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Neptune has a collection of incomplete narrow rings, known as ring arcs, which should in isolation be destroyed by differential motion in a matter of months. Yet since ®rst discovered 1 by stellar occultations in 1984, they appear to have persisted 2±6 , perhaps through a gravitational resonance effect involving the satellite Galatea 6±8. Here we report(More)
Properly apodized pupils can deliver point spread functions (PSFs) free of Airy rings, and are suitable for high dynamical range imaging of extrasolar terrestrial planets (ETPs). To reach this goal, classical pupil apodization (CPA) unfortunately requires most of the light gathered by the telescope to be absorbed, resulting in poor throughput and low(More)
In this paper, an alternative to the classical pupil apodization techniques (use of an amplitude pupil mask) is proposed. It is shown that an apodized pupil suitable for imaging of Extrasolar planets can be obtained by reflection of an un-apodized flat wavefront on 2 mirrors. By carefully choosing the shape of these 2 mirrors, it is possible to obtain a(More)
We present a new method for numerical propagations through Lyot-style coronagraphs using finite size occulting masks. Standard methods for coronagraphic simulations involve Fast Fourier Transforms (FFT) of very large arrays, and computing power is an issue for the design and tolerancing of coronagraphs on Extremely Large Telescopes (ELT) in order to handle(More)
Many high contrast coronagraph designs have recently been proposed. In this paper, their suitability for direct imaging of extrasolar terrestrial planets is reviewed. We also develop a linear-algebra based model of coronagraphy that can both explain the behavior of existing coronagraphs and quantify the coronagraphic performance limit imposed by fundamental(More)
The effects of photon noise, aliasing, wavefront chromaticity and scintillation on the point spread function (PSF) contrast achievable with ground based adaptive optics (AO) are evaluated for different wavefront sensing schemes. I show that a wavefront sensor (WFS) based upon the Zernike phase contrast technique offers the best sensitivity to photon noise(More)
This paper investigates the integration of the employee timetabling and production scheduling problems. At the first level, we manage a classical employee timetabling problem. At the second level, we aim at supplying a feasible production schedule for a set of interruptible tasks with qualification requirements and time-windows. Instead of hierarchically(More)
Using 2 aspheric mirrors, it is possible to apodize a telescope beam without losing light or angular resolution: the output beam is produced by " remap-ping " the entrance beam to produce the desired light intensity distribution in a new pupil. We present the Phase-Induced Amplitude Apodization Coronagraph (PIAAC) concept, which uses this technique, and we(More)
High contrast coronagraphic imaging of the immediate surrounding of stars requires exquisite control of low-order wavefront aberrations, such as tip-tilt (pointing) and focus. We propose an accurate, efficient and easy to implement technique to measure such aberrations in coronagraphs which use a focal plane mask to block starlight. The Coronagraphic Low(More)
High contrast coronagraphic imaging is challenging for telescopes with central obstructions and thick spider vanes, such as the Subaru Telescope. We present in this paper the first laboratory demonstration of a high efficiency PIAA-type coronagraph on such a pupil, using coronagraphic optics which will be part of the Subaru Coronagraphic Extreme-AO (SCExAO)(More)