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The European mission to map the
Cosmic Microwave Background
J. Tauber, on behalf of the Planck Collaboration
Main Observational Objective of
To image the whole sky at wavelengths near
the peak of the spectrum of the Cosmic
Microwave Background Radiation Field
(CMB), with an instrument sensitivity
∆T/T~10-6, an angular resolution ~5
arcminutes, wide frequency coverage, and
excellent rejection of systematics .
Planck:
3rd Generation
CMB space
experiment
2010
Theoretical angular power
spectrum of the CMB (CDM)
∆T
= ∑ almYl m (θ , ϕ )
T
l ,m
2
Cl = 〈 alm 〉
Theoretical angular power
spectrum of the CMB (CDM)
∆T
= ∑ almYl m (θ , ϕ )
T
l ,m
2
Cl = 〈 alm 〉
Fundamental
Parameters
From Freedman and Taylor 2004
Open (fundamental) Questions
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Did inflation occur ?
What is the shape of the inflaton potential ?
What is the nature of dark matter ?
What is dark energy ?
Why do we live at a time when expansion starts to
accelrate ?
• Are there topological defects ?
• .....
The CMB is not exhausted
We need an experiment which:
• Has a sensitivity at least 10x better than
WMAP
• Has an angular resolution at least 2x better
than WMAP
• Can map the polarization of the CMB over
the whole sky
• Can cope with systematics and local signals
Such an experiment is ~1000x more powerful than WMAP
The need for accuracy
From: Efstathiou 2004
The need for accuracy
From: Efstathiou 2004
Parameter recovery
WMAP 4 yr
WMAP 4 yr +ACT/SPT
Planck
From: Bond 2004
Science with accurate cosmological
parameters
•
Cosmological parameters to high accuracy
– Geometry of Universe
– Age of Universe, Ho, Ωo, Λ, …
– Neutrino mass, …
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Testing inflation, constraining the inflaton potential
Finding non-gaussianities
– Primordial
– “local”
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Finding signatures of gravitational waves
physics beyond standard model, e.g. superstrings
Evolution of structure and nature of dark matter, epoch of reionisation
…
Observational Strategy
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Two successive all-sky surveys
1.5 metre aperture telescope
wide frequency coverage (25 GHz - 950 GHz)
State-of-the-art detectors
extreme attention to systematic effects
Spacecraft elements
Payload
module
PFM
Spacecraft hardware
Prime contractor: Alcatel Space (Cannes)
Launch in 2007
Orbit and Observing strategy
Transfer to orbit around L2
300 K
Payload elements
Telescope
20 K
0.1 K
High Frequency Instrument
Low Frequency Instrument
Waveguides
HEMT LNAs
Bolometers
Preamps
Backend
20 K H2
Sorption cooler
Electronics
Electronics
Service Module
4 K/0.1 K
Cooling
System
Planck Telescope
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Primary: 1.50 x 1.89 m ellipsoid (CFRP)
Secondary: 1.02 x 1.04 m ellipsoid (CFRP)
System:
– 1.5 m circular projected aperture
– Total MWFE<40 µm rms
– Total ε <0.01
•
Reflectors are being developed by ESA and
a Consortium of danish institutes led by the
Danish Space Research Institute
(PI: Dr. H.U. Norgaard-Nielsen)
Reflectors
Manufacturer: Astrium Gmbh (Friedrichshafen)
Low Frequency Instrument
4 K Ref. Load
Sky
1st Hybrid
Σ
∆
20 K
HEMT LNAs
Φ
Φ
Phase switches
Waveguides
2nd Hybrid
Σ
∆
~1.5 m Waveguides
300 K
P.I.: R. Mandolesi, IASF (Bologna)
LNAs
Detectors & electronics
LFI
hardware
High Frequency Instrument
Back-to-back horns at 4 K
LFI horns at 20 K
Filters at 1.6 K
Bolometers, horns
and filters at 0.1 K
JFET Box at 50 K
(JFETs at 120 K)
Flange at 20 K
PI: J.-L. Puget, IAS (Orsay)
High Frequency Instrument
Filters
(QMW)
Figure 2.4.1
Filters
(QMW)
Filters
(QMW)
Plot of Prototype 143 GHz Channel Spectral Response
1
0.1
0.01
0.001
0.0001
Intensity
1E-05
1E-06
1E-07
1E-08
1E-09
2mm filter centre part
1E-10
55cm-1 edge
1E-11
C147: 12 cm-1 edge
1E-12
C169: 18 cm-1 edge
C146: 5.9 cm-1 edge
1E-13
Overall System Response
1E-14
50
150
250
350
450
550
650
Frequency (GHz)
750
850
950
Figure 2.5.1 Prototype spider bolometer CSK18. Active absorber diameter, outer spider
circle, is 5.675 mm. Inset shows NTD Ge sensor at the centre with the two thicker current
carrying and thermal conductance control lines running out horizontally to electrical contacts
on the silicon substrate.
Spider-web or polarisation-sensitive bolometers (CalTech/JPL)
HFI hardware
Estimated Instrument Performance Goals
Telescope
Instrument
Center Freq. (GHz)
Detector Technology
Detector Temperature
Cooling Requirements
Number of Unpol.
