Jean-Claude Fontanella

Deconvolution from wave-front sensing: a new technique for compensating turbulence-degraded images

A new technique of high-resolution imaging through atmospheric turbulence is described. As in speckle interferometry, short-exposure images are recorded, but in addition the associated wave fronts are measured by a Hartmann–Shack wave-front sensor. The wave front is used to calculate the point-spread function. The object is then estimated from the correlation of images and point-spread functions by a deconvolution process. An experimental setup is described, and the first laboratory results, which prove the capabilities of the method, are presented. A signal-to-noise-ratio calculation, permitting a first comparison with the speckle interferometry, is also presented.

Vertical Distribution of NO, NO 2 , and HNO 3 as Derived from Stratospheric Absorption Infrared Spectra

This paper is devoted to the results concerning NO, NO(2), and HNO(3) obtained during airborne experiments performed in June-July 1973 on Concorde 001. The altitude of flight was about 16 km. Results concerning NO are, within the accuracy of measurement, in agreement with results of a previousspectrometric balloonborne experiment conducted jointly by IASB and ONERA (14 May 1973). Nitric oxide is concentrated in stratospheric layers clearly above the flight altitude. Integrated amount of NO along the optical path is (4 +/- 1.5) x 10(16) mol cm(-2) for a solar elevation varying from +2 degrees above the horizontal plane to -1 degrees . A value of 6 x 10(8) mol cm(-3) may be given as an upper limit for the local concentration at the flight altitude. Thereis no significant difference in the integrated amount observed at sunset and sunrise. Measured value of NO(2) local concentration at 15.5 km is (1.1 +/- 0.2) x 10(9) mol cm(-3), in sunset conditions. This value is not greatly modified between 15 km and 30 km. Measured value of HNO(3). This value increases with altitude between 15 km and 20 km. The local concentration is maximum at 20 km. The measured value is (2 +/- 1) x 10(10) mol cm(-3) at 20 km. It seems that local concentration decreases rapidly above 20 km.

Adaptive optics prototype system for infrared astronomy: I. System description

This paper is a presentation of the so-called COME-ON adaptive optics prototype system developed jointly by four European institutions. This system has been tested on the 1.52m telescope of the Observatoire de Haute Provence on October 12 to 23 and November 13 to 24, 1989. Diffration-limited infrared imaging has been achieved during these first tests. The adaptive optics system consists of a 19 actuator deformable mirror and a Hartmann-Shack type wavefront sensor. In this instrument the wavefront sensing is performed at visible wavelengths while the correction is performed for near infrared imaging (1 .2 to 5 .tm). Specialized computers drive the deformable mirror and a tip-tilt mirror. The bandwidth of the servo-loop is 9 Hz at 0 dB point in open-loop. The results obtained with this instrument will be very useful for the design of the future adaptive optics system for the ESO Very Large Telescope (VLT).

Come-on-plus project: an upgrade of the come-on adaptive optics prototype system

This paper is a presentation of the Come-On-Plus adaptive optics system, based on the Come-On prototype. Come-On-PIus will be set up in 1992 on the ESO 3.6 m telescope in La Silla (Chile). It is an upgrade of the Come-On instrument, with a 52 actuator deformable mirror, and 30 Hz correction bandwidth. But the main improvement concerns the wavefront sensing, designed in this instrument for astronomical applications, with a high detectivity wavefront sensor and a specific mirror control algorithm. This system is planned for routine astronomical observing as well as providing design parameters for the adaptive optics system of the ESO Very Large Telescope (VLT).

ARTEMIS: first naval staring IRST in service

Dealing with military and asymmetric threats represents a key issue for any military vessel in various environment. In order to support ships self protection, Thales has designed a new generation of naval InfraRed Search and Track (IRST) called ARTEMIS. It has been selected to equip Future European Multi Roles Frigates (FREMM). ARTEMIS is a fully new passive staring IRST system capable of automatically detecting and tracking both air and surface targets simultaneously. It is able to detect and track maneuvering and stealthy new threats as well as surface asymmetric threats. The paper describes the novelties of the ARTEMIS staring architecture and some of its technologies. It describes also the advantages offered by this new concept of electro-optical surveillance with full static sensor heads compared to existing and future solutions, and its capabilities to comply with future integrated masts standards. The paper concludes by a presentation of the product for the French Navy.

High-resolution astronomical observations using deconvolution from wavefront sensing

Deconvolution from wavefront sensing is a new technique of high-resolution imaging through atmospheric turbulence developed at ONERA. The capabilities of the method have been demonstrated during first laboratory experiments. A deconvolution experimental set-up was installed on the 4.2 m William Herschel telescope on La Palma in November 1990. The results obtained during these observations are presented: the astronomical sources were observed at optical wavelengths; the resolution improvement reached a factor greater than 10.

Come-On: An Adaptive Optics Prototype Dedicated To Infrared Astronomy.

The paper presents the status of the COME-ON (C GE Observatoire de Meudon ESO ONERA) experiment. This instrument, developed and tested by several European laboratories, is an adaptive optical system with a 19 actuators deformable mirror and a Hartmann Shack type wavefront sensor. The wavefront sensing is performing at visible wavelengths; a special computer drives the deformable mirror which should achieve diffraction limited infrared imagery with large optical telescope. The different components and their individual characteristics are described. The results of the tests of some components are given: 19 actuators deformable mirror, tip-tilt mirror. The expected performances are summarized and possible applications of the instrument to astronomical sources are presented. The isoplanaticity aspect, the required temporal bandwidth and reference source brightness is discussed. The conclusions of the experiment will be used for the design of adaptive optics for the ESO Very Large Telescope.

Wavefront sensing in imaging through the atmosphere: a detector strategy

Wavefront sensing is a very powerful technique whose capability in the field of diffraction- limited imaging through turbulence has been demonstrated. The ultimate performance of a Hartmann-Shack wavefront sensor is analyzed and used to define a detector choice strategy.

Wavefront sensing in propagation and imaging through the atmosphere

Atmospheric turbulence is a major limitation to optical high resolution imaging systems observing through the lower atmosphere. In most conditions, it limits the angular resolution to about one arcsecond, which is the resolution of a small 10 cm telescope operating in the visible. From a theoretical standpoint, its effects on beam propagation can be rather well predicted with the knowledge of atmospheric conditions and the assumption of the Kolmogorov turbulence law. Then, the practical problem turns out to be the characterization of propagation conditions and the compensation of turbulence effects.

Come-On: An Adaptive Optics Prototype Dedicated To Infrared Astronomy

The paper presents the status of the COME-ON (CGE Observatoire de Meudon ESO ONERA) experiment. This instrument, developed and tested by several European laboratories, is an adaptive optical system with a 19 actuators deformable mirror and a Hartmann Shack type wavefront sensor. The wavefront sensing is performed at visible wavelengths; a special computer drives the deformable mirror which should achieve diffraction limited infrared imagery with large optical telescope. The different components and their individual characteristics are described. The results of the tests of some components are given: 19 actuators deformable mirror, tip-tilt mirror. The expected performances are summarized and possible applications of the instrument to astronomical sources are presented. The isoplanaticity aspect, the required temporal bandwidth and reference source brightness is discussed. The conclusions of the experiment will be used for the design of adaptive optics for the ESO Very Large Telescope.