# Presentation: 743206

## Exploring Dark Energy with the SuperNova / Acceleration Probe 

- Exploring Dark Energy with the SuperNova / Acceleration Probe

- Greg Aldering
*Wide-Field Imaging from Space*
- May 16 2004

## SNAP Collaboration

| LBNL | G. Aldering, C. Bebek, W. Carithers, C. Day, R. DiGennaro, S. Deustua†, D. Groom,
M. Hoff, S. Holland, D. Huterer†, A. Karcher, A. Kim, W. Kolbe, W. Kramer, 
B. Krieger, G. Kushner, N. Kuznetsova, R. Lafever, J. Lamoureux, M. Levi, E. Linder, S. Loken,
R. Miquel, P. Nugent, H. Oluseyi†, N. Palaio, S. Perlmutter, N. Roe, 
A. Spadafora, H. Von Der Lippe, J-P. Walder, G. Wang |
| --- | --- |
| UC Berkeley | M. Bester, E. Commins, G. Goldhaber, H. Heetderks, P. Jelinsky, M. Lampton, 
D. Pankow, M. Sholl, G. Smoot |
| Caltech | R. Ellis, R. Massey†, A. Refregier†, J. Rhodes, R. Smith, K. Taylor |
| Fermi National Laboratory | J. Annis, F. DeJongh, S. Dodelson, T. Diehl, J. Frieman, L. Hui,  S. Kent, P. Limon,
J. Marriner, H. Lin, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker,
W. Wester |
| Indiana U. | C. Bower, N. Mostek, J. Musser, S. Mufson |
| IN2P3 (France) | P. Astier, E. Barrelet, A. Bonissent, A. Ealet, D. Fouchez†, R. Pain, G. Smadja, 
A. Tilquin, D. Vincent |
| LAM (France) | S. Basa, R. Malina, A. Mazure, E. Prieto |
| University of  Michigan | B. Bigelow, M. Brown, M. Campbell, D. Gerdes, W. Lorenzon, T. McKay, S. McKee,
M. Schubnell, G. Tarle, A. Tomasch |
| University of Pennsylvania | G. Bernstein, L. Gladney, B. Jain, D. Rusin |
| University of  Stockholm | R. Amanullah, L. Bergström, A. Goobar, E. Mörtsell |
| SLAC | W. Althouse, R. Blandford, W. Craig, S. Kahn, M. Huffer, P. Marshall |
| STScI | R. Bohlin, A. Fruchter |
| Yale U. | C. Baltay, W. Emmet, J. Snyder, A. Szymkowiak,  D. Rabinowitz, N. Morgan |
|  | †Institutional affiliation |

**SNAP Collaboration**

## Narrowing in on Cosmological Parameters

## G

## HST Search for z > 1.2 Type Ia Supernovae

-  4 searches of the Northern GOODS field
-  Searches separated by 45 days
-  Search in 850LP w/ short F775W exposure
-  15 HST ACS pointings per search
-  Subaru I-band reference image
-  60 orbits ACS & NICMOS follow-up

## Slide 9

## Slide 10

## HST Follow-up: 

- HST Follow-up:
-  ACS imaging
-  ACS grism spectroscopy
-  NICMOS imaging

- HST ACS: 28000 sec in 22 exposures

## No Control of Systematics

- HST Follow-up:
-  ACS imaging
-  ACS grism spectroscopy
-  NICMOS imaging

- HST ACS: 28000 sec in 22 exposures

## Systematics Dominate

## Expansion History

**Expansion History**

## Expansion History of Leonard Parker

**Expansion History of Leonard Parker**

## Enabling Better Type Ia Standardization

## New Type Ia calibration techniques - Color-Magnitude Intercept Calibration 

**New Type Ia calibration techniques - ****C****olor-****Mag****nitude ****I****ntercept ****C****alibration **

**See poster by Alex Conley**

## From Science Objectives to Project Design

**Discover large numbers of supernovae **

**Large 2 meter class telescope, large field of view (0.7 sq degree)**
**Dedicated space-based mission**

## From Science Objectives to Project Design

**Discover large numbers of supernovae **
**Look back 3 - 10 billion years (z=0.5 - 1.7, light is redshifted up to 1.7 um)**

**Large 2 meter class telescope, large field of view (0.7 sq degree)**
**Dedicated space-based mission**
**Visible to near-infrared camera**
**Space-based to avoid absorption in earth’s atmosphere**

## From Science Objectives to Project Design

**Discover large numbers of supernovae **
**Look back 3 - 10 billion years (z=0.5 - 1.7, light is redshifted up to 1.7 um)**
**Measure each supernova in detail (light curve, spectrum)**

**Large 2 meter class telescope, large field of view (0.7 sq degree)**
**Dedicated space-based mission**
**Visible to near-infrared camera**
**Space-based to avoid absorption in earth’s atmosphere**
**Detailed spectrum at maximum light to characterize supernovae**
**Observing program of repeated images in visible to near-infrared**

