Marco De Petris & MITO teamDipartimento di Fisica - Università La Sapienza

Rome - Italy

(*) F. Melchiorri & B. Melchiorri, Procs of Intern. School of Physics “Enrico Fermi” Course CLIX SIF (2005)

MITO: a "creative approach“ (*)for SZE observations from ground

L. LamagnaG. LuzziS. De GregoriE. Caca L. BonaveraA. MorgiaS. StefaniC. TombariR. CoratellaF. ManciniF. Vasciarelli+ nat. & int. collabs

Brute force approachbetter instrumentation under

better conditions than beforeExpensive, several groups, long time …

Two possible approaches for reaching an observational goal:

Creative approachclever application of techniques

for optimising the instrument Cheap, few researchers, quick …

MITO project has always followed a creative approach…

The history of MITO (in brief)

Francesco suggested in the 70’s to develop a medium-size telescope fully dedicated to FIR-cosmology in high mountain ranges. He pioneered the observational capabilities of Testa Grigia mountain as a valuable site for CMB obs with a 1.5 m in dia. telescope.

Upper limit of 10-4 on CMB anisotropies at an angular scale of 25 arcmin [Caderni,.. Melchiorri et al. Phys. Rev. D, 16, 2424 (1977)]

Atmospherical characterization in mm bands[Dall’Oglio, … Melchiorri et al. Infr. Phys. 14, 303, (1974)]

Measurements of TCMB in the atmo window 1.0÷1.4 mm[Dall’Oglio,.. Melchiorri et al. Phys. Rev. D, 13, 1187 (1976)]

But the TIRGO spectral coverage was mainly blueshifted (-> IR) respecting Francesco’s first proposal and so..

.. after a few years of no activity at Testa Grigia laboratory, finally in 1991 the collaboration with CNR in Turin (prof. C. Castagnoli) was renewed and a 2.6-m in dia. telescope, specifically designed for mm observations, was installed and so the MITO project started.

An Italian National project, TIRGO (Telescopio InfraRosso del GOrnergrat), was born with the effort of several groups managed by CNR in Florence: 1.5-m in dia. Cassegrain telescope located in Switzerland near Zermatt – 3135 m asl

Today we can say that MITO alternative was a good choice because TIRGO has completed its activity and it has been

disassembled last September.

Notiziario INAF – November 2005

MITO (Millimetre & Infrared Testagrigia Observatory)Testa45° 56' 03" N –

Logistical support from IFSI/the highest (3480 m a.s.l.) & olde

Grigia (Plateau Rosà) in front of the Matterhorn in Val d’Aosta (Italy)07° 42' 28" W

INAF station (proff. Castagnoli, Picchi, Coradini): st (1947) laboratory in Europe!

OBSERVATIONAL GOALS• Multifrequency observation of Sunyaev Zel’dovich Effect with low

angular resolution (FotoMITO, fov=16 arcmin) or high angular resolution (MAD, fov=4.5 arcmin)

see Lamagna’s talk on peculiar cosmological implications by SZE• High accuracy photometry of mm-sources (HII regions, radio

sources,…)• Specific obs of “bumps” detected in CMB maps by ground based,

balloon borne or satellite experiments see Battistelli’s talk on Corona Borealis Supercluster obs

• Polarimetry of FIR sources and search for CMB polarization

SITE CHARACTERISTICS

low pwv content high atmosphericaltransmittance in the mm region

high spectral correlation & low atmo fluctuations fast and efficientdecorrelation procedure

-5 0 5 10 15 20 25 30 350

50

100

# c

ount

s

Ch4/Ch1

-2 -1 0 1 2 3 4 5 6 7 80

50100150200

Ch3/Ch1

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

306090

120150

Ch2/Ch1

0 1 2 3 4 5 6 7 8 9 10 110

10

20

# co

unts

Ch2/Ch1

Ch3/Ch1

Ch4/Ch1

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.80

10

20

30

0.0 0.4 0.8 1.2 1.6 2.0 2.40

102030405060

pwv lower then 1mm

MITO telescope characteristics

•Aplanatic Cassegrain (R-C) configuration with a 2.6-m primary mirror and a 41-cm wobbling subreflector•Monolithic Al Mirrors with extremely low surface roughness•Corrected focal plane for diffraction limited performances up to 350μm•Radiation shields and baffles for local emission rejection

