Performance comparison between JWST/MIRI+NIRCam & VLT/SPHERE for exoplanet detection

Performance comparison between JWST/MIRI and VLT/SPHERE for exoplanet detection Charles Hanot, Olivier Absil, Anthony Boccaletti, Céline Cavarroc, Jean Surdej In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast imaging has allowed direct images of several exoplanetary systems to be taken (cf. HR 8799, Fomalhaut). In the near future, several new instruments are going to dramatically improve our sensitivity to exoplanet detection. Among these, SPHERE ( Spectro Polarimetric High contrast Exoplanet REsearch ) at the VLT and MIRI ( Mid Infra-Red Instrument) onboard JWST will both be equipped with coronagraphs to reveal faint objects in the vicinity of nearby stars. In this paper, we make use of the most recent evolutionary models of young (sub-)stellar objects and exoplanets to derive their luminosities in order to compare the sensitivity of SPHERE to that of MIRI. From this comparison, we present a catalogue of targets which are particularly well suited for MIRI with possible detections of planets down to (sub-)Saturn masses

Development of nulling interferometry devices for the detection and characterization of extrasolar planets

Most of the 500 extra-solar planets detected to date have been discovered either by radial velocity measurements or photometric transits but very few by direct techniques. Direct imaging of exoplanets, however, gives access to a wider variety of information on the planet, from its orbital position to its spectrum, but is a difficult task to achieve because of the small angular separation between the star and its planet and the large flux ratio between them. For these two reasons, direct imaging of exoplanets has up to now been limited to the most favorable cases of bright giant exoplanets orbiting at large distances from their host stars.%The present work aims at developing the high dynamic range capabilities of single- and multi-aperture imaging techniques for the detection and characterization of planetary systems. The first part of this work reports studies of adaptive optics-aided ground-based telescopes and their complementarity with space-based facilities for the detection of extra-solar planets. Results obtained with the Well-Corrected Subaperture at Palomar observatory on narrow multiple systems are then used to illustrate this study. The second part of this work is dedicated to stellar and nulling interferometry. We first present a new data reduction technique for interferometry using the statistical distributions of the noise sources to significantly improve the precision of interferometric measurements. This technique is then applied to the Palomar Fiber Nuller instrument at Palomar observatory to constrain the presence of dust and companions in the innermost regions of Vega's stellar environment and to derive stellar angular diameters with very high accuracies. Finally, we introduce an on-going survey that we are pursuing with the AMBER interferometric instrument at the Very Large Telescope (Cerro Paranal, Chile) aiming at detecting sub-stellar companions around young main sequence stars

3D seismic for design and derisking of dual geothermal boreholes in sedimentary sequences and new prospects in the Paris Basin (Adapted methodology using petroleum industry techniques)

International audienceThe use of existing geological and structural maps, previous 2D seismic profiles, boreholes and correlation models between these data is sufficient to understand basin structure and thermal systems on a regional scale. However, this is not sufficient on a scale of a geothermal site to be sure of the hydraulic connectivity (or of the presence of a permeability barrier) between two boreholes 1.5 or 2 km apart.To ensure that there is enough hydraulic connectivity, it i s necessary to understand the controls on the network of fractures which affects the aquifer (fracture permeability) and the physical properties of the rock, namely the porosity and clay content in order to obtain a matrix permeability.The latest generation of broadband (six octaves) 3D seismic reflection will provide the following information: the similarity attribute will give an accurate structural map of the fault network at the seismic resolution and, in many cases, at a higher resolution than seismic; seismic velocity anisotropy analysis techniques will make it possible to visualize a 3D volume of information on the fracture network [Michel et al. (2013) Application of Azimuthal Seismic Inversion for Shale Gas Reservoir – Proceedings of the 11th SEGJ International Symposium, Yokohama]; acoustic impedance inversion or petrophysical inversion techniques will predict the porosity throughout the whole volume of the aquifer from a porosity log recorded in a pilot-hole. It allows a real 3D mapping of predicted porosity inside the aquifer much more reliably than from modelling alone.These seismic techniques were initially developed for petroleum exploration and development. They have rapidly progressed throughout the last decade, both in acquisition, processing and interpretation with new methodologies and high-performance softwares. They are efficient for modelling reservoirs to be produced.And, consequently, they can be used for geothermal applications as data to design dual deviated drillings with horizontal drains in carbonate and clastic reservoirs – not only for new projects, but also to revisit old ones to improve their performance or develop another reservoir.Broadband 3D seismic will secure the exploration of Triassic sandstones which stay an interesting prospect for deep geothermal projects.New prospects are proposed in the Paris Basin: Regional faults overlap the substratum. Inside faulted zones, hydrothermal circulations arriving by convection at the top of granitic basement could be geothermal objectives, as in the Alsace Upper Rhine Graben.A production pilot site is suggested to test superimposed aquifers and a regional fault and, at the same time, two different architectures of boreholes doublets: horizontal drains for aquifers and deviated wells for crossing a regional fault.The first site that will use this approach could be instrumented and used as an experiment with a small addition of measurements and sensors, thus becoming a showcase for geothermal energy in France. The objective of this experiment would be to determine the transit time, the heating time of the re-injected water and the circulation speed to define the optimal direction, spacing and length of drains, and also, to realize the thermal modelling of the site for different options