## SNAP Mission

**SNAP Mission**

**SNAP design meets these scientific objectives**
_**Telescope:**_** 2 meter aperture sensitive to light from distant SNe and galaxies.**

## SNAP Mission

**SNAP Mission**

- Field of View Optical ( 36 Sensors) = 0.34 sq. deg.
- 	Four filters on each 10.5 m pixel CCD detector
- Field of View IR (36 Sensors) = 0.34 sq. deg.
- 	One filter on each 18 m pixel HgCdTe detector

- guider

- spectrograph

**SNAP design meets these scientific objectives**
_**Photometry:**_** half-billion pixel mosaic camera, 0.7****o**** instrumented FOV**

## Detailed, Systematics-Controlled Lightcurves

**SNAP**

**Ground 8m ONIR**

*z *= 0.8
*z* = 1.0
*z *= 1.2
*z* = 1.4
*z* = 1.6

## Simulated Hubble Diagrams

- Here, SNAP is computed for one year, and 8m-class ground-based telescope is computed for two years, *with only ****SNe with spectra**** plotted*.  Ground based telescope assumed to have wide-field NIR capability in addition to visible and access to 8-10m spectroscopy.
- SNAP-quality spectra are assumed (not possible from the ground)

- SNAP

- 8m Ground Visible & NIR imager
- + SNAP-quality spectra

- SNAP

## Power of Weak Lensing from Space

- Plot from Gardner and Satyapal, AJ, 119,2589, 2000

- SNAP PSF

- 0.5 arcsecond seeing (currently best consistent seeing is 0.7 arcseconds)

- Many faint galaxies are too small to be resolved from the ground

## Photo-Z Accuracy for WL Requires NIR

- SNAP With NIR                                                 SNAP without NIR

- NIR Filters are crucial for photo-z accuracy and to reduce catastrophic failures (see Massey et al astro-ph/0304418).

## SNAP Level 1 Science RequirementsTwo Methods: SNe & WL

**SNAP Level 1 Science Requirements****Two Methods: SNe & WL**

**Four Key Level 1 Science Requirements:**
**SNe Quantity**
**SNe Quality**
**SNe Spectroscopy**
**Weak Lensing Surveys**

- 2000

**Tomographic density maps: Deep multi-band visible-NIR surveys **
**with field sizes of up to 1000 square degrees (much larger surveys are possible)**

## SNAP Surveys

**SNAP Surveys**

- Synergy of Supernovae + Weak Lensing
-  Comprehensive: no external priors required!
-  Independent test of flatness to 1-2%
-  Complementary (SNe + WL only):
- conservative:						   			*w**0* to ±0.05, variation *w*** to ±0.12 (*with systematics*)  model			*w**0** *to* **±*0.03* *variation *w*** to ±0.06 (*with systematics*) SUGRA model
- Adding panoramic survey and better systematics:					*w**0* to ±0.03, variation *w*** to ±0.06 (*with systematics*)  model			*w**0** *to* **±*0.015* *variation *w*** to ±0.03 (*with systematics*) SUGRA model
-  Flexible: Panoramic is available if improved systematics in space warrant greater than 1000 sq. deg.

**Survey       Area(sq.deg)   Depth(AB mag)   n****gal****(arcmin****-2****)    N****gal**
**Deep/SNe          15                  30.3****	****            250                 10****7**
**Wide              300-1000           27.7                     100                 10****8.5**
**Panoramic  7000-10000         26.7                    40-50               10****9**

## Combined Power of SNe and WL

## Instrument Concept

## Evolution of SNAP instruments

**1999:**
- Objective prism concept, all visible wide-field
- Single NIR detector
**2000:**
- Separated functions, but multiple focal planes to keep focused
- Filter wheel - no constraint on observation scan, but single point failure
- Small number (4) of NIR detectors
**2002:**
- Imager detectors and spectrograph on one focal plane.
- All detectors near radiator.
- Filter wheel allows flexible observation program, but a single point of failure.
- Most efficient if dual band filters used for visible and NIR observing simultaneously.

## Current Focal Plane

**2003:**
- All instruments coalesced on one focal plane.
- Common 140K operating temperature.
- Single focal plane simplifies optics, pointing and focusing
- Photometer sensors in one focal plane, example.
- 36 2k x 2k, 18 μm HgCdTe NIR sensors.
- 36 3.5k x 3.5k, 10.5 μm CCD sensors
- Spectrograph mounted to focal plane.
- Two channel spectrograph with light access port 		in the focal plane.
- Objects dropped into spectrograph light port by 	steering the satellite.
- Fixed filter mosaic
- 3 Fixed Filter array eliminates wheel risk
- 3 NIR bandpass filter types organized in 3 x 3 arrays.
- 6 visible bandpass filter types organized in 6 x 6 arrays.
- Guide off the focal plane during exposures.
- 4 regions of star guider CCDs.
- Telescope I&T and on-orbit calibration hardware

- Guider

- Spectrograph
- port

- Visible

- NIR

- Focus star
- projectors

- Calibration projectors

## Focal plane - spectrograph

- Integral field unit based on an imager slicer.
- Input aperture is 3” x 6” – reduces pointing accuracy req.
- Simultaneous SNe and host galaxy spectra.
- Internal beam split to visible and NIR.

