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Thermal background fluctuations at 10 micron measured with VLTI/MIDI
Absil, Olivier; Bakker, Eric; Schoeller, Markus et al.
2004In Traub, Wesley; Monnier, John; Schöller, Markus (Eds.) New Frontiers in Stellar Interferometry
 

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Keywords :
Interferometry; Infrared; MIDI; GENIE; Thermal background; Turbulence
Abstract :
[en] We present an experiment to measure the thermal background level and its fluctuations with the European Southern Observatory (ESO) Very Large Telescope Interferometer (VLTI). The Mid Infrared Instrument (MIDI) operating between 8 and 12 micron was used in both dispersed and non-dispersed modes. By using an interferometric instrument, in non-interferometric mode, we probe the same optical path as can be expected for other infrared interferometric instruments, e.g. GENIE and MIDI itself. Most of the infrared thermal background detected with MIDI originates from the VLTI infrastructure. This can be attributed to the absence of a pupil re-imaging mirror. Only for a small region around the optical axis of the system the signal from the VLTI infrastructure can be considered small and the atmospheric background fluctuations can be characterized. The fluctuations of the thermal emission are described in terms of their power spectral densities (PSD). We have identified two regions in the PSD. For the low frequency range (0-10 Hz) the fluctuations are dominated by the Earth atmosphere. The slope of the log-log PSD is close to -1. For the high frequency (larger than 10 Hz) range the fluctuations are due to photon noise and the PSD flattens off. Many narrow peaks are present in the PSD. Peaks at 1 and 50 Hz occur in almost all data sets and are identified as the effects of the MIDI closed cycle cooler and the power lines respectively. Other peaks at 10 and 30 Hz, as well as peaks above 50 Hz, are assumed to be VLTI or MIDI-specific frequencies.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Absil, Olivier  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS)
Bakker, Eric
Schoeller, Markus
Gondoin, Philippe
Language :
English
Title :
Thermal background fluctuations at 10 micron measured with VLTI/MIDI
Publication date :
01 October 2004
Event name :
New Frontiers in Stellar Interferometry
Event organizer :
SPIE
Event place :
Glasgow, United Kingdom
Event date :
du 21 au 25 juin 2004
Audience :
International
Main work title :
New Frontiers in Stellar Interferometry
Editor :
Traub, Wesley
Monnier, John
Schöller, Markus
Publisher :
SPIE, Bellingham, United States - Washington
Collection name :
Proceedings of the SPIE, volume 5491
Pages :
1320-1332
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since 17 February 2011

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