One of the key component of an Adaptive Optics system is the deformable mirror. This mirror can c... more One of the key component of an Adaptive Optics system is the deformable mirror. This mirror can correct the atmospheric turbulence effects by changing its shape. In the last years Adaptive Secondary Mirrors (ASM) have been developed and the Large Binocular Telescope (LBT) will be soon equipped with two ASMs. Each LBT ASM unit has 672 voice-coil force actuators to change the shape of the mirror shell. Because the actuators apply force, an internal position control is required. The LBT ASM internal control uses a local feedback of position and velocity, then the control law for each actuator has two characteristic parameters which define the closed-loop shell dynamics. In this paper, an analysis of the dynamical behavior of the ASM under the proposed control law is provided. Then an algorithm is suggested that, based on a simplified model of the shell dynamics, tunes the controller parameters by means of an automatic procedure, as a replacement for a manual procedure based on the operator skill.
Astronomical Adaptive Optics Systems and Applications III, 2007
We report on the current status of production of the thin shells for the LBT adaptive secondary m... more We report on the current status of production of the thin shells for the LBT adaptive secondary mirrors. These shells are made of Zerodur and have a front (optical) surface highly aspherical whereas the other (rear) surface is spherical. They have a 910mm diameter and an average thickness of 1.6mm. The manufacturing of these shells starts with a thick blank of Zerodur and follows the steps of: 1) optical surface figuring, 2) blank thinning, 3) rear surface grinding and polishing, 4) edges machining and 5) rear surface aluminizing. Of the three (two plus a spare) shells planned for LBT the first shell was completed and shipped to Italy for integration with magnets and the second is in advanced state of production. The third shell (spare) is planned to start production soon. In the paper we report details of production of these shells as well as the 'as built' characteristics. Details concerning the operations that follow the production, i.e. surface aluminum coating as well as handling and shipping fixtures are also reported.
Proceedings of SPIE - The International Society for Optical Engineering, 2004
The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) ar... more The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) are currently under construction. The design of the units has been based on the extensive experience made on the MMT adaptive secondary mirror during laboratory tests and telescope runs. Mechanics, electronics and control logic have been revised to improve performances and reliability. Each unit has 672 electro-magnetic force actuators. They control the figure of the Gregorian secondary 1.6mm-thick mirrors with an internal loop using the signal of co-located capacitive sensors. The improvement in the computational power of the on-board control electronics allows to use it as real-time computer for wavefront reconstruction. We present the progress of the final unit construction and the preliminary laboratory results obtained with a 45-actuator sub-system used to test the new features introduced in the electronics and mechanics of LBT adaptive secondary mirrors.
We present recent developments of the CAOS &a... more We present recent developments of the CAOS "system", an IDL-based Problem Solving Environment (PSE) whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system, from the atmospheric propagation of light, to the sensing of the wave-front aberratoins and the correction through a deformable mirror. The different developments made through
The paper is describing the present status of the LBT first light AO system. The system design st... more The paper is describing the present status of the LBT first light AO system. The system design started in January 2002 and is now approaching the final test in the Arcetri solar tower. Two key features of this single conjugate AO system are the use of an adaptive secondary mirror having 672 actuators and a pyramid wavefront sensor with a
In this paper we present the laboratory characterization and performance evaluation of the First ... more In this paper we present the laboratory characterization and performance evaluation of the First Light Adaptive Optics (FLAO) the Natural Guide Star adaptive optics system for the Large Binocular Telescope (LBT). The system uses an adaptive secondary mirror with 672 actuators and a pyramid wavefront sensor with adjustable sampling of the telescope pupil from 30×30 down to 4×4 subapertures. The
ABSTRACT The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the t... more ABSTRACT The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the telescope conversion into the Adaptive Optics test Facility (AOF). The adaptive unit is based on the well proven contactless, voice coil motor technology that has been already successfully implemented in the MMT, LBT and Magellan adaptive secondaries, and is considered a promising technical choice for the forthcoming ELT-generation adaptive correctors, like the E-ELT M4 and the GMT ASM. The VLT adaptive unit has been recently assembled after the completion of the manufacturing and modular test phases. In this paper, we present the most relevant aspects of the system integration and report the preliminary results of the electromechanical tests performed on the unit. This test campaign is a typical major step foreseen in all similar systems built so far: thanks to the metrology embedded in the system, that allows generating time-dependent stimuli and recording in real time the position of the controlled mirror on all actuators, typical dynamic response quality parameters like modal settling time, overshoot and following error can be acquired without employing optical measurements. In this way the system dynamic and some aspect of its thermal and long term stability can be fully characterized before starting the optical tests and calibrations.
