PSF knowledge is central to extract science from observations with adaptive optics.
However, it is often challenging to have a good PSF estimate. For instance, this is a problem for the integral field unit (IFU) OSIRIS at Keck Observatory. OSIRIS has a field of only few arcseconds, and it is often impossible to obtain a good empirical PSF. OSIRIS is equipped with an imager designed to track changes in the PSF on a reference star. However, the imager is 20 arcseconds away, which prevents to apply the observed PSF directly to spectroscopic data.
We developed a new software package to predict PSF variability for Keck AO images (AIROPA, see Paolo Turri’s contribution, this conference). To properly use the parallel imager to predict a PSF on the IFU, we adapted the code to the OSIRIS case (AIROPA-IFU).
Here, we present results of the application of this post-processing tools to Galactic Center observation. We also discuss the challenges encountered and the lessons learned when doing PSF
For almost two decades, large volumes of technical data, in a variety of formats, have resulted from the normal operations at the observatory. Similarly, in the last few years, dealing with huge amounts of data has become a priority for several industries, and as consequence, terms like "Big Data" or "Data Lake" have started to be more and more commonly used. Under these circumstances, frameworks and tools have proliferated and later released as "Open Software"; the hardware, on the other hand, has also changed giving the power to deal with this volume of data in a reasonable timeframe, and at a reasonable price.
We hereafter present the first version of a modern data lab developed for the Maintenance Support and Engineering Department (MSE) at the Paranal Observatory, “The MSE DataLab”. This DataLab will allow us to take advantage of this new technological evolution and to be prepared for the current and further challenges to come. These challenges, of course, refer to improving the overall observatory dependability (Reliability, Availability and Maintainability) by supporting the operations in our current and forthcoming telescopes. First, in our Very Large Telescopes (VLT), the VLT Interferometer (VLTI) and the survey telescopes (VISTA and VST). Secondly, in the Extremely Large Telescope (ELT) and the Cherenkov Telescope Array (CTA).
The SPHERE (spectro-photometric exoplanet research) extreme-AO planet hunter saw first light at the VLT observatory on Mount Paranal in May 2014 after ten years of development. Great efforts were put into modelling its performance, particularly in terms of achievable contrast, and to budgeting instrumental features such as wave front errors and optical transmission to each of the instrument’s three focal planes, the near infrared dual imaging camera IRDIS, the near infrared integral field spectrograph IFS and the visible polarimetric camera ZIMPOL. In this paper we aim at comparing predicted performance with measured performance. In addition to comparing on-sky contrast curves and calibrated transmission measurements, we also compare the PSD-based wave front error budget with in-situ wave front maps obtained thanks to a Zernike phase mask, ZELDA, implemented in the infrared coronagraph wheel. One of the most critical elements of the SPHERE system is its high-order deformable mirror, a prototype 40x40 actuator piezo stack design developed in parallel with the instrument itself. The development was a success, as witnessed by the instrument performance, in spite of some bad surprises discovered on the way. The devastating effects of operating without taking properly into account the loss of several actuators and the thermally and temporally induced variations in the DM shape will be analysed, and the actions taken to mitigate these defects through the introduction of specially designed Lyot stops and activation of one of the mirrors in the optical train will be described.
Paranal Observatory has a set of astroclimate monitoring instruments; such as DIMM, MASS-DIMM and SLODAR which are delivering information about the sky quality in terms of; seeing, coherence time, high altitude wind speed (200mb) and Cn2 profiles to support the observations. SPHERE instrument is an Extreme Adaptive Optics that uses a Shack-Hartmann wavefront sensor running at close loop frequency of 1.3KHz. The instrument saves close loop snapshot every minute and from the data saved the system retrieves the r0 and the cross wind speed. The wind speed is calculated using a cross-corrrelation based on the peak identification. The knowledge of t his parameter is essential to understand the performances of the AO system, and to optimize its control laws every minutes. The data from the astroclimatic system monitor will help to correlate the turbulence events with the transverse wind speed retrieved from SPHERE close loop data. The goal of this work is also to compare the different atmospheric monitors with the effective turbulence estimation from the focal plane itself (Differential Tip-Tilt Sensor).
