Dr. Julien Woillez Profile

Dr. Julien Woillez

Interferometry Scientist at European Southern Observatory

SPIE Involvement:

Conference Program Committee | Author

Publications (54)

PROCEEDINGS ARTICLE | July 17, 2018

Characterization of ALPAO deformable mirrors for the NAOMI VLTI Auxiliary Telescopes adaptive optics

Proc. SPIE. 10703, Adaptive Optics Systems VI

KEYWORDS: Actuators, Telescopes, Astronomy, Interferometers, Calibration, Wavefronts, Adaptive optics, Deformable mirrors, Turbulence

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PROCEEDINGS ARTICLE | July 10, 2018

Data reduction of the VLTI/GRAVITY interferometric instrument (Conference Presentation)

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Telescopes, Interferometers, Fourier transforms, Interferometry, Signal processing, Software development, Integrated optics, Phase measurement, Algorithm development, Information operations

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PROCEEDINGS ARTICLE | July 9, 2018

Hi-5: a potential high-contrast thermal near-infrared imager for the VLTI

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Mid-IR, Stars, Imaging systems, Interferometers, Interferometry, L band, Exoplanets, Integrated optics, Planets, Astrophysics

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PROCEEDINGS ARTICLE | July 9, 2018

Image-plane fringe tracker for adaptive-optics assisted long baseline interferometry

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Telescopes, Sensors, Interferometry, Wavefront sensors, Adaptive optics, Visibility

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PROCEEDINGS ARTICLE | July 9, 2018

NAOMI: the adaptive optics for the auxiliary telescopes of VLTI

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Telescopes, Mirrors, Interferometers, Sensors, Interferometry, Wavefronts, Adaptive optics, Deformable mirrors, Real-time computing

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PROCEEDINGS ARTICLE | July 9, 2018

VLTI status update: three years into the second generation

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Telescopes, Metrology, Stars, Interferometers, Adaptive optics

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PROCEEDINGS ARTICLE | July 9, 2018

MATISSE: performance in laboratory, results of AIV in Paranal, and first results on sky

Proc. SPIE. 10701, Optical and Infrared Interferometry and Imaging VI

KEYWORDS: Photovoltaics, Telescopes, Spatial filters, Sensors, Calibration, Interferometry, L band, Spectral resolution, Astatine, Visibility

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MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer for the VLTI of the European Southern Observatory (ESO), operating in the L-, M- and N- spectral bands, and combining up to four beams from the unit or the auxiliary telescopes (UTs or ATs). MATISSE will offer new breakthroughs in the study of circumstellar environments by allowing the mapping of the material distribution, the gas and essentially the dust. The instrument consists in a warm optical system (WOP) accepting four beams from the VLTI and relaying them after a spectral splitting to cold optical benches (COB) located in two separate cryostats, one in L-M- band, and one in N-band. The test plan of the complete instrument has been conducted at the Observatoire de la Côte d’Azur in order to confirm the compliance of the performance with the high-level requirements. MATISSE has successfully passed the Preliminary Acceptance in Europe the 12th September 2017. Following this result, ESO gave approval for the instrument to be shipped to Paranal. The Alignment, Integration and Verification phase was conducted until end of February 2018, at the end of which first observations on sky have been performed to test the operations with the VLTI and to obtain first stellar light. The two first runs of the commissioning followed, respectively in March and in May 2018. It has the goal to optimize the MATISSE-VLTI communication, the acquisition procedures and the interface parameters. The observations were performed on bright L-M- and N- stars, with four ATs located on short baselines and UTs. The limit magnitudes will be deduced.

This paper reports on the performance of the instrument measured in laboratory (results of test plan in Nice and AIV in Paranal) in terms of spectral coverage, dispersion laws and spectral resolutions, and transfer function analysis: instrumental contrast, visibility accuracy, accuracy of the differential phase, of the closure-phase and of the differential visibility. It also provides results of the first tests on sky and the planning of the on-going commissioning.

