# Presentation: 947581

## SuperNova Acceleration Probe IMDC  Kickoff

**M.Lampton**
**Space Sciences Lab**
**University of California Berkeley**
**March 2005**

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## Montage of Magazine covers

**Montage of Magazine covers**

**Breakthrough of the Year:**

## Current Crisis

**General Relativity**
**A.Einstein 1915 + 10,000 follow-on papers books movies etc.**
**Amazingly accurate and well verified!**
**Deflection of starlight observed 1919: mass curves space!**
**Explains Galileo’s principle of equivalence**
**Explains gravity as geometry**
**Explains precession of Mercury’s orbit**
**Predicts frame dragging!**
**Predicts black holes!**
**overall, an amazing success**
**Quantum Mechanics**
**W.Heisenberg 1923 + 10,000 follow-on papers books movies etc.**
**Amazingly accurate and well verified!**
**Extensions to chromodynamics etc**
**overall, an amazing success**
**GR and QM are inconsistent. They are approximations to something else.**

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## Discoveries

**Major discoveries happen when new observations become possible**
**The 1990’s saw two major observatories begin operation.....**
**Keck with large format efficient CCDs**
**Hubble with ultra low foreground and superb seeing**
**These could see fainter and more distant objects than ever before**
**Permits tests of cosmological models**
**Yikes! 1998: Matter + gravity + big bang is seriously wrong.**
**Perlmutter et al 1998**
**Schmidt et al 1998**
**Since then, many corroborating observations!**
**Maybe 1000 papers, books, ....**

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## The Expansion History of the Universe

- <footer>

- Expansion vs Time

## Current* Results on Cosmological Parameters

**Current* Results on ****Cosmological Parameters**

- What people used to think...

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## Energy budget of Universe

***Dark***
***Energy:***
***65%***

***Dark***
***Matter:***
***30%***

*Energy budget of Universe*

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## What is Dark Energy?

- Not predicted by current theories of space/time/gravity
- Yet one form “Λ” is permitted by Einstein’s general relativity
- Physicists propose a variety of alternative theories
- Supergravity
- Brane worlds with a few or many higher dimensions
- Vacuum metamorphosis; quintessence; ....
- Each theory raises profound questions about the nature of space, time, fundamental particles, gravity, and reality
- Each theory has unique **predictions** for the observable history of the expansion of the universe
- Those **predictions** are the handle we use to eliminate the wrong theories

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## How to measure dark energy?

- Standard candles   <<SNAP
- idea is the inverse square law: flux ~luminosity/distance2
- a standard candle has a calibrated luminosity
- a measured flux gives the distance hence the lookback **time**
- the light’s redshift gives the universe’s **expansion**
- use many candles, many redshifts: get cosmic history of the expansion
- Weak gravitational lensing  <<SNAP
- matter has mass, hence gravity
- over cosmic history, matter aggregates through gravitation
- mass aggregation w.r.t. redshift is determined by expansion history
- mapping lensing vs. redshift can constrain expansion models
- Other methods
- Baryon oscillations: use individual galaxy redshifts as tracers
- Sunyaev-Zeldovich effect: probe cluster masses

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## Standard Candles?

**Cepheid variable stars? Way too faint.**
**Galaxies?  Wildly discrepant.**
**Quasars? Wildly discrepant & variable too.**
**Supernovae?**
**Type Ia: no H, no He, strong Si**
**white dwarf has binary partner**
**accretion: reaches 1.4 Msun**
**limit set by electron pressure**
**excellent uniformity, 1E62photons**
**Type Ib: no H, strong He**
**Type Ic: no H, no He, no Si**
**Type II: strong H**
**core collapse stars**
**output depends on mass**
**poor standard candle**

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## 1998: Acceleration!

**Supernova Cosmology Project (S.Perlmutter et al)**
**High-Z Supernova Team (B.Schmidt, R.Kirschner, et al)**
**Teams began searching for high-Z supernovae ~ 1990s**
**By 1996, seven had been found**
**By 2004, 120 were known**
**Distant supernovae recede more slowly than the nearby Hubble-law prediction based on brightness!**

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## Weak Lensinghttp://www.cita.utoronto.ca/~hoekstra/lensing.html

- Gravitational lenses are formed by concentrations of mass
- Lenses bend light from distant objects and distort their shapes
- Wide field surveys have a lot of information about how mass is distributed along each line of sight
- To probe cosmological distances
- need extreme sensitivity
- need excellent image quality
- need lots of sky coverage
- SNAP will (as part of the SNe sweeps) do a deep survey and find many mass aggregations
- SNAP will (in wide field survey) cover much larger hunks of the sky
- Present plans include a 300 to 10000 sqdeg survey

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## Slide 13

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## Volume Lensing

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## What next?

