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Transcript of lezione11 2016 cos.ppt [modalità compatibilità]oberon.roma1.infn.it/lezioni/cosmologia...stack...
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CMB observables• Spectrum (specific brightness <I()>) :
• Measured by COBE‐FIRAS• Blackbody, T=2.725K• Deviations < 0.01% of peak brightness
• Anisotropy (map of the brightness I(,)):
• Measured full sky, by many experiments, latest is Planck• Gaussian, rms around 90 K• Power spectrum cl consistent with the adiabatic inflationary model for structure formation
• Linear Polarization (maps of Q(,) and U(,) ):
• rms around 3 K, consistent with anisotropy results• Power spectrum of E‐modes (irrotational component) measured by several experiments
• Power spectrum of B‐modes (curl component) due to dark matterstructures lensing detected
• Power spectrum of B‐modes from Inflation not detected yet2
http://arxiv.org/abs/1502.01589
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CMB polarization map from Planck (Feb.5, 2015)r < 0.1
D. Molinari et al.
Polarized foregrounds
Planck coll. 2015
Foregrounds are complex and polarized
http://arxiv.org/abs/1409.5738
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Polarized emission of the ISM
• Often the result of superposition of several clouds along the line of sight
• Different temperature distribution for dust, different magnetic field orientation in different clouds, different electron populations, …
• For example, the orientation of linear polarization resulting from the superposition of dust grains differently aligned and with different temperatures changes with frequency.
• For this reason, scalar extrapolation, based on the brightness spectrum alone, is only a zero‐order approximation. Has worked to some extent to point‐out the presence of ISD emission in BICEP2 data (using 350GHz data from Planck extrapolated to 150GHz, see arXiv:1409.5738). But this is just a rough approximation. For the final mission we need to carry out precise corrections.
• Similar arguments apply to synchrotron emission at low frequencies.
• Extrapolation of dust to long wavelengths and of synchrotron to high frequencies is non‐trivial, unless you have a number of high and low frequency channels.
T1
T2
CMB
B1
B2
Need for space‐based measurements
• Extrapolation of dust to long wavelengths and of synchrotron to high frequencies is non‐trivial, unless you have a number of highly sensitive channels at high and at low frequencies, basically filling the range 30 to 700 GHz.
• Because of the earth atmosphere, this frequency coverage cannot be obtained entirely from the ground.
• In addition, operation in space (L2)
– Permits the use of cold telescopes, reducing the radiative background on the detectors and improving their sensitivity
– Enhances the stability of the instrument
– Avoids atmospheric noise
– Reduces ground‐spillover signals.
COrE+26/11/2014 9
0.5 mm PWV2 mm PWV
40 km
240K=2%
240K=0.1%
Atmospheric fluctuations : quantum
space • Just taking into account photon background from the atmophere and its noise, you need many more detectors in a ground‐based experiment than in a space‐based experiment, to obtain the same instantaneous sensitivity.
• Integration time can be longer for a ground‐based experiment, but not for a large factor.
• High‐frequency measurements are necessary, and require space‐based observations.
J. Delabrouille
Atmospheric fluctuations : Turbulence
measuring CMB fluctuations from the ground at f > 220 GHz is extremely difficult, even in the best sites
We need more bands than componentsCount components (or parameters)
CMBThermal SZ2‐component thermal dust2‐component synchrotronFree‐freeSpinning dustCIBZodiacal lightRadio source backgroundSurprises
TOTAL
I
1264‐61‐2a fewmany1‐3a few?
15‐20 +
P
1064‐60 ??0 ?0 ?
a few?
11‐13 +
In cleaner regions of the sky, less parameters are needed, but this depends on the sensitivity of the survey.
