Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillatio... more Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillations inside the mouthpiece of a simplified clarinet is studied experimentally. Two time profiles are used for the blowing pressure: in a first set of experiments the pressure is increased at constant rates, then decreased at the same rate. In a second set of experiments the pressure rises at a constant rate and is then kept constant for an arbitrary period of time. In both cases the experiments are repeated for different increase rates. Numerical simulations using a simplified clarinet model blown with a constantly increasing mouth pressure are compared to the oscillating pressure obtained inside the mouthpiece. Both show that the beginning of the oscillations appears at a higher pressure values than the theoretical static threshold pressure, a manifestation of bifurcation delay. Experiments performed using an interrupted increase in mouth pressure show that the beginning of the oscillation occurs close to the stop in the increase of the pressure. Experimental results also highlight that the speed of the onset transient of the sound is roughly the same, independently of the duration of the increase phase of the blowing pressure.
The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory's submil... more The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory's submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 μm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 μm (447-1550 GHz). The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 0.3 K. The photometer has a field of view of 4 × 8 , observed simultaneously in the three spectral bands. Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired. The spectrometer has an approximately circular field of view with a diameter of 2.6. The spectral resolution can be adjusted between 1.2 and 25 GHz by changing the stroke length of the FTS scan mirror. Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data. For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view. The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling. Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products. The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 1.5-2.
The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will b... more The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will be installed in around 2017. It is a multi-object spectrograph fed by about 2400 fibers placed at the prime focus covering a hexagonal field-ofview with 1.35 deg diagonals and capable of simultaneously obtaining data of spectra with wavelengths ranging from 0.38 um to 1.26 um. The spectrograph system is composed of four identical modules each receiving the light from 600 fibers. Each module incorporates three channels covering the wavelength ranges 0.38-0.65 mu ("Blue"), 0.63-0.97 mu ("Red"), and 0.94-1.26 mu ("NIR") respectively; with resolving power which progresses fairly smoothly from about 2000 in the blue to about 4000 in the infrared. An additional spectral mode allows reaching a spectral resolution of 5000 at 0.8mu (red). The proposed optical design is based on a Schmidt collimator facing three Schmidt cameras (one per spectral channel). This architecture is very robust, well known and documented. It allows for high image quality with only few simple elements (high throughput) at the expense of the central obscuration, which leads to larger optics. Each module has to be modular in its design to allow for integration and tests and for its safe transport up to the telescope: this is the main driver for the mechanical design. In particular, each module will be firstly fully integrated and validated at LAM (France) before it is shipped to Hawaii. All sub-assemblies will be indexed on the bench to allow for their accurate repositioning. This paper will give an overview of the spectrograph system which has successfully passed the Critical Design Review (CDR) in 2014 March and which is now in the construction phase.
We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner... more We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner solar system, developed in the framework of the MarcoPolo-R asteroid sample return mission. THERMAP is very well suited to characterize the surface thermal environment of a NEO and to map its surface composition. The instrument has two channels, one for imaging and one for spectroscopy: it is both a thermal camera with full 2D imaging capabilities and a slit spectrometer. THERMAP takes advantage of the recent technological developments of uncooled microbolometer arrays, sensitive in the mid-infrared spectral range. THERMAP can acquire thermal images (8-18 μm) of the surface and perform absolute temperature measurements with a precision better than 3.5 K above 200 K. THERMAP can acquire mid-infrared spectra (8-16 μm) of the surface with a spectral resolution Δλ of 0.3 µm. For surface temperatures above 350 K, spectra have a signal-to-noise ratio >60 in the spectral range 9-13 µm where most emission features occur.
ABSTRACT The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (Su... more ABSTRACT The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope consists in four identical spectrographs feed by 600 fibers each. Each spectrograph is composed by an optical entrance unit that creates a collimated beam and distributes the light to three channels, two visible and one near infrared. We present here the integration process of the first spectrograph channel. The verification requirements, the specific integration requirements and the product tree are the main drivers from the top plan for the Assembly Integration and Test (AIT) development process. We then present the AIT flow-down, the details for the AIT processes as well as opto-mechanical alignment procedures and tests setup. In parallel, we are developing and validating dedicated tools to secure and facilitate the AIT activities, as we have to assemble eight visible cameras, integrate and align four fiber slits, integrate and align the components of four spectrographs.