The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used ... more The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl ( 75% at 2.16µm) near infrared narrowband (Brγ: 2.16µm and [FeII]: 1.64µm) images of 47 young (∼ 1 Myr) Orion Trapezium θ 1 Ori cluster members. The inner ∼ 41 × 53 ′′ of the 01 The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; cluster was imaged at spatial resolutions of ∼ 0.050 ′′ (at 1.64µm). A combination of high spatial resolution and high S/N yielded relative binary positions to ∼ 0.5 mas accuracies. Including previous speckle data, we analyze a 15 year baseline of high-resolution observations of this cluster. We are now sensitive to relative proper motions of just ∼ 0.3 mas/yr (0.6 km/s at 450 pc) this is a ∼ 7× improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the θ 1 Ori B 2 B 3 system of 4.9 ± 0.3 km/s and 7.2 ± 0.8 km/s in the θ 1 Ori A 1 A 2 system (with correlations of PA vs. time at > 99% confidence). All five members of the θ 1 Ori B system appear likely as a gravitationally bound "mini-cluster". The very lowest mass member of the θ 1 Ori B system (B 4 ; mass ∼ 0.2M ⊙ ) has, for the first time, a clearly detected motion (at 4.3 ± 2.0 km/s; correlation=99.7%) w.r.t B 1 . However, B 4 is most likely in an long-term unstable (non-hierarchical) orbit and may "soon" be ejected from this "mini-cluster". This "ejection" process could play a major role in the formation of low mass stars and brown dwarfs.
A Zernike decomposition of the pupil phase variance that is due to focus anisoplanatism for a sod... more A Zernike decomposition of the pupil phase variance that is due to focus anisoplanatism for a sodium laser guide star is calculated, including the angular error variance associated with overall tilt. This quantity, or tilt focus anisoplanatism FA,tt 2 , is necessary in evaluating the usefulness of new techniques developed to measure the wave-front tilt from a sodium laser guide star. The analytical expression of FA,tt 2 in the case of refractiveindex fluctuation with a Kolmogorov power spectral density is given together with numerical results for two different C n Ј 2 (z) profiles. Numerical calculations show that tilt focus anisoplanatism may be a limitation when a sodium laser guide star is used to sense the overall wave-front tilt at visible wavelengths, especially for 8-m-class telescopes.
We describe the scientific rationale and the preliminary optomechanical design for a 2 m class te... more We describe the scientific rationale and the preliminary optomechanical design for a 2 m class telescope designed to achieve ground layer correction over a ≈15 arcmin Field of View (FoV) to be located at the Dome-C site. The proposed science case is the detection of microlensing events in and by globular clusters and nearby galaxies that, for a high probability of success, requires exceptional seeing (≈0.2 arcsec or better) and a large target density (the centre of a globular cluster with a corresponding telescope FoV of ≈15 arcmin). This approach can capitalise on some of the unique qualities already observed above the Dome-C site, namely that the atmospheric turbulence is largely limited to a ground layer of small thickness only, a relatively low Greenwood frequency and uniterrupted sky coverage during the winter months for objects such as the globular cluster 47-Tuc. Further to the central science case of microlensing the telescope could provide a technological testbed for future telescopes and, given the unique atmospheric properties witnessed already during previous site testing compaigns, has the chance to provide a large amount of data (based on accurate and continuous light curves lasting several months) for fields of research outside that of microlensing. Details of the specific concepts of adaptive optics to be adopted for this telescope are outlined.
ABSTRACT The simulation results obtained using a multidisciplinary model of a deformable, massive... more ABSTRACT The simulation results obtained using a multidisciplinary model of a deformable, massively actuated adaptive mirror are compared with experimental data retrieved using an adaptive shell equipped with 45 non-contacting voice coils actuators. A description of the physical model and of the experimental setup is followed by the results obtained simulating actual experimental tests and by their correlation with the related true measurements. The significance of various modeling details and their effects on the correlation is discussed. The results show a remarkable match between numerical and experimental data.
