Jean-Michel Reess

Paris Diderot University, Lutetia Parisorum, Île-de-France, France

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Publications (23)80.16 Total impact

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    ABSTRACT: Nowadays, astronomers want to observe gaps in exozodiacal disks to confirm the presence of exoplanets, or even make actual images of these companions. Four hundred and fifty years ago, Jean-Dominique Cassini did a similar study on a closer object: Saturn. After joining the newly created Observatoire de Paris in 1671, he discovered 4 of Saturn's satellites (Iapetus, Rhea, Tethys and Dione), and also the gap in its rings. He made these discoveries observing through the best optics at the time, made in Italy by famous opticians like Giuseppe Campani or Eustachio Divini. But was he really able to observe this black line in Saturn's rings? That is what a team of optical scientists from Observatoire de Paris - LESIA with the help of Onera and Institut d'Optique tried to find out, analyzing the lenses used by Cassini, and still preserved in the collection of the observatory. The main difficulty was that even if the lenses have diameters between 84 and 239 mm, the focal lengths are between 6 and 50 m, more than the focal lengths of the primary mirrors of future ELTs. The analysis shows that the lenses have an exceptionally good quality, with a wavefront error of approximately 50 nm rms and 200 nm peak-to-valley, leading to Strehl ratios higher than 0.8. Taking into account the chromaticity of the glass, the wavefront quality and atmospheric turbulence, reconstructions of his observations tend to show that he was actually able to see the division named after him.
    Proc SPIE 09/2013;
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    ABSTRACT: Context. To characterize their atmospheres in order to find evidences of life, one has to detect directly photons from the exoplanets to measure their spectra. One possible technique is dark fringe interferometry that needs an achromatic π phase shift in one arm of the interferometer. We have conceived a phase shifter made of two cellular mirrors, in which each cell position and phase shift is specific, so that the behaviour of the nulling with respect to wavelength is flat within a broad range. Aims. We want to validate experimentally two versions of this achromatic phase shifter: a transmissive one in bulk optics and a reflective one using a segmented deformable mirror. What we present in this paper are the last results obtained in the lab. Methods. We built an optical bench in the visible that allows us to test the principle and characterize the performances and the limits of this phase shifter. Results. We tested several transmissive and one reflective phase shifter and obtained, for instance, an attenuation of about 2.10-3 for a white source (from 430 to 830 nm) that proved the achromatic behavior of the phase shifter. The preliminary performances and limitations are analyzed.
    Proc SPIE 09/2012;
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    ABSTRACT: SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450–900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5–10 AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (∼2 Earth radii, ∼10 M⊕) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.
    Experimental Astronomy 01/2012; 34(2). · 2.97 Impact Factor
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    ABSTRACT: Stabilizing a nulling interferometer at a nanometric level is the key issue to obtain deep null depths. The PERSEE breadboard has been designed to study and optimize the operation of a cophased nulling bench in the most realistic disturbing environment of a space mission. This presentation focuses on the current results of the PERSEE bench. In terms of metrology, we cophased at 0.33 nm rms for the piston and 80 mas rms for the tip/tilt (0.14% of the Airy disk). A Linear Quadratic Gaussian (LQG) control coupled with an unsupervised vibration identi?cation allows us to maintain that level of correction, even with characteristic vibrations of nulling interferometry space missions. These performances, with an accurate design and alignment of the bench, currently lead to a polychromatic unpolarised null depth of 8.9E-6 stabilized at 3E-7 on the [1.65-2.45] \mum spectral band (37% bandwidth).
