One year and an half after ARGOS first light, the Large Binocular Telescope (LBT) laser guided ground-layer adaptive optics (GLAO) system has been operated on both sides of the LBT. The system fulfills the GLAO promise and typically delivers an improvement by a factor of 2 in FWHM over the 4'×4' field of view of both Luci instruments, the two near-infrared imagers and multi-object spectrographs.
In this paper, we report on the first on-sky results and analyze the performances based on the data collected so far. We also discuss adaptive optics procedures and the joint operations with Luci for science observations.
Argos is the ground-layer adaptive optics system for the Large Binocular Telescope. In order to perform its wide-field correction, Argos uses three laser guide stars which sample the atmospheric turbulence. To perform the correction, Argos has at disposal three different wavefront sensing measurements : its three laser guide stars, a NGS tip-tilt, and a third wavefront sensor. We present the wavefront sensing architecture and its individual components, in particular: the finalized Argos pnCCD camera detecting the 3 laser guide stars at 1kHz, high quantum efficiency and 4e- noise; the Argos tip-tilt sensor based on a quad-cell avalanche photo-diodes; and the Argos wavefront computer. Being in the middle of the commissioning, we present the first wavefront sensing configurations and operations performed at LBT, and discuss further improvements in the measurements of the 3 laser guide star slopes as detected by the pnCCD.
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 multi- Rayleigh 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.
The Large Binocular Telescope (LBT) has eight Acquisition, Guiding, and wavefront Sensing Units (AGw units). They provide guiding and wavefront sensing capability at eight different locations at both direct and bent Gregorian focal stations. Recent additions of focal stations for PEPSI and MODS instruments doubled the number of focal stations in use including respective motion, camera controller server computers, and software infrastructure communicating with Guiding Control Subsystem (GCS). This paper describes the improvements made to the LBT GCS and explains how these changes have led to better maintainability and contributed to increased reliability. This paper also discusses the current GCS status and reviews potential upgrades to further improve its performance.
ARGOS the Advanced Rayleigh guided Ground layer adaptive Optics System for the LBT (Large Binocular Telescope)
is built by a German-Italian-American consortium. It will be a seeing reducer correcting the turbulence in the lower
atmosphere over a field of 2' radius. In such way we expect to improve the spatial resolution over the seeing of about a
factor of two and more and to increase the throughput for spectroscopy accordingly. In its initial implementation,
ARGOS will feed the two near-infrared spectrograph and imager - LUCI I and LUCI II.
The system consist of six Rayleigh lasers - three per eye of the LBT. The lasers are launched from the back of the
adaptive secondary mirror of the LBT. ARGOS has one wavefront sensor unit per primary mirror of the LBT, each of the
units with three Shack-Hartmann sensors, which are imaged on one detector.
In 2010 and 2011, we already mounted parts of the instrument at the telescope to provide an environment for the main
sub-systems. The commissioning of the instrument will start in 2012 in a staged approach. We will give an overview of
ARGOS and its goals and report about the status and new challenges we encountered during the building phase. Finally
we will give an outlook of the upcoming work, how we will operate it and further possibilities the system enables by
ARGOS, the laser-guided adaptive optics system for the Large Binocular Telescope (LBT), is now under construction at
the telescope. By correcting atmospheric turbulence close to the telescope, the system is designed to deliver high
resolution near infrared images over a field of 4 arc minute diameter. Each side of the LBT is being equipped with three
Rayleigh laser guide stars derived from six 18 W pulsed green lasers and projected into two triangular constellations
matching the size of the corrected field. The returning light is to be detected by wavefront sensors that are range gated
within the seeing-limited depth of focus of the telescope. Wavefront correction will be introduced by the telescope's
deformable secondary mirrors driven on the basis of the average wavefront errors computed from the respective guide
star constellation. Measured atmospheric turbulence profiles from the site lead us to expect that by compensating the
ground-layer turbulence, ARGOS will deliver median image quality of about 0.2 arc sec across the JHK bands. This will
be exploited by a pair of multi-object near-IR spectrographs, LUCIFER1 and LUCIFER2, with 4 arc minute field already
operating on the telescope. In future, ARGOS will also feed two interferometric imaging instruments, the LBT
Interferometer operating in the thermal infrared, and LINC-NIRVANA, operating at visible and near infrared
wavelengths. Together, these instruments will offer very broad spectral coverage at the diffraction limit of the LBT's
combined aperture, 23 m in size.
