The European mission to map
the Cosmic Microwave Background
“Polarisation 2005” Orsay, 12-16 September 2005
The Planck mission and Polarisation
• Introduction to Planck:– Concept & Practice of a CMB
polarisation experiment– Payload and spacecraft design
The Concept ofa CMB polarisation
experiment
“Polarisation 2005” Orsay, 12-16 September 2005
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 .
“Polarisation 2005” Orsay, 12-16 September 2005
The microwave sky (as seen by COBE)
“Polarisation 2005” Orsay, 12-16 September 2005
Sky emission components
Finkbeiner & Schlegel 1999
Planck
“Polarisation 2005” Orsay, 12-16 September 2005
Imaging the sky emissionImaging the sky emission
at many frequenciesat many frequencies
CMB
ClustersThermal Doppler
Galaxies Galactic
Free-freeSynchrotron
DustDetector noise
Peeling back the layersPeeling back the layers
Recovering the Recovering the
cosmological informationcosmological information
“Polarisation 2005” Orsay, 12-16 September 2005
Theoretical angular power spectrum of the CMB (CDM)
),(,
ϕθ∑=∆
ml
ml
ml Ya
TT
⟩⟨=2m
ll aC
“Polarisation 2005” Orsay, 12-16 September 2005
“Polarisation 2005” Orsay, 12-16 September 2005
Expected CMB polarisation spectra
Hu et al 2002
“Polarisation 2005” Orsay, 12-16 September 2005
Hu 2002
The shape of the power spectrum
depends sensitively on the value of cosmological parameters
“Polarisation 2005” Orsay, 12-16 September 2005
Main Cosmological Parameters• Ωo Cosmological total density parameter• Ηo Hubble constant• Ωb Baryon density• Ωc Cold dark matter density• Λ Cosmological constant• ns Spectral index of scalar perturbations• Q Amplitude of fluctuation spectrum• r Ratio of Gravitational wave to density perturbations• τr Residual optical depth due to reionisation• ….
“Polarisation 2005” Orsay, 12-16 September 2005
Key Scientific Objectives• All-sky CMB anisotropy maps to an accuracy
∆T~5µK, on angular scales larger than 5 arcminutes• All-sky CMB polarisation maps (I, U, Q)• Cosmological parameters, Ho, Ωo, Ωb, ..... to a
precision of a few percent• Tests of inflationary models of the early Universe• Search for non-gaussianity/topological defects• Initial conditions for formation of large-scale structure• Nature of dark matter
“Polarisation 2005” Orsay, 12-16 September 2005
E-mode
The Planck results
(in a few years’ time)
Predicted power spectrum
recovery for Planck
B-mode<TE>
“Polarisation 2005” Orsay, 12-16 September 2005
Recovery of cosmological parameters
WMAP (4 yr)
Planck (1 yr)
WMAP (4 yr)WMAP (4 yr) + ACT/SPT
Planck (1 yr)
“Polarisation 2005” Orsay, 12-16 September 2005
Key non-CMB Scientific Objectives• Detection of Sunyaev-Zeldovich effect in
thousands of rich clusters of galaxies• Measurement of y in > 104 clusters• Cosmological evolution of clusters to z > 1• Ho and X-ray measurements, gas properties• Bulk velocities on scales > 300 Mpc
• Extragalactic sources (>10000) and backgrounds
• 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
“Polarisation 2005” Orsay, 12-16 September 2005
Galactic ISM studies: highlights– Dust properties– Cloud and cirrus morphology– Star forming regions– Cold molecular clouds– Maps of free-free and synchrotron emission– Cosmic ray distribution– Polarisation-specific science
• Galactic magnetic field• Magnetic field in local structures• Dust alignment• …..
