Reference : Inherent Modulation: a fast chopping method for nulling interferometry
Scientific conferences in universities or research centers : Scientific conference in universities or research centers
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
Inherent Modulation: a fast chopping method for nulling interferometry
Absil, Olivier mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Astronomical Telescopes and Instrumentation 2002: Interferometry in Space
22/08/2002 - 28/08/2002
Hawaii, USA
[en] The reduction of the thermal background emission from the local and exo-zodiacal dust clouds is a
critical element for the success of ESA's space mission, DARWIN. Internal modulation, a technique
using fast signal chopping, isolating the planetary signal from these noise sources, was proposed
by Mennesson and Mariotti (Icarus 128, 1997). In this paper, we investigate a modification to the
implementation of internal modulation, which provides similar performance with a single detector
and a greatly simplified optical layout: the number of beam combiners is reduced by a factor of
about two. For example, a Robin Laurance six-telescope interferometer (Karlsson and Mennesson,
Proc. SPIE 4006, 2000) can be implemented on five beam combiners instead of twelve. It is demonstrated that inherent modulation can be applied to all existing nulling configurations, including linear arrays. The principle of inherent modulation relies on two nulling interferometers using the same telescopes and beam combination with opposite phase shifts, some of them being different from 0 or pi. During operations, multiplexing between the two interferometers is performed, such that at any time only one interferometer is being used. Since the method lends itself for implementation with four-telescope linear arrays, inherent modulation would also be well suited for the detection of hot Jupiters with a ground-based nulling interferometer on the VLTI.

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