- Input port

- Slicer

- Prism
- BK7

- Prism
- CaF2

- NIR
- detector

- Vis
- Detector

## Spectrograph:  IFU Slicer principles

- Aligned pupil mirrors
- Each subfield imaged along an entrance slit
- Spectrum of each subfield

- 1

- 2

- 3

**Spectrograph:  IFU Slicer principles**

- How to rearrange 2D field to enter spectrograph slit:

- 4

**Notes:**
You should say here that there are in fact 20 slices in the SNAP concept.

## Spectrograph image slicerAll Sub-elements Prototyped

**LAM prototype slicer**

## High CCD QE & Radiation Tolerance

- Preliminary USAF/NRL/GSFC results:
***“...******see about an order of magnitude***
***improvement in the CTE degradation as***
***compared to that observed in our WFC3 data.”***

-  New kind of CCD developed at LBNL
-  Better red response
-  Better radiation tolerance for space applications
-  Smaller pixel sizes enabling compact arrays

## Near-Infrared Detectors

- Rockwell 2k x 2k, 1.7 um HgCdTe

- Raytheon 1k x 1k, 1.7 um HgCdTe

- InGaAs  2k x 2k, 1.6 um concept

## Current Concept: Compact & Extremely Simple

- Focal plane

- Xmit Dish

**Current Concept: Compact & Extremely Simple**

**90 deg Symmetric Focal Plane allows continuous year round science data taking**
**one side always sunward, allowing ****fixed solar panels ****hence a**** ****rigid spacecraft**
**other side always dark,  allowing ****fixed **_**passive**_** thermal radiator**** serving sensor array**
**Innovative telescope design does IR imaging with ****room temperature optics**
**three mirror anastigmat has accessible exit pupil and complete cold stop baffling**
**Built in end-to-end ****optical test capability**** simplifies Integration and Testing**
**The ****fixed telemetry antenna**** eliminates a major mission risk: **
**no gimbals**
**rigid spacecraft eases ACS task**
**No onboard data analysis: all images are downlinked to Earth**
**lossless onboard compression via hardware **

## Mission Design

**“****SNAP”:****SuperNova****Acceleration Probe**

## Mission Design

## Mission Design

## Mission Design

## Mission Design

## Mission Design

## Mission Design

## Mission Design

- shutter

- Focal plane

- Spectrograph

- electronics

## SNAP Orbit

- L2 lagrange point
- Allows passive cooling
- >90% duty cycle

**~1,500,000 km**

**~374,000 km**

**~1,500,000 km**

**L2**

- L2 lagrange point
- Allows passive cooling
- >90% duty cycle

## SNAP Deep Field scan strategy

- Given patch of sky seen 4 times in each filter on each pass
- Cadence of 4 days
- 90 degree rotation every 3 months

## On the Road from Idea to Launch

## SNAP Reviews/Studies/Milestones/Outreach

- Nov 1999	Preproposal ad hoc committee review
- Mar 2000	SAGENAP-1 (recommends R&D)
- Sep 2000	NASA Structure and Evolution of the Universe (SEU)
- Dec 2000	NAS/NRC Committee on Astronomy and Astrophysics
- Jan 2001	DOE-HEP Review R&D (SNAP is uniquely able)
- Jan 2001   AAS special session
- Mar 2001	DOE High-Energy Physics Advisory Panel (HEPAP)
- Jun 2001	NASA Integrated Mission Design Center (determines feasibility)
- July 2001	Snowmass Workshop (Community analysis)
- July 2001	NAS/NRC Committee on Physics of the Universe
- Dec 2001	NASA/SEU Strategic Planning Panel
- Jan 2002	HEPAP subpanel report: HEP Long Range Planning
- Jan 2002   AAS special session
- Mar 2002	SAGENAP-2
- Apr 2002	NRC/Committee on Physics of the Universe releases report
- July 2002	DOE/SC-CMSD R&D (Lehman)
- Dec 2002	JPL Team-X Study (studies potential NASA cost)
- Jan 2003	NASA releases SEU roadmap:  Beyond Einstein
- Feb 2003	SNAP in the DOE budget
- Mar 2003	DOE HEP releases Facilities 20 Year Roadmap
- Nov 2003	JDEM Announcement
- April 2004 SAGENAP-3

## JDEM

- “To fully characterize the expansion history and probe the dark energy will require a wide-field telescope in space (such as the Supernova/Acceleration Probe).”

## Summary

- The nature of Dark Energy is a fundamental question, which astronomical observations can address
- Type Ia Supernova & Weak Lensing are the most developed powerful techniques for studying DE
- Reaching required statistical & systematics accuracy requires a wide-field imager in space
- SNAP represents a very advanced concept for such a WFI
- The SNAP instrument suite is powerful yet versatile
- The planned DE program will produce a treasure trove of data for archival study
- GO programs could further exploit this powerful instrument
- Now, tell us what you’d do with such a capability!