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CMB research strategy
CMB Stage 4Ground based
500000+ polarizationsensitive pixels (several
large telescopes)1‐2’FWHM @CMB f40, 95, 150 GHz
CMB ESA‐M5Space mission
5000 polarization sensitive pixels (20 bands, 1.5m telescope in space)
1‐2’FWHM @high f (220 +)4‐6’ @CMB f
CMB Stage 3A large number of current experiments, to demonstrate
technologies and methods (in Europe: OLIMPO, QUBIC, LSPE …)
1‐2’FWHM high fidelity maps of polarization
anisotropy of the CMB and the foregrounds
CMB SpectrumsatelliteAbsolute
measurement, 1‐2°, many bands, clear large scales
(PIXIE)
1‐2’FWHM high fidelity, absolute mapsof the CMB and the
foregrounds
Examples of S3 experiment
• BICEP‐2: a ground‐based experiment
• LSPE: a balloon‐borne experiment
http://www.kicc.cam.ac.uk/sites/default/files/talks/BICEP2_IoA_2014.pdf
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http://www.kicc.cam.ac.uk/sites/default/files/talks/BICEP2_IoA_2014.pdf
LSPEthe Large‐Scale
Polarization Explorerhttp://planck.roma1.infn.it/lspe
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Scientific Target : B‐modes• Red line : contribution from each
multipole to the total mean square fluctuation of the tensor component of CMB polarization (B-modes, r = 1).
• Thin blue line : the cumulative of the B-modes, i.e. the variance measured by an experiment sensitive from multipole 2 to a given multipole l.
• The top blue thick line : the beam function B2
l for an experiment with a 1.5o FWHM Gaussian beam.
• Despite of the coarse angular resolution such an experiment collects most of the polarization signal from B-modes.
2
main target : reionization peak
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A difficult but important target, to complement measurements of the l=80 peak !
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the reionization peak is difficult• Large angular scales: wide sky
coverage required.
• Foreground contamination ishigh. From Planck intermediate results XXX: The angular power spectrum of polarized dust emission at intermediate and high Galactic latitude
Dust B-modes in the best 30% of sky at 350 GHz:
Extrapolating to 150 GHz (factor 0.04^2)
2
south
north
402.8
402.8
402.8
• Large sky coverage and wide frequency coverage call for a space mission. See e.g. COrE+.
• On a shorter time‐scale, experimentation is required to qualify specific instrumentation (optical systems, polarization modulators, detectors …) and methods (sky scan, mapping procedures, polarized foregrounds separation …) and possibly to get detections !
• A balloon‐borne instrument can
– avoid atmosperic noise and loading
– exploit a wide frequency coverage
– access a large fraction of the sky during night‐time
– offer a stable environment during night‐time
– reject ground spillover using very large ground‐shields
Experiment Strategy
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29/Dec/1998
Balloon at 30 Km of altitude:Note the spherical shape
• The disadvantage of these balloons is that they can vent He when the temperature increases. So the volume decreases at each diurnal cycle. As a consequence, the float altitude decreases.
• Long Duration Balloon flights of a few weeks can be obtained in polar regions, where the diurnal illumination change is minimum. Example: The BOOMERanG flight in 1998, 10.6 days long:
0 1 2 3 4 5 6 7 8 9 1 0 1 12 0 0 0 0
2 5 0 0 0
3 0 0 0 0
3 5 0 0 0
4 0 0 0 0
B 9 8
alti
tud
e (
m)
t (d a ys )
• The Large‐Scale Polarization Explorer is :– an instrument to measure the polarization of the Cosmic Microwave Background at
large angular scales
– using a spinning stratospheric balloon payload to avoid atmospheric noise
– flying long‐duration, in the polar night
– using a polarization modulator to achieve high stability
• Frequency coverage: 40 – 250 GHz (5 channels, 2 instruments: STRIP & SWIPE)
• Angular resolution: 1.3o FWHM
• Sky coverage: 20‐25% of the sky per flight
• Combined sensitivity: 10 K arcmin per flight
• Current collaboration: Sapienza, UNIMI, UNIMIB, IASFBO‐INAF, IFAC‐CNR, Uni.Cardiff, Uni.Manchester. INFN‐GE, INFN‐PI, INFN‐RM1, INFN‐RM2
• See astro‐ph/1208.0298, 1208.0281, 1208.0164 and forthcoming updates
LSPE in a nutshell
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SWIPE
STRIP
STAR SENSORS
PIVOT
RACK
BATTERIES
BALLAST
FRAME
LSPE gondola : frame + pivot + STRIP + SWIPE to balloon
Actuators: Azimuth pivot with torque motors
Linear elevation actuators
Processor: PC104 with ADC in / PWM out
H-bridges for motors
Attitude sensors: Star sensors (Nati et al. RSI 2003)
Laser GyroscopesElevation Encoders
TMTC
ACSblock diagram
Preliminary sketch of the LSPE experiment, without thermal protections. The total mass is around 2.5 tons, the overall dimensions are 5.8m(w) x 3.2m(d) x 4.6m (h).A 800000 m3 balloon is used to lift the instrument at 37 km of altitude.
