Combination of nulling interferometer and modified pupil for observations of exo-planets

Abstract

Abstract. We consider a combination of two techniques, namely the nulling interferometer and halo suppression by modified pupil such as shaped pupils and apodized square apertures, which achieves very high dynamic range, in order to detect faint extra-solar planets around nearby stars. The effects of the nulling interferometer and the modified pupil are independent and in combination hence multiplied. We show that one can achieve higher dynamic range in the case of a resolved star than with either method alone. By numerical simulations, we show that the combination method can achieve dynamic range levels of 10 −10 at 3λ/D. Used alone, the two-telescope interferometer would give the nulling depth of 10 −3 whilst the halo suppression by a shaped aperture would do 10 −7 , with a point-spread-function core radius less than 3λ/D for a shaped aperture. The introduction of the modified pupil has the same effect whether it is made at the entrance apertures of the interferometer or at a re-imaged common pupil plane after the nulling interferometry. From another point of view, a nulling interferometer works as pre-optics in front of any single telescope methods, which reduces the intensity of a resolved source transmitting some uniform wavefront residuals.

Theoretical Limits on Extrasolar Terrestrial Planet Detection with Coronagraphs

“…The multistep APLC concept (Aime & Soummer 2004) illustrates how such a ''cascade'' can simultaneously improve IWA and throughput by designing each step for a lower contrast level. Nishikawa et al (2005) showed how a nulling interferometer can benefit from a CPA, and a similar combination may also be advantageous on a circular pupil (VNC-CPA for example). The entrance pupil apodization required for the APLCs may be performed by a PIAA unit to improve IWA and throughput.…”

Removal of central obscuration and spider arm effects with beam-shaping coronagraphy

“…This multi-stage approach was also recently considered for coronagraphy with a combination of a classical Lyot coronagraph and a shaped pupil mask (Chakraborty et al 2005). Another way consists in combining nulling interferometry and coronagraphy (Nishikawa et al 2005). The perfect example of multi-stage coronagraphy is, however, proposed by Aime & Soummer (2003b) with the cascading Multi-Stage Prolate-(amplitude) 1 -Apodized Lyot Coronagraph (MS-PALC).…”

Characteristics of lateral-shearing nulling interferometry by use of double Fresnel rhombs

“…Our simulations suggest that extremely small amplitude and OPD errors would be required for achieving excellent nulling performance such as 10 −10 at 5 λ 0 /D. We note that these requirements would be relaxed by introducing additional high-contrast imaging techniques, such as a pupil apodization, behind the nulling interferometer [23].…”