We present the results from the commisioning of the first three off-axis
Acquisition, Guiding and Wavefront Sensing Units on the Large Binocular
Telescope. In particular we report on the performance of the units with
respect to image quality, optical efficiency and scattered light.
We also present the procedure for calibrating the stage
coordinate system astrometrically to the focal plane coordinates of the
telescope as well as the positional performance of the system.
The first of a total of four units was mounted on the telescope in
October 2007 and in the mean time three units have been mounted on the
telescope. The units have been used for commisioning of the focal stations as well as for scientific observations since the end of 2008 with LUCIFER-I, the near-IR images and MOS spectrograph
ARGOS is the Laser Guide Star adaptive optics system for the Large Binocular Telescope. Aiming for a wide field
adaptive optics correction, ARGOS will equip both sides of LBT with a multi laser beacon system and corresponding
wavefront sensors, driving LBT's adaptive secondary mirrors. Utilizing high power pulsed green lasers the artificial
beacons are generated via Rayleigh scattering in earth's atmosphere. ARGOS will project a set of three guide stars above
each of LBT's mirrors in a wide constellation. The returning scattered light, sensitive particular to the turbulence close to
ground, is detected in a gated wavefront sensor system. Measuring and correcting the ground layers of the optical
distortions enables ARGOS to achieve a correction over a very wide field of view. Taking advantage of this wide field
correction, the science that can be done with the multi object spectrographs LUCIFER will be boosted by higher spatial
resolution and strongly enhanced flux for spectroscopy. Apart from the wide field correction ARGOS delivers in its
ground layer mode, we foresee a diffraction limited operation with a hybrid Sodium laser Rayleigh beacon combination.
We present the status of PEPSI, the bench-mounted fibre-fed and stabilized "Potsdam Echelle Polarimetric and
Spectroscopic Instrument" for the 2×8.4m Large Binocular Telescope in southern Arizona. PEPSI is under construction
at AIP and is scheduled for first light in 2009/10. Its ultra-high-resolution mode will deliver an unprecedented spectral
resolution of approximately R=310,000 at high efficiency throughout the entire optical/red wavelength range 390-1050nm without the need for adaptive optics. Besides its polarimetric Stokes IQUV mode, the capability to cover the
entire optical range in three exposures at resolutions of 40,000, 130,000 and 310,000 will surpass all existing facilities in
terms of light-gathering-power times spectral-coverage product. A solar feed will make use of the spectrograph also
during day time. As such, we hope that PEPSI will be the most powerful spectrometer of its kind for the years to come.
Laser guide star adaptive optics and interferometry are currently revolutionizing ground-based near-IR astronomy, as
demonstrated at various large telescopes. The Large Binocular Telescope from the beginning included adaptive optics in
the telescope design. With the deformable secondary mirrors and a suite of instruments taking advantage of the AO
capabilities, the LBT will play an important role in addressing major scientific questions. Extending from a natural guide
star based system, towards a laser guide stars will multiply the number of targets that can be observed. In this paper we
present the laser guide star and wavefront sensor program as currently being planned for the LBT. This program will
provide a multi Rayleigh guide star constellation for wide field ground layer correction taking advantage of the multi
object spectrograph and imager LUCIFER in a first step. The already foreseen upgrade path will deliver an on axis
diffraction limited mode with LGS AO based on tomography or additional sodium guide stars to even further enhance
the scientific use of the LBT including the interferometric capabilities.
The paper describes the single conjugate AO system called WLBT to
be mounted at LBT in late summer 2004. The WLBT is part of the
Acquisition, Guiding & Wavefront sensing unit (AGW) attached to the front bent Gregorian foci derotator. The two key features of this system are the use of a pyramid wavefront sensor with variable sampling between 30x30 and 5x5 sub apertures plus the use of an adaptive secondary mirror having 672 actuators as wavefront corrector. The AO system is mainly working as atmospheric disturbance correction system in the near infrared (J,H and K band). However due to the large number of actuators and sub apertures, it can obtain good
performance even in R and I band. The paper reports about
development and integration of the system final unit in the lab.
Then some initial tests aimed to do a system characterization are
reported. The results we obtained are used to give an estimation
of the performance that the system can reach at the telescope in
terms of limiting magnitude.
