High dynamic range imaging with a single-mode pupil remapping system: a self-calibration algorithm for redundant interferometric arrays

• Published in: Monthly notices of the Royal Astronomical Society Vol. 374; no. 3; pp. 832 - 846
• Main Authors: Lacour, S., Thiébaut, E., Perrin, G.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2007; Blackwell Science; Oxford University Press; Oxford University Press (OUP): Policy P - Oxford Open Option A
• Subjects: Algorithms; Astronomy; Astrophysics; Atmosphere; atmospheric effects; Earth, ocean, space; Exact sciences and technology; instrumentation: adaptive optics; Noise; Physics; planetary systems; Radio astronomy; Radio telescopes; Scientific imaging; stars: imaging; techniques: high angular resolution; techniques: interferometric; instrumentation: adaptive optics; techniques: high angular resolution; stars: imaging; planetary systems; atmospheric effects; techniques: interferometric; Adaptive systems; Signal-to-noise ratio; Central stars; Planetary system; Algorithms; Disturbances; Adaptive optics; Corrections; Stellar dynamics
• ISSN: 0035-8711; 1365-8711; 1365-2966; 1365-2966
• DOI: 10.1111/j.1365-2966.2006.11198.x

The correction of the influence of phase corrugation in the pupil plane is a fundamental issue in achieving high dynamic range imaging. In this paper, we investigate an instrumental set-up which consists of applying interferometric techniques on a single telescope, by filtering and dividing the pupil with an array of single-mode fibres. We developed a new algorithm, which makes use of the fact that we have a redundant interferometric array, to completely disentangle the astronomical object from the atmospheric perturbations (phase and scintillation). This self-calibrating algorithm can also be applied to any – diluted or not – redundant interferometric set-up. On an 8-m telescope observing at a wavelength of 630 nm, our simulations show that a single-mode pupil remapping system could achieve, at a few resolution elements from the central star, a raw dynamic range up to 106, depending on the brightness of the source. The self-calibration algorithm proved to be very efficient, allowing image reconstruction of faint sources (magnitude = 15) even though the signal-to-noise ratios of individual spatial frequencies are of the order of 0.1. We finally note that the instrument could be more sensitive by combining this set-up with an adaptive optics system. The dynamic range would however be limited by the noise of the small, high-frequency displacements of the deformable mirror.