Echoes is a project of a spaceborne Doppler Spectro-Imager (DSI) which has been proposed as payload to the JUICE mission project selected in the Cosmic Vision program of the European Space Agency (ESA). It is a Fourier transform spectrometer which measures phase shifts in the interference patterns induced by Doppler shifts of spectral lines reflected at the surface of the planet. Dedicated to the seismology of Jupiter, the instrument is designed to analyze the periodic movements induced by internal acoustic modes of the planet. It will allow the knowledge of the internal structure of Jupiter, in particular of the central region, which is essential for the comprehension of the scenario of the giant planets’ formation. The optical design is based on a modified Mach-Zehnder interferometer operating in the visible domain and takes carefully into account the sensitivity of the optical path difference to the temperature. The instrument produces simultaneously four images in quadrature which allows the measurement of the phase without being contaminated by the continuum component of the incident light. We expect a noise level less than 1 cm2s-2µHz-1 in the frequency range [0.5 -10] mHz. In this paper, we present the prototype implemented at the Observatoire de la Côte d’Azur (OCA) in collaboration with Institut d'Astrophysique Spatiale (IAS) to study the real performances in laboratory and to demonstrate the capability to reach the required Technology Readiness Level 5.
This paper describes instrumentation used to adapt the Dunn Solar Telescope (DST) located on Sacramento Peak in Sunspot, NM for observations using the Doppler Spectro Imager (DSI). The DSI is based on a Mach-Zehnder interferometer and measures the Doppler shift of solar lines allowing for the study of atmospheric dynamics of giant planets and the detection of their acoustic oscillations. The instrumentation is being designed and built through a collaborative effort between a French team from the Observatoire de la Cote d’Azur (OCA) that designed the DSI and a US team at New Mexico State University (NMSU). There are four major components that couple the DSI to the DST: a guider/tracker, fast steering mirror (FSM), pupil stabilizer and transfer optics. The guider/tracker processes digital video to centroid-track the planet and outputs voltages to the DST’s heliostat controls. The FSM removes wavefront tip/tilt components primarily due to turbulence and the pupil stabilizer removes any slow pupil “wander” introduced by the telescope’s heliostat/turret arrangement. The light received at a science port of the DST is sent through the correction and stabilization components and into the DSI. The FSM and transfer optics designs are being provided by the OCA team and serve much the same functions as they do for other telescopes at which DSI observations have been conducted. The pupil stabilization and guider are new and are required to address characteristics of the DST.
Echoes is a project of a space-borne instrument which has been proposed as part of the JUICE mission which is selected
in the Cosmic Vision program of the European Space Agency (ESA) to perform seismic and dynamics studies
of Jupiter's interior and atmosphere. Based on an original Mach-Zehnder design, the instrument aims to measure Doppler
shifts of solar spectral lines, which are reflected by cloud layers of Jupiter's upper troposphere, coupled with imaging
capabilities. It is specified to detect global oscillations with degree up to l = 50 and amplitude as low as 1 cm/s at the
surface of Jupiter. In order to check the compliance of the instrument, and its capability to operate in representative
environment (TRL5), we build a prototype to perform tests. In this paper, we present the prototype implemented
at Observatoire de la Côte d'Azur in collaboration with Institut d'Astrophysique Spatiale. We describe the design of the
Mach-Zehnder and the procedure of control and adjustment. We present the necessary tests and we show on simulation
that the measurements will provide the required precision. In conclusion, we will explain the perspective for such a new
The ASTEP program is dedicated to exo-planet transit search from the Concordia Station located at Dome C, Antarctica.
It comprises two instruments: a fixed 10cm refractor pointed toward the celestial South Pole, and a 400mm Newton
telescope with a 1x1 degree field of view. This work focuses on the latter instrument. It has been installed in November
2009, and has been observing since then during the two polar winters 2010 and 2011. After presenting the main science
observing programs, we review the telescope installation, performance, and describe its operating conditions as well as
the data reduction and handling strategy. The resulting lightcurves are generally very stable and of excellent quality, as
shown by continuous observations of WASP-19 that we present here.
Fourier transform spectrometry allows us to detect small Doppler velocity shifts of spectral lines by measuring phase
shifts of their associated interference patterns. In this paper, we present the project of space-borne Doppler Spectro
Imager (DSI), Echoes, dedicated to Jovian seismology and aeronomy, which is proposed as payload to the JUICE
mission project (ex-EJSM/Laplace), which competes in the Cosmic Vision program of the European Space Agency
(ESA). The instrumental principle inherits from the ground based experiment SYMPA (Schmider et al, 2007, Gaulme et
al, 2008): it is a Mach-Zehnder interferometer working in the visible domain that is sensitive to Doppler shifts of solar
spectral lines reflected on the planetary atmosphere. It aims to detect small periodic movements of Jupiter's upper
troposphere generated by internal acoustic modes, and to measure their temporal frequencies and spatial geometry. Such
measurement would bring unprecedented knowledge on the internal structure of Jupiter, especially on the central region,
and would provide unique constraints on giant planet formation models. We are currently realizing a prototype to
measure the real instrumental performance in laboratory and to demonstrate the capacity to reach the Technology
Readiness Level 5. We describe the experimental set-up and the expected results.