We present the final opto-mechanical design of the Large Binocular Telescope (LBT) Acquisition, Guiding and Wavefront Sensing Units (AGW-units) together with the laboratory test performance of the units. The units will be installed at the LBT shortly after this conference, at several of the different Gregorian focal positions available. Each AGW-unit consists of a probe with a camera and a wavefront sensor located in front of the science instrument. The probe can move in two axes allowing it to patrol a field off-axis to the science field.
A dichroic beam-splitter on the probe transmits the blue light to the
acquisition and guide camera and the red light is reflected into a
Shack-Hartmann wavefront sensor. The guide camera is equipped with a
2.5x focal reducer giving a field of view of 28"x28" on a 512x1024
frame-transfer CCD. The 12x12 sub-pupil wavefront sensor uses a
micro lenslet array made using an ion-exchange technique on
a flat substrate with diffraction limited performance.
The LBT Adaptive first light is foreseen for summer 2004. The first light AO system will be part of the Acquisition Guiding and Wavefront sensor unit (AGW) placed at the front bent Gregorian Foci of the telescope. The development and construction of the AO system is an undergoing process at Arcetri Observatory. The main features of the system are: the use of an adaptive secondary mirror with 672 actuators, the adoption of a pyramid wavefront sensor with a maximum sampling of 30x30 subaperture and the use of a small (400x320mm) movable wavefront sensor unit for reference star acquisition. After a brief description of the system the paper report about the progresses made in the design, realization and lab testing of the various parts of the AO system. In particular we describe the new beams configuration for the wavefront sensor board, the lab prototype of the sensor opto-mechanics, the sensor fast camera and its controller, the glass pyramid, the AO system real time and control software.
The paper describes the design of the single conjugate Adaptive Optics system to be installed on the LBT telescope. This system will be located in the Acquisition, Guiding and Wavefront sensor unit (AGW) mounted at the front bent Gregorian focus of LBT. Two innovative key features of this system are the Adaptive Secondary Mirror and the Pyramid Wavefront Sensor. The secondary provides 672 actuators wavefront correction available at the various foci of LBT. Due to the adaptive secondary mirror there is no need to optically conjugate the pupil on the deformable mirror. This allows having a very short sensor optical path made up using small dimension refractive optics. The overall AO system has a transmission of 70 % and fits in a rectangle of about 400×320mm. The pyramid sensor allows having different pupil sampling using on-chip binning of the detector. Main pupil samplings for the LBT system are 30×30, 15×15 and 10×10. Reference star acquisition is obtained moving the wavefront sensor unit in a field of view of 3×2 arcmin. Computer simulations of the overall system performance show the good correction achievable in J, H, and K. In particular, in our configuration, the limiting magnitude of pyramid sensor results more than one magnitude fainter with respect to Shack- Hartmann sensor. This feature directly translates in an increased sky coverage that is, in K band, about doubled with respect to the same AO system using a Shack-Hartmann sensor.
The Large Binocular Telescope (LBT) will see first light with a single primary mirror in January 2003. It will be equipped with fully adaptive secondary mirrors from the beginning as well as a complete on-axis wavefront sensing and tip-tilt guiding system. Here we present the preliminary design of the Acquisition, Guiding, and Wavefront sensing system for the LBT. The system is divided in an off-axis system for target acquisition, guiding, and slow wavefront sensing, and an on- axis system for rapid wavefront sensing and tip-tilt guiding. The on-axis system operates on the optical light reflected off a tilted entrance window for the instrument science camera. In this way both the correction to the wavefront (done with the secondary mirrors) and the wavefront sensing (done on the light reflected off the dewar entrance windows) is performed without introducing a single additional optical surface in the science beam. In this way the design follows the lead of the upgraded MMT system. However, the present design differs from the MMT design, in that it does tip-tilt sensing in addition to the rapid wavefront sensing. To enable the system to use a tip-tilt guiding star up to 1 arcmin away from the science target, a significantly larger field of view is required for the on-axis system. The off-axis part of the system can do classical guiding and slow wavefront sensing in parallel which will enable the control system to maintain the optimum setting of the optical system during observations. It will also include a high resolution wavefront sensing mode which will allow quick and detailed checks of the secondary mirrors.