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Outline I. The Cologne MIR Heterodyne Spectrometer THIS

Heterodyne Interferometry A New Start Long Baseline Interferometry in the Mid-Infrared Schloß Ringberg, Sept. 1-5, 2003 Andreas Eckart I.Physikalisches Institut der Universität zu Köln. Outline I. The Cologne MIR Heterodyne Spectrometer THIS

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Outline I. The Cologne MIR Heterodyne Spectrometer THIS

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  1. Heterodyne InterferometryA New Start Long Baseline Interferometry in the Mid-InfraredSchloß Ringberg, Sept. 1-5, 2003Andreas Eckart I.Physikalisches Institut der Universität zu Köln

  2. Outline I.The Cologne MIR Heterodyne SpectrometerTHIS II. Future Developements in MIR Heterodyne Detection III. Future Perspectives for Heterodyne VLTI

  3. I. THIS Cologne Tuneable Heterodyne Infrared Spectrometer Daniel Wirtz / Guido Sonnabend / Volker Vetterle / Rudolf Schieder I. Physikalisches Institut Universität zu Köln The group of Kostiuk et al. GSFC/NASA is running a CO2 heterodyne spectrometer system

  4. HeNe QCL PC AOS IF Experimental Setup HeNe-Detector Diplexer Scanner- mirror HgCdTe- Detector +HEMT Signal Reference Hot Cold Telescope Loads

  5. The Diplexer Ring FP Diplexer tuned to LO frequency 60% transmission signal in reflection 100% reflection principle of notch filter accepts a broad range of beam modes! LO locked through diplexer-detector line: stabile performance long integration up to 8 hours.

  6. HgCdTe Detector / MCT Array capability of system!

  7. MIR-Heterodyne-Receiver QCL: Quantum Cascade Laser • 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.)

  8. Quantum Cascade Laser

  9. Performance: QCL versus CO2-Laser Tsys=NEP/k 3 x quantum limit ( 1440 K) Comparable noise temperatures are reached with both LOs

  10. TDL-QCL Beat-Experiment MIDI ~10e-2 THIS 4e-8 Narrow linewidths; useful for heterodyne operation

  11. MIR-Heterodyne-Receiver Transportable Spektrometer Setup • Dimensions 60x60x45 cm • Weight 80 kg stabilized HeNe-Laser blackbody diplexer HeNe-Laser detector LN2-dewar with QCL and MCT detector to the telescope

  12. 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

  13. Science Applications: • atmospheric measurements • molecules in sunspots • CO2-laser emission from Venus

  14. Ozone against the Moon

  15. SiO in a Sunspot

  16. None-LTE CO2 Emission from Venus

  17. II. The Future • 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)

  18. QWIP: Quantum Well Photodiode Large Bandwidths with QWIPs Liu et al. 1995 Appl.Phys.Lett. 67, 1594

  19. QWIP: Quantum Well Photodiode QWIP plus CO2-LASER

  20. III. Prospects for Heterodyne VLTI

  21. Possible Heterodyne Observing Modes using the the VLTI 1) Receivers at the telescopes 2) Receivers in the VLTI Lab 3) Phase referencing operation

  22. 1) VLTI Heterodyne Operation at the UTs or ATs Use one receiver per telescope at each of the telescope foci. Full delay compensation could be performed in the radio domain. In a test phase two of the ATs could be equipped with MIR heterodyne receivers for single dish measurements and for interferometric measurements. Problem: LO reference has to be provided across the array to phase lock the receivers (LASER-line)

  23. 2) Heterodyne Operation in the VLTI Laboratory Use one receiver per telescope at each of the input ports in the beam combination laboratory. The system makes use of the VLT delay lines and can correct for differential delays at radio frequencies in the ‘usual way‘. Advantages: 1) LO can be distributed locally (low power LO distribution?!) [2) Could use available delay compensation system]

  24. VLTI Auxiliary Telescopes The first 2 of 4 Ats will be ready for the VLTI in the first half of 2004. AMOS, Liege

  25. VLTI Delay Line

  26. VLTI with Unite and Auxiliary Telescopes The telescopes are relocatable on 30 stations of the arry providing baselines between 8m and 200m

  27. Possible Locations of a VLTI Heterodyne Backend

  28. 3) Phase Referencing The broad continuum capabilities of the VLTI could 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

  29. Phase Referencing 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

  30. Sky Coverage

  31. Summary I.The Cologne MIR Heterodyne SpectrometerTHIS 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

  32. END

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