For two years starting in February 2014, the AO modules GRAAL for HAWK-I and GALACSI for MUSE of the Adaptive Optics Facility project have undergone System Testing at ESO's Headquarters. They offer four different modes: NGS SCAO, LGS GLAO in the IR, LGS GLAO and LTAO in the visible. A detailed characterization of those modes was made possible by the existence of ASSIST, a test bench emulating an adaptive VLT including the Deformable Secondary Mirror, a star simulator and turbulence generator and a VLT focal plane re-imager. This phase aimed at validating all the possible components and loops of the AO modules before installation at the actual VLT that comprises the added complexity of real LGSs, a harsher non-reproducible environment and the adaptive telescope control.
In this paper we present some of the major results obtained and challenges encountered during the phase of System Tests, like the preparation of the Acquisition sequence, the testing of the Jitter loop, the performance optimization in GLAO and the offload of low-order modes from the DSM to the telescope (restricted to the M2 hexapod). The System Tests concluded with the successful acceptance, shipping, installation and first commissioning of GRAAL in 2015 as well as the acceptance and shipping of GALACSI, ready for installation and commissioning early 2017.
KEYWORDS: Observatories, Calibration, Iterated function systems, Optical spheres, Sensors, Optical filtering, Stars, Polarimetry, Control systems, K band
The Paranal Very Large Telescopes (VLT) Observatory is a complex multifunctional observatory where many different systems are generating telemetry parameters.As systems becoming more and more complex, also the amount of telemetry data is increasing. This telemetry data is usually saved in various data repositories.In order to obtain a full system overview, it is necessary to link all that data in a meaningful and easy to interpret way. A step forward from simple telemetry data visualisation has been done by developing a new tool that can combine different data sources and has a powerful graphing capability.This new tool, called SystMon, is developed in iPython an interactive-web browser environment under the philosophy of notebooks which combine the code and the final product. The application can be shared among other colleagues and having the code side by side gives the accessibility to inspect and review the process improving and adding new capabilities to the application. SystMon allows to manipulate, generate andvisualise data in different types of graphs and also to create directly statistical reports. SystMon helps the user tomodel, visualiseand interpret telemetry data in a web-based platform for monitoring the health of systems, understanding short- and long-term behaviour and to anticipate corrective interventions.
The design of adaptive optics systems is driven by the local characteristics of the atmospheric turbulence. Site
characterization campaigns utilizing a variety of atmospheric monitoring equipment provides a statistical description of
parameters such integrated seeing, vertical distribution of turbulence strength as well as the coherent time of the
turbulence. Modeling work, intended to understand the operation bandwidth of adaptive optics systems make use of
Kolmogorov turbulence theory as well as time series of atmospheric parameters obtained from regression analysis based
on site characterization data. However, most of the time, even in the more detailed studies, one parameter though
important is not measured and monitored with the same attention than the other turbulence parameters, namely, the outer
scale of the turbulence.
The image quality in large aperture telescopes has been shown to have an important dependence on the instantaneous
magnitude of the outer scale of the turbulence. In general terms, the shorter the outer scale of the turbulence, the lower
the wavefront variance over the aperture of the imaging system and consequently the higher the image quality.
This study focuses in using reconstructed open loop wavefront sensor data observed simultaneously by the two apertures
of the Large Binocular Telescope (LBT) to compute and monitor the outer scale of the turbulence.