Astronomy and Astrophysics Supplement Series, 1998
It is shown that, in the multiple LGS configuration proposed by used for the correction of the co... more It is shown that, in the multiple LGS configuration proposed by used for the correction of the conical anisoplanatism, one can derive the correction for the conical anisokinetism effect also, provided that absolute tilt sensing is performed for only one of the various LGSs projected on the sky.
We present the laboratory characterization and performance evaluation of the First Light Adaptive... more We present the laboratory characterization and performance evaluation of the First Light Adaptive Optics (FLAO), the natural guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses an adaptive secondary mirror with 672 actuators and a pyramid wavefront sensor with adjustable sampling of the telescope pupil from 30 × 30 down to 7 × 7 subapertures. The system was fully assembled in the Arcetri Observatory laboratories and passed its acceptance test in December 2009. The performance measured at different star magnitudes during the acceptance test is shown to lie between the baseline and the goal specifications. In particular, FLAO obtained a 77% Strehl ratio (SR) in the bright end (8.5 magnitude star in the R band) using an H-band filter and correcting 495 modes with 30 × 30 subaperture sampling. In the faint end (16.4 magnitude), a 5% SR correcting 36 modes with 7 × 7 subapertures was measured. The seeing conditions for these tests were 0.8 arcsec (r 0 ¼ 0:14 m at 550 nm) and an average wind speed of 15 m=s. The results for other seeing conditions up to 1.5 arcsec are also presented. The system has been shipped to the LBT site in Arizona, and its commissioning started in March 2010.
The NGSAO, a single conjugated AO system operating with natural guide star, will be the first AO ... more The NGSAO, a single conjugated AO system operating with natural guide star, will be the first AO system to be operative at the Giant Magellan Telescope. The Natural Guide star Wavefront Sensor will be in charge of the entire wavefront error measurement, namely atmospheric turbulence and telescope aberrations, including the segment differential piston error. In this paper we report the opto-mechanical design of the NGWS that successfully passed the preliminary design review in July 2013. Moreover, we present the NGSAO control strategy identified for the GMT segmented pupil and the system performances for different conditions of seeing and reference star magnitude.
One of the key component of an Adaptive Optics system is the deformable mirror. This mirror can c... more One of the key component of an Adaptive Optics system is the deformable mirror. This mirror can correct the atmospheric turbulence effects by changing its shape. In the last years Adaptive Secondary Mirrors (ASM) have been developed and the Large Binocular Telescope (LBT) will be soon equipped with two ASMs. Each LBT ASM unit has 672 voice-coil force actuators to change the shape of the mirror shell. Because the actuators apply force, an internal position control is required. The LBT ASM internal control uses a local feedback of position and velocity, then the control law for each actuator has two characteristic parameters which define the closed-loop shell dynamics. In this paper, an analysis of the dynamical behavior of the ASM under the proposed control law is provided. Then an algorithm is suggested that, based on a simplified model of the shell dynamics, tunes the controller parameters by means of an automatic procedure, as a replacement for a manual procedure based on the operator skill.
Astronomical Adaptive Optics Systems and Applications III, 2007
We report on the current status of production of the thin shells for the LBT adaptive secondary m... more We report on the current status of production of the thin shells for the LBT adaptive secondary mirrors. These shells are made of Zerodur and have a front (optical) surface highly aspherical whereas the other (rear) surface is spherical. They have a 910mm diameter and an average thickness of 1.6mm. The manufacturing of these shells starts with a thick blank of Zerodur and follows the steps of: 1) optical surface figuring, 2) blank thinning, 3) rear surface grinding and polishing, 4) edges machining and 5) rear surface aluminizing. Of the three (two plus a spare) shells planned for LBT the first shell was completed and shipped to Italy for integration with magnets and the second is in advanced state of production. The third shell (spare) is planned to start production soon. In the paper we report details of production of these shells as well as the 'as built' characteristics. Details concerning the operations that follow the production, i.e. surface aluminum coating as well as handling and shipping fixtures are also reported.