The Concordia Base in Dome C, Antarctica, is an extremely promising site for photometric astronomy due to the 3-
month long night during the Antarctic winter, favorable weather conditions, and low scintillation. The ASTEP project
(Antarctic Search for Transiting ExoPlanets) is a pilot project which seeks to identify transiting planets and understand
the limits of visible photometry from this site. ASTEP 400 is an optical 40cm telescope with a field of view of 1° x 1°.
The expected photometric sensitivity is 1E-3, per hour for at least 1,000 stars. The optical design guarantees high
homogeneity of the PSF sizes in the field of view. The use of carbon fibers in the telescope structure guarantees high
stability. The focal optics and the detectors are enclosed in a thermally regulated box which withstands extremely low
temperatures. The telescope designed to run at -80°C (-110°F) was set up at Dome C during the southern summer 2009-
2010. It began its nightly observations in March 2010.
MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very
Large Telescope Interferometer (VLTI) of the European Southern Observatory. The related science case study
demonstrates the enormous capability of a new generation mid-infrared beam combiner.
MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. MIDI is a very successful
instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in
MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar
environments by using a wide mid-infrared band coverage extended to L, M and N spectral bands. The four beam
combination of MATISSE provides an efficient UV-coverage : 6 visibility points are measured in one set and 4 closure
phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.
Long baseline interferometry now faces two main challenges. The first one is the image reconstruction from interferometric data. Indeed, the reduced information on the phase of the object Fourier transform during an observation makes image reconstruction quite critical. The second challenge is the improvements of the
overall sensitivity. Strong improvement are expected from double field interferometry : For instance, double field
interferometry enables phase referencing which is a way to obtain information on phases. In addition, double
field interferometry increases the sensitivity of an interferometer.
In this paper we present simulations of double field interferometry. Our simulations take into account; the turbulence conditions, the detection noise, the fringe tracking error. For simulated double field data, we perform an image reconstruction using the coaddition of fringes in the image plane. Since the performances of a double field interferometer are very closely related to and dependent on the site characteristics we studied the results for two different locations: Paranal and Dome C. The comparison shows that Dome C offers much better results, and that it is probably the best site on Earth to build a double-field interferometer.
At Dome C, Antarctica, the whole turbulence is reduced to a boundary layer of about 50 meters. WHITE is a project of an infrared survey based on a 2-m telescope using a ground-layer adaptive-optics instrument to obtain high angular resolution on a wide field of view. Simulation results obtained both analytically and from a numerical end-to-end approach are presented and then compared.
Recent site testing (see: http://www-luan.unice.fr/Concordiastro/indexantartic.html) has shown that Dome C in Antarctica might have a high potential for stellar interferometry if some solutions related to the surface atmospheric layer are found. A demonstrator interferometer could be envisioned in order to fully qualify the site and prepare the future development of a large array. We analyse the performances of a prototype interferometer for Dome C made with 3 telescopes of 40 cm diameter. It assumes classical Michelson recombination. The most recent atmospheric and environmental conditions measured at Dome C are considered (see K. Agabi "First whole atmosphere night-time seeing measurements at Dome C, Antarctica"). We also study the possible science reachable with such a demonstrator. Especially we evaluate that even such small aperture interferometer could allow the detection and low resolution spectroscopy of the most favorable pegaside planets.
We outline the concept and laboratory results of our coronagraphic testbed which has been shipped on automn
2005 to Dome C in Antarctica. We also describe the principle of our coronagraph achromatization and the
laboratory first data like the coronographic nulling results which attain more than 103 at least. The future
development of our experiment for a much larger telescope is also outlined. We finally present CORONA's
on-sky first results.
Our objective is the development of mid-infrared imaging at the VLTI. The related science case study demonstrates the enormous capability of a new generation mid-infrared beam combiner. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI by increasing the number of recombined beams up to four. MIDI is a very successful instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar environments by using a wide mid-infrared band coverage extended to L, M, N and Q spectral bands. The four beam combination of MATISSE provides an efficient UV-coverage: 6 visibility points are measured in one set and 4 closure phase relations which can provide for the first time aperture synthesis images in the mid-infrared spectral regime. The mid-infrared spectral domain is very relevant for the study of the environment of various astrophysical sources. Our science case studies show the wide field of applications of MATISSE. They will be illustrated in the first part of this presentation through the perspective of imaging the circumstellar environments/discs of young stellar objects. The MATISSE characteristics will be given in a second part of the presentation.
Recent site seeing testing campaigns conducted by our team from University of Nice1 show that Dome C represents the best site on Earth for astronomical high angular resolution (HAR) observations at optical and IR wavelengths. The dramatic gain over relevant HAR parameters r0, L0, θ0 and τ0, added to very low temperatures during the polar winter nights (-70°C), the dry atmosphere and the possibility of continuous observations during several nights make Dome C the ideal site for deploying a kilometric optical interferometer before the 2015 horizon. Here we describe the concept of Kiloparsec Explorer for Optical Planet Search (KEOPS) that is studied by our group at LUAN. KEOPS is an interferometric array of 36 off-axis telescopes, each 1.5m in diameter. Its kilometric baselines open sub-mas snap-shot imaging possibilities to detect and characterize extra-solar planetary systems, especially exo-Earths out to 300 parsecs from the visible to the thermal IR. KEOPS can be considered as a DARWIN/TPF challenger but at a much lower cost.