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South
B-modes from dust @140 GHz, as estimated from Planck 343 GHz dust polarization - Planck PIP XXX 1409.5738
1010.10.01
North
Sky coverage of LSPE (Launch from Longyearbyen, Svalbard)
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The STRIP Instrument• STRIP is the STRatospheric Italian Polarimeter, aimed at accurate measurements of the low‐frequency (44 and 90 GHz) polarized emission, dominated by Galactic synchrotron. • Its sensitivity at 44 GHz in a single flight is twice better than the final sensitivity of the Planck LFI survey. • The correlation radiometers are contained in a large cryostat and cooled at 20K by evaporating 4He.
2100
mm
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The STRIP Instrument The beam is defined by a 600 mm aperture side‐fed crossed‐Dragone telescope, selected for best polarization purity
Challenging for spillover, stray‐light and obscuration
Modular Primary and secondary mirrors to reduce fabrication costs
Lightened structure to reduce weight
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The STRIP Instrument• In the focal plane, an array of 44 GHz platelet feedhorns (already manufactured) feeds high performance OMTs and LNAs derived from the QUIET exp.• The measured response of the corrugated feedhorns confirms the expected performance down to ‐55 dB
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• SWIPE is the Short Wavelength Instrument for the Polarization Explorer
• It is a Stokes Polarimeter, based on a simple 50 cm aperture refractive telescope, a cold HWP polarization modulator, a beamsplitting polarizer, and two large focal planes, filled with multimode bolometers at 140, 220, 240 GHz.
• Everything is cooled by a large L4He cryostat and a 3He refrigerator, for operation of the bolometers at 0.3K
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The SWIPE Instrument
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Low inputwindow
thermal fliters stack
cold, stepping HWP
polarizerarrays of multimode feedhorns and bolometers
UHMWPE
lens
4He tank (290L) 3He fridge
1370
A cryogenic Stokes polarimeter
SWIPE
SWIPE – polarization modulator• Is a cold (2K), large (50 cm
useful dia.), wide band metamaterials HWP, placed immediately behind the window and thermal filters stack.
• HWP characteristics for the ordinary and extraordinary rays are well matched:(To-Te)/To < 0.001, Xpol<0.01, over the 100-300 GHz band.
• Its orientation is stepped by 11.25° or 22.5° every few scans.
500 mm
The cryogenic HWP rotator made for the PILOT experiment. The LSPE one will be based on the same design, and scaled up in dimensions (see Salatino et al. A&A 528 A138 2011)
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SWIPE – optical system• Single lens UHMWPE @4K,
AR coating, D=480, f=800• Two curved focal planes
populated with multimode bolometric detectors, resulting in 1.2°FWHM beams
reflected focal plane transmitted focal plane
Scan direction
1.2°
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Band (GHz)
Width (%) Total # detectors
# 2
modes
140 GHz 30 110 10
220 GHz 5 110 21
240 GHz 5 110 23
M. De Petris
SWIPE – multimode feedhorns• 20 mm aperture• High efficiency coupling
structure, easy to machine• Nice top-hat beams• 10, 21, 23 2 modes @ 140,
220, 240 GHz
150 GHz
cold aperture stop
dB
Feedhorn + detector assemblyFinal design23g each
Feedhorn + detector assemblyTested Prototype
L. Lamagna
G. CoppiT. Marchetti
SWIPE ‐ multimode absorbers & TES• The absorbers are large Si3N4
spider-webs (8 mm diameter, multimode)
• Sensors are Ti-Au TES• Photon noise limited• = 2 ms
SWIPE ‐ cryostat• mass = 460 kg
• He volume = 0.9 x 290 lt
• Hold time = 19 .. 23 days
S. Masi, A. Schillaci
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• Scanning strategy: payload spin in azimuth, at 3 rpm (18°/s)
• Coverage of the same sky area by the two instruments
• Elevation changes once a day, at the same time for both instruments
• Specific calibration observations of
– Jupiter (to map the main beam, see figure below, samples = white dots)
– the Crab nebula and the Moon Limb (to calibrate the main axis of the polarimeters)
– the Moon can be used to map sidelobes
Observations and Calibration PlanElevation Coverage Unmasked
SWIPE [30‐40] 31% 23%
SWIPE [40‐50] 27% 20%
SWIPE 35 24% 19%
SWIPE 45 22% 18%
SWIPE [30‐50] 35% 26%
STRIP 45 27% 20%
STRIP 30 33% 24%
LSPE coverage for different sets of elevation changes. The first column reports the boresight elevation range in degrees for the two instruments. Second column, the full coverage. Third column, the coverage after masking the galaxy with the WMAP polarization mask.
