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The Einstein Inflation Probe: Mission Concept Study

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Title: The Einstein Inflation Probe: Mission Concept Study


1
The Einstein Inflation ProbeMission Concept
Study
Gary Hinshaw, NASA/GSFC
May 12, 2004 Beyond Einstein _at_ SLAC
2
1916 Einstein Shows How Gravity Works
  • Einstein applied the General Theory of Relativity
    to the Universe as a whole
  • Future collapse or expand forever
  • Static Universe (Einsteins requirement)

3
The Evolution of the Universe
Early universe remarkably uniform, Current
universe is not
HOW DID THIS HAPPEN?
Inflation?... Cyclic model?... (Beyond Einstein)
4
Beyond Einstein - The Einstein Probes
  • NASA/NSF/DOE are planning a line of 3 Einstein
    Probe missions
  • A mission to study the dark energy, jointly with
    DOE, the Joint Dark Energy Mission (JDEM)
    a.k.a. SNAP.
  • A survey mission to find black holes in the
    nearby universe, the Black Hole Finder.
  • A mission to measure the polarization of the CMB
    to search for gravity waves from inflation, the
    Inflation Probe or CMBPOL.
  • NASA issued an AO soliciting mission concept
    studies for each of these missions. In November
    2003, several groups were selected to undertake
    studies.
  • Three groups will study the Inflation Probe
    mission. Their goals are to define the mission
    requirements for sensitivity, sky coverage,
    angular resolution, frequency coverage, and the
    key experimental technologies.

5
The Concept Study Team
  • Chuck Bennett (GFSC)
  • Mark Devlin (U. Penn)
  • Dale Fixsen (GSFC)
  • Gary Hinshaw (GSFC, PI)
  • Wayne Hu (U. Chicago)
  • Kent Irwin (NIST/Boulder)
  • Norm Jarosik (Princeton)
  • Alan Kogut (GSFC)
  • Arthur Kosowsky (Rutgers)
  • Michele Limon (GSFC)
  • Steve Meyer (U. Chicago)
  • Amber Miller (Columbia)
  • Harvey Moseley (GSFC)
  • Barth Netterfield (U. Toronto)
  • Barth Netterfield (U. Toronto)
  • Angelica Oliviera-Costa (U. Penn)
  • Lyman Page (Princeton)
  • John Ruhl (Case Western)
  • Uros Seljak (Princeton)
  • David Spergel (Princeton)
  • Suzanne Staggs (Princeton)
  • Max Tegmark (U. Penn)
  • Bruce Winstein (U. Chicago)
  • Ed Wollack (GSFC)
  • Ned Wright (UCLA)
  • Matias Zaldarriaga (Harvard)
  • Cliff Jackson (GSFC)

6
Why the Inflation Probe?
  • The B mode signal in CMB polarization (at llt100)
    is produced by gravity waves left over from
    inflation. This signal is the only current
    observational handle we have on physics at the
    1016 GeV scale -- 12 orders of magnitude beyond
    the LHC.
  • A measurement of the llt100 B mode signal would
    directly measure the energy scale of inflation
    and probe the fluctuation spectrum. It is also a
    test for alternate models of inflation (e.g., the
    cyclic universe).
  • CMB polarization acts as a filter on cosmological
    processes. It allows one to probe directly the
    decoupling epoch, the matter power spectrum
    (through gravitational lensing), the ionization
    history, and cosmological parameters.

7
CMB Polarization
TT - temperature from scalar and tensor modes
100
TT
TE - temperature polarization covariance
10
DASI
TE
DASI EE, 2002
dT l(l1)Cl/2p1/2 µK
EE gradient polarization from scalar tensor
modes
1
EE
(r limit?BB)
0.1
BB
BB curl polarization from tensor modes (only)
r0.1
(gravity waves)
0.01
r0.01
(lensing)
BB
10
100
1000
Multipole l
8
E mode B mode Polarization
  • Polarization decomposable into E mode (gradient)
    and B mode (curl) components.
  • Tensor fluctuations produce both E and B mode
    components.
  • Scalar fluctuations produce only E mode component
    (except for transformation by gravitatiuonal
    lensing).
  • B modes directly probe gravity waves.

