Technologies for the SNAP

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Technologies for the SNAP Supernova /
Acceleration Probe
Physics Discoveries
Launch
Assembly
Configuration
Development
Supernova / Acceleration Probe
2010
2002
Integration
Technology
Engineering
Physics
Michael Levi (LBNL)
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Overview

• SuperNova /Acceleration Probe

• Talk Outline
• Introduction
• Science
• Mission Overview
• Focal Plane Technology
• Orbit/Launch Vehicle
• Project Status
• Summary

• Technologies

AN ARRAY OF DETECTORS WILL BE ASSEMBLED INTO AN
ANNULUS NEARLY ONE HALF METER WIDE, THE LARGEST
AND MOST SENSITIVE ASTRONOMICAL IMAGER EVER
CONSTRUCTED
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The Cosmological Constant

• Einstein 1917
• Field equations show contracting or expanding
  universe, but the universe was thought to be
  static.
• Einstein postulated a cosmological constant, L
  called dark energy (with negative pressure), to
  maintain a static universe.

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Einsteins field equations (1917)

• L and r add in determining H
• L and r subtract in determining acceleration of
  universe
• Danger! Runaway solution if L is large and
  positive!

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Hubbles Law

• Measure the velocity of every galaxy.
• Nearly all are receding.
• Use Cepheids to measure distances to nearby
  galaxies.
• Result The faster its moving, the farther away
  it is.

Hubbles Data (1929)
Recessional Velocity (km/sec)
Distance Mpc)
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The Universe, its Expanding!
Hubbles 1929 evidence that the universe is not
static. The Cosmological Constant is unnecessary
-- Einsteins proclaimed his Biggest
Blunder.
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Future possibilities expand/collapse
Big Bang
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Borderline Universe

• Density (?)
• ? density/critical density
• ?/?c
• ?c 10-26 kg.m-3
• 6 H atoms per m3!

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Inflation

• Alan Guth....
• enormous (but brief!) cosmic expansion
• Age 10-33 sec to 10-31 sec
• Vast expansion, roughly 1066
• predicts a completely flat universe today
• in accord with Cosmic Microwave Background (CMB)
• predicts a nearly uniform universe today
• small fluctuations accord with CMB
• One teensy problem

experiment
theory
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Future possibilities expand/collapse
Future
Past
(today)
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Finding Supernovae
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Type Ia Supernovae
Type Ia supernovae can be seen from 10 billion
light years away
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(No Transcript)
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The Accelerating Universe Sciences Breakthrough
of the Year
-accelerates -expands forever -slows but never
collapses
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Evidence for Acceleration
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Current Results on Cosmological Parameters
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Energy budget of Universe
Dark Matter 30
Dark Energy 65
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Whats wrong with a non-zero L
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Fundamental Physics Questions

• What is the Nature of the dark energy?
• The dominant component of our universe.
• Dark energy does not fit in current physics
  theory.
• Theory proposes a number of alternative new
  physics explanations, each with different
  properties we can measure.
• Two key contrasting theories of dark energy.
• vacuum energy, constant over time
• Deep philosophical implications, why are the
  matter (WM) and energy densities (WL) nearly the
  same today, they have totally different time
  evolution. Why now? Why is L so small?
• or, time dependent possibly a dynamical scalar
  field
• Might explain WM _at_ WL and so small, weve seen
  these fields elsewhere in particle physics and in
  the theory of inflation. Points to new physics.

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Future possibilities expand/collapse
Need Lots of Data to Study This Region
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Need Lots more Data!
Turn 42 Supernovae ? 2500 Supernovae
The 42 SNe from the SCP Project peters out by
Zgt0.6
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Supernova / Acceleration Probe

• SNAP a dedicated experiment to study dark energy
• Dedicated instrument, few moving parts
• Mirror 2 meter aperture sensitive to light from
  distant SN

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SNAPs Target Results
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Understanding Dark Energy
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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(-gtU.Penn), D. Levin, T. McKay, S.
McKee, M. Schubnell, G. Tarle , A. Tomasch (U.
Michigan) R. Ellis, R. Massey, J. Rhodes, A.
Refregier (CalTech) C. Bower, 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) http//snap.lbl.gov/
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Space Mission

• SNAP a dedicated experiment to study dark energy
• Large Field of View to see lots of SNe, has
  half-billion pixel mosaic camera (100x larger
  Field than Hubble)

