Thermalizing a telescope in Antarctica: Analysis of ASTEP observations

The installation and operation of a telescope in Antarctica represent particular challenges, in particular the requirement to operate at extremely cold temperatures, to cope with rapid temperature fluctuations and to prevent frosting. Heating of electronic subsystems is a necessity, but solutions must be found to avoid the turbulence induced by temperature fluctua- tions on the optical paths. ASTEP 400 is a 40 cm Newton telescope installed at the Concordia station, Dome C since 2010 for photometric observations of fields of stars and their exoplanets. While the telescope is designed to spread star light on several pixels to maximize photometric stability, we show that it is nonetheless sensitive to the extreme variations of the seeing at the ground level (between about 0.1 and 5 arcsec) and to temperature fluctuations between --30 degrees C and --80 degrees C. We analyze both day-time and night-time observations and obtain the magnitude of the seeing caused by the mirrors, dome and camera. The most important effect arises from the heating of the primary mirror which gives rise to a mirror seeing of 0.23 arcsec K--1 . We propose solutions to mitigate these effects.Comment: Appears in Astronomical Notes / Astronomische Nachrichten, Wiley-VCH Verlag, 2015, pp.1-2

The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI

The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.Comment: Published in the ESO Messenge

SPEED design optimization via Fresnel propagation analysis

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A Fresnel propagation analysis for SPEED (Segmented Pupil Experiment for Exoplanet Detection)

Direct detection and characterization of exoplanets is a major scientific driver of the next decade. Direct imaging requires challenging techniques to observe faint companions around bright stars. The development of future large telescopes will increase the capability to directly image and characterize exoplanets thanks to their high resolution and photon collecting power. The E-ELT will be composed of a segmented ~40 m-diameter primary mirror. High contrast imaging techniques for E-ELT will thus need to deal with amplitude errors due to segmentation (pupil discontinuities between the segments). A promising technique is the wavefront shaping. It consists in the use of deformable(s) mirror(s) to cancel the intensity inside the focal plane region. Algorithm improvements and laboratory demonstrations have been developed since the last 20 years. The use of 2 deformable mirrors (DM) in non-conjugated planes will allow correcting not only for phase aberrations but also for the amplitude errors. Lagrange laboratory has begun in 2013 the development of an instrumental project called SPEED (Segmented Pupil Experiment for Exo-planet Detection). Its goal is to develop and test high-contrast imaging techniques optimized for segmented pupil. In this paper we present a detailed end-to-end simulation for the optimization of the SPEED experiment optical design. In particular, we pay attention to the optimal separation between the two DMs necessary for phase and amplitude correction. The trade-off between various parameters (field of correction, field of view, size constraints,...) is presented and discussed

An end-to-end Fresnel propagation model for SPEED: PIAACMC implementation and performance

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The segmented pupil experiment for exoplanet detection. 4. A versatile image-based wavefront sensor for active optics

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A metrological characterization of the SPEED test-bed PIAACMC components.

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System analysis of the Segmented Pupil Experiment for Exoplanet Detection - SPEED - in view of the ELTs

SPEED is a new experiment in progress at the Lagrange laboratory to study some critical aspects to succeed invery deep high-contrast imaging at close angular separations with the next generation of ELTs. The SPEEDbench will investigate optical, system, and algorithmic approaches to minimize the ELT primary mirrordiscontinuities and achieve the required contrast for targeting low mass exoplanets. The SPEED projectcombines high precision co-phasing architectures, wavefront control and shaping using two sequential high orderdeformable mirrors, and advanced coronagraphy (PIAACMC). In this paper, we describe the overall systemarchitecture and discuss some characteristics to reach 10-7 contrast at roughly 1λ/D

System analysis of the Segmented Pupil Experiment for Exoplanet Detection - SPEED - in view of the ELTs

SPEED is a new experiment in progress at the Lagrange laboratory to study some critical aspects to succeed invery deep high-contrast imaging at close angular separations with the next generation of ELTs. The SPEEDbench will investigate optical, system, and algorithmic approaches to minimize the ELT primary mirrordiscontinuities and achieve the required contrast for targeting low mass exoplanets. The SPEED projectcombines high precision co-phasing architectures, wavefront control and shaping using two sequential high orderdeformable mirrors, and advanced coronagraphy (PIAACMC). In this paper, we describe the overall systemarchitecture and discuss some characteristics to reach 10-7 contrast at roughly 1λ/D