“Polarisation 2005” Orsay, 12-16 September 2005
CMB
ClustersThermal Doppler
Galaxies Galactic
Free-freeSynchrotron
DustDetector noise
Imaging the sky emissionImaging the sky emission
at many frequenciesat many frequencies
Peeling back the layersPeeling back the layers
Recovering the Recovering the
cosmological informationcosmological information
The concept
“Polarisation 2005” Orsay, 12-16 September 2005
The concept works !The Galaxy as seen by WMAP
23 GHz
SynchrotronFree-free
Dust
33 GHz 61 GHz
41 GHz 94 GHz
“Polarisation 2005” Orsay, 12-16 September 2005
WMAP+Angular Power Spectra
“Polarisation 2005” Orsay, 12-16 September 2005
Predicted TT power spectrum recovery by WMAP and Planck
From: Efstathiou 2004
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Observational status (CMB pol.): Boomerang
BOOMERANG <EE>: Montroy et al 2005
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Observational status (CMB pol.)BOOMERANG <EE>: Montroy et al 2005
“Polarisation 2005” Orsay, 12-16 September 2005
Observational status (CMB pol.)BOOMERANG <TE>: Piacentini et al 2005
The Practice ofa CMB polarisation
experiment
• Design •Foregrounds• Systematics
Payload and Spacecraft
Design
“Polarisation 2005” Orsay, 12-16 September 2005
Observational Strategy• Temperature sensitivity (per pixel) of ∆T/T~10-6
based on state-of-the-art detectors• Ability to measure polarisation (Stokes I, Q, U) in
the CMB bands, with “reasonable” cross-polar characteristics
• 1.5 metre aperture telescope to provide ~5’ resolution for the CMB
• Extreme attention to systematic effects:– wide frequency coverage (25 - 950 GHz for temperature
and 25 - 400 GHz for polarisation)– Far-Earth orbit– Redundancy built in at many time-scales, from one minute
to half-year
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Launch in late 2007
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Orbit and Observing strategy
Transfer to orbit around L2
Spacecraft elements
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Payload elements
HEMT LNAs
20 K H2 Sorption cooler
Backend
Electronics Electronics
4 K/0.1 K CoolingSystem
Preamps
Service Module
Bolometers
Low Frequency Instrument High Frequency Instrument
20 K
300 K
0.1 K
Telescope
Wav
egui
des
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“Polarisation 2005” Orsay, 12-16 September 2005
PFM
Payload module
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Spacecraft hardwarePrime contractor: Alcatel Space (Cannes)
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Planck Telescope
• 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 danishinstitutes led by the Danish Space Research Institute (PI: Dr. H.U. Norgaard-Nielsen)
“Polarisation 2005” Orsay, 12-16 September 2005
Low Frequency Instrument
Σ∆Φ
Σ∆
Φ
Sky4 K Ref. Load
1st Hybrid
HEMT LNAs
Phase switches
2nd Hybrid
~1.5 m Waveguides
LNAs
Detectors & electronics
20 K300 K
Waveguides
P.I.: R. Mandolesi, IASF (Bologna)
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LFI hardware
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High Frequency InstrumentBack-to-back horns at 4 K
Filters at 1.6 K
Bolometers, hornsand filters at 0.1 K
Flange at 20 K
LFI horns at 20 K
JFET Box at 50 K(JFETs at 120 K)
PI: J.-L. Puget, IAS (Orsay)
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High Frequency Instrument
Figure 2.5.1 Prototype spider bolometer CSK18. Active absorber diameter, outer spidercircle, is 5.675 mm. Inset shows NTD Ge sensor at the centre with the two thicker currentcarrying and thermal conductance control lines running out horizontally to electrical contactson the silicon substrate.
Figure 2.4.1 Plot of Prototype 143 GHz Channel Spectral Response
1E-14
1E-13
1E-12
1E-11
1E-10
1E-09
1E-08
1E-07
1E-06
1E-05
0.0001
0.001
0.01
0.1
1
50 150 250 350 450 550 650 750 850 950
Frequency (GHz)
Inte
nsity
2mm filter centre part
55cm-1 edge
C147: 12 cm-1 edge
C169: 18 cm-1 edge
C146: 5.9 cm-1 edge
Overall System Response
Spider-web or polarisation-sensitive bolometers (CalTech/JPL)
Filters (QMW)Filters (QMW)Filters (QMW)
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HFI hardware
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Optical configuration
Scan direction
~8o
In the focal plane On the sky
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Optical configuration
Scan direction
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Polarisation Measurement Principle with the Planck HFI
Both bolometers in a PSB pair share the same optics but have different readouts
INTENSITY
POLARISATION
• Each PSB pair measures (I & U) or (I & Q)
• Two pairs, rotated by 45o, together measure (I, U, Q)
Scan
Stokes Parameters
I = Ex2 + Ey
2 Q = Ex2 - Ey
2 U = 2ExEy
“Polarisation 2005” Orsay, 12-16 September 2005
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
“Polarisation 2005” Orsay, 12-16 September 2005
Estimated Instrument Performance Goals1.5 m (proj. aperture) aplanatic; shared focal plane; system emissivity 1%Telescope
Viewing direction offset 85o from spin axis; Field of View 8o Instrument LFI HFI Center Freq. (GHz) 30 44 70 100 143 217 353 545 857 Detector Technology HEMT LNA arrays Bolometer arrays Detector Temperature ~20 K 0.1 K Cooling Requirements H2 sorption cooler H2 sorption + 4 K J-T stage + Dilution cooler Number of Unpol. Detectors
0 0 0 0 4 4 4 4 4
Number of Linearly Polarised Detectors
4 6 12 8 8 8 8 0 0
Angular Resolution (FWHM, arcmin)
33 24 14 9.5 7.1 5 5 5 5
Bandwidth (GHz) 6 8.8 14 33 47 72 116 180 283 Average ∆T/TI
* per pixel#
2.0 2.7 4.7 2.5 2.2 4.8 14.7 147 6700
Average ∆T/TU,Q* per
pixel# 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
Foregrounds
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Foreground temp. fluctuation levels
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Predicted polarised foreground fluctuations
Burigana et al 2004 astro-ph/0411415
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Synchrotron intensity & Synchrotron intensity & polarisationpolarisationSimulations (e.g. Giardino et al 2002) based on extrapolations from data, e.g.•Haslam 408 MHz observations•low & medium Galactic latitude data (e.g. Duncan 1997, 1999, Uyaniker 1999)
We wait for the WMAP polarisation data !