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Mission Design

• Telescope 2 meter aperture sensitive to light
  from distant SNe

Flat focal plane Delivers lt 0.04 arcsecond FWHM
geometrical blur over field Provides side-mounted
detector location for best detector cooling
TMA63
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Camera

• Largest Astronomical Flight Camera

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Mission Design
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Mission Design
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Mission Design
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Mission Design
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Mission Design
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Mission Design
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Mission Design
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New Technologies for SNAP
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Mission Design

• Photometry 0.7 FOV half-billion pixel mosaic
  camera, high-resistivity, rad-tolerant n-type
  CCDs (0.35-1.0 mm) and, HgCdTe arrays (0.9-1.7
  mm).

Field of View Optical ( 36 CCDs) 0.34 sq.
deg. Four filters on each 10.5 mm pixel CCD
detector Field of View IR (36 HgCdTes) 0.34
sq. deg. One filter on each 18 mm pixel HgCdTe
detector
spectrograph
guider
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Mission Design
All detectors occupy same mechanical, thermal,
optical environment.
Readout Electronics
Cryostat/Cosmic Ray Shield
Shutters
Spectrograph
Thermal Links
Cold Plate
Filters
CCDs/HgCdTe
Guiders
Radiator
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Mission Design
Spectrograph
Focal plane
shutter
electronics
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Focal plane concept

• Coalesce all sensors at one focal plane.
• Imager sensors on the front.
• Spectrograph on the back with access ports
  through the focal plane.
• Common 140K operating temp.
• Fixed filter mosaic atop the imager sensors.
• Mechanical shutter near the folding mirror.
• Particle/thermal/light shield between folding
  mirror and focal plane
• Guide spacecraft from the focal plane.

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High-Resistivity CCDs

• New kind of Charged Coupled Device (CCD)
  developed at LBNL
• Better overall response than more costly
  thinned devices in use
• High-purity radiation detector silicon has
  better radiation tolerance for space applications
• The CCDs can be abutted on all four sides
  enabling very large mosaic arrays

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High-Resistivity CCDs

• New kind of Charged Coupled Device (CCD)
  developed at LBNL
• Better overall response than more costly
  thinned devices in use
• High-purity radiation detector silicon has
  better radiation tolerance for space applications
• The CCDs can be abutted on all four sides
  enabling very large mosaic arrays

LBNL Red Hots NOAO September 2001 newsletter
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LBNL 2k x 4k
Trap sites found by pocket pumping.
USAF test pattern.
Back-illumination technology development
completed for LBNL manufactured devices.
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Commercially fabricated 150 mm waferDALSA
Semiconductor
Front-illuminated 2k x 4k (15mm
pixel) Back-illumination technology development
in progress
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SNAP Prototype CCD Test Image
2880 x 2880 10.5 mm pixels Front illuminated
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Fe55X-ray spectrum
10.5 mm pixel CCD
s17.2 e-
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CTE Measurement
Charge transfer efficiency in CCD bucket brigade
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Radiation Damage
Gain is measured using the 55Fe X-ray method at
128 K. 13 MeV proton irradiation at LBNL 88
Cyclotron SNAP will be exposed to about 1.8?107
MeV/g (solar max).
1.0000
0.9999
0.9998
0.9997
Gain CTE
0.9996
0.9995
0.9994
0.9993
0.9992
LBNL CCD
HST/Marconi
0.9991
Tektronix
0.9990
0
200
400
600
800
1000
1200
1400
1600
6
Dose (10
MeV/g)
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Measurement of PSF
VSUB 12V
VSUB 80V 1100 x 800
pixels, 300 mm thick back-illuminated CCD, 15 mm
pixels
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CCD support electronics

• Goals
• Photons-to-bits focal plane
• Eliminate large cable plant to reduce system
  noise problems.
• Reduce power dramatically relative to
  conventional implementation.
• ASIC Challenges
• Large dynamic range from 2 e- readnoise and 130
  ke- well depth.
• Radiation tolerance
• Operation at 140K to reduce cable plant and
  associated problems requires low power

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Front end readout Concept

• Low noiseCCD electronic noise ? 4e rms
• Large dynamic range96dB from noise floor to
  130ke well depth
• Readout frequency ? 100 kHz
• Low power ? 200mJ/image/channel

