The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the te... more The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the telescope, providing laser guidestar generation, wavefront sensing, and wavefront correction to every instrument currently planned on the 25.4 m diameter GMT. There will be three first generation AO observing modes: Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments.
Optical cophasing has a key role in ensuring that segmented mirror telescopes reach their best pe... more Optical cophasing has a key role in ensuring that segmented mirror telescopes reach their best performance. To measure and correct segments misalignment it is necessary to have a wavefront sensor (WFS) in the telescope optical path. All the cophasing WFS suffer the phase ambiguity problem that limits the piston error measurements to a unit of wavelength. To overcome this problem we have developed a new cophasing technique based on the wavelength sweep. This paper will present the results of laboratory and on-sky tests of this technique, comparing them with the expected performance obtained in a previous work through numerical simulations. The laboratory test was carried out on the Active Phasing Experiment bench at ESO premises in Garching. We measured wavefront piston errors up to 15μm with an accuracy better than 0.25μm on a pupil conjugate segmented mirror using the Pyramid Phasing Sensor (PYPS) and a commercial tunable filter. We tested the possibility of propagating the differential piston measurements over the segmented mirror to cophase it, obtaining a residual surface error less than 0.2μm rms. The first on-sky test of the WST was carried out at William Hershel Telescope (WHT) using the NAOMI segmented mirror. We checked the effects of atmospheric turbulence on the measurements of large piston errors up to 15um wavefront and it was obtained an accuracy of 0.5μm, which is in agreement with simulation.
ARGOS, the Laser Guide Star (LGS) facility of the Large Binocular Telescope (LBT), implements a G... more ARGOS, the Laser Guide Star (LGS) facility of the Large Binocular Telescope (LBT), implements a Ground Layer Adaptive Optics (GLAO) system, using 3 low-altitude beacons, to improve the resolution over the 4'×4' FoV of the imager and Multi Object Spectrograph (MOS) LUCIFER. In this paper we discuss the performance and the reconstruction scheme of an hybrid AO system using the ARGOS Rayleigh beacons complemented with a single faint high-altitude star (NGS or sodium beacon) to sense the turbulence of the upper atmosphere allowing an high degree of on-axis correction. With the ARGOS system, the NGS-upgrade can be immediately implemented at LBT using the already existing Pyramid WFS offering performance similar to the NGS AO system with the advantage of a larger sky coverage.
The construction of ELT primary mirrors requires the integration of a hundreds of segments.1, 2 A... more The construction of ELT primary mirrors requires the integration of a hundreds of segments.1, 2 A frequent substitution of some segment is foreseen allowing the primary alumimization. Mechanical integration has to reduce residual piston errors up to the capture range of optical cophasing sensors. Enlarging this range, will relax the mechanical integration requirements, speeding up meaningfully the integration operations. In this work we tested the performance of the Wavelength Sweeping Technique3 (WST): a cophasing technique that allow a large piston capture range, with any need of initial calibration. To apply the WST is necessary couple a Liquid Crystal Tunable Filter (LCTF) to a phasing WaveFront Sensor (WFS). In laboratory we measured segment edge steps on a MEMS-DM applying the WST to the PYramid Phasing Sensor 4 (PYPS). We measured 72 wavefront phase steps from 0.5 to 3µm with an accuracy of less than 0.2µm. With numerical simulations we inquired the possibility to propagate WST edge step measures to cophase a segmented mirror. To do this we realized a cophasing algorithm and we compared its performace in different observing environments. The algorithm converges in 3 ÷ 5 iterations and all the residual edge steps on the mirror are in the capture range of high resolution cophasing techniques.
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.
The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the te... more The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the telescope, providing laser guidestar generation, wavefront sensing, and wavefront correction to every instrument currently planned on the 25.4 m diameter GMT. There will be three first generation AO observing modes: Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments.