PROCEEDINGS ARTICLE | July 6, 2018

SAGE: using CubeSats for gravitational wave detection

Proc. SPIE. 10699, Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray

KEYWORDS: Diffraction, Telescopes, Metrology, Interferometers, Satellites, Photons, Space telescopes, Space operations, Solar processes

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PROCEEDINGS ARTICLE | August 4, 2016

An overview of the mid-infrared spectro-interferometer MATISSE: science, concept, and current status

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Mid-IR, Telescopes, Stars, Cameras, Sensors, Fourier transforms, Interferometry, L band, Spectral resolution, Signal detection

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PROCEEDINGS ARTICLE | August 4, 2016

VLT interferometer upgrade for the 2nd generation of interferometric instruments

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Mid-IR, Telescopes, Mirrors, Stars, Interferometers, Sensors, Interferometry, Interferometry, Adaptive optics, Infrared radiation, Astatine

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PROCEEDINGS ARTICLE | August 4, 2016

Control bandwidth improvements in GRAVITY fringe tracker by switching to a synchronous real time computer architecture

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Actuators, Solar concentrators, Switching, Sensors, Reflectivity, Computing systems, Computing systems, Control systems, Computer architecture, Computer architecture, Real-time computing, Standards development

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The new VLTI (Very Large Telescope Interferometer) 1 instrument GRAVITY^{5, 22, 23} is equipped with a fringe tracker¹⁶ able to stabilize the K-band fringes on six baselines at the same time. It has been designed to achieve a performance for average seeing conditions of a residual OPD (Optical Path Difference) lower than ~300 nm with objects brighter than K = 10. The control loop implementing the tracking is composed of a four stage real time computer system compromising: a sensor where the detector pixels are read in and the OPD and GD (Group Delay) are calculated; a controller receiving the computed sensor quantities and producing commands for the piezo actuators; a concentrator which combines both the OPD commands with the real time tip/tilt corrections offloading them to the piezo actuator; and finally a Kalman¹⁵ parameter estimator. This last stage is used to monitor current measurements over a window of few seconds and estimate new values for the main Kalman¹⁵ control loop parameters. The hardware and software implementation of this design runs asynchronously and communicates the four computers for data transfer via the Reflective Memory Network³. With the purpose of improving the performance of the GRAVITY^{5, 23} fringe tracking^{16, 22} control loop, a deviation from the standard asynchronous communication mechanism has been proposed and implemented. This new scheme operates the four independent real time computers involved in the tracking loop synchronously using the Reflective Memory Interrupts² as the coordination signal. This synchronous mechanism had the effect of reducing the total pure delay of the loop from ~3.5 [ms] to ~2.0 [ms] which then translates on a better stabilization of the fringes as the bandwidth of the system is substantially improved. This paper will explain in detail the real time architecture of the fringe tracker in both is synchronous and synchronous implementation. The achieved improvements on reducing the delay via this mechanism will be quantified.

PROCEEDINGS ARTICLE | August 4, 2016

Status of the Planet Formation Imager (PFI) concept

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Signal to noise ratio, Telescopes, Optical spheres, Stars, Imaging systems, Adaptive optics, Space telescopes, Heterodyning, Planets, Optical instrument design

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PROCEEDINGS ARTICLE | August 4, 2016

The 2nd generation VLTI path to performance

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Telescopes, Mirrors, Stars, Interferometers, Wavefront sensors, Adaptive optics, Optical tracking, Infrared radiation, Infrared telescopes, Astatine

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PROCEEDINGS ARTICLE | August 4, 2016

NAOMI: a low-order adaptive optics system for the VLT interferometer

Proc. SPIE. 9907, Optical and Infrared Interferometry and Imaging V

KEYWORDS: Actuators, Telescopes, Mirrors, Stars, Interferometry, Adaptive optics, Deformable mirrors, Relays, Real-time computing, Astatine

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PROCEEDINGS ARTICLE | July 27, 2016

Rejuvenation of a ten-year old AO curvature sensor: combining obsolescence correction and performance upgrade of MACAO

Proc. SPIE. 9909, Adaptive Optics Systems V

KEYWORDS: Observatories, Avalanche photodetectors, Stars, Sensors, Calibration, Wavefront sensors, Wavefront sensors, Wavefronts, Adaptive optics, Software development, Real-time computing

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PROCEEDINGS ARTICLE | July 24, 2014

MATISSE status report and science forecast

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Mid-IR, Telescopes, Stars, Sensors, Fourier transforms, Interferometry, Spectral resolution, Photometry, Planets, Visibility

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PROCEEDINGS ARTICLE | July 24, 2014

VLTI status update: a decade of operations and beyond

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Observatories, Telescopes, Stars, Interferometers, Calibration, Interferometry, Adaptive optics, Space telescopes, Large telescopes, Astatine