• Operation at 140K and 300KAllow normal operation
  at 140K and chip testing at room temperature
• Compact
• Radiation tolerant 10 kRad ionization
• Robust, space qualified

Clocks, control
Front end IC
CCD
Analog input
Analog signal processing
ADC
Digital out
Amplification
(One channel)
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Multi range ADC concept
Gain 1
Digital out
Input
Signal processing
MUX
12 bits ADC
Gain 2
Gain 32
(CDS Integration)

• The dynamic range for the signal is 96dB (16
  bits)
• From 2 electrons (CCD noise) up to 130000
  electrons.
• The dynamic range is covered using 3 slopes and a
  12 bit ADC.
• The readout chain should digitize the signal with
  an LSB size which depends of the signal amplitude
  such that the quantization noise is still below
  the Poisson noise.

Poisson elec noise
Gain 32 quantization noise referred to the
input
Gain 1
Gain 2
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Technology Survey

• 10 commercial CMOS sub micron processes where
  investigated.
• Selection criteria
• Noise, Transistor performance
• Matching, precision
• Passive components availability and precision
• Expected production life time
• Radiation tolerance

Technologies studied for noise and power
performance
Minimum feature size
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Measurement of 0.25mm CMOS at low-T

• DC characteristic measurement of MOS transistors
• The main parameters varing with temperature are
  the threshold voltage and the mobility.
• Measurements performed on transistors using a
  LBNL test chip.
• Good agreement between measurement and simulation.

Mobility ratio NMOS 1u/0.24u
3.5
3
2.5
2
1.5
1
0.5
0
0
50
100
150
200
250
300
350
Temp (K)
Threshold voltage
Temp (K)
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Radiation Tolerance
Irradiation of deep sub micron test transistors
were performed at the lab.

• No significant change of threshold voltage was
  observed (lt50mV)
• Enclosed geometry prevents leakage at high dose
  (10 Mrad)
• Standard geometry could be used for dose lt100kRad

Standard geometry
Enclosed geometry
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NIR System Concept

• 150 NIR Megapixels
• 36 (2k ? 2k) 18 mm HgCdTe detectors (0.34 sq.
  deg)
• 3 special bandpass filters covering 1.0 1.7 mm
  in NIR
• T 140?K (to limit dark current)

HgCdTe
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HgCdTe Fabrication
Hybrid array has an array of HgCdTe detectors on
one layer and charge collection and addressing
circuitry (CMOS multiplexer) on another layer.
The two layers are connected with indium bump
bonds.
PACE Layer of CdTe is deposited on sapphire
substrate by chemical vapor deposition followed
by a layer of HgCdTe grown by liquid phase
epitaxy. Principally manufactured at
Raytheon. MBE - Rockwell has developed a process
of fabricating detector layers in HgCdTe using
molecular beam epitaxy (MBE).
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State of HgCdTe NIR Detectors

• Hg(1-x)CdxTe ?c determined by x this
  determines operating temperature.
• Rockwell Science Center (RSC) is the principal
  source for Mercury Cadmium Telluride (HgCdTe)
  infrared focal plane arrays (FPAs) used in
  astronomy.
• RSC has developed devices (NICMOS 256 x 256
  FPAs, WFC3 1024 x 1024) for the IR channel on
  HST. Also U Hawaii, ESO, Subaru, JWST

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Shortwave HdCdTe Development

• Hubble Space Telescope Wide Field Camera
  3
• WFC-3 replaces WFPC-2
• CCDs IR HgCdTe array
• 1.7 mm cut off
• 18 mm pixel
• 1024 x 1024 format
• Hawaii-1R MUX
• Dark current consistent with thermoelectric
  cooling
• lt 0.5 e/s at 150 K
• 0.02 e-/s at 140 K
• Expected QE 60 0.9-1.7 mm

NIC-2
WFC-3 IR
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Spectrograph IFU Slicer principles
How to rearrange 2D field to enter spectrograph
slit

1. Field divided by slicing mirrors in subfields (20
   for SNAP)
2. Aligned pupil mirrors
3. Sub-Field imaged along an entrance slit