This article presents a proposal aimed at investigating the technical feasibility and the scientific capabilities of high
contrast cameras to be implemented at LBT. Such an instrument will fully exploit the unique LBT capabilities in
Adaptive Optics (AO) as demonstrated by the First Light Adaptive Optics (FLAO) system, which is obtaining excellent
results in terms of performance and reliability. The aim of this proposal is to show the scientific interest of such a
project, together with a conceptual opto-mechanical study which shows its technical feasibility, taking advantage of the
already existing AO systems, which are delivering the highest Strehl experienced in nowadays existing telescopes.
Two channels are foreseen for SHARK, a near infrared channel (2.5-0.9 um) and a visible one (0.9 – 0.6 um), both
providing imaging and coronagraphic modes. The visible channel is equipped with a very fast and low noise detector
running at 1.0 kfps and an IFU spectroscopic port to provide low and medium resolution spectra of 1.5 x 1.5 arcsec
fields.
The search of extra solar giant planets is the main science case and the driver for the technical choices of SHARK, but
leaving room for several other interesting scientific topics, which will be briefly depicted here.
The Large Binocular Telescope has two adaptive secondary mirrors which are used for regular observing in both seeinglimited mode and for diffraction-limited mode unlike the adaptive secondaries at the MMT and Magellan telescopes which are swapped in for diffraction-limited observing only. The LBTO secondary mirrors have been in routine operation for ~ 4 years for the first and for ~ 2 years for the second. We review the operational history of these units and discuss the various failure modes unique to adaptive secondaries as compared with rigid secondaries for seeing-limited observing and more conventional adaptive optics systems for diffraction-limited observing.
The use of spectrographs with telescopes having high order adaptive optics systems offers the possibility of
achieving near diffraction-limited spectral resolving power. The adaptively corrected echelle spectrograph
(ACES) couples the AO-corrected stellar image to the instrument with a near single mode fiber (SMF) for
resolution of R~190,000. The First Light Adaptive Optics system (FLAO) at the Large Binocular Telescope
(LBT) achieves Strehl of >80% in H band, and also delivers useful Strehls in V and R bands. In this paper
we explore the possibility of using ACES with the LBT for simultaneous high resolution, high throughput,
and broad wavelength coverage.
The Large Binocular Telescope (LBT) is unique in that it is currently the only large telescope (2 x 8.4m primary
mirrors) with permanently mounted adaptive secondary mirrors (ASMs). These ASMs have been used for regular
observing since early 2010 on the right side and since late 2011 on the left side. They are currently regularly
used for seeing-limited observing as well as for selective diffraction-limited observing and are required to be fully
operational every observing night. By comparison the other telescopes using ASMs, the Multi Mirrot Telescope
(MMT) and more recently Magellan, use fixed secondaries of seeing-limited observing and switch in the ASMs
for diffraction-limited observing.
We will discuss the night-to-night operational requirements for ASMs specifically for seeing-limited but also
for diffraction-limited observations based on the LBT experience. These will include preparation procedures for
observing (mirror flattening and resting as examples); hardware failure statistics and how to deal with them
such as for the actuators; observing protocols for; and current limitations of use due to the ASM technology such
as the minimum elevation limit (25 degrees) and the hysteresis of the gravity-vector induced astigmatism. We
will also discuss the impact of ASM maintenance and preparation
The Adaptive Optics System at the Large Binocular Telescope Observatory consists of two
Adaptive Secondary (ASM) mirrors and two Pyramid Wavefront sensors. The first
ASM/Pyramid pair has been commissioned and is being used for science operation using the NIR
camera PISCES on the right side of the binocular telescope. The left side ASM/Pyramid system
is currently being commissioned, with completion scheduled for the Fall of 2012.
We will discuss the operation of the first Adaptive Optics System at the LBT Observatory
including interactions of the AO system with the telescope and its TCS, observational modes,
user interfaces, observational scripting language, time requirement for closed loop and offsets and
observing efficiency.
