The European mission to map the Cosmic Microwave Background · E-mode The Planck results (in a few years’ time) Predicted power spectrum recovery for Planck B-mode “Polarisation

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


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 .


The microwave sky (as seen by COBE)


Sky emission components

Finkbeiner & Schlegel 1999

Planck


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


Theoretical angular power spectrum of the CMB (CDM)

),(,

ϕθ∑=∆

ml

ml

ml Ya

TT

⟩⟨=2m

ll aC



Expected CMB polarisation spectra

Hu et al 2002


Hu 2002

The shape of the power spectrum

depends sensitively on the value of cosmological parameters


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• ….


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


E-mode

The Planck results

(in a few years’ time)

Predicted power spectrum

recovery for Planck

B-mode<TE>


Recovery of cosmological parameters

WMAP (4 yr)

Planck (1 yr)

WMAP (4 yr)WMAP (4 yr) + ACT/SPT

Planck (1 yr)


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


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• …..


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


The concept works !The Galaxy as seen by WMAP

23 GHz

SynchrotronFree-free

Dust

33 GHz 61 GHz

41 GHz 94 GHz


WMAP+Angular Power Spectra


Predicted TT power spectrum recovery by WMAP and Planck

From: Efstathiou 2004


Observational status (CMB pol.): Boomerang

BOOMERANG <EE>: Montroy et al 2005


Observational status (CMB pol.)BOOMERANG <EE>: Montroy et al 2005


Observational status (CMB pol.)BOOMERANG <TE>: Piacentini et al 2005

The Practice ofa CMB polarisation

experiment

• Design •Foregrounds• Systematics

Payload and Spacecraft

Design


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


Launch in late 2007


Orbit and Observing strategy

Transfer to orbit around L2

Spacecraft elements


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



PFM

Payload module


Spacecraft hardwarePrime contractor: Alcatel Space (Cannes)


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)


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)


LFI hardware


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)


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)


HFI hardware


Optical configuration

Scan direction

~8o

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

• 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 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


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


Foreground temp. fluctuation levels


Predicted polarised foreground fluctuations

Burigana et al 2004 astro-ph/0411415


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


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 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


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


Polarisedbeams

From: Leahy and Hamaker 2004

Polarisedstraylight




Power spectrum recovery: “Realistic” case



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


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


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


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


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….

Documents

The European mission to map the Cosmic Microwave Background · E-mode The Planck results (in a few years’ time) Predicted power spectrum recovery for Planck B-mode “Polarisation