# Presentation: 245201

## The Instrument

- The focal plane is like an HEP detector, larger than any present astronomical camera, but smaller than a vertex detector. 1⁄2 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 Outline
- A 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.

- Gravitational Weak Lensing:
- A 1000 sq-deg survey.
- Direct measurement of *P(k)* vs z.
- Mass selected cluster survey vs z.

- Strong Lensing Photo

## 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.

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

- “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

- 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