ARGOS is the Ground Layer Adaptive Optics system of the Large Binocular Telescope, it uses three ... more ARGOS is the Ground Layer Adaptive Optics system of the Large Binocular Telescope, it uses three Laser Guide Stars at 12 km altitude, generated by Rayleigh backscattered light of pulsed Nd:YAG lasers at 532nm. The wavefront distortion in the Ground Layer is measured by three Shack-Hartmann WFS, sampling with 15×15 subaperture the three LGS arranged on a single CCD with 8×8px per square subaperture. The SLOpe Detection And Ranging (SLODAR) is a method used to measure the turbulence profiles. Cross correlation of wavefronts gradient from multiple stars is used to estimate the relative strengths of turbulent layers at different altitudes. In the ARGOS case the LGS are arranged on a triangle inscribed in a 2 arcmin radius circle, so we expect an effective slopes correlation up to 5km altitude. We present here the results of a study aimed to implement the SLODAR method on ARGOS performed with the idl-based simulation code used to characterize the ARGOS performance. Simulation implements the atmospheric turbulence on different layers with variable strength, altitude and wind speed. The algorithm performance are evaluated comparing the input turbulence with the cross-correlation of the SH slopes acquired in open loop.
In this paper we present the integration status of the ARGOS wavefront sensor and the results of ... more In this paper we present the integration status of the ARGOS wavefront sensor and the results of the closed loop tests performed in laboratory. ARGOS is the laser guide star adaptive optics system of the Large Binocular Telescope. It is designed to implement a Ground Layer Adaptive Optics correction for LUCI, an infrared imaging camera and multi-object spectrograph, using 3 pulsed Rayleigh beacons focused at 12km altitude. The WFS is configured as a Shack-Hartman sensor having a 15 x 15 subaspertures over the telescope pupil. In the WFS each LGS is independently stabilized for on-sky jitter and range-gated to reduce spot elongation. The 3 LGS are arranged on a single lenslet array and detector by the use of off-axis optics in the final part of the WFS. The units of WFS are in the integration and testing phase at Arcetri Observatory premises. We describe here the test aimed to demonstrate the functionality of the WFS in an adaptive optics closed loop performed using the internal light sources of the WFS and a MEMS deformable mirror.
Software and Cyberinfrastructure for Astronomy III, 2014
Commissioning time for an instrument at an observatory is precious, especially the night time. Wh... more Commissioning time for an instrument at an observatory is precious, especially the night time. Whenever astronomers come up with a software feature request or point out a software defect, the software engineers have the task to find a solution and implement it as fast as possible. In this project phase, the software engineers work under time pressure and stress to deliver a functional instrument control software (ICS). The shortness of development time during commissioning is a constraint for software engineering teams and applies to the ARGOS project as well. The goal of the ARGOS (Advanced Rayleigh guided Ground layer adaptive Optics System) project is the upgrade of the Large Binocular Telescope (LBT) with an adaptive optics (AO) system consisting of six Rayleigh laser guide stars and wavefront sensors. For developing the ICS, we used the technique Test- Driven Development (TDD) whose main rule demands that the programmer writes test code before production code. Thereby, TDD can yield a software system, that grows without defects and eases maintenance. Having applied TDD in a calm and relaxed environment like office and laboratory, the ARGOS team has profited from the benefits of TDD. Before the commissioning, we were worried that the time pressure in that tough project phase would force us to drop TDD because we would spend more time writing test code than it would be worth. Despite this concern at the beginning, we could keep TDD most of the time also in this project phase This report describes the practical application and performance of TDD including its benefits, limitations and problems during the ARGOS commissioning. Furthermore, it covers our experience with pair programming and continuous integration at the telescope.
The use of tilted elements in fast convergent beams like a dichroic unit is always a delicate mat... more The use of tilted elements in fast convergent beams like a dichroic unit is always a delicate matter in optical design. In adaptive optics (AO) applications this issue proves itself to be more severe with respect to classical imaging or spectroscopy: this due to the fact that the laser is co-moving with the launch telescope system while the natural guide star is co-moving with the sky. Because of the GMT design, during AO operations this condition translates as that the laser guide star moves around the target while the natural guide star does not. In this context, we studied two options for a high-optical quality and an easy to-plug-in dichroic unit dividing lasers beacons (reflected) and natural stars (transmitted). Beyond their different optical performances and mechanical implementations, these options are able both to accomplish the main goal of simultaneous operation of natural and laser-oriented AO at the GMT. One of these two has successfully passed the GMT AO Preliminary Design Review (PDR) on July 2013.