•Angular sensitivity matching target pattern•Spectral coverage in sub-mm/mm range•Signal modulation by an optical component•Instrumental and local emission control

MITO telescope requirements

MITO Opticsprimary mirror diameter 2600 mmeffective primary mirror 2000 mmprimary f-number 0.48effective primary f-number 0.62primary vertex curvature radius 2494 mmsubreflector diameter 410 mmCassegrain f-number 4.1effective magnification 6.6effective focal length 8151 mmprimary mirror vertex - focal plane 461 mmvertex interdistance 1018.7 mmsubreflector vertex - pivot axis 228 mmfocal plane scale 25 “/mmmax beamthrow 63 arcminmax subreflector tilt angle 2.5 degangular resolution @λ=1 mm 1.6 arcmin

Telescope configuration by ACCOS V optimization due to wobbling subreflector

(De Petris et al. Appl. Opt. 28, 1785, 1989)

MITO Telescope

Mirrors manufactured byCostruzioni Ottico-Meccaniche MARCON (Italy)

The final quality of the 2.6-m Primary Mirror surface resulted in itsworldwide application. The same primary mirror with different subreflectors can be foundin:

OASI (Osservatorio Antartico Submillimetrico e Infrarosso)OLIMPO (Osservatorio nel Lontano Infrarosso Montato su Pallone Orientabile)COMPASS (Cosmic Microwave Polarization at Small Scales)COCHISE(Cosmological Observations at Concord with High-sensitivity Instrument

for Sources Extraction )QUaD: QUEST (Q and U Extra-Galactic Sub-mm Telescope) at DASI

Modulation system

0 8 0 0 1 6 0 0 2 4 0 0 3 2 0 0

- 8 0 0

- 4 0 0

0

4 0 0

8 0 0

- 1 .8

- 0 .9

0 .0

0 .9

1 .8

t im e (m s )

sign

al (

mV)

b e a m th r o w = 5 0 a r c m inf r e q = 0 .6 5 H z

subreflector tilt angle (deg) (X 0.23 sky angle)

0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0- 8 0 0

- 4 0 0

0

4 0 0

8 0 0

- 1 .8

- 0 .9

0 .0

0 .9

1 .8L V D To u tp u td u r y -c y c le = 7 5 %

b e a m th ro w = 4 5 a r c m inf r e q = 1 .1 H z

0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0

- 4 0 0

0

4 0 0

- 0 .9

0 .0

0 .9

in p u t g e n

d u ty -c y c le = 7 5 %b e a m th r o w = 3 5 a r c m inf r e q = 1 .1 8 H z

High modulation frequency ~10 Hz1/τBOL>mod freq> (1/fatmo)-1

Large beamthrow ~1 degHigh dutycycle tplateau/T ≥80%plateau connections by x4-type functiondigitally generatedAmpli stability < 2·10-3Freq stability < 1·10-3

(Mainella et al. Appl. Opt. 35, 13, 2246, 1996)

To eliminate the Narcissus Effect (i.e. instrumental emission): A) Conical fixed mirror on the axis of the subreflectorB) Baffles inside primary mirror hole

Telescope baffling: solution

A)

B)

A)

B)

Telescope radiation shieldsLocal emission (dome and ground) rejected by a light rigid octagonalshield with reflecting vanes inside minimising spatial offset dependence

vanes ≡roof mirrors forincoming radiation

FotoMITO cryogenicsSingle-pixel – 4-channel photometer with cold re-imaging optics and 0.3K detectorsGround-based version of ARGO photometer

Key points:☺ N & He4 cryostat☺ Double stage fridge He3-He4

Single shot cycle☺ No mechanical ext. pump☺ No microphonics & EMI

Performances:☺ Teva=290 mK☺ ΔTeva=0.2 mK/h☺ Holding time=80h☺ Cooling power=80μW

He3-He4 Fridge

(Maiani et al. Cryogenics, 39, 459, 1999)

1.2m h – 50 cm dia

FotoMITO spectral bands

2 4 6 8 10 12 14 16 180

20

40

60

80

100

1mm 2mm 3mm 3.5mm Ch1 Ch2 Ch3 Ch4

Tran

smiss

ion

(%)

wavenumber (cm-1)

