The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next M4 space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of about 1000 known transiting exoplanets using its metre-class telescope, a three-band photometer and three spectrometers that will cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum. The payload is designed to perform primary and secondary transit spectroscopy, and to measure spectrally resolved phase curves with a stability of < 100 ppm (goal 10 ppm). Observing from an L2 orbit, ARIEL will provide the first statistically significant spectroscopic survey of hot and warm planets. These are an ideal laboratory in which to study the chemistry, the formation and the evolution processes of exoplanets, to constrain the thermodynamics, composition and structure of their atmospheres, and to investigate the properties of the clouds.
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. <p> </p>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 The system is composed of a Michelson interferometer, whose mirrors have been replaced by gratings, a configuration studied in the early days of Fourier Transform spectroscopy, but only recently reused for space instrumentation, with the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. <p> </p>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.
The development of the planetary exploration for landers makes it more and more necessary to have at our disposal small and light instruments. This is why we are developing in our laboratory a light imaging spectrometer with a wedge filter making the spectral splitting. This design already developed in other laboratories has the great advantage to need a limited number of optical components. However its drawback is that at a given instant the different spectral pixels don’t see the same spot in the field. We propose a new design to remedy this drawback by the adjunction of a dispersive system in the fore-optics.
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey (ARIEL) is one of the three candidate missions selected by the European Space Agency (ESA) for its next medium-class science mission due for launch in 2026. The goal of the ARIEL mission is to investigate the atmospheres of several hundred planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve.
During its four (with a potential extension to six) years mission ARIEL will observe 500+ exoplanets in the visible and the infrared with its meter-class telescope in L2. ARIEL targets will include gaseous and rocky planets down to the Earth-size around different types of stars. The main focus of the mission will be on hot and warm planets orbiting close to their star, as they represent a natural laboratory in which to study the chemistry and formation of exoplanets.
The ARIEL mission concept has been developed by a consortium of more than 50 institutes from 12 countries, which include UK, France, Italy, Germany, the Netherlands, Poland, Spain, Belgium, Austria, Denmark, Ireland and Portugal. The analysis of the ARIEL spectra and photometric data in the 0.5-7.8 micron range will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favorable targets. It will also enable the study of thermal and scattering properties of the atmosphere as the planet orbit around the star.
ARIEL will have an open data policy, enabling rapid access by the general community to the high-quality exoplanet spectra that the core survey will deliver.
VIRTIS aboard ESA’s Rosetta mission is a complex imaging spectrometer that combines three unique data channels in one compact instrument to study nucleus and coma of comet 67P/Churyumov-Gerasimenko. Two of the spectral channels are dedicated to spectral mapping (-M) at moderate spectral resolution in the range from 0.25 to 5.1 μm. The third channel is devoted to high resolution spectroscopy (-H) between 2 and 5 μm. The VIRTIS-H field of view is approximately centered in the middle of the -M image. The spectral sampling of VIRTIS-M is 1.8 nm/band below 1 μm and 9.7 nm/band between 1-5 μm, while for VIRTIS-H λ/Δλ= 1300-3000 in the 2-5 μm range. This paper describes selected findings during the pre-landing phase of Philae’s robotic subsystem and the comet’s escort phase as well as prospects of further observations. The preliminary results include studies of surface composition, coma analyses, and temperature retrieval for the nucleus surface-coma system demonstrating the capability of the instrument.
The extraction of surface emissivity data provides the data base for surface composition analyses and enables to evaluate Venus’ geology. The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA’s Venus Express mission measured, inter alia, the nightside thermal emission of Venus in the near infrared atmospheric windows between 1.0 and 1.2 μm. These data can be used to determine information about surface properties on global scales. This requires a sophisticated approach to understand and consider the effects and interferences of different atmospheric and surface parameters influencing the retrieved values. In the present work, results of a new technique for retrieval of the 1.0 – 1.2 μm – surface emissivity are summarized. It includes a Multi-Window Retrieval Technique, a Multi-Spectrum Retrieval technique (MSR), and a detailed reliability analysis. The MWT bases on a detailed radiative transfer model making simultaneous use of information from different atmospheric windows of an individual spectrum. MSR regularizes the retrieval by incorporating available <i>a priori </i>mean values, standard deviations as well as spatial-temporal correlations of parameters to be retrieved. The capability of this method is shown for a selected surface target area. Implications for geologic investigations are discussed. Based on these results, the work draws conclusions for future Venus surface composition analyses on global scales using spectral remote sensing techniques. In that context, requirements for observational scenarios and instrumental performances are investigated, and recommendations are derived to optimize spectral measurements for Venus’ surface studies.