3
1
2
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Mirror Slicer Stack(L.A.M. Marseille)
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SPACECRAFT CONFIGURATION
Secondary Mirror Hexapod and Lampshade Light
Baffle
Door Assembly
Main Baffle Assembly
Secondary Metering Structure
Primary Solar Array
Primary Mirror
Optical Bench
Solar Array, Dark-Side
Instrument Metering Structure
Instrument Radiator
Tertiary Mirror
Fold-Flat Mirror
Instrument Bay
Spacecraft
Shutter
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NASA GSFC Spacecraft Study

• 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

Secondary Mirror and Active Mount
Primary Mirror
Optical Bench
Solar Array Wrap around, body mounted
Thermal Radiator
Sub-system electronics
Detector/Camera Assembly
Propulsion Tanks
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Orbit

• High Earth, 3 day synchronous orbit
• Good Overall Optimization of Mission Trade-offs
• Orbit Provides Multiple Advantages
• Minimum Thermal Change on Structure
• Excellent Coverage from Berkeley Groundstation
• Passive Cooling of Detectors
• Minimizes Stray Light

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Ground Station Coverage
Orbit perigee remains over Berkeley for 3 years
without adjustment. 5.2 hour ground pass over
Berkeley
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Ka-Band Ground Antennas
Manufacturer VertexRSI, Santa Clara,
CA Aperture Diameter 12 m Surface Accuracy
25 µm r.m.s. Max. Frequency 600
GHz Pointing Accuracy 0.6 arcsec
12-m Prototype Antenna for NRAOs 64-Element
Atacama Large Millimeter Array (ALMA) Presently
Installed at VLA Site in New Mexico
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Launch in 2009
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Delta IV Main Engine Test Firing
First launch scheduled for Nov. 16, 2002
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Current Status of SNAP

• SNAP currently in pre-conceptual design period
• Development of collaboration
• Performing critical RD of new technologies, risk
  mitigation
• Requirements development
• Feasibility and early trade studies
• A major review of SNAP was performed by DOE in
  July, 02 (The Lehman Review)
• Transition to conceptual design Jan. 2003
• Technology development currently funded by
  DOE/HEP.

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Current Status of SNAP

• Endorsement by HEPAP for development of cost,
  schedule, RD
• We endorse RD funding for SNAP from the
  high-energy physics program.
• SNAP reviewed by the NRC Committee on the Physics
  of the Universe (Turner panel) as part of their
  Phase II review of projects.
• 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).
• The Committee further recommends that NASA and
  DOE work together to construct a wide-field
  telescope in space to determine the expansion
  history of the universe and fully probe the
  nature of the dark energy.
• A major review of SNAP was performed by DOE in
  July, 02 (The Lehman Review)

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Technology Summary

• Instrument
• NIR sensors
• HgCdTe detectors are begin developed for
  WFC3/HST, JWST
• Need to demonstrate performance requirements for
  SNAP
• CCDs
• Industrialization of CCD fabrication has produced
  useful devices. Need to demonstrate volume,
  especially for commercially fabricated
  back-illuminated.
• Electronics
• ASIC development is required
• Spectrograph
• Challenging IR Detector Performance Requirements

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Technology Summary

• Spacecraft Systems
• On-board data handling
• We have opted to send all data to ground to
  simplify the flight hardware and to minimize the
  development of flight-worthy software,
• 300 Mbit/s Ka-band telemetry,
• large Solid State Recorder 375 Gbytes.
• Pointing
• Pointing requirements are challenging, but not
  state-of-the-art,
• Feedback from the focal plane, plus current
  generation attitude control systems, may have
  sufficient pointing accuracy,
• Telescope
• Primary mirror manufacture, stray light,
  end-to-end testing plan.

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Conclusion

• Exciting time for high energy and particle
  astrophysics.
• Dark Energy and Dark Matter comprise 95 of the
  constituents of the universe yet we know nothing
  about them.
• New particles fields yet to be discovered.
• Supersymmetry, extra-dimensions, quantum gravity,
  strings, etc
• Needed data is accessible to experimentation
• Accessible to current or planned technology
• My colleagues accuse me of wandering around the
  halls saying Were in a golden age of cosmology,
  were in a golden age of cosmology. Well, Im
  proudly saying that were in a golden age of
  cosmology. Michael Turner

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Expansion History of the UniverseWe live in
a special time when- we can ask questions
about the history and fate of the universe- and
hope to get an answer!