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PROCEEDINGS ARTICLE | July 24, 2014

The interferometric baselines and GRAVITY astrometric error budget

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Observatories, Telescopes, Mirrors, Metrology, Stars, Interferometers, Interferometry, Optical testing, Space telescopes, 3D metrology

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PROCEEDINGS ARTICLE | July 24, 2014

NAOMI: a new adaptive optics module for interferometry

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Telescopes, Mirrors, Stars, Cameras, Sensors, Interferometry, Wavefront sensors, Adaptive optics, Real-time computing, Astatine

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PROCEEDINGS ARTICLE | July 24, 2014

Improving the astrometric performance of VLTI-PRIMA

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Signal to noise ratio, Telescopes, Mirrors, Metrology, Retroreflectors, Stars, Polarization, Sensors, Exoplanets, Space telescopes

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PROCEEDINGS ARTICLE | July 24, 2014

New method for path-length equalization of long single-mode fibers for interferometry

Proc. SPIE. 9146, Optical and Infrared Interferometry IV

KEYWORDS: Optical fibers, Fiber optics, Interferometers, Copper, Composites, Resistance, Interferometry, Control systems, Fiber optics tests, Temperature metrology

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PROCEEDINGS ARTICLE | July 22, 2014

VLTI-UT vibrations effort and performances

Proc. SPIE. 9145, Ground-based and Airborne Telescopes V

KEYWORDS: Infrared sensors, Telescopes, Mirrors, Electronics, Metrology, IRIS Consortium, Interferometers, Sensors, Large telescopes, Infrared telescopes

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PROCEEDINGS ARTICLE | July 21, 2014

A software based de-rotation algorithm concept for the new adaptive optics module (NAOMI) for the auxiliary telescopes of the VLTI

Proc. SPIE. 9148, Adaptive Optics Systems IV

KEYWORDS: Actuators, Telescopes, Calibration, Interferometry, Adaptive optics, Monte Carlo methods, Zernike polynomials, Picosecond phenomena, Algorithm development, Astatine

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PROCEEDINGS ARTICLE | July 8, 2014

Development and recent results from the Subaru coronagraphic extreme adaptive optics system

Proc. SPIE. 9147, Ground-based and Airborne Instrumentation for Astronomy V

KEYWORDS: Point spread functions, Imaging systems, Speckle, Cameras, Sensors, Wavefront sensors, Wavefronts, Adaptive optics, Deformable mirrors, Coronagraphy

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PROCEEDINGS ARTICLE | September 26, 2013

Astrometric detection of exoplanets from the ground

Proc. SPIE. 8864, Techniques and Instrumentation for Detection of Exoplanets VI

KEYWORDS: Telescopes, Stars, Exoplanetary science, Interferometers, Cameras, Exoplanets, Space telescopes, Planets, Motion measurement, Atmospheric optics

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PROCEEDINGS ARTICLE | September 24, 2012

FIRST - a fibered aperture masking instrument: on-sky results

Proc. SPIE. 8446, Ground-based and Airborne Instrumentation for Astronomy IV

KEYWORDS: Optical fibers, Observatories, Diffraction, Telescopes, Stars, Speckle, Calibration, Adaptive optics, Phase measurement, Prototyping

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PROCEEDINGS ARTICLE | September 12, 2012

Keck Interferometer Nuller science highlights

Proc. SPIE. 8445, Optical and Infrared Interferometry III

KEYWORDS: Mid-IR, Stars, Data modeling, Interferometers, Remote sensing, Interferometry, Exoplanets, Silicates, Nulling interferometry, Visibility

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PROCEEDINGS ARTICLE | September 12, 2012

Recent progress at the Keck interferometer

Proc. SPIE. 8445, Optical and Infrared Interferometry III

KEYWORDS: Telescopes, Mirrors, Stars, Interferometers, Interferometry, L band, Adaptive optics, K band, Nulling interferometry, Visibility

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PROCEEDINGS ARTICLE | September 12, 2012

First faint dual-field phase-referenced observations on the Keck interferometer

Proc. SPIE. 8445, Optical and Infrared Interferometry III

KEYWORDS: Telescopes, Mirrors, Beam splitters, Metrology, Stars, Interferometers, Cameras, Adaptive optics, Optical tracking, Infrared radiation

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PROCEEDINGS ARTICLE | July 22, 2010

Science with the Keck Interferometer ASTRA program