In this paper we present the final design of the WFS unit of LBT's ARGOS facility, that will impl... more In this paper we present the final design of the WFS unit of LBT's ARGOS facility, that will implement a GLAO system using 3 Rayleigh pulsed beacons. The ARGOS WFS is composed of two main subunits: 1) a large dichroic window that deflects the laser beam toward the WFS and transmit the visible and near-infrared wavelength to the MOSimager LUCIFER and 2) the SH-WFS that collects the backscattered light of the 3 beacons and combines the beams on a single lenslet array and detector. The WFS unit includes Pockels cells for the range gating of the laser beams, field and pupil stabilizers to compensate for the fast jitter of the laser beams and for optical flexures and a calibration unit to check the internal alignment; this unit will be also used for closed-loop laboratory tests using a MEMS-DM.
ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. W... more ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. With first laser light on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multiRayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the adaptive correction by the deformable secondary’s, we expect ARGOS to enhance the image quality over a large range of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with Rayleigh beacon combination for a diffraction limited AO performance.
Ground-based and Airborne Instrumentation for Astronomy V, 2014
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics nea... more The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the MaxPlanck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio Astrofisico di Arcetri and will offer 1 – 5 μm imaging and 1 – 2.5 μm integral field spectroscopic capabilities with a high Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’ patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace, with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
ABSTRACT We present the results of the laboratory characterization of the ARGOS LGS wavefront sen... more ABSTRACT We present the results of the laboratory characterization of the ARGOS LGS wavefront sensor (LGSW) and dichroic units. ARGOS is the laser guide star adaptive optics system of the Large Binocular Telescope (LBT). It implements a Ground Layer Adaptive Optics (GLAO) correction for LUCI, an infrared imager and multi-object spectrograph (MOS), using 3 pulsed Rayleigh beacons focused at 12km altitude. The LGSW is a Shack-Hartman sensor having 15 × 15 subaspertures over the telescope pupil. Each LGS is independently stabilized for on-sky jitter and gated to reduce spot elongation. The 3 LGS pupils are stabilized to compensate mechanical flexure and are arranged on a single detector. Two units of LGSW have been produced and tested at Arcetri Observatory. We report on the results obtained in the pre-shipment laboratory test: internal active flexure compensation loop performance, optomechanical stability under different gravity conditions, thermal cycling, Pockels cells performance. We also update on the upcoming installation and commissioning campaign at LBT.
ARGOS is the laser guide star ground layer adaptive optics system of the LBT. ARGOS is designed t... more ARGOS is the laser guide star ground layer adaptive optics system of the LBT. ARGOS is designed to bring a moderate but uniform reduction of the PSF size over a FoV as large as 4x4arcmin, allowing a significative increase of the science throughput of LUCI, the LBT NIR imager and MOS. ARGOS relays on 3 Rayleigh beacons to sense the lower layers of the atmosphere achieving almost 100% sky coverage. The ground layer AO correction is allowed by the 2 adaptive secondaries of the LBT. This PhD thesis first discusses a study based on numerical simulations and aimed to evaluate the performance of ARGOS. This work has been carried out using CAOS and representing in the code most of the features that characterize the system itself: as the laser beacon propagation in the atmosphere, the SH type wavefront sensing, the AO reconstruction and closed loop delays and the atmosphere tip-tilt sensing done using a NGS and a quad-cell type sensor. The results obtained in this study are in agreement and definitively confirm the performance evaluated in the phase studies of the project. This study shows that ARGOS is able to produce a reduction of a factor 2 of the seeing bringing to a gain of a factor 4 in the integration time required by LUCI. This PhD thesis reports also the optical design and optimization of both the ARGOS dichroic window, used to separate the laser light from the science light, and the LGS WFS, that evaluates the ground layer aberrations averaging the SH measurements in the direction of the 3 LGS. For both of the subsystems the optimization process is analyzed. Then are evaluated the tolerances and specifications for the production and coating of the optics. Finally are evaluated the stability requirement for the mechanical design and the degrees of freedom needed for the alignment purposes.
The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the te... more The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the telescope, providing laser guidestar generation, wavefront sensing, and wavefront correction to every instrument currently planned on the 25.4 m diameter GMT. There will be three first generation AO observing modes: Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments.