This paper summarizes the activities and the principal results achieved during the commissioning of the two Natural
Guide Star (NGS) AO systems called FLAO#1 & 2 installed at the bent Gregorian focal stations of the 2x8.4m Large
Binocular Telescope (LBT). The commissioning activities of FLAO#1 took place in the period February 2010 - October
2011, while FLAO#2 commissioning started in December 2011 and should be completed by November 2012. The main
results of the commissioning campaign are presented in terms of the H-band Strehl Ratio values achieved under different observing conditions. We will also describe the automatic procedures to configure and set-up the FLAO systems, and in particular the modal gain optimization procedure, which has been proven to be a very important one in achieving the
nominal performance. Finally, some of the results achieved in two science runs using the near infra-red camera PISCES
are briefly highlighted.
The Large Binocular Telescope (LBT) is a unique telescope featuring two co-mounted optical trains with 8.4m primary
mirrors. The telescope Adaptive Optics (AO) system uses two innovative key components, namely an adaptive
secondary mirror with 672 actuators and a high-order pyramid wave-front sensor. During the on-sky commissioning such
a system reached performances never achieved before on large ground-based optical telescopes. Images with 40mas
resolution and Strehl Ratios higher than 80% have been acquired in H band (1.6 μm). Such images showed a contrast as
high as 10-4. Based on these results, we compare the performances offered by a Natural Guide Star (NGS) system
upgraded with the state-of-the-art technology and those delivered by existing Laser Guide Star (LGS) systems. The
comparison, in terms of sky coverage and performances, suggests rethinking the current role ascribed to NGS and LGS
in the next generation of AO systems for the 8-10 meter class telescopes and Extremely Large Telescopes (ELTs).
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.
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 system was fully assembled in the
Arcetri Observatory laboratories, passing the acceptance test in December 2009. The performance measured
during the test were closed to goal specifications for all star magnitudes. In particular FLAO obtained 83%
Strehl Ratio (SR) in the bright end (8.5 magnitudes star in R band) using H band filter and correcting 495
modes with 30×30 subapertures sampling. In the faint end (16.4 magnitude) a 5.0% SR correcting 36 modes
with 7×7 subapertures was measured. The seeing conditions for these tests were 0.8" (r0 = 0.14m @ 550 nm)
and an average wind speed of 15m/s. The results at other seeing conditions up to 1.5" are also presented. The
system has been shipped to the LBT site, and the commissioning is taking place since March to December 2010.
A few on sky results are presented.
The Laser Guide Star commissioned in 2007 at the WHT on La Palma is based on Rayleigh backscattering of a 515 nm
beam provided by a diode pumped Q-switched doubled frequency Yb:YAG laser launched from behind the WHT
secondary mirror. At the time the laser beam is focused at a distance of 15km above the telescope ground and its power
just under 20W. With such a pulsed laser, careful fine tuning of the range gate system is essential to isolate the most
focused part of the LGS and eliminate parts of the laser plume which would degrade the Shack-Hartmann spots and
consequently AO correction. This is achieved by an electro-optic shutter using Pockels cells, triggered by a delay
generator synchronised on the laser pulses, and by spatial filters. Images of 0.15" resolution in J and H bands, very close
to expected performance, have been routinely taken as soon as the third and fourth commissioning runs. Here we show
the performance of the range gate system as measured and improved over the successive commissioning runs, as well as
the off sky and on sky calibration procedures of the LGS AO system.
GLAS is an upgrade of the William Herschel Telescope's existing natural-guide-star (NGS) AO system NAOMI
to incorporate a 20-W Rayleigh laser guide star (LGS) projected to an altitude of 15 km. It is currently being
commissioned on-sky, and we review here the current status of the project. GLAS/NAOMI delivers dramatic
improvements in PSF in both the near-IR (AO-corrected FWHM close to the diffraction limit, >~ 0.15 arcsec)
and in the optical (factor of ~ 2 reduction in FWHM). The performance is similar to that with NGS, and is
consistent with predictions from modelling. The main advantage over NGS AO is the large gain in sky coverage
(from ~ 1% to ~ 100% at galactic latitude 40°). GLAS provides the first on-sky demonstration of closed-loop
ground-layer AO (GLAO), and is the first Rayleigh LGS AO system to be offered for general use, at any telescope.