The Exoplanet Characterisation Observatory (EChO) mission was one of the proposed candidates for the European Space Agency’s third medium mission within the Cosmic Vision Framework. EChO was designed to observe the spectra from transiting exoplanets in the 0.55-11 micron band with a goal of covering from 0.4 to 16 microns. The mission and its associated scientific instrument has now undergone a rigorous technical evaluation phase and we report here on the outcome of that study phase, update the design status and review the expected performance of the integrated payload and satellite.
The Exoplanet Characterisation Observatory, EChO, is a dedicated space mission to investigate the physics and chemistry of Exoplanet atmospheres. Using the differential spectroscopy by transit method, it provides simultaneously a complete spectrum in a wide wavelength range between 0.4μm and 16μm of the atmosphere of exoplanets. The payload is subdivided into 6 channels. The mid-infrared channel covers the spectral range between 5μm and 11μm. In order to optimize the instrument response and the science objectives, the bandpass is split in two using an internal dichroic. We present the opto-mechanical concept of the MWIR channel and the detector development that have driven the thermal and mechanical designs of the channel. The estimated end-to-end performance is also presented.
After six years in a polar Venus orbit, the visible and infrared thermal imaging spectrometer (VIRTIS) on ESA's Venus Express mission provided an enormous amount of new data, including a three-dimensional view of the atmosphere and information on global surface properties of the planet. An overview is given of selected scientific results achieved by use of VIRTIS data comprising atmospheric thermal structure, molecular and particulate composition, chemistry and dynamics, and surface features.
The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express, after five years in a polar Venus
orbit, provided an enormous amount of new data including a three-dimensional view of the atmosphere and information
on global surface properties of the planet. VIRTIS is a complex imaging spectrometer that combines three unique data
channels in one compact instrument. Two of the channels are committed to spectral mapping (VIRTIS-M) and a third
one to high spectral resolution studies (VIRTIS-H). The paper gives an overview about the experimental goals and the
instrument performance. It discusses some selected scientific results achieved by VIRTIS, among them thermal structure
and properties of the lower, middle and upper atmosphere including dynamics, polar vortex, nightglows, and NLTE
effects as well as surface features obtained from nightside emission measurements in the NIR atmospheric windows.
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).
In November 2001, the VLT has been equipped for the first time with an adaptive optics system, NAOS. NAOS has been designed to provide good image quality over a wide range of conditions, allowing thus a large variety of astrophysical programs, from Solar System to extragalactic studies. NAOS feeds a camera CONICA which provides imaging, coronagraphic, spectroscopic and polarimetric capabilities between 1 and 5 microns. NAOS and CONICA (hereafter NACO) have been commissioned over the past months. We present in this paper the first images recorded by NACO during the commissioning period, illustrating the capabilities of this new instrument.
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 0.5<sup>o</sup>C..
During the last 30 years, the Space Research Department (DESPA) of Paris Observatory has developed infrared instrumentation for space and ground-based telescopes. First, we present the PbS linear detector of the ISM IR imaging spectrometer of the Phobos mission. Then the CID InSb focal plane of ISOCAM-SW is described. The studies of this CID InSb focal plane allowed us to develop an IR camera for the first astronomical observations using adaptive optics. We also describe the linear array built for the OMEGA imaging spectrometer of the Mars 96 mission. The last chapter is dedicated to the IR spectrometer of the Huygens probe. To conclude, the needs and challenges in the area of mid-band infrared astronomy are discussed.
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
The design of adaptive optics system requires astrophysically driven requirements and specifications. We present here the study performed to help specifying and designing the ESO Nasmyth Adaptive Optics System of the VLT.
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.