Optical cophasing has a key role in ensuring that segmented mirror telescopes reach their best pe... more Optical cophasing has a key role in ensuring that segmented mirror telescopes reach their best performance. To measure and correct segments misalignment it is necessary to have a wavefront sensor (WFS) in the telescope optical path. All the cophasing WFS suffer the phase ambiguity problem that limits the piston error measurements to a unit of wavelength. To overcome this problem we have developed a new cophasing technique based on the wavelength sweep. This paper will present the results of laboratory and on-sky tests of this technique, comparing them with the expected performance obtained in a previous work through numerical simulations. The laboratory test was carried out on the Active Phasing Experiment bench at ESO premises in Garching. We measured wavefront piston errors up to 15μm with an accuracy better than 0.25μm on a pupil conjugate segmented mirror using the Pyramid Phasing Sensor (PYPS) and a commercial tunable filter. We tested the possibility of propagating the differential piston measurements over the segmented mirror to cophase it, obtaining a residual surface error less than 0.2μm rms. The first on-sky test of the WST was carried out at William Hershel Telescope (WHT) using the NAOMI segmented mirror. We checked the effects of atmospheric turbulence on the measurements of large piston errors up to 15um wavefront and it was obtained an accuracy of 0.5μm, which is in agreement with simulation.
ARGOS, the Laser Guide Star (LGS) facility of the Large Binocular Telescope (LBT), implements a G... more ARGOS, the Laser Guide Star (LGS) facility of the Large Binocular Telescope (LBT), implements a Ground Layer Adaptive Optics (GLAO) system, using 3 low-altitude beacons, to improve the resolution over the 4'×4' FoV of the imager and Multi Object Spectrograph (MOS) LUCIFER. In this paper we discuss the performance and the reconstruction scheme of an hybrid AO system using the ARGOS Rayleigh beacons complemented with a single faint high-altitude star (NGS or sodium beacon) to sense the turbulence of the upper atmosphere allowing an high degree of on-axis correction. With the ARGOS system, the NGS-upgrade can be immediately implemented at LBT using the already existing Pyramid WFS offering performance similar to the NGS AO system with the advantage of a larger sky coverage.
The construction of ELT primary mirrors requires the integration of a hundreds of segments.1, 2 A... more The construction of ELT primary mirrors requires the integration of a hundreds of segments.1, 2 A frequent substitution of some segment is foreseen allowing the primary alumimization. Mechanical integration has to reduce residual piston errors up to the capture range of optical cophasing sensors. Enlarging this range, will relax the mechanical integration requirements, speeding up meaningfully the integration operations. In this work we tested the performance of the Wavelength Sweeping Technique3 (WST): a cophasing technique that allow a large piston capture range, with any need of initial calibration. To apply the WST is necessary couple a Liquid Crystal Tunable Filter (LCTF) to a phasing WaveFront Sensor (WFS). In laboratory we measured segment edge steps on a MEMS-DM applying the WST to the PYramid Phasing Sensor 4 (PYPS). We measured 72 wavefront phase steps from 0.5 to 3µm with an accuracy of less than 0.2µm. With numerical simulations we inquired the possibility to propagate WST edge step measures to cophase a segmented mirror. To do this we realized a cophasing algorithm and we compared its performace in different observing environments. The algorithm converges in 3 ÷ 5 iterations and all the residual edge steps on the mirror are in the capture range of high resolution cophasing techniques.
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.
The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the te... more The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the telescope, providing laser guidestar generation, wavefront sensing, and wavefront correction to every instrument currently planned on the 25.4 m diameter GMT. There will be three first generation AO observing modes: Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments.
ARGOS is the Ground Layer Adaptive Optics system of the Large Binocular Telescope, it uses three ... more ARGOS is the Ground Layer Adaptive Optics system of the Large Binocular Telescope, it uses three Laser Guide Stars at 12 km altitude, generated by Rayleigh backscattered light of pulsed Nd:YAG lasers at 532nm. The wavefront distortion in the Ground Layer is measured by three Shack-Hartmann WFS, sampling with 15×15 subaperture the three LGS arranged on a single CCD with 8×8px per square subaperture. The SLOpe Detection And Ranging (SLODAR) is a method used to measure the turbulence profiles. Cross correlation of wavefronts gradient from multiple stars is used to estimate the relative strengths of turbulent layers at different altitudes. In the ARGOS case the LGS are arranged on a triangle inscribed in a 2 arcmin radius circle, so we expect an effective slopes correlation up to 5km altitude. We present here the results of a study aimed to implement the SLODAR method on ARGOS performed with the idl-based simulation code used to characterize the ARGOS performance. Simulation implements the atmospheric turbulence on different layers with variable strength, altitude and wind speed. The algorithm performance are evaluated comparing the input turbulence with the cross-correlation of the SH slopes acquired in open loop.