- Extend the supernova method
- many more SNe: thousands
- Much higher measurement precision
- accurate photometry
- many data points on each light curve
- systematically obtained spectroscopy
- Eliminate/manage systematic issues
- absorption? reddening? environment of each SN?
- classification of supernovae
- weed out the wierdos
- Extend the magnitude-redshift diagram back, to z>1, where matter should dominate the cosmological constant
- Perform a large field weak lensing survey
- constant point spread function
- eliminate “seeing” and other disturbances

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## What would this take?

- Huge amount of observing time!
- Dedicated facility
- Area*omega product
- Lots of pixels running in parallel
- revisit every object every few days
- moon, weather must not interfere with tight schedule of reobservation
- >>> **space observatory**
- Need to go beyond the atmospheric NIR cutoff to get our redshift range
- >>> **space observatory**
- Must eliminate telluric features that would corrupt key classification lines: CaII, SiII, H, as we chase them out into the near infrared
- >>> **space observatory**
- Need to have extremely dark sky free of varying emission/absorption lines
- >>> **space observatory**
- Must have rock steady seeing 24/7 to do precision weak lensing
**>>> space observatory**

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## SNAP Design

- Observe 2000 type Ia Supernovae per 16 month phase (1 North, 1 South)
- Survey area 7.5 square degrees, swept every 4 days
- Quality:  light curve allow fitting peak brightness with error < 3%
- Sensitive enough to reach SNe to z=1.7, detect well before peak
- Spectroscopy near peak: ~10nm resolution from 350 - 1700 nm
- Distribution:  Ability to detect supernovae as far away as 10 billion light years --- back to the epoch where gravity dominated dark energy.
- Construct a wide field weak-lensing map of galaxies
- Extremely stable and well understood point spread function
- Sufficient image sampling & resolution to recover accurate galaxy orientations
- Map coverage several hundred square degrees; option of many thousand sq deg
- SNAP design meets these scientific objectives
- Mirror: ~ 2 meter aperture
- Huge field of view 1.4 degrees across
- Camera: 0.6 billion pixels, vis + NIR
- Spectroscopy: optical/infrared spectrograph with  IFU
- Orbit: L2 minimizes stray light and thermal issues

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## Simulated SNAP data

- <footer>

**Simulated SNAP data**

- Each SNAP point
- represents ~50-supernovae per bin

## From Science Goalsto Project Design

- <footer>

**From Science Goals****to Project Design**

**Science**

- Measure *M* and 
- Measure *w* and *w *(*z*)

**Data Set Requirements**

- Discoveries 3.8 mag before max
- Spectroscopy with ~100
- Near-IR spectroscopy to 1.7 m

**Statistical Requirements**

- Sufficient (~2000) numbers of SNe Ia
- ...distributed in redshift
- ...out to *z* < 1.7

**Systematics Requirements**

- Identified and proposed systematics:
- Measurements to eliminate / bound each one to +/–0.02 mag

**Satellite / Instrumentation Requirements**

- 2-meter mirror	Derived requirements:
- 1-degree imager	 • 	High Earth orbit
- Low resolution spectrograph	 • 300 Mb/sec bandwidth    (0.35 m to 1.7 m)

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## Payload Features

- 90 deg Symmetric Focal Plane allows continuous year round science data taking
- one side always sunward, allowing fixed solar panels hence a rigid spacecraft (resonances > 10Hz)
- other side always dark,  allowing fixed _passive_ thermal radiator serving sensor array
- Telescope assembly is thermally and structurally separate from surrounding outer baffle and from spacecraft
- maneuvers do not compromise PSF stability
- 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 major mission risks and costs:
- no gimbals, no flex waveguide
- rigid spacecraft eases ACS task
- No onboard data analysis: all images are downlinked to Earth

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## SNAP Observatory Cross Section

