S.U. .E.R.M.A.N.

SUnyaev-Zeldovich B-Polarization ExploRing Microwave ANtenna

Laila Alabidi (UK); Paul Beck (Austria); Marcos Cruz

(Spain);Árdís Elíasdóttir (Denmark); Henning Gast (Germany);

Lara Sousa (Portugal); Thomas Kronberger (Germany);

Gemma Luzzi (Italy); Jens Melinder (Sweden); Peter Predehl

(Germany); Oliver Preuß (Germany); Mirko Tröller (Finland);

Elisabetta Valiante (Germany); Paul Anthony Ward (Ireland)

OVERVIEW

•Short Introduction to the Mission;

•Science case:

−B-Modes;

−Sunyaev-Zel‘dovich;

•Engineering:

−Mission scenario;

−Spacecraft design/Platform;

−Telescope and Instrumentation;

•Cost and administrative affairs;

•Summary

INTRODUCTION

The Su erman Mission

As the name suggests, this mission will be leaping over tall orders to achieve what might appear to the mere mortal as impossible!

•The most accurate and complete measurement of the B-mode polarisation anistropy to date;

•An all sky Sunyaev-Zel‘dovich survey, at a resolution of 1 arcmin;

IMPORTANCE FOR DARK MATTER AND DARK ENERGY

•It is an indication for a variable cosmological constant (Quintessence);

•It is a measurement of the reionization bump which is due to dark matter annihilation and will therefore probe primordial dark matter;

IMPLICATIONS OF DARK ENERGY (I)

IMPORTANCE OF DARK MATTER (II)

B-MODE POLARIZATION

B-MODE SCIENCE

•Polarization of CMB is due to Thomson scattering which occurs post photon decoupling and is enhanced during reionization;

•The amount of polarization depends on the free electron density in the direction of observation;

•Gravitational waves lead to an in-homogeneity in electron density in the plane perpendicular to the direction;

•This in-homogeneity leads to a phase shift in the photons, leading to B-mode polarization with an amplitude

21cos2 yxEEU

BY MEASURING THE B-MODE WE CAN (I):

•Independantly measure the thickness of the optical depth as measured by WMAP. This is a strong indicator of Dark Matter in the early universe;

•Make an Indirect measurement of gravitational waves;

•Constrain (or obtain a value) on the tensor to scalar ratio (r);

BY MEASURING THE B-MODE WE CAN (II):

•Obtain more information on the type and energy scale of inflationary scenarios;

•Probe quantum gravity;

•Confirm or Refute magnetic Parity Conservation;

•Study Physics of energy scales inaccessible to particle acelerators;

•Probe re-ionization history;

WHY SPACE?

•Stable environment that allows the reduction of system noises

•No disturbances caused by earth´s atmosphere and the earth itself;

INCREASE SENSITIVIT

Y

•All sky coverage that allows:

-Improved statistics;

-Detection of the lowest polarization modes, i. e., PROBE RE-IONIZATION BUMP,

FOREGROUND EMISSION

•Free-free emission (negligably polarized);

•Synchroton emission → low frequencies;

•Dust emission → high frequencies;

•Extragalactic emission from radiogalaxies and weak-lensing;

Deduced by making measurements at

low and high frequency channels

COMPLEMENTARITY AND COMPETITION

•Current missions don‘t have enough sensitivity;

•There are, at least, 8 missions planned for measuring the B-mode:

−Ground-based missions;

−Balloon-borne missions;

−Space missions;

Detectability of B-mode constrained by limited observed

area and atmospheric disturbances

•Our expected sensitivity of r~0,001 is of the same order as that of the next generation ground-based and balloon experiments;

•We will be probing the lower l modes which cannot be done without performing an all sky survey;

SUNYAEV-ZEL‘DOVICH EFFECT

COSMOLOGY WITH THE SUNYAEV-ZEL´DOVICH EFFECT

• Very powerful and versatile tool to study large scale structure of the universe

• Inverse-Compton scattering of the CMB photons off the high energy electrons of the ICM

PHYSICAL PRINCIPLES

• Expressed as a temperature change at dimensionless frequency :

radx

x

rad yTe

exT

41

1CMBbTk

hx

dncm

kTy eT

e

e 0 2

Compton y-parameter:

Kinetic SZE:

c

v

T

T pec

CMB

SZE

BASIC FEATURES

• Mass threshold nearly redshift independent;