    Proc SPIE 09/2011;
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    ABSTRACT: Nulling interferometry is still a promising method to characterize spectra of exoplanets. One of the main issues is to cophase at a nanometric level each arm despite satellite disturbances. The bench PERSEE aims to prove the feasibility of that technique for spaceborne missions. After a short description of PERSEE, we will first present the results obtained in a simplified configuration: we have cophased down to 0.22 nm rms in optical path difference (OPD) and 60 mas rms in tip/tilt, and have obtained a monochromatic null of 3E-5 stabilized at 3E-6. The goal of 1 nm with additional typical satellite disturbances requires the use of an optimal control law; that is why we elaborated a dedicated Kalman filter. Simulations and experiments show a good rejection of disturbances. Performance of the bench should be enhanced by using a Kalman control law, and we should be able to reach the desired nanometric stability. Following, we will present the first results of the final polychromatic configuration, which includes an achromatic phase shifter, perturbators and optical delay lines. As a conclusion, we give the first more general lessons we have already learned from this experiment, both at system and component levels for a future space mission. Comment: 12 pages, 13 figures
    Proc SPIE 08/2010;
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    ABSTRACT: Context. Dark fringe interferometry in the thermal infrared is one way to detect directly a planet orbiting a star, and so to characterize the planet's atmosphere through spectroscopy. This method demands a phase shift of pi1 in one arm of the interferometer. In order to detect various bio-tracers gases, a broad wavelength range (6-18 mum)2-3 is necessary, therefore an achromatic phase shift of pi is required. The achromatic device presented here is a phase shifter made of two cellular mirrors, in which each cell induces a specific phase shift. Aims. We wish to demonstrate that this theoretical concept is experimentally valid. We present in this paper the setup and the very first results. Methods. In a first step, we have consolidated the theoretical ground and in a second step we developed an optical bench in the visible domain to test the concept and measure the performances of this device. Results. The preliminary experimental tests show evidences that such a device is working as expected in terms of nulling and achromatism: in spite of an error on one cell of the prototype, it provides a nulling of 2.10-3 at one wavelength, and this value is close to the expected value. Besides, a nulling of 1.10-2 in a 450 to 750 nm bandwidth: a hint that a perfect device should be achromatic.
    01/2010;
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    ABSTRACT: One of the main objectives of the instrument MIRI, the Mid-InfraRed Instrument, of the JWST is the direct detection and characterization of extrasolar giant planets. For that purpose, a coronagraphic device including three Four-Quadrant Phase Masks and a Lyot coronagraph working in mid-infrared, has been developed. We present here the results of the first test campaign of the coronagraphic system in the mid-infrared in the facility developed at the CEA. The performances are compared to the expected ones from the coronagraphic simulations. The accuracy of the centering procedures is also evaluated to validate the choice of the on-board centering algorithm.
    Proc SPIE 08/2008;
  • Spie Newsroom. 01/2008;
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    ABSTRACT: We recently presented a new concept for designing an achromatic phase shifter. An APS is required in nulling interferometry, a technique that aims at directly detecting and characterizing planets around a star in the thermal infrared. Our solution is based on two cellular mirrors (alternatively, transparent plates can be used) where cells have thickness which introduce OPD that are respectively odd and even multiples of half the central wavelength, on the fraction of the wave it reflects. A destructive interference is thus produced on axis for the central wavelength when recombining the two beams. We have shown that if the thicknesses are distributed according to the Pascal triangle, a fair quasi-achromatism is also reached on typically one octave in wavelength, provided there is a suffcient number of cells. The major interest of this solution is that it allows a compact, simple and fully symmetric design, without complex sub-systems to adjust. In this paper, after reminding the basic concept, we first present the theoretical estimations for the expected performances in the two possible regimes of recombination: on axis and multi-axial (Fizeau). We then describe the laboratory setup of the demonstration bench we are developing, as well as the first results obtained.
    Proc SPIE 01/2008;
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    ABSTRACT: The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120 km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft and ground-based observations of infrared emission from CO2, O2 and NO have established that photochemical and dynamic activity controls the structure of the upper atmosphere of Venus. These data, however, have left unresolved the precise altitude of the emission owing to a lack of data and of an adequate observing geometry. Here we report measurements of day-side CO2 non-local thermodynamic equilibrium emission at 4.3 microm, extending from 90 to 120 km altitude, and of night-side O2 emission extending from 95 to 100 km. The CO2 emission peak occurs at approximately 115 km and varies with solar zenith angle over a range of approximately 10 km. This confirms previous modelling, and permits the beginning of a systematic study of the variability of the emission. The O2 peak emission happens at 96 km +/- 1 km, which is consistent with three-body recombination of oxygen atoms transported from the day side by a global thermospheric sub-solar to anti-solar circulation, as previously predicted.