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## SNAP Collaboration Dec 2004

| LBNL | G. Aldering, S. Bailey, C. Bebek, W. Carithers, T. Davis†, K. Dawson, 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, S. Loken, B. McGinnis, R. Miquel, P. Nugent, H. Oluseyi†, 
N. Palaio, S. Perlmutter, N. Roe, H. Shukla, A. Spadafora, H. Von Der Lippe, 
J-P. Walder, G. Wang |
| --- | --- |
| U.C. Berkeley | M. Bester, E. Commins, G. Goldhaber, H. Heetderks, P. Jelinsky, M. Lampton, 
E. Linder, D. Pankow, M. Sholl, G. Smoot, C. Vale, M. White |
| Caltech | R. Ellis, R. Massey†, A. Refregier†, J. Rhodes, R. Smith, K. Taylor, A. Weintein |
| Fermi National Laboratory | J. Annis, F. DeJongh, S. Dodelson, T. Diehl, J. Frieman, D. Holz†, L. Hui,  S. Kent, 
P. Limon, J. Marriner, H. Lin, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, 
D. Tucker, W. Wester |
| Indiana U.

IN2P3-Paris
    -Marseille | C. Bower, N. Mostek, J. Musser, S. Mufson

P. Astier, E. Barrelet, R. Pain, G. Smadja†, D. Vincent
A. Bonissent, A. Ealet, D. Fouchez, A. Tilquin |
| JPL | D. Cole, M. Frerking, J. Rhodes, M. Seiffert |
| LAM (France) | S. Basa, R. Malina, A. Mazure, E. Prieto |
| U. Michigan | B. Bigelow, M. Brown, M. Campbell, D. Gerdes, W. Lorenzon, T. McKay, S. McKee,
M. Schubnell, G. Tarle, A. Tomasch |
| U.  Penn | G. Bernstein, L. Gladney, B. Jain, D. Rusin |
| U. 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, D. Figer, A. Fruchter |
| Yale U. | C. Baltay, W. Emmet, J. Snyder, A. Szymkowiak,  D. Rabinowitz, N. Morgan |
|  | †Institutional affiliation |

**SNAP Collaboration Dec 2004**

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## SNAP Reviews/Studies/Milestones

- Nov 1999	Original SNAP proposal submitted to DOE
- Mar 2000	DOE/NSF SAGENAP committee recommends SNAP R&D
- Sep 2000	NASA Structure and Evolution of the Universe (SEU)
- Dec 2000	National Academy of Sciences Committee on Astro. & Astrophysics
- Jan 2001	DOE-HEP Review R&D (SNAP is uniquely able)
- Mar 2001	DOE High Energy Physics Advisory Panel (HEPAP)
- Jun 2001	NASA Integrated Mission Design Center (determines feasibility)
- July 2001	National Academy of Sciences, Committee on Physics of the Universe
- Dec 2001	NASA/SEU Strategic Planning Panel
- Dec 2001	NASA Instrument Synthesis & Analysis Lab
- Jan 2002	DOE subpanel report: High Energy Physics Long Range Planning
- Mar 2002	DOE/NSF SAGENAP committee update
- Apr 2002	National Academy of Sciences: Physics of the Universe report
- July 2002	DOE Office of Science R&D Review (Lehman)
- Dec 2002	JPL Team-X Study (studies potential NASA cost)
- Jan 2003	NASA releases SEU roadmap:  Beyond Einstein
- Feb 2003	DOE High Energy Physics Facilities Prioritization Panel
- Feb 2003	SNAP  R&D in the DOE budget
- Mar 2003	DOE High Energy Physics panel releases Facilities 20 Year Roadmap
- Nov 2003	JDEM Announcement  from DOE & NASA
- Nov 2003  Secretary of Energy’s 20-year Facilities Plan
- Nov 2003  Technical Review of SNAP (could be launched ~2011)
- May 2004  OSTP Strategic Plan (JDEM top recommendation)
- Jun 2004 	JDEM Science Definition Team empaneled

**Evolution of SNAP/JDEM**

- 1998 Discovery of the acceleration of the universe  and dark energy using supernovae.

- 2000 Confirmation of dark energy using cosmic microwave background measured from balloons.

- 2003 Confirmation of dark energy using cosmic microwave background measured from space (WMAP).