• Highly complementary to other observational diagnostics;

Carlstrom et al., 2002

SCIENTIFIC RATIONALE

• Cluster based Hubble diagram: • Uses different electron density dependencies of the SZE

and X-ray emission,

cex

eHA TS

TD

1)(

200

02

0

Quantities evaluated along the line of sight through the centre;

Carlstrom et al., 2002

SCIENTIFIC RATIONALE

• SZ-selected samples almost mass limited;

• Cluster counts and distribution strongly depends on cosmological parameters and cluster formation physics;

Da Silva et al., 2000

• FURTHER POSSIBLE

APPLICATIONS:

– Intra-supercluster gas;

– Time dependence of dark

energy density (Bartelmann

et al. 2005);

– Test TCMB ≈ (1 + z) by ratio of

SZ at 2 different frequencies;

– Kinetic SZE unique way to

measure large scale velocity

fields;Couchman, 1997

SCIENTIFIC RATIONALE

NECESSITY OF GOING TO SPACE

• The most powerful use of SZE are deep, large scale

surveys;

• Ground based observations suffer from systematics coming

from atmospheric variations;

COMPLEMENTARITY AND COMPETITION

• PLANCK will measure the

SZE but due to relatively

large beam width, resolve

only around 20.000

clusters;

• Atacama Cosmology

Telescope: ground based; OVRO millimetre wavelength array

FOREGROUND AND SYSTEMATICS

• Galactic emission, such as synchrotron and dust

emission and fluctuations of CMB itself;

• Point sources;

• Assumption as spherical symmetry, isothermality and

absence of clumping often used;

EXPECTED RESULTS

• In a ΛCDM we expect

around 20 clusters per

deg2, thus with the all sky

survey we should get

700.000 clusters;

•In a τCDM we expect

around 3 clusters per

deg2, thus with the all sky

survey we should get

105.000 clusters;

ENGINEERING

STARTING WITH PLANCK

Mission Scenario

L2

L2 (after ¼ year)

0,2 rpm

Spacecraft Designstarting from the bottom

380

0

Solar PanelLaunch Adapter (10,5m2)

SPACECRAFT DESIGNstarting from the bottom

356

6

S/C Bus"Service Module", SVM

DOES IT FIT INTO ST-FAIRING?

SolarpanelService Module

V-Grooves

Sec. Reflector

Prim. Reflector

654

5

Shield / Baffle

“TULIP“

V-GroovePanels

S/C Design

Service Module

V-Grooves

PayloadSupport Structure

Telescope

"Tulip"-Extension

THE TELESCOPE

Goals:

SZ Effect• high angular resolution

B-Mode• large field of view • no cross and instrumental-

polarization

Solutions:

• 3m diameter paraboloid aperture stop

• off-axis Gregorian satisfying the Mizuguchi-Dragone condition

INSTRUMENTATION

The focal plane unit – basic layout

• The focal plane size given by the optical design is 5° (or 300 mm in physical units).

• The FPU accomodates two different instruments sharing the same cryostat, the Total intensity Instrument (TI) and the Polarimetry Instrument (PI).

focal plane

TI

PI

To secondary mirror

INSTRUMENTATION

• Filters/Channels- The TI will observe the CMB in 3 channels; 143, 220 and 330 GHz optimized to study the SZ effect.

- The PI will observe in 3 channels; 40, 100 and 220 GHz

• Polarimetry- Uses a combination of a rotating half-wave plate (HWP) and a fixed polarizing grid (FPG) to modulate the signal.

- This technique provides immunity to a number of systematic effect (no detector differencing needed).

INSTRUMENTATION

Filter

PI

TI

INSTRUMENTATION

• Detector array setup

- For each of the six channels there will be an array of hornfed TES bolometers. The arrays will be constructed to fill the focal plane (diameter of 300 mm).

- In total a number of 690 detectors can be fitted inside the focal plane divided between the different channels and instruments (PI/TI).

- The number of detectors is limited by the fact that each horn has to have a diameter of at least the wavelength observed.

INSTRUMENTATION

• Transition edge sensors (TES)

- Has a great advantage in that they can be produced in large arrays (thin film deposition and optical lithography)

- Readout multiplexing technologies (SQUIDs) have been developed/are in development. These makes it possible to readout many detectors at once.

- Have low impedance => more insensitive to vibration.

