Dr. Véronique Pascal Profile

Dr. Véronique Pascal

Engineer at Ctr National d'Études Spatiales

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Publications (11)

Proceedings Article | 12 July 2019

Modelization and validation of the diffraction effects in the Microcarb instrument for accurately computing the instrumental spectral response function

M. Castelnau, E. Cansot, C. Buil, V. Pascal, V. Crombez, S. Lopez, L. Georges, M. Dubreuil

Proc. SPIE. 11180, International Conference on Space Optics — ICSO 2018

KEYWORDS: Diffraction, Telescopes, Optical design, Spectroscopy, Code v, Performance modeling, Atmospheric modeling, Instrument modeling, Diffraction gratings, Advanced distributed simulations

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MicroCarb is a space program which uses a passive Short Wave InfraRed (SWIR) spectrometer instrument. MicroCarb will provide measurements of the atmospheric concentration of the carbon dioxide at global level with a precision sufficient in order to permit to the scientific community to improve the model of the carbon cycle by understanding the mechanisms governing the exchanges of CO2 between the sources and the sinks.

The MicroCarb Instrument is currently under development at Airbus Defense & Space (ADS). Among the spectral requirements that it must meet, some concern the Instrumental Spectral Response Function (ISRF), which is a key quantity of spectrometers, needed for spectral instrument calibration and atmospheric inversion calculations.

During the development of the Instrument, ADS proposed a method based on several Fourier Transforms to compute the ISRF, based on the one developed by R. Berlich for the FLORIS Instrument ^[1], in order to have an accurate model of its spectral performances.

In this paper, we will explain the simulation method, which allows to take into account diffraction at the system entrance pupil, the spectrometer slit and the dispersion grating, and also the theoretical optical quality of the Instrument. We will describe the preliminary experiments ADS performed to validate this approach. We will then present the work done at ADS and CNES for validating and cross-checking the results of our computations, that required the use of advanced light propagation modules of CODE V.

Once validated, this tool allows to accurately compute the theoretical performances of a given working point, such as the Full-Width at Half Maximum (FWHM) of the ISRF, the resolution of the spectrometer and the likeness of the ISRF to a gaussian function. It is also a powerful tool to quickly compute many ISRFs and thus carry out trade-offs on several parameters of the instrument.

Finally, by including this static computation into a loop and by varying the radiance inside the slit, it is possible to obtain dynamic ISRFs of complex scenes on the ground, and thus have a complete and validated model of the spectral performances of the MicroCarb instrument.

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Proceedings Article | 5 January 2018

Microcarb polarization scrambler

J. Loesel, M. Dubreuil, V. Pascal, C. Buil, F. Buisson

Proc. SPIE. 10563, International Conference on Space Optics — ICSO 2014

KEYWORDS: Point spread functions, Prisms, Polarization, Birefringence, Sensors, Spectroscopy, Astronomical imaging, Tolerancing, Atmospheric modeling, Phase shifts

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Proceedings Article | 21 November 2017

From SPOT 5 to Pleiades HR: evolution of the instrumental specifications

A. Rosak, C. Latry, V. Pascal, D. Laubier

Proc. SPIE. 10568, International Conference on Space Optics — ICSO 2004

KEYWORDS: Signal to noise ratio, Telescopes, Mirrors, Cameras, Sensors, Satellites, Image resolution, Image quality, Charge-coupled devices, Modulation transfer functions

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Proceedings Article | 20 November 2017

A new space instrumental concept based on dispersive components for the measurement of CO2 concentration in the atmosphere

Véronique Pascal, Christian Buil, Elodie Cansot, Jacques Loesel, Laurie Tauziede, Clémence Pierangelo, François Bermudo

Proc. SPIE. 10564, International Conference on Space Optics — ICSO 2012

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Measuring the concentration of greenhouse gases from space is a current challenge. This measurement is achieved via a precise analysis of the signature of chemical gaseous species (CO2, CH4, CO, etc.) in the spectrum of the reflected sunlight. First at all, two families of spectrometers have been studied for the MicroCarb mission. The first family is based on the phenomena of interference between two radiation waves (Michelson Interferometer). The second family is based on the use of dispersive optical components. The second family has been selected for the forthcoming studies in the MicroCarb project. These instruments must have high radiometric and spectral resolutions, in narrow spectral bands, in order to discriminate between absorption lines from various atmospheric chemical species, and to quantify their concentration. This is the case, for example, for the instrument onboard the OCO-2 satellite (NASA/JPL).