In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasm... more In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasma device Mistral. The diagnostic is composed of 128 lines of sight covering a 20 cm diameter section and an acquisition rate up to 1 MHz. The measurements are done in the visible spectrum using silicon photomultiplier arrays that require a lower amplification voltage than photomultiplier tubes for similar gains and have a fast response. Tomographic reconstruction of a rotating plasma mode is shown to illustrate the capabilities of the diagnostic.
In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasm... more In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasma device Mistral. The diagnostic is composed of 128 lines of sight covering a 20 cm diameter section and an acquisition rate up to 1 MHz. The measurements are done in the visible spectrum using silicon photomultiplier arrays that require a lower amplification voltage than photomultiplier tubes for similar gains and have a fast response. Tomographic reconstruction of a rotating plasma mode is shown to illustrate the capabilities of the diagnostic.
The Journal of the Acoustical Society of America, 2009
In this paper, laboratory scale measurements of long-range across-slope propagation of broadband ... more In this paper, laboratory scale measurements of long-range across-slope propagation of broadband pulses in a shallow-water wedgeshaped environment with a sandy bottom are reported. The scaled model was designed to study the three-dimensional (3D) acoustic field in the presence of only a few propagating modes. The recorded time series exhibit prominent 3D effects such as mode shadow zones and multiple mode arrivals. Inspection of the spectral content of the time signals gives evidence of intra-mode interference and frequency dependence of the mode cut-off range in the across-slope direction.
POINTS is a dual astrometric optical interferometer with nominal baseline length of 2 m and measu... more POINTS is a dual astrometric optical interferometer with nominal baseline length of 2 m and measurement accuracy of 5 microarcsecs for targets separated by about 90 degrees on the sky. If selected as the ASEPS-1 mission, it could perform a definite search for extra-solar planetary systems, either finding and characterizing a large number of them or showing that they are far less numerous than now believed. If selected as AIM, it could be a powerful new multidisciplinary research tool, opening new areas of astrophysical research and changing the nature of the ...
Real-time regulation of air pressure in an artificial mouth is studied. A closed-loop strategy is... more Real-time regulation of air pressure in an artificial mouth is studied. A closed-loop strategy is developped, including a controller algorithm which updates (according to the difference between the target and the measured blowing pressure) the electrical command sent to the sero-valve providing air flow. In this paper the targets considered may be steady states or slowly varying trajectories. Since both the musical instrument and the servo-valve behave nonlinearly, the design of the controller algorithm requires preliminary modelling and identification steps in order to optimize the compromise performances/robustness. The controller finally adopted for the experiments is a PI (Proportional Integral) whose integral gain is adapted according to an online estimator. Moreover, a carefully tuned dither signal is added on the electric command in order to limit consequences of friction inside the servo-valve. The high-precision regulation is used to investigate the functionning of the recorder. Firstly, it allows to highlight the existence of aeolian sounds which had never been observed on a recorder. Moreover, the influence of some small "details" of the chamfers geometry on the global behavior of the instrument is investigated. Hence the influence of the maker's work can be evaluated, as well as the important consequences on the possibilities offered to the player: with the optimized chamfers, the instrument can sound louder and the transition between the two regimes is safer (larger hysteresis width).
An instrumented saxophone mouthpiece has been developed to measure, during the player's performan... more An instrumented saxophone mouthpiece has been developed to measure, during the player's performance, the evolution of important variables : the mouth pressure, the mouthpiece pressure and the force applied on the reed by the lower lip. Moreover, according to the pressure signals in the mouth and in the mouthpiece, the instantaneous ratio of the vocal tract input impedance and of the saxophone input impedance is estimated at frequencies multiple of the playing frequency (using the concept of Gabor mask). On the selected sound examples, analyses reveal many aspects of the strategies of the player. First of all, the role of the vocal tract in the characteristics of the sound production is sometimes prominent. Secondly, the sound production on the desired note (and register) as well as pitch correction seem to be the result of complementary adjustments of the mouth pressure and of the lip pressure on the reed. This is not in agreement with musicians feeling, since they often claim to let their force on the reed unchanged during the note and from note to note.