Q lt 0 U 0
Q gt 0 U 0
Q 0 U lt 0
Q 0 U gt 0
9
Inflation Probe Sensitivity
  • One goal of the mission concept study is to
    define the mission requirements for sensitivity.
    Roughly
  • The amplitude of B mode polarization follows
  • ?TBB r1/2 E2infl
  • The power in B mode polarization follows
  • (?TBB )2 Ptensor(k)/Pscalar(k) r E4infl
  • Inflationists anticipate r 0.01
  • The current limits are rlt0.9 (95 cl) at
    k0.002/Mpc (l10) from WMAP (Spergel et al.),
    and rlt0.5 (95 cl) at k0.05/Mpc from WMAPSDSSS
    (Tegmark et al.)
  • To reach r0.01, require gt100 sensitivity of
    WMAP (see later).
  • If the energy scale of inflation is low
    (rltlt0.01), the Inflation Probe could rule out
    inflation occurring at the GUT-scale!

10
Sensitivity Advances
COBE 1989
60
WMAP 2001
gt20
Planck 2007
??
Inflation Probe
11
Detector Development History
COBE FIRAS 1 pixel, handmade
KAO spectrometer 24 pixels, handmade
KAO, SHARC I 24 pixels, micromachined
SHARC II on CSO 12x32 384 pixels Largest array
in operation
SCUBA-2 4000 pixels in quadrants Multiplexer
behind detectors
12
WMAP (Handmade) Microwave Receivers
10 Differencing Assemblies 4 _at_ 94 GHz W-band 2
_at_ 61 GHz V-band 2 _at_ 41 GHz Q-band 1 _at_ 33 GHz
Ka-band 1 _at_ 23 GHz K-band
Jarosik et al. (2003) ApJS, 145, 413 Jarosik et
al. (2003) ApJS, 148, 29
13
Foreground Emission
  • Polarized foreground emission arises from our
    galaxy. The signal from our galaxy is currently
    poorly known, but it is likely comparable to or
    larger than the gravity wave signal over most of
    the sky.
  • Foreground emission has both E and B mode
    symmetry.
  • Multiple frequencies are necessary to
    discriminate CMB emission from galactic
    foreground emission. Unlike the temperature case,
    modeling and subtracting polarized foreground
    emission will be necessary.
  • Foreground contamination also results from the
    conversion of primordial E mode signal to B mode
    signal by gravitational lensing.
  • If the lensing contamination not cleaned, it sets
    a lower detection limit on r of 10-4 at l100
    (the recombination peak) and 10-5 at l10 (the
    reionization peak).

14
Temperature Foreground Spectra
  • WMAP foreground estimates from 1st year
    temperature data (WMAP observing bands shown in
    grey)
  • CMB dominates foregrounds over most of the sky
  • Free-free emission is unpolarized
  • Key question what is polarization fraction of
    foregrounds relative to B-mode CMB?
  • WMAP and other polarization data will be very
    helpful in guiding our study of foregrounds.

Bennett et al. (2003) ApJS, 148, 97
15
Projected Lensing Foreground (Green)
16
Projected Galactic Foreground (Dust/Synch)
17
Angular resolution
  • The angular resolution required of the Inflation
    Probe is a major topic of the mission concept
    study.
  • High resolution permits more thorough cleaning of
    the B-mode signal due to gravitational lensing ?
    better signal to noise at low l
  • High resolution is a major cost driver for a
    space mission!
  • Concept Study must perform a careful trade study
    of the cost-benefit of high angular resolution
  • High resolution optical coupling vs. high
    throughput
  • Thermal loading with large optics
  • Spacecraft attitude control requirements/costs
  • Data rate requirements/costs

18
Noise Floor for Strawman I
675 background limited detectors _at_ 3 frequencies
19
Noise Floor for Strawman II
2100 background limited detectors _at_ 3 frequencies
20
Control of Systematic Errors
  • Control of systematic errors is critical to the
    success of any CMB polarization measurement.
  • A key element in rejecting systematic errors is
    to modulate the signal on many different time
    scales. The efficiency of different modulation
    schemes must be assessed.
  • It is crucial to verify in flight that systematic
    effects have been reduced to acceptable levels.
  • The most sensitive detectors (e.g. bolometers)
    are power detectors. Any effect that leads to a
    difference in power can be confused with a
    polarization signal, e.g. bandpass mismatch, far
    side-lobe pick-up, higher order beam effects,
    etc.
  • The gain of the system has to be stable on the
    time scale that one can measure it in flight.