Source Culmination (deg)
S/N per sampleat 44 GHz
S/N per sampleat 90 GHz
S/N persampleat 145 GHz
S/N per sampleat 245 GHz
Moon 30 37500 200000 700000 2000000
Crab 34 20 18 23 28
Mars 0 0.30 1.6 5.6 18
Jupiter 27 15 80 275 850
Saturn -6 1.4 7 24 70
Uranus 16 0.05 0.24 0.8 2.5
Sources culmination angle, and expected S/N per sample. Sampling rate is set at 60 Hz. We assume full Moon, as it is when it is observable by LSPE. The Crab flux is based on the free‐free spectrum reported in Macías‐Pérez, et al. Ap. J., 711, 417 (2010)
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STRIP SWIPE
Performance Forecast• The presence of
the HWP allows to fully exploit the sensitivity of LSPE-SWIPE.
• Realistic simulations to assess systematic effects (mainly beam asymmetries) which become irrelevant if the HWP is used.
• The final sensitivity target for r is around 0.02
LSPE noise level
LSPE noise level Spurious signal
Spurious signal
Expected / measured signals
Expected / measured signal
14L. Pagano, F. Piacentini
SWIPE Performance Forecast (1st flight)
L. Pagano, F. Piacentini
SWIPE Performance Forecast (1st flight)
L. Pagano, F. Piacentini
• The experiment is flown as a stratospheric balloon payload during the polar night, in a long duration flight launched from Longyearbyen (Svalbard). In this way it can access most of the northern sky in a single flight,
– without contamination from the sun in the sidelobes
– within a very stable (cold!) environment
– Accumulating more than 14 days of integration at float (38 km altitude).
• Flight scheduled by ASI for end of 2016
Mission
See Peterzen, S., Masi, S., et al., “Long Duration Balloon flights development ”, Mem. S. A. It., 79, 792-798 (2008) for further information on balloon flights from the Svalbard.
Bottom: Ground path of a small pathfinder test flight performed in January 2011, in the middle of the polar night. The eastward trajectory is evident.. Top: Launch of a heavy-lift balloon from the Longyearbyen airport (Svalbard Islands, latitude 78oN).
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Launched - June 14th, 2006
Svalbard
Impact – July 1st, 2006
17 DAY FLIGHT
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55
34km
Ballast Drop
sample flight profile
Ballast release
termination
launch
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1° LDB launched on Jan. 9°, 2011From CNR Dirigibile Italia base With support from ISTAR, AWIPEV Ny Alesund, Svalbard Islands
5 days at 32 Km, Eastward pathPayload prepared by La Sapienza
Night Time Long Duration Stratospheric Balloon Flights
57 58
References
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• The LSPE collaboration: “The Large-Scale Polarization Explorer (LSPE)” Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84467A (2012); doi: 10.1117/12.926095; astro-ph/1208.0281
• P. de Bernardis, et al. “SWIPE: a bolometric polarimeter for the Large-Scale Polarization Explorer” Proc. SPIE 8452, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 84523F (October 5, 2012); doi: 10.1117/12.926569; astro-ph/1208.0282 (2012).
• M. Bersanelli, et al. “A coherent polarimeter array for the Large Scale Polarization Explorer balloon experiment” Proc. SPIE 8452, Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84467C (24 September 2012); doi: 10.1117/12.925688 ; astro-ph/1208.0164 (2012).
