Outline I. The Cologne MIR Heterodyne Spectrometer THIS
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Heterodyne InterferometryHeterodyne InterferometryA New Start A New Start
Long Baseline Interferometry in the Mid-InfraredLong Baseline Interferometry in the Mid-InfraredSchloß Ringberg, Sept. 1-5, 2003Schloß Ringberg, Sept. 1-5, 2003
Andreas EckartAndreas Eckart I.Physikalisches Institut der Universität zu Köln I.Physikalisches Institut der Universität zu Köln
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CO2 Emission from Venus 9.2 m-laser-band
R(36) @ 1087.94465 cm-1
Doppler-Shift 1102 MHzIntegration time 6000 sT
sys 5000 K
Resolution 20 MHz
T* [K
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i.f. [MHz]
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Outline
I. The Cologne MIR Heterodyne Spectrometer THIS
II. Future Developements in MIR Heterodyne Detection
III. Future Perspectives for Heterodyne VLTI
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I. THIS
Cologne Tuneable Heterodyne Infrared Spectrometer
Daniel Wirtz / Guido Sonnabend /Volker Vetterle / Rudolf Schieder
I. Physikalisches InstitutUniversität zu Köln
The group of Kostiuk et al. GSFC/NASA is running a CO2 heterodyne spectrometer system
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HeNe
PC AOS IF
DiplexerScanner-mirror
HeNe-Detector
HgCdTe-Detector+HEMT Signal Reference Hot
Telescope
Cold
Loads
QCL
Experimental Setup
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The Diplexer
Ring FP Diplexertuned to LO frequency60% transmissionsignal in reflection100% reflectionprinciple of notch filteraccepts a broad range ofbeam modes!
LO locked throughdiplexer-detector line:stabile performancelong integrationup to 8 hours.
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HgCdTe Detector / MCT
Array capability of system!
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QCL: Quantum Cascade Laser
MIR-Heterodyne-Receiver
•Semicinductor (AlGaAs,GaAs) device based on tunneling and quantum confinement, tunable via temperature and diode current•cascade of up to 40 light emitting cells•FIR-NIR 20 - 100 mW power (Bell Labs, Alpes Laser CH etc.)
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Quantum Cascade Laser
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MCT300 mV2 mA
detector: bias:photo-current:
CO2- vs. QC-laser
QC-laser CO
2-laser
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Tem
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i.f. [MHz]
Performance: QCL versus CO2-Laser
Comparable noise temperatures are reached with both LOs
Tsys=NEP/k
3 x quantumlimit ( 1440 K)
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Fit: Gauss
Gauss = 1,3 MHz
co
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TDL-QCL Beat-Experiment
Narrow linewidths; useful for heterodyne operation
MIDI ~10e-2THIS 4e-8
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Transportable Spektrometer Setup
MIR-Heterodyne-Receiver
•Dimensions 60x60x45 cm•Weight 80 kg
stabilizedHeNe-Laser blackbody
to the telescope
diplexer
HeNe-Laser detectorLN2-dewar
with QCLand MCTdetector
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THIS: Present Technical Specifictions
MIR-Heterodyne-Receiver
•wavelength range: 3-30 microns (requires change of LO, diplexer or detector) •spectroscopic resolution: up to 1 MHz
•bandwidth 1.4 GHz
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• atmospheric measurements
• molecules in sunspots
• CO2-laser emission from Venus
Science Applications:
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integration time:1600s
systemtemperature: 7000K
resolution: 1 MHz
6 K
8 K
stratospheric
ozone-absorption seen against
the moon at 1088,8cm-1
T* [
K]
re
l. In
t.
intermediate frequency [MHz]
Ozone against the Moon
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Combined Gauss fit Gauss fit Peak 1 Gauss fit Peak 2 Data binned to 5 MHz resolution
2
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28SiO [5-4 P56] @ 1088.64 cm-1
second feature not assigned
Peak Molecule Center Width------------------------------------------------1 SiO 819,16 332,572 n.a. 1190,7 240,48------------------------------------------------
rel.
Inte
nsi
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i.f.[MHz]
SiO in a Sunspot
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400 500 600 700 800 900 1000 1100 12000,70
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Dec 1st, 2002
CO2 Emission from Venus 9.2 m-laser-band
R(36) @ 1087.94465 cm-1
Doppler-Shift 1102 MHzIntegration time 6000 sT
sys 5000 K
Resolution 20 MHz
T* [
K]
i.f. [MHz]
None-LTE CO2 Emission from Venus
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• Ozone and CO2 observations on Mars/Venus
• Titan‘s atmosphere resolvable with large telescopes
• Other molecules in planetary atmospheres / bright IR-sources (IRC+10216, CRL 618)
• Bandwidth enhancement- next generation AOS (3-4 GHz)- QWIP (and HEB) detectors ?
• 17µm development H2 S0(1) line
• Second generation instrument for SOFIA (2007)
II. The Future
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Large Bandwidths
with QWIPs
Liu et al. 1995Appl.Phys.Lett. 67, 1594
QWIP: Quantum Well Photodiode
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QWIP (100 periods) with an area of 120µm2 U
Bias=8V
PCO
2-Laser
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IPhoto
=1,2 mA
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i.f. [MHz]
QWIP plus CO2-LASER
QWIP: Quantum Well Photodiode
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III. Prospects for Heterodyne VLTI
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1) Receivers at the telescopes
2) Receivers in the VLTI Lab
3) Phase referencing operation
Possible Heterodyne Observing Modes using the the VLTI
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1) VLTI Heterodyne Operation at the UTs or ATs
Use one receiver per telescope at each of thetelescope foci.
Full delay compensation could be performed in the radio domain.
In a test phase two of the ATs could be equippedwith MIR heterodyne receivers for single dishmeasurements and for interferometric measurements.
Problem: LO reference has to be provided across the array to phase lock the receivers (LASER-line)
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2) Heterodyne Operation in the VLTI Laboratory
Use one receiver per telescope at each of theinput ports in the beam combination laboratory.
The system makes use of the VLT delay lines and can correct for differential delays at radiofrequencies in the ‘usual way‘.
Advantages: 1) LO can be distributed locally (low power LO distribution?!)[2) Could use available delay compensation system]
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VLTI Auxiliary Telescopes
The first 2 of 4 Atswill be ready for the VLTI in the first half of 2004.
AMOS, Liege
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VLTI Delay Line
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The telescopes are relocatable on 30 stationsof the arry providing baselines between8m and 200m
VLTI with Unite and Auxiliary Telescopes
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Possible Locations of a VLTI Heterodyne Backend
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3) Phase Referencing
The broad continuum capabilities of the VLTIcould be used to phase the interferometer and at the same time to integrate on a faint sources in the vicinity of a bright continuum source.
Advantages: 1) LO can be distributed locally (low power LO distribution?!) 2) System makes use of available delay compensation system 3) highest sensitivity plus large sky coverage
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Finito: On axis NIR fringe tracker ESO/OA di Torino First Lab-fringes in Garching 2003 First Paranal fringes planned end of 2003
PRIMA: separation to reference star - 1 arcmin field of view - 2 arcsec reference star brightness 12-13 UTs/ 9-10 ATs
Phase Referencing
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Sky Coverage
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Summary
I. The Cologne MIR Heterodyne Spectrometer THIS
Tunable system operational
II. Future Developements in MIR Heterodyne Detection
Sensitive broad band operation over several GHz bandwidth
III. Future Perspectives for Heterodyne VLTI
Promissing operation modes could be installed
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END