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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-