Ch 1 Ch 2 Ch 3 Ch 4

WAVELENGTH (μm) 2000 1430 1110 895

FREQUENCY (GHz) 143 214 272 353

WAVENUMBER (cm-1) 5.0 6.9 9.0 11.2

hν/KTCBR 2.64 3.69 4.75 5.89

BANDWIDTH (% FWHM) 21 14 12 10

Cold Optics with spectral selection

10 20 30 40 50 601E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

FotoMITO bandslamellar grating interferometer spect. range = 62.5 cm-1 spect. resol. = 0.24 cm-1

Ch1 Ch2 Ch3 Ch4

Tran

smiss

ion

wavenumber (cm-1)

Atmospherical + observative goal good matching

FotoMITO detectors

Composite bolometers by E.Kreysa, i.e. a classical solution

Absorber:sapphire 4X4 mm, 35 micron thicknesstitanium layer on back side (200 Ohm)

Thermistor:Large α = high responsivity!NTD-Ge 200X200X500 micron 2 brass wires, 8 micron in dia, 0.9 mm long

Load Resistance10 MOhm flat metal film

Gold coated copper flange

Cold flange temperature : 280 or 300mK (@3.5km a.s.l. or sea level condition)Operating impedance : 1-2 MOhmTime constant : 10 msElectrical responsivity : 12 MV/WDetector noise : 10nV/Hz-1/2

FotoMITO @ telescope focal plane

Observations towards A1656 with FotoMITO..large fov means large cluster of galaxies

Several observational strategies plus data analysis have been applied to the COMA cluster

…in order to deserve the title of “Coma’s group”

• Nodding, Drift scans, Lead-Main-Trail and Tracking pointing solutions

• 2- or 3-fields sky modulation with several profiles and beamthrows

• Data reduction with several creative approaches:

- decorrelation technique in the case of good atmospherical bad conditions- non-linear amplified data for increasing S/N eliminating non-gaussianity- spatial filtering when source profile is known

30

0

0

100.84)(5.05μK 36)172((272GHz)∆T

μK 79)32((214GHz)∆TμK 39)184((143GHz)∆T

−⋅±=⇒

±+=

±−=

±−=

0τ

SZ Effect on A1656 by MITO

(De Petris M. et al. Ap.JL 574, 119-122, 2002 & Savini G. et al. New Astr. 8, 7, 727-736, 2003)

Observatory ν (GHz) Δν (GHz) fov (FWHM) (arcmin) Sensitivity (mK s1/2) ΔT (μK)

OVRO 32.0 6.5 7.35 1.40 -520 ± 83

WMAP (V) 60.8 13.0 20 1.13 -240 ± 180

WMAP (W) 93.5 19.0 13 1.48 -340 ± 180

MITO (1) 143 30 16 1.21 -184 ± 39

MITO (2) 214 30 16 1.14 -32 ± 79

MITO (3) 272 32 16 0.89 172 ± 36

A1656 by MITO + OVRO & WMAP (I year): wide range SZE spectra

…from SZE spectra -> TCMB(z)Lamagna’s talk

3100.67)(5.35 −⋅±=⇒ 0τ(Bennet et al. Ap.J.Suppl. 148, 97, 2003 & Battistelli et al. Ap.JL 598, 75-78, 2003)

OVRO

WMAP V W

MITO

Ho from A1656• X-ray data from ROSAT

(Mohr et al., ApJ 517, 627, 1999)• Thomson optical depth τo

(Battistelli et al. Ap.JL 598, 75, 2003)• accurate analytic calculation of the Gaunt factor

(Itoh et al., ApJS 128, 125, 2000)

110 Mpcs26)km(84H −− ⋅⋅±=

11

11

Mpcskm 15

Mpcskm 21

−−

−−

⋅⋅±

⋅⋅±Error on τo ⇒ i.e. SZ data

[ΩM=0.27 & ΩΛ=0.73]var2/)1(32 ])/(1[)( βγ −−+= crrr e0e TT

Non-isothermal profile (i.e. polytropic gas model with Te(r))

6/51 ≤≤ γ)3/(4)( γβγβ += isovar

Ho consistent within 5%

Error on β ⇒ i.e. X data

SZE from Supercluster of galaxiesMITO+VSA obs towards Corona Borealis Supercluster

Battistelli’s talk

MITO upgrading: MAD & CASPER2

•Higher angular resolution = 4.5 arcmin/pixel ( better detection efficiency over smaller clusters, smaller chopping angles needed, higher chopping frequencies allowed from the present modulationsystem), better control of atm. fluctuations

• Focal plane pixelization into 3x3 bolometer arrays (moderate imaging capabilities) field of view derotator

•4 channelsFirst Version: the same bands as FotoMITO for ensuring reliable

control of spurious signals and good coupling to atm. transparencywindows and the spectral signature of the SZ effect.

