Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · astro-ph/0703077

Calibration and Pre-Compensation of Non-Common Path Aberrations for extreme Adaptive Optics

J. -F. Sauvage·T. Fusco·G. Rousset·C. Petit
View original source ↗Read source document ↗Export metadata ↓

Abstract

Non-Common Path Aberrations (NCPA) are one of the main limitations for extreme Adaptive Optics (AO) system. NCPA prevent extreme AO systems to achieve their ultimate performance. These static aberrations are unseen by the wave front sensor and therefore not corrected in closed loop. We present experimental results validating new procedures of measurement and pre-compensation of the NCPA on the AO bench at ONERA. The measurement procedure is based on new refined algorithms of phase diversity. The pre-compensation procedure makes use of a pseudo-closed loop scheme to overcome the AO wavefront sensor model uncertainties. Strehl Ratio obtained in the images reaches 98.7% @ 632.8 nm. This result allows us to be confident of achieving the challenging performance required for extrasolar planet direct observation.

Explore related subjects

astro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J. -F. Sauvage, T. Fusco, G. Rousset, C. Petit. 2007-03-05. Calibration and Pre-Compensation of Non-Common Path Aberrations for extreme Adaptive Optics. https://doi.org/10.1364/josaa.24.002334

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Oscillation frequencies and mode lifetimes in alpha Centauri A

We analyse our recently-published velocity measurements of alpha Cen A (Butler et al. 2004). After adjusting the weights on a night-by-night basis in order to optimize the window function to minimize sidelobes, we extract 42 oscillation frequencies with l=0 to 3 and measure the large and small frequency separations. We give fitted relations to these frequencies that can be compared with theoretical models and conclude that the observed scatter about these fits is due to the finite lifetimes of the oscillation modes. We estimate the mode lifetimes to be 1-2 d, substantially shorter than in the Sun.

astro-ph↗
arXiv2026

Hipparcos period-luminosity relations for Miras and semiregular variables

We present period-luminosity diagrams for nearby Miras and semiregulars, selecting stars with parallaxes better than 20 per cent and well-determined periods. Using K-band magnitudes, we find two well-defined P-L sequences, one corresponding to the standard Mira P-L relation and the second shifted to shorter periods by a factor of about 1.9. The second sequence only contains semiregular variables, while the Mira sequence contains both Miras and semiregulars. Several semiregular stars show double periods in agreement with both relations. The Whitelock evolutionary track is shown to fit the data, indicating that the semiregulars are Mira progenitors. The transition between the two sequences may correspond to a change in pulsation mode or to a change in the stellar structure. Large amplitude pulsations leading to classical Mira classification occur mainly near the tip of the local AGB luminosity function.

astro-ph↗
arXiv2025

A Cyclical Baryonic Big Bang Explains the Universe

Our universe has multiple examples of unexplained gravitational losses in black holes and neutron stars. The smallest black holes of about 4 solar masses means the maximum baryon density ρ\approx 10^{17} grams/cm^3. Any collapse of the universe will stop with a scale factor \approx 10^{13} cm. and radiation energy \approx 10 GeV. Due to higher squeezed core baryons, the outer part of the mass transferred energy to the core and became dark matter. After contraction reduced particle motion and gravitation, the core radiation energy propelled pieces of the shell into the universe. Each of these masses captured hot core gases according to its gravitational size, forming proto-galaxies. A cold shell and a hot core explain the Planck spectrum and large galaxy formation in the early universe. Thus the universe was never radiation dominant.The universe will remain cyclical as any increase in entropy of matter will be crushed back to neutrons during the contraction phase.

astro-ph↗