A European Laser Guide Star (LGS) test facility is proposed for the 4.2m William Herschel Telescope (WHT) on La
Palma. It will test the next-generation Adaptive Optics (AO) LGS technologies to aid risk mitigation of Extremely Large
Telescope (ELT) LGS AO systems. In particular, critical scaling of current LGS AO technologies to ELT dimensions
will be tested. For example, experiments addressing increased spot elongation, cone effect and the order of correction
required.
A pan-European consortium proposes to construct test facility infrastructure on the WHT for a number of risk mitigating
experiments. The infrastructure includes the construction of a Nasmyth platform based controlled environment 'Ground-based
Adaptive optics Innovative Laboratory' (GRAIL), an experimental test environment 'Testbed integration facility'
(TIF) and some common-experiment equipment such as the Common Re-Imaging AO System.
Experiments that are proposed for this facility cover the areas of laser technologies, spot elongation, LGS wavefront
sensing, parallel launch concepts, Multi-Object AO, atmospheric characterisation, co-phasing and real-time control
system risk mitigation.
In order to get a better understanding of the optical turbulence at the free atmosphere we present a statistical analysis of the wind and temperature profiles at different heights measured by balloon-born sonde during the years 2003,2004 and until mid 2005, and the stellar image twinkling measurements from a DIMM. The data from the balloon-borne measurements shows the variation of the strength of the jet stream and temperature gradient that are related to formation of turbulent layers in the upper air which contribute to the degradation of the optical images or to laser propagation through the atmosphere. The use of standard radiosonde data compared with the seeing can be used as a tool to define the vertical distribution of the strength of the turbulence in the atmosphere and that will contribute to better optimization of the performance of Adaptative Optics systems.
We report on the development of a prototype portable monitor for profiling of the altitude and velocity of atmospheric optical turbulence. The instrument is based on the SLODAR Shack-Hartmann wave-front sensing technique, applied to a portable telescope and employing an electron-multiplication (EM) CCD camera as the wave-front sensor detector. Constructed for ESO by the astronomical instrumentation group at the University of Durham, the main applications of the monitor will be in support of the ESO multi-conjugate adaptive optics demonstrator (MAD) project, and for site characterization surveys for future extremely large telescopes. The monitor can profile the whole atmosphere or can be optimized for profiling of low altitude (0-1km) turbulence, with a maximum altitude resolution of approximately 150m. First tests of the system have been carried out at the La Palma observatory.
Since summer 2001, dust pollution of the air is regularly measured through a particle counter at the Telescopio Nazionale Galileo (TNG) located at the Roque de los Muchachos Observatory (La Palma - Canary Islands). Canary Islands are normally interested by a dominant atmospheric circulation with NE winds. Depending on their strenght, and their exact direction, winds may bring with themselves small to large amount of dust from the Sahara desert, with important consequences on the transparency of the sky. Meteorological satellites gave us some impressive examples of such these phenomenon.
We show here the results of trying a correlation between dust-pollution data and the nightly atmospheric extinction measured at other telescopes. While the transparency is mostly affecting the astronomical work, other effects like changes of air temperature and humidity are clearly visible; for this reason dust-pollution data are also compared with the weather data recorded at the TNG meteo tower.
SLODAR (SLOpe Detection And Ranging) is a technique for real-time monitoring of the vertical profile of atmospheric optical turbulence strength and velocity from Shack-Hartmann wavefront sensor observations of bright binary stars. Results are presented from SLODAR systems deployed at the William Herschel telescope and Mercator telescope in La Palma. We describe the design of a prototype portable SLODAR instrument which is being developed as a site characterization tool for ELTs, and for real-time support of astronomy with adaptive optics.
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