    Nature 12/2007; 450(7170):641-5. · 38.60 Impact Factor
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    ABSTRACT: Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright 'dipole' feature surrounded by a cold 'collar' at its north pole. The polar dipole is a 'double-eye' feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus' south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.
    Nature 12/2007; 450(7170):637-40. · 38.60 Impact Factor
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    ABSTRACT: We present a new design for an imaging heterodyne FT spectrometer and the first test results. The use of SHS combined with cylindrical optics records an interferogram for each point of the slit height.
    02/2007;
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    ABSTRACT: Direct detection and characterization of a planet around a star by nulling interferometry, must be efficient in a large wavelength domain in order to detect simultaneously the infrared bio-tracers CO2, O3 and H2O. This condition requires that an achromatic phase shift of pi be implemented, with an accuracy sufficient for achieving a deep nulling at all considered wavelengths. Several solutions have been presented. We present here a new concept for designing such an achromatic phase shifter. It is based on two cellular mirrors (alternatively, transparent plates can be used) where cells have thickness which are respectively odd and even multiples of a quarter of the central wavelength. Each cell introduces then a phase shift of (2k + 1)pi or of 2kpi, on the fraction of the wave it reflects. Each mirror is introduced in the collimated beam issued from one or the other telescopes. Because of the odd/even distribution, a destructive interference is obviously produced on axis for the central wavelength when recombining the two beams. The trick to obtain a quasi-achromatisation is to distribute the thickness of the cells, so that the nulling is also efficient for a wavelength not too far from the central wavelength. We show that if the thicknesses are distributed according to the Pascal triangle, a fair quasi-achromatism is reached. This effect is the more efficient that the number of cells is large. For instance, with 256 × 256 cells, where phase shift range is between -6pi and +6pi one shows that the nulling reaches 10-6 on the wavelength range [0.7lambda0, 1.3lambda0] which corresponds roughly to the DARWIN specification. In a second step, we study the optimum way to distribute the cells in the plane of the pupil. The most important criterion is the isolation of the planet image from the residual image of the star. Several efficient configurations are presented. Finally we consider some practical aspects on a device belonging to the real world and on the bench we are developing. The major interest of this solution is that it allows a compact, simple and fully symmetric design, with essentially no ajustable sub-systems ; extension to multi-telescopes interferometers with phase shift other than pi can also be envisioned.
    Proc SPIE 01/2007;
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    ABSTRACT: The selection of the Venus Express mission by ESA in 2002 was the occasion to propose the VIRTIS imaging spectrometer for the payload of this mission to Venus. After the discovery of the infrared windows in the near infrared from ground based observations in the 80ies, it was realized that the surface of Venus is accessible to infrared observation on the night side of Venus. Imaging spectroscopy in the visible and near infrared is therefore a powerful tool to study the Venus atmosphere down to its deepest levels. VIRTIS, the imaging spectrometer of the Rosetta mission (Coradini et al, 1998), as the second generation instrument of this kind after the Phobos/ISM (Bibring et al, 1989), Galileo/NIMS (Carlson et al, 1990) Mars Express/OMEGA (Bibring et al, 2004) and Cassini/VIMS (Brown et al, 2000), is perfectly fitted for extensive observations of the infrared and visible spectral images of Venus, with its unique combination of mapping capabilities at low spectral resolution (VIRTIS-M channel) and high spectral resolution slit spectroscopy (VIRTIS-H channel).© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    11/2004;
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    ABSTRACT: Future planetary exploration on telluric or giant planets will need a new kind of instrumentation combining imaging and spectroscopy at high spectral resolution to achieve new scientific measurements, in particular for atmospheric studies in nadir configuration. We present here a study of a Fourier Transform heterodyne spectrometer, which can achieve these objectives, in the visible or infrared. The system is composed of a Michelson interferometer, whose mirrors have been replaced by gratings, a configuration studied in the early days of Fourier Transform spectroscopy, but only recently reused for space instrumentation, with the availability of large infrared mosaics. A complete study of an instrument is underway, with optical and electronic tests, as well as data processing analysis. This instrument will be proposed for future planetary missions, including ESA/Bepi Colombo Mercury Planetary Orbiter or Earth orbiting platforms.