Proceedings of SPIE - The International Society for Optical Engineering, 2004
The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) ar... more The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) are currently under construction. The design of the units has been based on the extensive experience made on the MMT adaptive secondary mirror during laboratory tests and telescope runs. Mechanics, electronics and control logic have been revised to improve performances and reliability. Each unit has 672 electro-magnetic force actuators. They control the figure of the Gregorian secondary 1.6mm-thick mirrors with an internal loop using the signal of co-located capacitive sensors. The improvement in the computational power of the on-board control electronics allows to use it as real-time computer for wavefront reconstruction. We present the progress of the final unit construction and the preliminary laboratory results obtained with a 45-actuator sub-system used to test the new features introduced in the electronics and mechanics of LBT adaptive secondary mirrors.
We present recent developments of the CAOS &a... more We present recent developments of the CAOS "system", an IDL-based Problem Solving Environment (PSE) whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system, from the atmospheric propagation of light, to the sensing of the wave-front aberratoins and the correction through a deformable mirror. The different developments made through
The paper is describing the present status of the LBT first light AO system. The system design st... more The paper is describing the present status of the LBT first light AO system. The system design started in January 2002 and is now approaching the final test in the Arcetri solar tower. Two key features of this single conjugate AO system are the use of an adaptive secondary mirror having 672 actuators and a pyramid wavefront sensor with a
In this paper we present the laboratory characterization and performance evaluation of the First ... more In this paper we present the laboratory characterization and performance evaluation of the First Light Adaptive Optics (FLAO) the Natural Guide Star adaptive optics system for the Large Binocular Telescope (LBT). The system uses an adaptive secondary mirror with 672 actuators and a pyramid wavefront sensor with adjustable sampling of the telescope pupil from 30×30 down to 4×4 subapertures. The
ABSTRACT The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the t... more ABSTRACT The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the telescope conversion into the Adaptive Optics test Facility (AOF). The adaptive unit is based on the well proven contactless, voice coil motor technology that has been already successfully implemented in the MMT, LBT and Magellan adaptive secondaries, and is considered a promising technical choice for the forthcoming ELT-generation adaptive correctors, like the E-ELT M4 and the GMT ASM. The VLT adaptive unit has been recently assembled after the completion of the manufacturing and modular test phases. In this paper, we present the most relevant aspects of the system integration and report the preliminary results of the electromechanical tests performed on the unit. This test campaign is a typical major step foreseen in all similar systems built so far: thanks to the metrology embedded in the system, that allows generating time-dependent stimuli and recording in real time the position of the controlled mirror on all actuators, typical dynamic response quality parameters like modal settling time, overshoot and following error can be acquired without employing optical measurements. In this way the system dynamic and some aspect of its thermal and long term stability can be fully characterized before starting the optical tests and calibrations.
The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used ... more The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl ( 75% at 2.16µm) near infrared narrowband (Brγ: 2.16µm and [FeII]: 1.64µm) images of 47 young (∼ 1 Myr) Orion Trapezium θ 1 Ori cluster members. The inner ∼ 41 × 53 ′′ of the 01 The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; cluster was imaged at spatial resolutions of ∼ 0.050 ′′ (at 1.64µm). A combination of high spatial resolution and high S/N yielded relative binary positions to ∼ 0.5 mas accuracies. Including previous speckle data, we analyze a 15 year baseline of high-resolution observations of this cluster. We are now sensitive to relative proper motions of just ∼ 0.3 mas/yr (0.6 km/s at 450 pc) this is a ∼ 7× improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the θ 1 Ori B 2 B 3 system of 4.9 ± 0.3 km/s and 7.2 ± 0.8 km/s in the θ 1 Ori A 1 A 2 system (with correlations of PA vs. time at > 99% confidence). All five members of the θ 1 Ori B system appear likely as a gravitationally bound "mini-cluster". The very lowest mass member of the θ 1 Ori B system (B 4 ; mass ∼ 0.2M ⊙ ) has, for the first time, a clearly detected motion (at 4.3 ± 2.0 km/s; correlation=99.7%) w.r.t B 1 . However, B 4 is most likely in an long-term unstable (non-hierarchical) orbit and may "soon" be ejected from this "mini-cluster". This "ejection" process could play a major role in the formation of low mass stars and brown dwarfs.