• P. de Bernardis, S. Masi, for the OLIMPO and LSPE teams, “Precision CMB measurements with long-duration stratospheric balloons: activities in the Arctic”, In Astrophysics from Antarctica - IAU Symposium 288, Proceedings of the Internatonal Astronomical Union, 8, 208-213 (2013) M. G. Burton, X. Cui & N. F. H. Tothill, eds., Cambridge. doi: 10.1017/S1743921312016894
• Peterzen, S., Masi, S., et al., “Long Duration Balloon flights development ”,Mem. S. A. It., 79, 792-798 (2008)
• F. Nati, A. Benoit, P. de Bernardis, A. Iacoangeli, S. Masi, D. Yvon, A fast and reliable star sensor for spinning balloon payloads, Review of Scientific Instruments, 74, 4169-4175, (2003)
• http://planck.roma1.infn.it/lspe
Cosmic Origins Explorer ++
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Overview
1.Scientific goals of the ESA-M5 CMB polarization mission
2.Why in space3.Fundamental limits and mission/instrument
design4.Mission implementation5.Conclusions
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
COrE++ science
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
COrE++ is optimized to measure inflationary B-modes
Goals of the CMB polarization mission for M5
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Final measurement of B-mode polarization, able to extract the cosmological signal from overwhelming polarized foregrounds.
• Starobinsky model, R2 (Higgs) inflation have a tensor to scalar ratio r > 2x10-3.
• The mission should target at r<4x10-4 .
• Such a sensitivity tests Planck-scale physics of the field values in the large-field inflation models:
o Lyth bound: o A null-result would disfavor the entire class of large-
field (>Mp) models, and very few would survive.
• r<4x10-4 should be possibly established without l<10 .
223
60102.2
P
slowslow
M
Nr
(Boubeker and Lyth 2005)
Goals of the CMB polarization mission for M5
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
ns would also be measured much better, so that Trehcan be estimated.
Grey: WMAPBlue: PlanckOrange: COrE+
Goals of the CMB polarization mission for M5
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
COrE++ has enough angular resolution to vastly improve the measurement of gravitational lensing from LSS
Gravitational lensing from dark matter structures
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
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Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Gravitational lensing from dark matter structures
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Gravitational lensing from dark matter structures
With the same angular resolution and sensitivity required for the inflationary B-modes, COrE+ produces a high fidelity map of the gravitational potential integral, due to dark matter structures from here to recombination:Direct detection of dark matter structures.
COrE+ (simulation)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Gravitational lensing from dark matter structures
With the same angular resolution and sensitivity required for the inflationary B-modes, COrE+ produces a high fidelity map of the gravitational potential integral, due to dark matter structures from here to recombination:Direct detection of dark matter structures.
Goals of the CMB polarization mission for M5
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
COrE++ has enough angular resolution and frequency coverage to extract 100000 SZ clusters from the maps.
Extract and catalogue 100000 SZ clusters !
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Simulation SZ only (input) Mixed to other components and noiseReconstructed after component separation (output)
Catalogue
COrE+ simulations(Remazeilles, Karakci,..)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Constraining the neutrino sector
3.046
60meV m(eV)
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Why in space: 1) background fluctuations
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Photon background
Ratio of the number of detectors needed, for a given sensitivity, due to statistical photon background fluctuations.
200
>200GHzforbiddenfrom the ground, butneeded for foregroundsremoval
Why in space: 2) atmospheric instability
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
10K
0.1% fluctuations of atmospheric parameters
upper limit for B-modes signal
10‐5
Why in space: 3) systematic effects
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Atmospheric fluctuations larger at large scales, where the inflation signal is. • The effects of ground pickup (from the sidelobes) are larger at large scales.• The environment temperature is not stable at long timescales• Duty cycle of ground-based measurements << 100%
• All these effects can be vastly reduced with a space mission in L2 (as WMAP, Planck).
• In L2, the solid angle occupied by the Earth is reduced by a factor 10000.• Looking at anti-solar directions, the Earth, the Moon and the Sun are very
far from the boresight, so that pickup is minimized.• As long as the solar elongation is kept constant, the environment is
extremely stable, and so is the instrument performance.
• The effect of cosmic rays is heavier in space than on the ground, and must be properly mitigated with special detector design, and monitored in the data analysis.