    06/2004;
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    ABSTRACT: MIRI is the mid infrared instrument planned for the NGST. Working in the 5-28 μm band, it includes 3 units: a spectrograph, an imager and a calibration facility. We describe here the optical design of the MIRI imager channel as it is at teh end of the phase A study. The MIRI imager provides 3 observing modes: an imaging mode with a field of view of 1.3 arcmin x 1.7 arcmin and a Pixel Field of View of 0.1 arcsec/pixel, a coronagraphic mode and a low resolution spectroscopic mode for point sources, between 5 μm and 10 μm, with a spectral resolution R = λ/Δλ around 100.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    03/2003;
  • Jean-Pierre Maillard, Benoit Mosser, Jean-Michel Reess
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    ABSTRACT: An interferometer consisting entirely of optically contacted optical elements is described. The interferometer is part of a system to measure the p-mode oscillations of stars from the Doppler signal on a fringe, in the visible.
    Fourier Transform Spectroscopy; 02/2003
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    ABSTRACT: Virtis-H is the high spectral resolution channel of the visible and infrared imaging spectrometer VIRTIS, an instrument of the ESA/ROSETTA mission devoted to the in-orbit remote sensing study of the comet P/46 Wirtanen. After successful tests and calibration, the flight model has been delivered to the European Space Agency for integration on the satellite before the launch foreseen in January 2003. The Virtis-H channel is a cross-dispersion spectrometer in the spectral range 2-5um with a resolution between 1200 and 3000. Its design consists in an afocal telescope-collimator off-axis parabola mirrors, a prism-grating system performing the cross-dispersion, and a three-lens objective imaging the entrance slit on a 436x270 HgCdTe array from Raytheon/IRCOE. At each recorded image, a full spectrum of the observed scene is reconstructed allowing the study of the fine spectral details of the coma and the cometary nucleus. The calibration have shown the fully compliance of the instrument performances with the simulations in terms of spectral resolution, radiometric accuracy and sensibility. For example, spectra of gas, water ice and mineral powders have been measured with Virtis-H showing either its ability to resolve fine spectral lines but also its sensitivity to low fluxes; furthermore, measurements on a 250K blackbody shows its sensibility to relative temperature variation lower than 0.5oC..© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    11/2002;
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    ABSTRACT: VIRTIS, the infrared imaging spectrometer of the ESA/ROSETTA mission, to be launched in January 2003, is devoted to the in-orbit remote sensing study of comet P/46 Wirtanen. Within the infrared imaging spectrometer VIRTIS, the high spectral resolution channel, VIRTIS-H, has for main scientific objectives to study the fine spectral details of the coma and cometary nucleus, with their composition and physical parameters, in parallel with the imaging spectrometer channel VIRTIS-M. The instrument is a cross-dispersor spectrometer, working in the range 2 - 5 micrometers , at about approximately 1200 spectral resolving power. Its design consists of a telescope, an entrance slit, followed by a collimator, and a prism separating 8 orders of a grating© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    11/2000;
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    ABSTRACT: The visible infrared thermal imaging spectrometer (VIRTIS) is one of the principal payloads to be launched in 2003 on ESA's Rosetta spacecraft. Its primary scientific objective s are to map the surface of the comet Wirtanen, monitor its temperature, and identify the solids and gaseous species on the nucleus and in the coma. VIRTIS will also collet data on two asteroids, one of which has been identified as Mimistrobell. The data is collected remotely using a mapping spectrometer co-boresighted with a high spectral resolution spectrometer. The mapper consists of a Shafer telescope matched to an Offner grating spectrometer capable of gathering high spatial, medium spectral resolution image cubes in the 0.25 to 5 micrometers waveband. The high spectral resolution spectrometer uses an echelle grating and a cross dispersing prism to achieve resolving powers of 1200 to 300 in the 1.9 to 5 micrometers band. Both sub-systems are passively cooled to 130 K and use two Sterling cycle coolers to enable two HgCdTe detector arrays to operate at 70 K. The mapper also uses a silicon back-side illuminated detector array to cover the ultra-violet to near-infrared optical band.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    11/1996;