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394... more The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394 science fibers, which are distributed in 1.3 degree diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide wavelength coverage from 0.38 um to 1.26 um, with the resolving power of 3000, strengthens its ability to target three main survey programs: cosmology, Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with resolving power of 5000 for 0.71 um to 0.89 um also will be available by simply exchanging dispersers. PFS takes the role for the spectroscopic part of the Subaru Measurement of Images and Redshifts project, while Hyper Suprime-Cam works on the imaging part. To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated glass-molded microlens is glued to each fiber tip. A higher transmission fiber is selected for the longest part of cable system, while one with a better FRD performance is selected for the fiber-positio...
Depuis Helmholtz, le fonctionnement des instruments entretenus est represente par un systeme bouc... more Depuis Helmholtz, le fonctionnement des instruments entretenus est represente par un systeme boucle faisant apparaitre un bloc excitateur et un bloc resonateur. Dans le cas de la clarinette etudiee ici, l'excitateur designe l'anche modulant le debit d'air entrant et le resonateur le corps de l'instrument. Si cette representation est communement admise, se pose la question de la separabilite de ces deux blocs et de l'observabilite des grandeurs physiques qui les lient. Dans le cadre de l'etude du seuil d'oscillation, nous inspectons la validite de cette representation independamment de toute modelisation des blocs : les seuils mesures sont compares avec ceux obtenus par la theorie des oscillateurs dans laquelle sont introduites les valeurs experimentales des parametres du modele. Les pressions de seuil et les frequences emergentes obtenues en (3) et (4) sont comparees. L'interpretation des differences fait intervenir les difficultes d'acceder exact...
In a previous work, results of laboratory scale measurements of long-range, across-slope propagat... more In a previous work, results of laboratory scale measurements of long-range, across-slope propagation of broadband pulses in a shallow-water wedge-shaped oceanic waveguide with a sandy bottom were reported and analyzed [A. Korakas, F. Sturm, J.-P. Sessarego, and D. Ferrand, Proceedings of the 9th ECUA (Paris, France, 29 June-4 July 2008)]. The experiments were conducted at the LMA-CNRS laboratory in Marseille (France). Strong 3D effects like mode shadow zones and multiple mode arrivals were observed, in agreement with theoretical predictions. In the present work, we focus on the frequency dependence of the received signals along the cross-slope direction. The recorded time series are analyzed mode-by-mode. The wave packets associated to each mode are extracted from the time series at several ranges and their spectra are examined by means of appropriate Fourier transforms. It turns out that, as we move out in range across-slope, the low frequency part of the spectral content of the mo...
Ground-based and Airborne Instrumentation for Astronomy VI, 2016
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Tel... more PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ∼1.6−2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
Ground-based and Airborne Instrumentation for Astronomy IV, 2012
ABSTRACT SPHERE, a second-generation instrument for the VLT, is currently under performance valid... more ABSTRACT SPHERE, a second-generation instrument for the VLT, is currently under performance validation before shipping to Chile. The IRDIS sub-system, an Infra-Red Dual-Imager and Spectrograph, was integrated on the SPHERE bench last December, and this paper tells the story of the 12 months preceding this milestone: the Assembly, integration and Tests (AIT) performed at Laboratoire d'Astrophysique de Marseille (LAM). Key points of the AIT strategy are then presented, and the successes and failures-human, technical, and managerial-of this adventure are discussed. We also report on the excellent optical quality achieved, paramount to guarantee ultimate performance of the SPHERE instrument, thanks to high-quality optical manufacture and a successfully applied alignment strategy.
Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillatio... more Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillations inside the mouthpiece of a simplified clarinet is studied experimentally. Two time profiles are used for the blowing pressure: in a first set of experiments the pressure is increased at constant rates, then decreased at the same rate. In a second set of experiments the pressure rises at a constant rate and is then kept constant for an arbitrary period of time. In both cases the experiments are repeated for different increase rates. Numerical simulations using a simplified clarinet model blown with a constantly increasing mouth pressure are compared to the oscillating pressure obtained inside the mouthpiece. Both show that the beginning of the oscillations appears at a higher pressure values than the theoretical static threshold pressure, a manifestation of bifurcation delay. Experiments performed using an interrupted increase in mouth pressure show that the beginning of the oscillation occurs close to the stop in the increase of the pressure. Experimental results also highlight that the speed of the onset transient of the sound is roughly the same, independently of the duration of the increase phase of the blowing pressure.
The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory's submil... more The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory's submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 μm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 μm (447-1550 GHz). The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 0.3 K. The photometer has a field of view of 4 × 8 , observed simultaneously in the three spectral bands. Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired. The spectrometer has an approximately circular field of view with a diameter of 2.6. The spectral resolution can be adjusted between 1.2 and 25 GHz by changing the stroke length of the FTS scan mirror. Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data. For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view. The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling. Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products. The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 1.5-2.
The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will b... more The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will be installed in around 2017. It is a multi-object spectrograph fed by about 2400 fibers placed at the prime focus covering a hexagonal field-ofview with 1.35 deg diagonals and capable of simultaneously obtaining data of spectra with wavelengths ranging from 0.38 um to 1.26 um. The spectrograph system is composed of four identical modules each receiving the light from 600 fibers. Each module incorporates three channels covering the wavelength ranges 0.38-0.65 mu ("Blue"), 0.63-0.97 mu ("Red"), and 0.94-1.26 mu ("NIR") respectively; with resolving power which progresses fairly smoothly from about 2000 in the blue to about 4000 in the infrared. An additional spectral mode allows reaching a spectral resolution of 5000 at 0.8mu (red). The proposed optical design is based on a Schmidt collimator facing three Schmidt cameras (one per spectral channel). This architecture is very robust, well known and documented. It allows for high image quality with only few simple elements (high throughput) at the expense of the central obscuration, which leads to larger optics. Each module has to be modular in its design to allow for integration and tests and for its safe transport up to the telescope: this is the main driver for the mechanical design. In particular, each module will be firstly fully integrated and validated at LAM (France) before it is shipped to Hawaii. All sub-assemblies will be indexed on the bench to allow for their accurate repositioning. This paper will give an overview of the spectrograph system which has successfully passed the Critical Design Review (CDR) in 2014 March and which is now in the construction phase.
We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner... more We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner solar system, developed in the framework of the MarcoPolo-R asteroid sample return mission. THERMAP is very well suited to characterize the surface thermal environment of a NEO and to map its surface composition. The instrument has two channels, one for imaging and one for spectroscopy: it is both a thermal camera with full 2D imaging capabilities and a slit spectrometer. THERMAP takes advantage of the recent technological developments of uncooled microbolometer arrays, sensitive in the mid-infrared spectral range. THERMAP can acquire thermal images (8-18 μm) of the surface and perform absolute temperature measurements with a precision better than 3.5 K above 200 K. THERMAP can acquire mid-infrared spectra (8-16 μm) of the surface with a spectral resolution Δλ of 0.3 µm. For surface temperatures above 350 K, spectra have a signal-to-noise ratio >60 in the spectral range 9-13 µm where most emission features occur.
ABSTRACT The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (Su... more ABSTRACT The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope consists in four identical spectrographs feed by 600 fibers each. Each spectrograph is composed by an optical entrance unit that creates a collimated beam and distributes the light to three channels, two visible and one near infrared. We present here the integration process of the first spectrograph channel. The verification requirements, the specific integration requirements and the product tree are the main drivers from the top plan for the Assembly Integration and Test (AIT) development process. We then present the AIT flow-down, the details for the AIT processes as well as opto-mechanical alignment procedures and tests setup. In parallel, we are developing and validating dedicated tools to secure and facilitate the AIT activities, as we have to assemble eight visible cameras, integrate and align four fiber slits, integrate and align the components of four spectrographs.