The development and applications of a ground-based fiber nulling coronagraph

A rotating nulling coronagraph has been built for use on ground-based telescopes. The system is based on the concept of sub-aperturing the pupil of the telescope with two elliptical apertures and combining the resulting two input beams on a single-mode fiber. By a relative π phase shift of the beams, the starlight can be nulled and a relatively faint companion star can be detected. Rotation of the aperture mask on the telescope pupil results in a signal similar to that expected from a space-borne telescope system such as the proposed TPF/Darwin interferometer. The design of the nulling coronagraph and the ancillary systems that are needed, such as the fringe tracker, are described and the potential for observations on telescopes such as the Palomar 200" is discussed. Results of a nulling experiment using a single mode fiber as a beam combiner for broadband light between 1.50 μm and 1.80 μm are shown

Infrared Imaging

A mid‐infrared mission would enable the detection of biosignatures of Earth‐like exoplanets around more than 150 nearby stars. The mid‐infrared spectral region is attractive for characterizing exoplanets because contrast with the parent star brightness is more favorable than in the visible (10 million vs. 10 billion), and because mid‐infrared light probes deep into a planet’s troposphere. Furthermore, the mid‐infrared offers access to several strong molecular features that are key signs of life, and also provides a measure of the effective temperature and size of a planet. Taken together, an infrared mission plus a visible one would provide a nearly full picture of a planet, including signs of life; with a measure of mass from an astrometric mission, we would have a virtually complete picture. A small infrared mission would have several telescopes that are rigidly connected, with a science return from the detection and characterization of super‐Earth sized to larger planets near the HZ, plus a direct measure of the exozodi brightness in the HZ. In a large infrared mission, with formation‐flying telescopes, planets from an Earth‐twin and upwards in mass could be detected and characterized, as well as the exozodi. If proceeded by an astrometric mission, the detection phase could be skipped and the mission devoted to characterization, as in the visible case; lacking an astrometric mission, an infrared one could proceed alone, as was discussed for a visible coronograph, and with similar caveats. The technology needed for a large formation‐flying mission is similar to that for a small connected‐element one (e.g., cryogenics and detectors), with the addition of formation-flying technology. The technology is now in hand to implement a probe‐scale mission; starlight suppression has even been demonstrated to meet the requirements of a flagship mission. However, additional development of formation‐flying technology is needed, particularly in‐space testing of sensors and guidance, navigation, and control algorithms

First manufactured diamond AGPM vector vortex for the L- and N-bands: metrology and expected performances

The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period smaller than λ/n (λ being the observed wavelength and n the refractive index of the grating substrate). Since it is a phase mask, it allows to reach a high contrast with a small working angle. Moreover, its subwavelength structure provides a good achromatization over wide spectral bands. Recently, we have manufactured and measured our first N-band prototypes that allowed us to validate the reproducibility of the microfabrication process. Here, we present newly produced mid-IR diamond AGPMs in the N-band (~10 µm), and in the most wanted L-band (~3.5 µm). We first give an extrapolation of the expected coronagraph performances. We then present the manufacturing and measurement results, using diamond-optimized microfabrication techniques such as nano-imprint lithography (NIL) and reactive ion etching (RIE). Finally, the subwavelength grating profile metrology combines surface metrology (scanning electron microscopy, atomic force microscopy, white light interferometry) with diffractometry on an optical polarimetric bench and cross correlation with theoretical simulations using rigorous coupled wave analysis (RCWA).VORTE

First manufactured diamond AGPM vector vortex for the L- and N-bands: metrology and expected performances

The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period smaller than λ/n (λ being the observed wavelength and n the refractive index of the grating substrate). Since it is a phase mask, it allows to reach a high contrast with a small working angle. Moreover, its subwavelength structure provides a good achromatization over wide spectral bands. Recently, we have manufactured and measured our first N-band prototypes that allowed us to validate the reproducibility of the microfabrication process. Here, we present newly produced mid-IR diamond AGPMs in the N-band (~10 µm), and in the most wanted L-band (~3.5 µm). We first give an extrapolation of the expected coronagraph performances. We then present the manufacturing and measurement results, using diamond-optimized microfabrication techniques such as nano-imprint lithography (NIL) and reactive ion etching (RIE). Finally, the subwavelength grating profile metrology combines surface metrology (scanning electron microscopy, atomic force microscopy, white light interferometry) with diffractometry on an optical polarimetric bench and cross correlation with theoretical simulations using rigorous coupled wave analysis (RCWA).VORTE

SPICES: Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems

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 2020/22, 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 ($<$25 pc) with masses ranging from a few Jupiter masses to Super Earths ($\sim$2 Earth radii, $\sim$10 M$_{\oplus}$) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System

Technology for a Mid-IR Flagship Mission to Characterize Earth-like Exoplanets

The exploration of Earth-like exoplanets will be enabled at mid-infrared wavelengths through technology and engineering advances in nulling interferometry and precision formation flying. Nulling interferometry provides the dynamic range needed for the detection of biomarkers. Formation flying provides the angular resolution required in the mid-infrared to separately distinguish the spectra of planets in multi-planet systems. The flight performance requirements for nulling have been met and must now be validated in a flight-like environment. Formation-flying algorithms have been demonstrated in the lab and must now be validated in space. Our proposed technology program is described