Abstract

Studying the formation of planet and protoplanetary disks around young stars requires angular resolutions of less than 1milli-arcsecond which can only be achieved using interferometry. The Planet Formation Imager initiative expressed the need for kilometric baseline mid-infrared interferometry with tens of telescopes [1]. Current state-of-the-art [8,13]µm interferometer at VLTI is able to combine four telescopes on up to 130m baselines with a direct interferometry approach. Direct interferometry uses bulky mid-infrared free space delay lines to recombine the light from separated telescopes and recover the interferometric observable from the astronomical object. Heterodyne interferometry relies on a different approach which consists in detecting the heterodyne beating between the astronomical signal and a local oscillator at each telescope. The resulting heterodyne signals are radio-frequency signals that can be either digitized or analogically transmitted, amplified and processed before being correlated. Unlike direct schemes, heterodyne interferometry can be easily scaled up to N telescopes without any major additionnal noise contribution, making it competitive for studying planet formation despite its relatively lower sensitivity.

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