In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasm... more In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasma device Mistral. The diagnostic is composed of 128 lines of sight covering a 20 cm diameter section and an acquisition rate up to 1 MHz. The measurements are done in the visible spectrum using silicon photomultiplier arrays that require a lower amplification voltage than photomultiplier tubes for similar gains and have a fast response. Tomographic reconstruction of a rotating plasma mode is shown to illustrate the capabilities of the diagnostic.
In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasm... more In this paper, we describe a newly installed tomography diagnostic on the linear magnetized plasma device Mistral. The diagnostic is composed of 128 lines of sight covering a 20 cm diameter section and an acquisition rate up to 1 MHz. The measurements are done in the visible spectrum using silicon photomultiplier arrays that require a lower amplification voltage than photomultiplier tubes for similar gains and have a fast response. Tomographic reconstruction of a rotating plasma mode is shown to illustrate the capabilities of the diagnostic.
The Journal of the Acoustical Society of America, 2009
In this paper, laboratory scale measurements of long-range across-slope propagation of broadband ... more In this paper, laboratory scale measurements of long-range across-slope propagation of broadband pulses in a shallow-water wedgeshaped environment with a sandy bottom are reported. The scaled model was designed to study the three-dimensional (3D) acoustic field in the presence of only a few propagating modes. The recorded time series exhibit prominent 3D effects such as mode shadow zones and multiple mode arrivals. Inspection of the spectral content of the time signals gives evidence of intra-mode interference and frequency dependence of the mode cut-off range in the across-slope direction.
POINTS is a dual astrometric optical interferometer with nominal baseline length of 2 m and measu... more POINTS is a dual astrometric optical interferometer with nominal baseline length of 2 m and measurement accuracy of 5 microarcsecs for targets separated by about 90 degrees on the sky. If selected as the ASEPS-1 mission, it could perform a definite search for extra-solar planetary systems, either finding and characterizing a large number of them or showing that they are far less numerous than now believed. If selected as AIM, it could be a powerful new multidisciplinary research tool, opening new areas of astrophysical research and changing the nature of the ...
Real-time regulation of air pressure in an artificial mouth is studied. A closed-loop strategy is... more Real-time regulation of air pressure in an artificial mouth is studied. A closed-loop strategy is developped, including a controller algorithm which updates (according to the difference between the target and the measured blowing pressure) the electrical command sent to the sero-valve providing air flow. In this paper the targets considered may be steady states or slowly varying trajectories. Since both the musical instrument and the servo-valve behave nonlinearly, the design of the controller algorithm requires preliminary modelling and identification steps in order to optimize the compromise performances/robustness. The controller finally adopted for the experiments is a PI (Proportional Integral) whose integral gain is adapted according to an online estimator. Moreover, a carefully tuned dither signal is added on the electric command in order to limit consequences of friction inside the servo-valve. The high-precision regulation is used to investigate the functionning of the recorder. Firstly, it allows to highlight the existence of aeolian sounds which had never been observed on a recorder. Moreover, the influence of some small "details" of the chamfers geometry on the global behavior of the instrument is investigated. Hence the influence of the maker's work can be evaluated, as well as the important consequences on the possibilities offered to the player: with the optimized chamfers, the instrument can sound louder and the transition between the two regimes is safer (larger hysteresis width).
An instrumented saxophone mouthpiece has been developed to measure, during the player's performan... more An instrumented saxophone mouthpiece has been developed to measure, during the player's performance, the evolution of important variables : the mouth pressure, the mouthpiece pressure and the force applied on the reed by the lower lip. Moreover, according to the pressure signals in the mouth and in the mouthpiece, the instantaneous ratio of the vocal tract input impedance and of the saxophone input impedance is estimated at frequencies multiple of the playing frequency (using the concept of Gabor mask). On the selected sound examples, analyses reveal many aspects of the strategies of the player. First of all, the role of the vocal tract in the characteristics of the sound production is sometimes prominent. Secondly, the sound production on the desired note (and register) as well as pitch correction seem to be the result of complementary adjustments of the mouth pressure and of the lip pressure on the reed. This is not in agreement with musicians feeling, since they often claim to let their force on the reed unchanged during the note and from note to note.