In this paper we present the integration status of the ARGOS wavefront sensor and the results of ... more In this paper we present the integration status of the ARGOS wavefront sensor and the results of the closed loop tests performed in laboratory. ARGOS is the laser guide star adaptive optics system of the Large Binocular Telescope. It is designed to implement a Ground Layer Adaptive Optics correction for LUCI, an infrared imaging camera and multi-object spectrograph, using 3 pulsed Rayleigh beacons focused at 12km altitude. The WFS is configured as a Shack-Hartman sensor having a 15 x 15 subaspertures over the telescope pupil. In the WFS each LGS is independently stabilized for on-sky jitter and range-gated to reduce spot elongation. The 3 LGS are arranged on a single lenslet array and detector by the use of off-axis optics in the final part of the WFS. The units of WFS are in the integration and testing phase at Arcetri Observatory premises. We describe here the test aimed to demonstrate the functionality of the WFS in an adaptive optics closed loop performed using the internal light sources of the WFS and a MEMS deformable mirror.
Software and Cyberinfrastructure for Astronomy III, 2014
Commissioning time for an instrument at an observatory is precious, especially the night time. Wh... more Commissioning time for an instrument at an observatory is precious, especially the night time. Whenever astronomers come up with a software feature request or point out a software defect, the software engineers have the task to find a solution and implement it as fast as possible. In this project phase, the software engineers work under time pressure and stress to deliver a functional instrument control software (ICS). The shortness of development time during commissioning is a constraint for software engineering teams and applies to the ARGOS project as well. The goal of the ARGOS (Advanced Rayleigh guided Ground layer adaptive Optics System) project is the upgrade of the Large Binocular Telescope (LBT) with an adaptive optics (AO) system consisting of six Rayleigh laser guide stars and wavefront sensors. For developing the ICS, we used the technique Test- Driven Development (TDD) whose main rule demands that the programmer writes test code before production code. Thereby, TDD can yield a software system, that grows without defects and eases maintenance. Having applied TDD in a calm and relaxed environment like office and laboratory, the ARGOS team has profited from the benefits of TDD. Before the commissioning, we were worried that the time pressure in that tough project phase would force us to drop TDD because we would spend more time writing test code than it would be worth. Despite this concern at the beginning, we could keep TDD most of the time also in this project phase This report describes the practical application and performance of TDD including its benefits, limitations and problems during the ARGOS commissioning. Furthermore, it covers our experience with pair programming and continuous integration at the telescope.
The use of tilted elements in fast convergent beams like a dichroic unit is always a delicate mat... more The use of tilted elements in fast convergent beams like a dichroic unit is always a delicate matter in optical design. In adaptive optics (AO) applications this issue proves itself to be more severe with respect to classical imaging or spectroscopy: this due to the fact that the laser is co-moving with the launch telescope system while the natural guide star is co-moving with the sky. Because of the GMT design, during AO operations this condition translates as that the laser guide star moves around the target while the natural guide star does not. In this context, we studied two options for a high-optical quality and an easy to-plug-in dichroic unit dividing lasers beacons (reflected) and natural stars (transmitted). Beyond their different optical performances and mechanical implementations, these options are able both to accomplish the main goal of simultaneous operation of natural and laser-oriented AO at the GMT. One of these two has successfully passed the GMT AO Preliminary Design Review (PDR) on July 2013.