Instrument/mission design driven by fundamental limitations
• Current precision (Planck) r~0.05; our goal r~0.0004 • Fundamental limitations to Accuracy:
• Overwhelming B-mode signals are produced:o Along the path of CMB photons, by gravitational lensing (to be monitored
with high angular resolution)o In our Galaxy, by polarized foregrounds (to be monitored with many
bands and wide frequency coverage)o In the instrument, if not properly designed (minimize polarizing
components in the optical path, use proper optical design)• Fundamental limitations to Sensitivity:
• Photon noise: the CMB and the emission of the instrument are fluctuating according to photon statistics.
• Mitigation: work in a stable, low-background environment, for a long time (cold telescope, in space, with active coolers) with many detectors (kilopixel arrays)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Frequency coverage to monitor foregrounds
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Frequency coverage to monitor foregrounds
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Results from WMAP show that at low frequency the polarized synchrotron background is strong and has spectral index fluctuations.
• Preliminary results from Planck-HFI show that polarized dust emission must be monitored with great spectral and spatial accuracy to avoid biases in r, even at l=100 (fluctuations of the spectral index).
• Monitoring polarized dust at 340 GHz and extrapolating at 140 GHz to remove it (as in BicepKeckPlanck) is only a first approximation, and is not enough for our goal accuracy. Same for monitoring synchrotron at 30 GHz.
• The final mission must have excellent sensitivity and accuracy in a wide interval of frequencies above 200 GHz (which cannot be monitored from the ground) to extrapolate reliably the polarized emission from interstellar dust at 90-140 GHz.
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Multipoles coverage to monitor lensing B-modes
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Required sensitivity and resolution
• The survey sensitivity (K arcmin) depends on total integration time, number
of detectors, noise of the detectors.
• Limit on r : depends on survey sensitivity, multipoles coverage, and lensing
confusion (below 4.5K arcmin the survey becomes lensing‐limited).
• De‐lensing efficiency depends on the angular resolution of the telescope :
• Requirements: ~ 2 K arcmin and ~ 6’ resolution in the CMB channels
• High resolution implies additional science results (SZ, neutrino masses etc.)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Kendrick Smith et al, JCAP, 06, id. 014 (2012)
Beam ellipticity
• The ellipticity of the beam converts unpolarized CMB anisotropy into spurious
polarization. The effect at large scales is mitigated for small beams:
• For small apertures, a Half‐Wave Plate is a must (e.g. LITEBIRD, D = 40 cm)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Inflationary B-modes (r=0.05)
spurious B-modes (e=0.05)FWHM=20’D=0.4m140GHz
FWHM=6’D=1.5m140GHzFWHM=3.8’D=1.5m220GHz
Additional considerations
• We want to detect CMB polarization with more than one channel (preferably 3 channels for cross-spectra, jackknives, comparisons), with enough sensitivity in each CMB channel individually. Long integration time and excellent stability needed.
• We will observe small signals embedded in many polarized local foregrounds and instrumental effects.
• Need to increase the number of spectral channels above the number of components parameters
• Need to increase the angular resolution to mask polarized compact sources (radio & IR)
• Very large scales will be hard to measure, since foregrounds increase at large scales. But detection of both the reionization and recombination bumps will be convincing.
• Systematic effects at very low level must be forecasted and monitored.
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Systematics: focal plane rotation
Inflationary B-modes (r=0.05)
spurious B-modes produced by an uncorrected rotation (1o) of the main axis of the polarimeter
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Systematics: pointing errors
Inflationary B-modes (r=0.05)
spurious B-modes produced by a direction mismatch in the directions of the two orthogonal intensity measurements =1"
=6"
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Mission/instrument implementation
Given all this, we need to implement an imaging polarimeter: • With a cold (< 60K) telescope• Aperture > 1.2m (4.8’FWHM@220GHz) • Covering a wide frequency range: 60 to 600 GHz • With a large number of single-mode photon-noise-limited detectors optimally
distributed among different frequencies, but with several hundred detectors in the CMB bands (90-140-220 GHz). If wide band (/ ~ 0.5), a total of 2000 detectors will be needed for a survey sensitivity of 2 K arcmin.