Detectors
Number of Linearly
Polarised Detectors
Angular Resolution
(FWHM, arcmin)
Bandwidth (GHz)
Average ∆T/TI* per
pixel#
Average ∆T/TU,Q* per
pixel#
1.5 m (proj. aperture) aplanatic; shared focal plane; system emissivity 1%
Viewing direction offset 85o from spin axis; Field of View 8o
LFI
HFI
30
44
70
100
143
217
353
545
857
HEMT LNA arrays
Bolometer arrays
~20 K
0.1 K
H2 sorption cooler
H2 sorption + 4 K J-T stage + Dilution cooler
0
0
0
0
4
4
4
4
4
4
6
12
8
8
8
8
0
0
33
24
14
9.5
7.1
5
5
5
5
6
2.0
8.8
2.7
14
4.7
33
2.5
47
2.2
72
4.8
116
14.7
180
147
283
6700
2.8
3.9
6.7
4.0
4.2
9.8
29.8
*
Sensitivity (1σ) to intensity (Stokes I) fluctuations observed on the sky, in thermodynamic temperature (x10-6) units, relative to the
average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).
#
A pixel is a square whose side is the FWHM extent of the beam.
*
Sensitivity (1σ) to polarised intensity (Stokes U and Q) fluctuations observed on the sky, in thermodynamic temperature (x10-6)
units, relative to the average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).
Table last updated Feb. 2004
Acquiring and processing
Time-ordered information
Converting TOI to maps of
the sky emission
at many frequencies
Converting frequency
Maps to component maps
CMB
Free-free
Dust
Synchrotron Detector noise
Thermal Doppler
Clusters Galaxies Galactic
Estimating the CMB
Angular power spectrum
And cosmological parameters
Power spectrum recovery
From: Efstathiou 2004
E-mode recovery
From: Efstathiou 2004
B-mode recovery
From: Efstathiou 2004
Extracting the science
Measurements (15 Gbit/day)
105 detectors, 15000 samples/sec, total ~ 6x1011 samples
Frequency maps
10 channels, total ~3x107 pixels
Instrument response
Systematic effects
Foreground maps
Point source catalogs
~6 foreground components
~500 parameters
>104 sources
CMB temperature map
CMB polarisation maps
~5x106 pixels
~107 pixels
CMB temp. ang. power spectrum
CMB pol. ang. Power spectrum
~2000 numbers
~1000 numbers
Cosmological parameters
~12 numbers
Key Non-CMB Science with Planck
• Sunyaev-Zeldovich effect
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Measurement of y in > 104 galaxy clusters
Cosmological evolution of clusters to z > 1
Ho and X-ray measurements, gas properties
Bulk velocities on scales > 300 Mpc
• Extragalactic sources and backgrounds
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IR and radio galaxies
AGN's, QSO's, blazars
Evolution of galaxy counts to z > 1
Far-IR background fluctuations
• Maps of Galaxy at frequencies 30 - 1000 GHz
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Dust properties, Cloud and cirrus morphology
Star forming regions, Cold molecular clouds
Cosmic ray distribution
Polarisation-based science, e.g. Galactic magnetic field
Planck Data Products
• Cleaned & calibrated time-ordered data
• All-sky maps in nine frequency bands
• “First generation” all-sky component maps
– Cosmic Microwave Background
– Galactic emission maps (synchrotron, free-free,
dust)
– Extra-galactic source catalogues
Key dates
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First proposal (COBRAS/SAMBA): 1993
Start of spacecraft manufacture: end-2002
Payload model deliveries: 2004-2005
Launch: August 2007
Insertion into orbit: December 2007
Operations: 2008- mid 2009
Scientific product delivery: mid-2011
Optical configuration
~8o
Scan direction
In the focal plane
On the sky
Optical configuration
Scan direction
Polarisation Measurement
Principle with the Planck HFI
Both bolometers in a PSB pair
share the same optics but
have different readouts
INTENSITY
POLARISATION
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Scan
Stokes Parameters
I = Ex2 + Ey2
Q = Ex2 - Ey2
U = 2ExEy
Each PSB pair measures (I &
U) or (I & Q)
Two pairs, rotated by 45o,
together measure (I, U, Q)
Polarisation Measurement with
LFI and HFI
• Principle is the same for both
LFI and HFI
• Polarisation separation
mechanism is different
– LFI: Ortho-mode Transducer
separates two orthogonal
polarisations
– HFI: Orthogonally oriented
grids select polarisation and
deliver to separate thermistors
WMAP vs Planck: Key differences
WMAP
P/L Technology
Planck
Detectors
Dual telescope
Passive cooling
HEMT LNAs
Freq. range
22-94 GHz
Single telescope
Active cooling
HEMT LNAs
Bolometers
30-857 GHz
Ang. resolution
13.8 arcmin
5 arcmin
Sensitivity @ 90100 GHz
35 µK
(0o.3x0o.3)
2.2 µK
(0o.3x0o.3)
Sensitivity to CMB Min. 31 µK
(after avg. & fg.
Typ. 35 µK
Subtr.)
Min. 3 µK
Typ. 5 µK