21
Sky Coverage and Scan Strategy
  • The maximum S/N for B modes is at l5. To
    reliably measure llt10 (to really be sure we are
    seeing B modes) nearly full sky coverage is
    required.
  • Depending on the degree to which the lensing and
    galactic foreground may be cleaned, smaller
    patches might yield a detection of gravity waves.
  • The scan pattern used to modulate the signal and
    achieve sky coverage will be critical. Detailed
    mission simulations of different scan modes,
    coupled with realistic instrument models will be
    used to assess scan patterns and other
    experimental approaches.
  • The decomposition of the polarization signal into
    E and B modes is sensitive to sky coverage and
    correlations between data points.

22
WMAP Scan Pattern as Example
Bennett et al. (2003) ApJ, 583, 1
23
Do We Need a Satellite?
Only in space can one achieve the stability and
vantage needed to probe large angular scales
(gt1) This is the range where the telltale
remnants of inflation are most likely to be
found Therefore yes!
24
Inflation Probe Concept Study - Summary
  • Study period is two years.
  • Starting in June 2004, study teams will
    participate a joint NASA/NSF/DOE task force to
    chart the next steps CMB polarization studies.
  • The obstacles to detecting gravity waves are
    sensitivity, systematic errors, and astrophysical
    foregrounds. With a well designed mission, these
    obstacles can be surmounted. The goal of directly
    measuring the energy scale of inflation is within
    sight!

25
The 6 Phases of a Project
  1. Enthusiasm! (Now)
  2. Disillusionment
  3. Panic!!
  4. Search for the Guilty
  5. Punishment of the Innocent!!!
  6. Praise and Honors for the Non-Participants ?

26
The End
27
Experimental ApproachMinimize Systematic
Measurement Errors
  • Differential design to minimize systematic errors
  • 5 microwave frequencies to understand foregrounds
  • 20 radiometers to allow multiple cross checks
  • Sensitivity to polarization
  • Accurate calibration (lt0.5)
  • ? calibration using modulation of the dipole from
    Earths velocity
  • In-flight beam measurements on Jupiter
  • Minimize sidelobes diffracted signals from
    Earth, Sun, Moon
  • ? L2 orbit
  • Multiple modulation periods to identify
    systematic effects
  • Minimize all observatory changes
  • ? L2 orbit constant survey mode operations
  • Rapid and complex sky scan
  • ?observe 30 of the sky in an hour

SPIN-SYNCHRONOUS NON-SKY SIGNALS WERE THE LEADING
CONCERN
Bennett et al. (2003) ApJ, 583, 1
28
Systematic Error Cross-Checks
(Q1Q2)/2
(Q1-Q2)/2
(V1-V2)/2
(V1V2)/2
(W12-W34)/2
(W12W34)/2
Hinshaw et al. (2003) ApJS, 148, 63
29
Temp x E-Polarization Power Spectrum
from z1089 scattering of CMB from electrons
with non-random velocities
Kogut et al. (2003) ApJS, 148, 161 Bennett et al.
(2003) ApJS, 148, 1
30
http//lambda.gsfc.nasa.gov
31
Temperature-Polarization Correlation
Radial pattern around cold spots Tangential
pattern around hot spots
Temperature quadrupole at z1089 generates
polarization
32
Jupiter Beam Maps
B-side
A-side
33
CMB Polarization
  • z20 reionization
  • scattering of CMB from free electrons
  • uniformly suppress lgt40 anisotropy by 30 (!)
  • Now detected
  • z1089 decoupling
  • scattering of CMB from electrons with non-random
    velocities
  • polarization correlates with temperature map
  • 1st detected by DASI, now have power spectrum
  • Gravity waves
  • Inflation-generated gravity waves polarize CMB
  • need new mission (e.g., NASAs Einstein
    Inflation Probe

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Sky Coverage
MAP990159
39
Designed by M. Pospieszalski at NRAO
40
Lay of the Land
Temperature (T) from scalar and tensor
fluctuations
E polarization from scalars and tensors
B modes from lensing of E modes.
Current limit on tensors
B polarization from tensors (gravity waves) only
Recombination peak (z1089)
Gravity waves decay inside the horizon.
Reionization peak (z20)
41
1948 Big Bang Theory
  • Universe began unimaginably hot and dense -
    billions of years ago
  • Expanded and cooled
  • Predictions
  • A microwave afterglow light from the Big Bang
  • Specific spectrum (intensity with wavelength)
  • Many other predictions - all predictions since
    verified

42
1965 Discovery of Afterglow Light from Big Bang
Full sky image, green represents the afterglow
Measurement Receiver Bell Telephone Labs New
Jersey
1978 Nobel Prize in Physics
43
Beyond Einstein Inflationary Universe
  • One slide summary of inflation.
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