A Zernike decomposition of the pupil phase variance that is due to focus anisoplanatism for a sod... more A Zernike decomposition of the pupil phase variance that is due to focus anisoplanatism for a sodium laser guide star is calculated, including the angular error variance associated with overall tilt. This quantity, or tilt focus anisoplanatism FA,tt 2 , is necessary in evaluating the usefulness of new techniques developed to measure the wave-front tilt from a sodium laser guide star. The analytical expression of FA,tt 2 in the case of refractiveindex fluctuation with a Kolmogorov power spectral density is given together with numerical results for two different C n Ј 2 (z) profiles. Numerical calculations show that tilt focus anisoplanatism may be a limitation when a sodium laser guide star is used to sense the overall wave-front tilt at visible wavelengths, especially for 8-m-class telescopes.
We describe the scientific rationale and the preliminary optomechanical design for a 2 m class te... more We describe the scientific rationale and the preliminary optomechanical design for a 2 m class telescope designed to achieve ground layer correction over a ≈15 arcmin Field of View (FoV) to be located at the Dome-C site. The proposed science case is the detection of microlensing events in and by globular clusters and nearby galaxies that, for a high probability of success, requires exceptional seeing (≈0.2 arcsec or better) and a large target density (the centre of a globular cluster with a corresponding telescope FoV of ≈15 arcmin). This approach can capitalise on some of the unique qualities already observed above the Dome-C site, namely that the atmospheric turbulence is largely limited to a ground layer of small thickness only, a relatively low Greenwood frequency and uniterrupted sky coverage during the winter months for objects such as the globular cluster 47-Tuc. Further to the central science case of microlensing the telescope could provide a technological testbed for future telescopes and, given the unique atmospheric properties witnessed already during previous site testing compaigns, has the chance to provide a large amount of data (based on accurate and continuous light curves lasting several months) for fields of research outside that of microlensing. Details of the specific concepts of adaptive optics to be adopted for this telescope are outlined.
ABSTRACT The simulation results obtained using a multidisciplinary model of a deformable, massive... more ABSTRACT The simulation results obtained using a multidisciplinary model of a deformable, massively actuated adaptive mirror are compared with experimental data retrieved using an adaptive shell equipped with 45 non-contacting voice coils actuators. A description of the physical model and of the experimental setup is followed by the results obtained simulating actual experimental tests and by their correlation with the related true measurements. The significance of various modeling details and their effects on the correlation is discussed. The results show a remarkable match between numerical and experimental data.
Astronomy and Astrophysics Supplement Series, 1998
It is shown that, in the multiple LGS configuration proposed by used for the correction of the co... more It is shown that, in the multiple LGS configuration proposed by used for the correction of the conical anisoplanatism, one can derive the correction for the conical anisokinetism effect also, provided that absolute tilt sensing is performed for only one of the various LGSs projected on the sky.
We present the laboratory characterization and performance evaluation of the First Light Adaptive... more We present the laboratory characterization and performance evaluation of the First Light Adaptive Optics (FLAO), the natural guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses an adaptive secondary mirror with 672 actuators and a pyramid wavefront sensor with adjustable sampling of the telescope pupil from 30 × 30 down to 7 × 7 subapertures. The system was fully assembled in the Arcetri Observatory laboratories and passed its acceptance test in December 2009. The performance measured at different star magnitudes during the acceptance test is shown to lie between the baseline and the goal specifications. In particular, FLAO obtained a 77% Strehl ratio (SR) in the bright end (8.5 magnitude star in the R band) using an H-band filter and correcting 495 modes with 30 × 30 subaperture sampling. In the faint end (16.4 magnitude), a 5% SR correcting 36 modes with 7 × 7 subapertures was measured. The seeing conditions for these tests were 0.8 arcsec (r 0 ¼ 0:14 m at 550 nm) and an average wind speed of 15 m=s. The results for other seeing conditions up to 1.5 arcsec are also presented. The system has been shipped to the LBT site in Arizona, and its commissioning started in March 2010.
The NGSAO, a single conjugated AO system operating with natural guide star, will be the first AO ... more The NGSAO, a single conjugated AO system operating with natural guide star, will be the first AO system to be operative at the Giant Magellan Telescope. The Natural Guide star Wavefront Sensor will be in charge of the entire wavefront error measurement, namely atmospheric turbulence and telescope aberrations, including the segment differential piston error. In this paper we report the opto-mechanical design of the NGWS that successfully passed the preliminary design review in July 2013. Moreover, we present the NGSAO control strategy identified for the GMT segmented pupil and the system performances for different conditions of seeing and reference star magnitude.
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Papers by A. Riccardi