• The sky survey will be long (3yrs) and thermal stability is a must (detectors: continuous dilution cooler at 100 mK, no ADR; telescope: passive cooling)
• The satellite should operate in L2 (as WMAP and Planck) with a sky scan strategy covering a large sky fraction in a short time (days) and observing the same sky pixel with very different orientations of the polarimeter.
• A rotating HWP should be avoided, to reduce complexity and cost, if at all possible.
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
~
Mission/instrument implementation
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Mission/instrument implementation: scan strategy
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
The telescope and the polarimeter must be heavily shielded from solar radiation, and solar illumination angle depends on scan strategy.
Spin
Mission/instrument implementation: scan strategy
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Spin (1 rpm) +Precession (0.25 rpd)
• Advantage: with far from 90o every pixel is observed with a wide range of orientations of the polarimeter: necessary condition for avoiding the HWP.
• For full sky coverage +> 90°.
• Baseline: ==45o.cfr: Planck =80o, =0o.
• To be optimized during phase-A.
• Feasible with large flywheels (5-6).
Anti‐solarDirection =PrecessionAxis
=beam off-axis wrt spin axis
=precession angle
Mission/instrument implementation: shielding
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
The best way to cool the telescope and the instrument is to use passive cooling V-grooves.Wrt Planck (open V-grooves), is smaller, and the solar illumination angle has a wider range, so V-grooves must have a «bucket» configuration:
With a bucket configuration, the telescope beam can be orthogonal to solar illumination
Mission/instrument implementation: telescope
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Aperture: 1.2 – 1.5 m• Optimized for wide focal
plane and polarizationpurity.
• Consideredconfigurations:
• Cross-Dragone• Open-Dragone• Gregorian
• The Gregorianconfiguration offers the best combination of usedvolume in the bucket, wide polarization-pure focal plane, and control of straylight.
Focal Plane Unit
Primary
Secondary
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Mission/instrument implementation: telescope
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Aperture: 1.2 – 1.5 m• Optimized for wide focal
plane and polarizationpurity.
• Consideredconfigurations:
• Cross-Dragone• Open-Dragone• Gregorian
• The Gregorianconfiguration offers the best combination of usedvolume in the bucket, wide polarization-pure focal plane, and control of straylight.
Focal Plane Unit
Primary
Secondary
Cold baffle, black inside
Mission/instrument implementation: telescope
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Images from ESA CDF study: «CMB B-modes polarization mission». To be published (April 2016).
The telescope fits in the V-grooves and the assembly fits in the fairing
Mission/instrument implementation: telescope
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
Images from ESA CDF study: «CMB B-modes polarization mission». To be published (April 2016).
The bucket V-grooves radiatively cool the telescope assembly down to < 50K
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
HWP / no HWP tradeoff
Two purposes for the HWP:
1. Move the signal bandwidth above the 1/f noise knee of detectors
2. Modulate polarization so that beam ellipticity and othersystematic are mitigated.
M4 approach: No HWP, no mechanisms, wider bandwidths and frequency coverage, no HWP-related systematic effects.
Solve 1. and 2. in the post-processing:
1. Can be solved with good detectors (1/f knee < 0.1Hz) and proper decorrelation/destriping.
2. Can be solved if the aperture of the telescope is large, i.e. the beams are much smaller than the large-scale where B-modesare to be detected.
Mission/instrument implementation: focal plane
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• M4 proposal baseline: horns-coupled focal plane.• Main advantages: high TRL, consolidated technology;
clean definition of bolometer FOV and edge-taper on reflectors; reduction of straylight; polarization clean
• Main disadvantages: high cost, high mass@100mK• Recent developments (in Europe):
– 3D-printed horns in plastic material, metal coated(for low freq. bands)
– Planar lenses arrays (EAS-ITT study ITT AO/1-7393/12/NL/MH)
• Alternative: Filled-array focal plane. • Main advantages: Fabrication simplicity; reduced cost;
low mass@100mK.• Main disadvantages: Nyquist sampling of Airy disk
requires 4x sensors and lower detector NEP; requires coldstop in optical system and cold (< 1K) BB box surrounding the focal plane to reduce stray-light and loading.