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## Andreas Albrecht – UC Davis

- Charles Baltay - Yale
- Barry Barish – Caltech
- Charles Bennett – GSFC – co-chair
- Gary Bernstein – U. Penn
- Robert Caldwell – Dartmouth
- Edward Cheng  – Conceptual Analytics
- Susana Deustua – AAS
- Megan Donahue – STScI
- Daniel Eisenstein – U. Arizona
- Richard Ellis – Caltech
- Wendy Freedman – Carnegie Observatories
- Josh Frieman – FNAL/Univ. Chicago
- Jonathan Gardner – GSFC

- Karl Glazebrook – Johns Hopkins
- Kim Griest – UCSD – co-chair
- Tod Lauer – NOAO
- Michael Levi – LBNL
- Eric Linder – UC/Space Sciences
- Robert Lupton – Princeton
- Warren Moos – Johns Hopkins
- Jon Morse – Arizona State
- Saul Perlmutter – U.C. Berkeley
- Bernard Rauscher – GSFC
- Adam Riess – STScI
- Michael Seiffert – JPL
- Craig Wheeler – U. Texas
- Edward Wright – UCLA

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## SNAP Tasks & Teams

**Science**
**Continuing groundbased & HST observing**
**Supernova Cosmology Project (Perlmutter)**
**Supernova Factory (Aldering)**
**Requirements**
**Simulation team**
**Theory & modelling**
**Calibration Team**
**Instruments**
**Silicon CCD group**
**HgCdTe NIR groups**
**Spectrometer**
**Electronics**
**Telescope**
**Design, tolerances, performance**
**Stray light**
**Fabrication, Integration & Test**
**Science ops, especially software pipeline**
**Spacecraft and flight systems**
**Industry, NASA, Berkeley campus group **

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## SNAP Reference Model

- Orbit:			L2 halo orbit
- 			(similar to JWST, MAP)
- Working field of view:	0.7 square degrees
- Survey fields: 		7.5 square degrees near north ecliptic pole
- 			7.5 square degrees near south ecliptic pole
- 			additional weak-lensing fields, ~300 sq degrees
- Field revisit period:		approx 4 days
- Time allocations:		50% survey, 36% spectroscopy, 14% downlink
- Wavelength range:		0.35 to 1.7 microns
- Telescope aperture:		2.0 meters

- These reference model parameters have been obtained through mission simulations that explore the cosmological parameter constraints – in particular, on acceleration versus redshift – that various mission scenarios would yield.

**Sun is 90deg to view direction**

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## Telescope Requirements

- Light Gathering Power
- must measure SNe almost 4 magnitudes  fainter than 26 magnitude  peak
- want SNR of  30:1 at peak brightness, aggregate exposure fit
- presence of zodiacal light foreground radiation
- time-on-target limited by revisit rate & number of fields
- spectroscopy demands comparable time-on-target
- requires geometric diameter ~ 2 meters
- Angular resolution
- signal to noise ratio is driver
- PSF for weak lensing is driver
- diffraction limit is an obvious  bound
- Airy disk  at one micron wavelength is 0.12 arcseconds FWHM
- need to match this to pixel size of VIS and NIR detectors
- Field of View
- set by required supernova discovery rate and WL mapping speed
- volume of space is proportional to field of view
- one degree field of view will meet our requirements
- Wavelength Coverage
- 0.35 to 1.7 microns will deliver everything we need
- drives us to an all-reflector optical train

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## Telescope Milestones

**1999**
**Comparisons of many alternative wide field telescope configurations; ****consultant**** on board**
**Discarded off-axis designs, TMTs (Willstrop etc) as unpackageable**
**Korsch 1978 annular-field TMA concept rediscovered, developed, adopted **
**2000**
**TMA43 (f/11): longitudinal rear axis, separate NIR/VIS;  filter wheel**
**Began mechanical, structural studies w/ ****subcontractor****: SM support, strongback, Finite Element Models**
**2001**
**Efforts to achieve shorter optical package for stiffness, stray light: TMA55/56**
**Explored longer focal lengths for potentially higher sampling: TMA59 (f/15)**
**Mission developed at ****NASA/GSFC IMDC**
**Instrument validated at ****NASA/GSFC ISAL**
**image quality**
**stray light**
**metering structure**
**actuators**