- Optimal sensitivity is achieved at very low temperatures (100 mK), good cryostat needed. Detector noise power is on the order of 2·10-17 W/√Hz.

INSTRUMENTATION

INSTRUMENTATION

• Sensitivity calculations- In modern bolometers the sensitivity is no longer determined by the detector noise but rather by background optical loading (photon noise) => Larger amount of detectors

- The photon noise in the instrument is complicated to determine (depends, among other things, on transmissivity of the optics and the crystat effectivity).

- In the sensitivity estimates presented here, we are assuming the photon noise level reached by PLANCK.

INSTRUMENTATION

Frequency (GHz) Beamsize*(arcmin)

Time/Beam **(s/beam)

Sensitivity/Beam**(μK/beam)

No. of detectors

40 (PI) 8.6 5.82 3.31 9

100 (PI) 3.4 2.30 2.64 36

143 (TI) 2.6 1.76 3.47 32

220 (PI) 1.6 1.07 3.14 144

220 (TI) 1.6 1.07 2.81 180

330 (TI) 1.0 0.67 9.22 289

INSTRUMENTATION

Telescope Frequency(GHz)

Noise/Beam (μK) Beam FWHM(‘)

Sky Coverage(sq. Deg.)

QUIET 40 0.43 23 4 × 400

PolarBeaR 90150

1.62.4

6.74.0

500

Planck 100143

10.96.0

9.27.1

51840

INSTRUMENTATION

Telescope Frequency(GHz)

Noise/Beam (μK) Beam FWHM(‘)

Sky Coverage(sq. Deg.)

QUIET 40 0.43 23 4 × 400

PolarBeaR 90150

1.62.4

6.74.0

500

Planck 100143

10.96.0

9.27.1

51840

Superman 100 2.30 3.4 51840

The cooling chain includes a hydrogen sorption cooler, providing a 18K stage; a closed-loop Joule-Thomson refrigerator which provides a temperature of 4K; and a diluition refrigerator which provides the final operating temperature of the bolometers of 0.1K, with a cooling power of 100nW.

(Pla

nck H

FI coolin

g sy

stem

)

COOLING SYSTEM

V-Groove Radiator (TO 60k)

20K H2 sportion cooler (TPL)

4K stirling cooler (RAL/MMS)

O,1K 3He/4He dilution Cooler

POWER SUPPLY

• Total Power Requirements: 800W;• Power generation: circular solar array (10,5 sqm);• Distribution and storage:

– Power Control Subsystems– Power Control and distribution unit– Li-Ion Battery → provides electric power during eclipses

AMCS

DATA PROCESSING & TRANSFER

Detector Signal Proc.Unit, SPU

Digital Proc.Unit, DGU

reading outraw dataexpected: 86 kbits/sec

Reducing glitchesand zero-counts

Comp. Entities, storage until TM, backup,

expected: 7430 Mbits/day

TELEMETRY AND TELECOMMAND

For cost reasons only one ground station,+ 1 backup max: 8 hours for transmission, down to 3 hours, depending on antenna

Telemetry rate: 1,5 Mbit/sec, MGA oriented to Earth 1,5 hours/day for transmission timebackup for 2 transmission

Telecommand rate 5kbit/sec, LGA for comunicating with probe independend on attitude

New Norcia ground station

Planck Satellite

satellite

Groundstation

ESTIMATED MASS

• Since we are going to L2 and we are using the Soyuz-Fregat launcher, the maximum mass allowed is:

2200Kg

COST AND ADMINISTRATIVE AFFAIRS

GROUND SEGMENT

• Operation Ground Segment (OGS):– Observation/scanning plan within the spacecraft systems;– Perform the classical spacecraft operations;– Maintenance tasks;

• Science Ground Segment (SGS):– Science Telemetry;– Revelant ancilliary spaceccraft data from OGS;– Transforming data from spacecraft into a scientist handy form;– Distribute this data to scientists;– Realize the data archive and improvement on reduction

algorithmic;

GROUND SEGMENT

ESTIMATED COST

SUMMARY

SUMMARY

• The mission plans to measure B-Polarization of the CMB and

Sunyaev-Zel’dovich effect;

• To do this we must increase the sensitivity and the angular

resolution of previous telescopes;

• Our instrument reaches both of these science

requirements;

• The technical design meets requirements on weight, size,

data rate, etc. ;

• The cost budget is adequate for such a mission;