Mission/instrument implementation: focal plane
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
CMB channels
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Mission/instrument implementation: focal plane
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
horn-horn spacing = 3FF/#=2
2408
Dual polarization, single f pixels
Mission/instrument implementation: focal plane
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
horn-horn spacing = 3FF/#=2
4816 Dual polarization dichroic pixels
focal plane: European detectors for CMB
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• TES• Developed in Europe in Paris, Cambridge, Genova …• European MUX tecnology demonstrated in the lab (128:1, QUBIC) • Single-mode TES successfully operated at telescopes (SPT, ACT, BICEP, ….) and flown on
balloons (EBEX, SPIDER) by US teams • European multimode TES to be flown on a balloon with LSPE (ASI)
• KID• Developed in Europe in Grenoble, Groningen, Cambridge, Rome, ….• Operation down to 60-80 GHz demostrated (A&A 580, A15 (2015), astro-ph/1601.01466)• Large European matrix already operated at a telescope (NIKA & NIKA2) • For a filled array, 10 aW/sqrt(Hz) sensitivity demostrated in a laboratory setup simulating the
radiative background in L2 and 30% bands @100 and 150 GHz - Astro-ph/1511.02652; The sensitivity target for use in COrE+ is around 3 aW/sqrt(Hz) for a 35% band.
• Study of cosmic ray effects on-going (space-KIDs, see e.g. Astro-ph/1511.02652). Glitches are very short; cross section slightly larger than for TESs.
• To be flown on balloons (Adv.Blastpol in the USA, OLIMPO and Plan-B in Europe)• MID
• MEMS metal insulator detectors developed at CEA-Leti for Herschel-PACS have been improved to reach aW/sqrt(Hz) sensitivity operating at <100 mK, and in-pixel polarization measurements. European program CESAR developed suitable readout electronics.
• Still to be operated at telescopes• CEB
• Developed in Chalmers• Instrinsically insensitive to Cosmic Rays• Still to be operated at telescopes.
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: TES
TES multimode detectors for LSPE
TES detectors for QUBIC(Paris)
(Genova / Rome)
focal plane: European detectors for CMB: TES
Frequency coverage: Down to 40 GHz : CLASS, see astro-ph/1408.4789
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: KIDs
LEKID for 150 GHz(Rome)
NIKA2 array 200-300 GHz(Grenoble) -> IRAM30m
AMKID array - submm(Groningen) -> APEX ALMA
THz camera for safety scanner(Cardiff)
Horn-coupled KIDs for CMB(Cardiff + ASU)
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Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: KIDs
Low-f operation of KIDs demonstrated:• Catalano et al. A&A 580, A15 (2015)• Paiella et al. Astro-ph/1601.01466
Al-Tif > 65 GHz
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: KIDs
Catalano et al. Astro-ph/1511.02652
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: KIDs
Catalano et al. Astro-ph/1511.02652
Flagged data : 1%
Flagged data : 10-15 %
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
focal plane: European detectors for CMB: KIDs
Requirement for COrE+(horns-based)
Requirement for COrE+(filled array) Catalano et al. Astro-ph/1511.02652
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
cryo chain
Progress with this design and synergies with ATHENA - Gerard Vermeulen (inst. Néel, Grenoble)
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
cryo chain
Image from ESA CDF study: «CMB B-modes polarization mission». To be published (April 2016).
Martin Linder (ESA)
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Preliminary budgets
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
• Wet Mass: 2185 kg• Volume: diameter 4m,
h=4.5m• Momentum: 420 Nms• v: 131 m/s for large
amplitude Lissajous orbit around L2
• Power: 1970 W (requires hinged solar panels)
• Communications: 200 Gb/day (K-band, 20 cm derotated antenna)
Image from ESA CDF study: «CMB B-modes polarization mission». To be published (April 2016).
COrE++ : Conclusion
Paolo de Bernardis – CORE++ – New challenges in Cosmic Microwave Backgroud studies – ASI 30 March 2016
1. A space mission for CMB polarization like CORE++ is the only way to obtain a reliable detection of B-modes. This cannot be done from the ground only.
2. This mission promises outstanding results for cosmology and fundamental physics, and an extremely rich legacy of data for Astrophysics.
3. The mission is technically feasible with current European technology and scientific competence, and within the timeframe 2025-2030.
4. This mission is expensive, and proper support from ESA member states and other partners is mandatory to fit within the budget of M5.
5. The Italian community can have a leading role, but support is required to keep it alive and well.