Second Version: bands optimised (peak freq, bandwidth & profile) for efficient parameter extraction (TCMB,Te,v,…)

MAD (Multi Array of Detectors)(L. Lamagna et al., Procs of Intern. School of Physics “Enrico Fermi” Course CLIX SIF (2005))

MAD cryostat

OFFNER

Cold OpticsHe3-He4 Fridge

Tank N2

Tank 4He

4 Array 3X3

Lyot Stop

Slide: L.Lamagna

Lyot Stop = image of the common portion of subreflector duringmodulation

Cold Optics: 1 flat + 3 spherical mirrors

LS

M1M2

M3arrays

Readout electronics

•Differential layout, AC or DC coupled•Based on dual Jfet IF3602 andOP27 opamp•Gain 103•CMRR > 50dB•Noise @ 10Hz

CASPER2(Concordia Atmospherical SPectroscopy of Emitted Radiation2=Testa Grigia Version)(M.De Petris et al. EAS Publ. Series, Vol. 14, (2005))

Testa Grigia Version of the spectrometer for absolute measurements of low resolution atmospherical emission spectra in the FIR/mm range proposed in 2003 to PNRA for the italian-french station in Antarctica, Dome C.

Low resolution spectra + atmo model (ATM) -> transmission (1%) -> pwvReal time atmospherical monitoring for improving

telescope calibration avoiding wasting time by skydips

Spectrometer Martin-Puplett Fourier Transform Spectrometer withfast scan and/or phase modulationField of viewBeam diameter

26 arcminutes, alligned with MITO telescope60 mm (f/3.5)

Frequency range 3-12 cm-1 (low frequency band of CASPER: - 55 cm-1)

Resolution 0.2 cm-1

Detectors Composite Bolometers @ 300mK

Throughput 0.05 cm2srTemperature calibrators Eccosorb AN72 @ LN2 & Amb. Temp.

The spectrometer is based on 4 main subsystems:I. Martin-Puplett Fourier Trasform Spectrometer enriched by a fast

scan & phase modulatorII. Sky radiation collector (Pressman-Camichel 62-cm in dia.

telescope) with altaz mountIII. 4He/N2 Cryostat with detectors cooled down to HeL @ 0.3KIV. Acquisition system, data handling and pointing control

PC telescope

MP FTS Photometer

Altaz mount

WG1

Lyot StopWG2

CAD: S. De Gregori

shield

MP interferometer with the roof mirror on the left for fast scan and the roof mirror on the bottom as phase modulator

Pressman-Camichel 62-cm telescope shielded with reflecting vanes (only 2 panels in the photo).Foam on the top supporting the subreflector

“A joint effort for SZ science”

proposed by Francesco in 2004 is underway

http://oberon.roma1.infn.it/gemini

OASI

OLIMPO

MITO

COCHISE

Gemini-SZ-facilities and plans-

•3 ground-based 2.6-m telescopes: MITO (N.H.) and OASI & COCHISE (S.H.) to perform routine observations of SZ effect in the mm/submm region

•1 balloon-borne platform OLIMPO based on the best available detector technology, first dedicated balloon 2.6-m telescope for SZE measurements

•1 multipixel, multicolor photometer (MAD) and 1 interferometer for measurements in both hemispheres

•1 radiometer (MASTER) for SZE obs and for line measurements in the submm region and atm. line absorption monitoring

•1 wideband atmospherical spectrometer (CASPER)

Despite the big workload the group is still highly motivated and together with Francesco’s enthusiasm,

which is always present, the final scientific goals will be

achieved!!

MITO: a "creative approach“ (*) �for SZE observations from ground�MITO OpticsMITO TelescopeModulation systemTelescope baffling: solutionTelescope radiation shieldsFotoMITO cryogenicsFotoMITO spectral bandsFotoMITO detectorsFotoMITO @ telescope focal planeObservations towards A1656 with FotoMITO�..large fov means large cluster of galaxies�A1656 by MITO + OVRO & WMAP (I year): wide range SZE spectraHo from A1656Readout electronicsGemini-SZ�-facilities and plans-