ERIS is an instrument that will both extend and enhance the fundamental diffraction limited imaging and spectroscopy capability for the VLT. It will replace two instruments that are now being maintained beyond their operational lifetimes, combine their functionality on a single focus, provide a new wavefront sensing module that makes use of the facility Adaptive Optics System, and considerably improve their performance. The instrument will be competitive with respect to JWST in several regimes, and has outstanding potential for studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS had its final design review in 2017, and is expected to be on sky in 2020. This contribution describes the instrument concept, outlines its expected performance, and highlights where it will most excel.
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.
We report on the development of the laser system of ARGOS, the multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses a total of six high powered, pulsed Nd:YAG lasers frequency-doubled to a wavelength of 532 nm to generate a set of three guide stars above each of the LBT telescopes. The position of each of the LGS constellations on sky as well as the relative position of the individual laser guide stars within this constellation is controlled by a set of steerable mirrors and a fast tip-tilt mirror within the laser system. The entire opto-mechanical system is housed in two hermetically sealed and thermally controlled enclosures on the SX and DX side of the LBT telescope. The laser beams are propagated through two refractive launch telescopes which focus the beams at an altitude of 12 km, creating a constellation of laser guide stars around a 4 arcminute diameter circle by means of Rayleigh scattering. In addition to the GLAO Rayleigh beacon system, ARGOS has also been designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system was successfully installed at the LBT in April 2013. Extensive functional tests have been carried out and have verified the operation of the systems according to specifications. The alignment of the laser system with respect to the launch telescope was carried out during two more runs in June and October 2013, followed by the first propagation of laser light on sky in November 2013.
ARGOS, a multi-star adaptive optics system is designed for the wide-field imager and multi-object spectrograph LUCI on the LBT (Large Binocular Telescope). Based on Rayleigh scattering the laser constellation images 3 artificial stars (at 532 nm) per each of the 2 eyes of the LBT, focused at a height of 12 km (Ground Layer Adaptive Optics). The stars are nominally positioned on a circle 2’ in radius, but each star can be moved by up to 0.5’ in any direction. For all of these needs are following main subsystems necessary: 1. A laser system with its 3 Lasers (Nd:YAG ~18W each) for delivering strong collimated light as for LGS indispensable. 2. The Launch system to project 3 beams per main mirror as a 40 cm telescope to the sky. 3. The Wave Front Sensor with a dichroic mirror. 4. The dichroic mirror unit to grab and interpret the data. 5. A Calibration Unit to adjust the system independently also during day time. 6. Racks + platforms for the WFS units. 7. Platforms and ladders for a secure access. This paper should mainly demonstrate how the ARGOS Laser System is configured and designed to support all other systems.
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.
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
The Laser Guide Star facility ARGOS will provide Ground Layer Adaptive Optics to the Large Binocular
Telescope (LBT). The system operates three pulsed laser beacons above each of the two primary mirrors, which
are Rayleigh scattered in 12km height. This enables correction over a wide field of view, using the adaptive
secondary mirror of the LBT. The ARGOS laser system is designed around commercially available, pulsed
Nd:YAG lasers working at 532 nm. In preparation for a successful commissioning, it is important to ascertain
that the specifications are met for every component of the laser system. The testing of assembled, optical
subsystems is likewise necessary. In particular it is required to confirm a high output power, beam quality and
pulse stability of the beacons. In a second step, the integrated laser system along with its electronic cabinets
are installed on a telescope simulator. This unit is capable of carrying the whole assembly and can be tilted
to imitate working conditions at the LBT. It allows alignment and functionality testing of the entire system,
ensuring that flexure compensation and system diagnosis work properly in different orientations.
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.
Wide field correction allowing large field to benefit from adaptive optics (AO) is challenging in more than one
aspect. We address here the wavefront sensor (WFS) detector side where, in addition to high sensitivity and low
noise, the simultaneous detection of multiple laser beacons and the large number of sub-apertures in a
Shack-Hartmann WFS require a detector to have a large imaging area while preserving a very high readout frame
rate. The detector considered has a frame area of 264×264 pixels with a pixel size of 48 microns. By splitting
the image into two framestore areas during readout, repetition rates of more than 1000 frames per second can
be achieved. The electronic noise contribution is approximately 3 electrons at the operating temperature. We
therefore analyze its performances, showing it fulfills the requirements, in a wavefront sensing application: the
measurement of centroids in the case of a Shack-Hartmann WFS for the Argos AO project.
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.
ARGOS is an innovative multi-star adaptive optics system being built for use with LUCIFER on the Large Binocular
Telescope (LBT). LUCIFER is a wide field imager and multi-object spectrograph. Using a constellation of laser guide
stars permits PSF correction over a wide field in exchange for a relatively small sacrifice in achievable correction. The
laser constellation consists of three stars per each of the two eyes of the LBT. The stars are nominally positioned on a circle
2' in radius, but each star can be moved by upto 0.5' in any direction. Nd:YAG (SHG) lasers from InnoLas Laser GmbH
are used to create the green (532nm) laser stars, and have an output above 18 W each at the planned pulsing frequency of
10kHz. The lasers are launched using a 40cm telescope and focused at a height of 12 km. The laser system is designed
to be optically simple yet configurable. It also provisions for a central sodium laser to be installed later. We detail the
characteristics of the laser system and the current state of its development.
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.