Our analysis has led us to define a new instrumental concept, based on a dispersive grating spectrometer, with the aim of providing the same accuracy level as the OCO-2, but with a more compact design for accommodation on the Myriade Evolution microsatellite class. This compact design approach will allow us to offer a moderate-cost solution to fulfil mission objectives. Two other studies based on dispersive grating are in progress by CNES prime contractors (ASTRIUM and THALES ALENIA SPACE).

A summary of the main specifications of this design will be described, in particular the approach with the so-called “merit function”. After a description of such a space instrument, which uses a specific grating component, a preliminary assessment of performances will be presented, including the theoretical calculations and formula. A breadboard implementation of this specific grating has allowed us to show the practicality of this concept and its capabilities. Some results of this breadboard will be described. In addition, an instrument simulator is being developed to validate the performances of this concept. A grating component prototype has been built, and the specifications, together with the expected performances, will be described, in particular the polarisation ratio. Some elements about detectors will be also given regarding their suitability for the mission. This preliminary design is encouraging and shows that such a spectrometer may be compatible with a microsatellite platform (low mass, low power and compact design). Some prospects of improvements will also be considered.

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Proceedings Article | 17 November 2017

An improved microcarb dispersive instrumental concept for the measurement of greenhouse gases concentration in the atmosphere

V. Pascal, C. Buil, J. Loesel, L. Tauziede, D. Jouglet, F. Buisson

Proc. SPIE. 10563, International Conference on Space Optics — ICSO 2014

KEYWORDS: Diffraction, Telescopes, Polarization, Sensors, Spectroscopy, Gases, Multiplexing, Spectral resolution, Carbon monoxide, Diffraction gratings

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Proceedings Article | 25 September 2017

The microcarb instrument

Frederick Pasternak, Philippe Bernard, Laurent Georges, Véronique Pascal

Proc. SPIE. 10562, International Conference on Space Optics — ICSO 2016

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Proceedings Article | 4 October 2011 Paper

A new space instrumental concept for the measurement of CO2 concentration in the atmosphere

Christian Buil, Véronique Pascal, Jacques Loesel, Clémence Pierangelo, Lionel Roucayrol, Laurie Tauziede

Proc. SPIE. 8176, Sensors, Systems, and Next-Generation Satellites XV

KEYWORDS: Signal to noise ratio, Diffraction, Carbon dioxide, Sensors, Satellites, Spectroscopy, Error analysis, Spectral resolution, Earth's atmosphere, Diffraction gratings

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Proceedings Article | 21 October 2005 Paper

Pleiades image quality: from users' needs to products definition

Philippe Kubik, Véronique Pascal, Christophe Latry, Simon Baillarin

Proc. SPIE. 5978, Sensors, Systems, and Next-Generation Satellites IX

KEYWORDS: Signal to noise ratio, Cameras, Sensors, Satellites, Image processing, Image resolution, Satellite imaging, Image quality, Image sensors, Modulation transfer functions

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Proceedings Article | 4 November 2004 Paper

AMETHIST: a method for equalization thanks to HISTograms

Philippe Kubik, Veronique Pascal

Proc. SPIE. 5570, Sensors, Systems, and Next-Generation Satellites VIII

KEYWORDS: Cameras, Sensors, Calibration, Satellites, Image segmentation, Retina, Image quality, Charge-coupled devices, Space operations, Signal detection

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Proceedings Article | 4 November 2004 Paper

A new method for in-flight radiometric noise assessment: application to SPOT5

Véronique Pascal, Francois-Xavier Chaffaut, Philippe Kubik, Laurent Lebegue, Christophe Valorge, Mathieu Jung

Proc. SPIE. 5570, Sensors, Systems, and Next-Generation Satellites VIII

KEYWORDS: Signal to noise ratio, Image compression, Sensors, Calibration, Satellites, Image processing, Lamps, Interference (communication), Image quality, Statistical methods

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Proceedings Article | 8 April 2003 Paper

SPOT5: first in-flight radiometric image quality results

Veronique Pascal, Laurent Lebegue, Aime Meygret, Marie-Christine Laubies, Jean-Noel Hourcastagnou, Emmanuel Hillairet

Proc. SPIE. 4881, Sensors, Systems, and Next-Generation Satellites VI

KEYWORDS: Signal to noise ratio, Short wave infrared radiation, Sensors, Calibration, Satellites, Image processing, Interference (communication), Satellite imaging, Image quality, Signal detection

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Showing 5 of 11 publications

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