**2002**
**Adopted FIDO detector package, single focal plane, transverse rear axis**
**TMA62 (f/11) with filter wheel and TMA63 (f/11) no filter wheel**
**Detailed mirror FEM analysis, materials & fab/test trades with ****subcontractor**
**2003**
**Telescope engineering team enlarged**
**Detailed FEMs of PM, SM, TM, folding flat, and metering structure were explored**
**Launch stress**
**Bipod loads and torques**
**1-gravity test plan**
**Received top-down fab/test plan from one prospective ****contractor**
**Prospective PM ****blank manufacturer**** visited and briefed; cost/schedule estimates**
**2004**
**Telescope Specification written**
**Stray light study written**
**Integration & Test plan initiated**
**2005**
**NASA/GSFC IMDC**** study**
**Two telescope concept studies w/****industry**

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## Korsch AF-TMA configuration

**Prolate ellipsoid concave primary mirror**
**Hyperbolic convex secondary mirror**
**Flat folding mirror with central hole**
**Prolate ellipsoid concave tertiary mirror**
**Delivers < 0.06 arcsecond FWHM geometrical blur over  annular field 1.37 sqdeg**
**Flat focal surface**
**EFL adapts 15 to 30m; **
**           ****baseline=21.66m**
**Side-mounted detector**
**Telephoto advantage = 7**

- meters

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## Compact & Simple

- Focal plane

- Xmit Dish

**Compact & 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**

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## Focal Plane Concept

**Coalesce all sensors**
**Imager sensors**
**36 HgCdTe 2kx2k 18 ********m**
**36 CCD 3.5kx3.5k 10.5 ********m**
**600 megapixels**
**Filters**
**Spectrograph on the back with access ports through the focal plane.**
**140K operating**** ****temperature**
**Dedicated**** CCDs for**** ****guiding ****from the focal plane**
**Exposure times of 300 s**** with four/eight exposures in CCDs/HgCdTe**
**20 s readout**** slow enough for CCD noise and 4 post exposure and 4 pre exposure reads of HgCdTe**

- 560mm diameter  1.5 degrees

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## Modularization and Packaging

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## LBNL High-Resistivity CCD’s

- LBNL “Red Hots”: NOAO September 2001 newsletter

- New kind of Image Sensor developed at LBNL
- Better red response
- “radiation detector” silicon has better radiation tolerance for space applications
- Smaller pixel sizes enabling compact arrays
- Readout IC being developed “photons to bytes”

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## Integration & Test

**Integration & Test**

**The SNAP observatory was designed to be simple to test, calibrate, and verify**
**Interface ring between payload and spacecraft (spacecraft bolts on)**
**Direct insertion and removal of science package from telescope without telescope deintegration**
**Semi-kinematic mount for focal plane assembly and spectrograph**
**Comprehensive test plan in work**

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## DoE HEPAP 20-year Roadmap

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## Robin Staffin, DoE Assoc Director HEP April 2004

- our job

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## IMDC Objectives

**Spacecraft Accommodation**
**low profile structure**
**easy servicing**
**stiff, strong**
**mechanically independent of instrument**
**permit separate checkout**
**Attitude Control System**
**Dog simple!  but.....tight jitter spec!**
**rigid package: no deployables**
**built-in “through-the-lens” star tracker**
**Telemetry**
**DSN: the right choice?**
**alternatives? USN? DSO?**
**L2 Orbit**
**review no-shadows halo orbit plan**
**validate/correct launch constraints, prop margins....**

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## Conclusions

**Dark Energy continues to motivate the community**
_**[http://](http://arxiv.org/archive/astro-ph)**__**[arxiv](http://arxiv.org/archive/astro-ph)**__**[.org/archive/](http://arxiv.org/archive/astro-ph)**__**[astro](http://arxiv.org/archive/astro-ph)**__**[-ph](http://arxiv.org/archive/astro-ph)**_
_**[http://](http://arxiv.org/archive/gr-qc)**__**[arxiv](http://arxiv.org/archive/gr-qc)**__**[.org/archive/](http://arxiv.org/archive/gr-qc)**__**[gr](http://arxiv.org/archive/gr-qc)**__**[-qc](http://arxiv.org/archive/gr-qc)**_
_**[http://](http://arxiv.org/archive/hep-th)**__**[arxiv](http://arxiv.org/archive/hep-th)**__**[.org/archive/](http://arxiv.org/archive/hep-th)**__**[hep](http://arxiv.org/archive/hep-th)**__**[-](http://arxiv.org/archive/hep-th)**__**[th](http://arxiv.org/archive/hep-th)**_
**lots of ideas!**
**DoE continues to support our R&D on SNAP**
**NASA is in turmoil**
**Visit us at....      http://snap.LBL.gov**

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