In this paper we present the final design of the WFS unit of LBT's ARGOS facility, that will impl... more In this paper we present the final design of the WFS unit of LBT's ARGOS facility, that will implement a GLAO system using 3 Rayleigh pulsed beacons. The ARGOS WFS is composed of two main subunits: 1) a large dichroic window that deflects the laser beam toward the WFS and transmit the visible and near-infrared wavelength to the MOSimager LUCIFER and 2) the SH-WFS that collects the backscattered light of the 3 beacons and combines the beams on a single lenslet array and detector. The WFS unit includes Pockels cells for the range gating of the laser beams, field and pupil stabilizers to compensate for the fast jitter of the laser beams and for optical flexures and a calibration unit to check the internal alignment; this unit will be also used for closed-loop laboratory tests using a MEMS-DM.
ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. W... more ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. With first laser light on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multiRayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the adaptive correction by the deformable secondary’s, we expect ARGOS to enhance the image quality over a large range of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with Rayleigh beacon combination for a diffraction limited AO performance.
Ground-based and Airborne Instrumentation for Astronomy V, 2014
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics nea... more The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the MaxPlanck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio Astrofisico di Arcetri and will offer 1 – 5 μm imaging and 1 – 2.5 μm integral field spectroscopic capabilities with a high Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’ patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace, with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
ABSTRACT We present the results of the laboratory characterization of the ARGOS LGS wavefront sen... more ABSTRACT We present the results of the laboratory characterization of the ARGOS LGS wavefront sensor (LGSW) and dichroic units. ARGOS is the laser guide star adaptive optics system of the Large Binocular Telescope (LBT). It implements a Ground Layer Adaptive Optics (GLAO) correction for LUCI, an infrared imager and multi-object spectrograph (MOS), using 3 pulsed Rayleigh beacons focused at 12km altitude. The LGSW is a Shack-Hartman sensor having 15 × 15 subaspertures over the telescope pupil. Each LGS is independently stabilized for on-sky jitter and gated to reduce spot elongation. The 3 LGS pupils are stabilized to compensate mechanical flexure and are arranged on a single detector. Two units of LGSW have been produced and tested at Arcetri Observatory. We report on the results obtained in the pre-shipment laboratory test: internal active flexure compensation loop performance, optomechanical stability under different gravity conditions, thermal cycling, Pockels cells performance. We also update on the upcoming installation and commissioning campaign at LBT.
ARGOS is the laser guide star ground layer adaptive optics system of the LBT. ARGOS is designed t... more ARGOS is the laser guide star ground layer adaptive optics system of the LBT. ARGOS is designed to bring a moderate but uniform reduction of the PSF size over a FoV as large as 4x4arcmin, allowing a significative increase of the science throughput of LUCI, the LBT NIR imager and MOS. ARGOS relays on 3 Rayleigh beacons to sense the lower layers of the atmosphere achieving almost 100% sky coverage. The ground layer AO correction is allowed by the 2 adaptive secondaries of the LBT. This PhD thesis first discusses a study based on numerical simulations and aimed to evaluate the performance of ARGOS. This work has been carried out using CAOS and representing in the code most of the features that characterize the system itself: as the laser beacon propagation in the atmosphere, the SH type wavefront sensing, the AO reconstruction and closed loop delays and the atmosphere tip-tilt sensing done using a NGS and a quad-cell type sensor. The results obtained in this study are in agreement and definitively confirm the performance evaluated in the phase studies of the project. This study shows that ARGOS is able to produce a reduction of a factor 2 of the seeing bringing to a gain of a factor 4 in the integration time required by LUCI. This PhD thesis reports also the optical design and optimization of both the ARGOS dichroic window, used to separate the laser light from the science light, and the LGS WFS, that evaluates the ground layer aberrations averaging the SH measurements in the direction of the 3 LGS. For both of the subsystems the optimization process is analyzed. Then are evaluated the tolerances and specifications for the production and coating of the optics. Finally are evaluated the stability requirement for the mechanical design and the degrees of freedom needed for the alignment purposes.
Uploads
Papers by Marco Bonaglia
substitution of some segment is foreseen allowing the primary alumimization. Mechanical integration has to
reduce residual piston errors up to the capture range of optical cophasing sensors. Enlarging this range, will
relax the mechanical integration requirements, speeding up meaningfully the integration operations.