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394... more The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394 science fibers, which are distributed in 1.3 degree diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide wavelength coverage from 0.38 um to 1.26 um, with the resolving power of 3000, strengthens its ability to target three main survey programs: cosmology, Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with resolving power of 5000 for 0.71 um to 0.89 um also will be available by simply exchanging dispersers. PFS takes the role for the spectroscopic part of the Subaru Measurement of Images and Redshifts project, while Hyper Suprime-Cam works on the imaging part. To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated glass-molded microlens is glued to each fiber tip. A higher transmission fiber is selected for the longest part of cable system, while one with a better FRD performance is selected for the fiber-positio...
Depuis Helmholtz, le fonctionnement des instruments entretenus est represente par un systeme bouc... more Depuis Helmholtz, le fonctionnement des instruments entretenus est represente par un systeme boucle faisant apparaitre un bloc excitateur et un bloc resonateur. Dans le cas de la clarinette etudiee ici, l'excitateur designe l'anche modulant le debit d'air entrant et le resonateur le corps de l'instrument. Si cette representation est communement admise, se pose la question de la separabilite de ces deux blocs et de l'observabilite des grandeurs physiques qui les lient. Dans le cadre de l'etude du seuil d'oscillation, nous inspectons la validite de cette representation independamment de toute modelisation des blocs : les seuils mesures sont compares avec ceux obtenus par la theorie des oscillateurs dans laquelle sont introduites les valeurs experimentales des parametres du modele. Les pressions de seuil et les frequences emergentes obtenues en (3) et (4) sont comparees. L'interpretation des differences fait intervenir les difficultes d'acceder exact...
In a previous work, results of laboratory scale measurements of long-range, across-slope propagat... more In a previous work, results of laboratory scale measurements of long-range, across-slope propagation of broadband pulses in a shallow-water wedge-shaped oceanic waveguide with a sandy bottom were reported and analyzed [A. Korakas, F. Sturm, J.-P. Sessarego, and D. Ferrand, Proceedings of the 9th ECUA (Paris, France, 29 June-4 July 2008)]. The experiments were conducted at the LMA-CNRS laboratory in Marseille (France). Strong 3D effects like mode shadow zones and multiple mode arrivals were observed, in agreement with theoretical predictions. In the present work, we focus on the frequency dependence of the received signals along the cross-slope direction. The recorded time series are analyzed mode-by-mode. The wave packets associated to each mode are extracted from the time series at several ranges and their spectra are examined by means of appropriate Fourier transforms. It turns out that, as we move out in range across-slope, the low frequency part of the spectral content of the mo...
Ground-based and Airborne Instrumentation for Astronomy VI, 2016
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Tel... more PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ∼1.6−2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
Ground-based and Airborne Instrumentation for Astronomy IV, 2012
ABSTRACT SPHERE, a second-generation instrument for the VLT, is currently under performance valid... more ABSTRACT SPHERE, a second-generation instrument for the VLT, is currently under performance validation before shipping to Chile. The IRDIS sub-system, an Infra-Red Dual-Imager and Spectrograph, was integrated on the SPHERE bench last December, and this paper tells the story of the 12 months preceding this milestone: the Assembly, integration and Tests (AIT) performed at Laboratoire d'Astrophysique de Marseille (LAM). Key points of the AIT strategy are then presented, and the successes and failures-human, technical, and managerial-of this adventure are discussed. We also report on the excellent optical quality achieved, paramount to guarantee ultimate performance of the SPHERE instrument, thanks to high-quality optical manufacture and a successfully applied alignment strategy.
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Papers by Didier Ferrand