Q U
mKRJSmoothed, 1deg
Archeops
Taurus complex
12
34
1234
5
5
6
6
7
8
8
9
9
10
10
P (%) θ (deg)
89 ± 3.216.3 ± 1.887 ± 6.612.3 ± 2.9
175 ± 7.423.3 ± 6.546 ± 3.57.5 ± 0.978 ± 3.722.3 ± 3.359 ± 4.612.1 ± 1.8 87 ± 3.211.0 ± 1.17
23 ± 14.5< 2.4133 ± 11.77.3 ± 2.7 101± 13.85.2 ± 3.2
Gemini Taurus
Cassiopeia
Archeops
“Polarisation 2005” Orsay, 12-16 September 2005
Observational status (dust pol.)Dust contamination from BOOMERANG <TE>: Montroy et al 2005
• <TB>~0 indicates that dust contamination of
<TE> is very low• <TdustE> << <TE>
(Tdust from dust template)
Low contamination achievedby careful selection of FOV
Systematics
“Polarisation 2005” Orsay, 12-16 September 2005
Polarisation Systematics
• Instrument specific– 1/f noise– Noise mismatch– Bandpass mismatch– Time constant mismatch
• Thermal• Scan strategy• Calibration
– Incorrect polarization calibration parameters
• Far sidelobes– Galactic I straylight– (Galactic p straylight)
• Main beam– Differences between Q,U
beams– “Cross polarization”
• Pointing
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Calibration (temperature)• No on-board standards• External calibrators:
– FIRAS (0.1% on CMB temperature)– CMB dipole (~3 mK amplitude, known to ~10 mK)– CMB dipole modulation with orbital motion (~0.3 mK amplitude)– celestial sources
• Precise determination of beam patterns:– main beam using outer planets– mid- and far- side lobes using Sun, Moon, Earth, and Milky Way
• Goal: 1% photometric calibration in all CMB channels, 5% at the highest frequencies
• No polarised calibrators on the sky
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Polarisedbeams
From: Leahy and Hamaker 2004
Polarisedstraylight
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From: Leahy and Hamaker 2004
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Power spectrum recovery: “Realistic” case
From: Leahy and Hamaker 2004
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Polarisation destriping• Rely on redundant measurements
to invert a linear system involving several polarised detectors
• Sit = AitpsIps + nit– i indexes detector– t indexes time (sample number)– p indexes pixel on the sky– s indexes Stokes parameter
• For Planck, model nit as “offsets” after averaging on rings
• Revenu et al, A&A SS 142, 499 (2000)
BEAM
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Concluding remarks• The Planck dataset will make a huge impact on the
astrophysics of the galactic ISM– All-sky survey, 5’-30’ resolution– High sensitivity (~µK)– Unexplored frequencies – High photometric accuracy– High polarisation sensitivity
• Plenty of problems to be solved– Separation of CMB and foregrounds– Transformation of observables to physical quantities– …
System Schedule (Jan 2005)
Payload Development
S/C Development
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Operations and Data Processing
CQM FSInstruments
FMReflectors QM
FM1PACE FM2Sorption Cooler
2002 2003 2004 2005 2006 2007 2008 2009 2010
PDR CDR QR FAR IOCR
TransferLaunch
PVSurvey 1
Survey 2Data Reduction
Data Exploitation
Product Delivery
ERCSC Delivery
3 Aug. 2007
AVMFM
Products:•All sky channel maps
•Component maps•Compact source catalogues
•Calibrated timelines
“Polarisation 2005” Orsay, 12-16 September 2005
Key dates• Start of spacecraft Phase B: mid-2001• Start of spacecraft Phase C/D: end-2002• Payload model deliveries: 2004-2005• Launch: August 2007 (TBC)• Insertion into orbit: January 2008• Operations: 2008 - mid 2009• Scientific product delivery: mid 2011
“Polarisation 2005” Orsay, 12-16 September 2005
Status• A full qualification model of the satellite is
being tested in a space simulator• The flight model of the ‘service module’ is
built and delivered• The flight model of the telescope and
payload model is built and being tested• The flight models of the instruments are
being integrated for testing later this year• We are about 2 years from launch….