation environment (hardware data compression). Prior to our work there was widespread bias against use of flash memory in space applications. We tested “next generation” devices.

• Next: Work towards other aspects of space qualification and Contribute to design documents, technology recommendation, and procurement plan.

• Investigate compression algorithms through software and hardware. We found compression algorithms can provide 2x to 4x reduction in expected SNAP data size using novel techniques. Understand impact with telemetry.

15Krads26Krads

47Krads

64Krads

Radiation studies show FPGA current rising after ~50Krads. Significant Single-event-upsets (SEUs) but periodic reloading of the configuration bits should work operationally

Proceedings of the IEEE Radiation Effects Data WorkshopAtlanta, GA, July, 2004.

“COSMIC RAY” SHIELD Conceptual Design Studies–Protects the focal plane from stray light, external thermal sources, and cosmic rays.

Photo-z Simulations–Translate magnitude errors to photometric redshift (photo-z) errors shows•Photo-z error distribution can be a complicated function of z, magnitude, and galaxy type.

–SNAP Filter Set Studies.–Ground vs. Space Simulations.–Goals: Optimize photo-z’s & minimize the systematics.

Calibration–Identify and measure the optical spectrum of calibration stars.• ID using SDSS

•Use APO 3.5m telescope to measure spectrum.

–Develop a point-spread function simulation and calculate effect on potential systematic errors.

Simulation & Software Management–SNAPSim: end-to-end simulation of SN and W.L. images

–Starting full Pixel-level Simulations

Filter “I”AB < 26.5 MagnitudeA Simulated SNAP Filter Set

“I”

Confusion between Lyman and 4000A break

Galaxy Type

Redder

Visible

IR

Optical Ray-Tracing DiagramDetermines Size of the Shield and Minimizes Reflection onto Focal Plane

Primary Mirror

Secondary Mirror

Focal Plane

SN1a Light

Envelope of Shield

Cosmic Ray Flux During “Worst Day” Solar Flare

2/3 cm of Aluminum

Crème 96

Simulated Image of a Star

S. Allam, J. Annis, F. DeJongh, H.T. Diehl, S. Dodelson, J. Frieman, S. Kent, P. Limon, H. Lin, J. Marriner, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker, W. Wester

HST Spectrophotometric Standard

Hot White Dwarf (V=11.77)

APO