In this work we tested the performance of the Wavelength Sweeping Technique3 (WST): a cophasing technique
that allow a large piston capture range, with any need of initial calibration. To apply the WST is necessary
couple a Liquid Crystal Tunable Filter (LCTF) to a phasing WaveFront Sensor (WFS). In laboratory we measured
segment edge steps on a MEMS-DM applying the WST to the PYramid Phasing Sensor 4 (PYPS). We measured
72 wavefront phase steps from 0.5 to 3µm with an accuracy of less than 0.2µm. With numerical simulations
we inquired the possibility to propagate WST edge step measures to cophase a segmented mirror. To do this
we realized a cophasing algorithm and we compared its performace in different observing environments. The
algorithm converges in 3 ÷ 5 iterations and all the residual edge steps on the mirror are in the capture range of
high resolution cophasing techniques.
using 3 Rayleigh pulsed beacons. The ARGOS WFS is composed of two main subunits: 1) a large dichroic
window that deflects the laser beam toward the WFS and transmit the visible and near-infrared wavelength to the MOSimager LUCIFER and 2) the SH-WFS that collects the backscattered light of the 3 beacons and combines the beams on
a single lenslet array and detector. The WFS unit includes Pockels cells for the range gating of the laser beams, field and
pupil stabilizers to compensate for the fast jitter of the laser beams and for optical flexures and a calibration unit to check
the internal alignment; this unit will be also used for closed-loop laboratory tests using a MEMS-DM.
on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and
design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multiRayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in
constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the
adaptive correction by the deformable secondary’s, we expect ARGOS to enhance the image quality over a large range
of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both
imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field
correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with
Rayleigh beacon combination for a diffraction limited AO performance.
spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full
use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable
Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for
construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the MaxPlanck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio
Astrofisico di Arcetri and will offer 1 – 5 μm imaging and 1 – 2.5 μm integral field spectroscopic capabilities with a high
Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or
with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly
sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’
patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace,
with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by
NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP)
coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be
upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector
replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension
of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on
the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet
detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI
upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
Books by Marco Bonaglia
substitution of some segment is foreseen allowing the primary alumimization. Mechanical integration has to
reduce residual piston errors up to the capture range of optical cophasing sensors. Enlarging this range, will
relax the mechanical integration requirements, speeding up meaningfully the integration operations.
In this work we tested the performance of the Wavelength Sweeping Technique3 (WST): a cophasing technique
that allow a large piston capture range, with any need of initial calibration. To apply the WST is necessary
couple a Liquid Crystal Tunable Filter (LCTF) to a phasing WaveFront Sensor (WFS). In laboratory we measured
segment edge steps on a MEMS-DM applying the WST to the PYramid Phasing Sensor 4 (PYPS). We measured
72 wavefront phase steps from 0.5 to 3µm with an accuracy of less than 0.2µm. With numerical simulations
we inquired the possibility to propagate WST edge step measures to cophase a segmented mirror. To do this
we realized a cophasing algorithm and we compared its performace in different observing environments. The
algorithm converges in 3 ÷ 5 iterations and all the residual edge steps on the mirror are in the capture range of
high resolution cophasing techniques.
using 3 Rayleigh pulsed beacons. The ARGOS WFS is composed of two main subunits: 1) a large dichroic
window that deflects the laser beam toward the WFS and transmit the visible and near-infrared wavelength to the MOSimager LUCIFER and 2) the SH-WFS that collects the backscattered light of the 3 beacons and combines the beams on
a single lenslet array and detector. The WFS unit includes Pockels cells for the range gating of the laser beams, field and
pupil stabilizers to compensate for the fast jitter of the laser beams and for optical flexures and a calibration unit to check
the internal alignment; this unit will be also used for closed-loop laboratory tests using a MEMS-DM.
on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and
design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multiRayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in
constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the
adaptive correction by the deformable secondary’s, we expect ARGOS to enhance the image quality over a large range
of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both
imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field
correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with
Rayleigh beacon combination for a diffraction limited AO performance.
spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full
use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable
Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for
construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the MaxPlanck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio
Astrofisico di Arcetri and will offer 1 – 5 μm imaging and 1 – 2.5 μm integral field spectroscopic capabilities with a high
Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or
with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly
sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’
patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace,
with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by
NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP)
coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be
upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector
replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension
of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on
the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet
detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI
upgrade strategy, which is part of the ERIS development plan and the overall project timeline.