CaNaPy is an experimental Laser Guide Star Adaptive Optics facility designed to demonstrate pre-compensation of a sodium LGS uplink beam, and to investigate wavefront sensing on the pre-compensated LGS using a Pyramid wavefront sensor. CaNaPy was installed at the 1m ESA OGS telescope at the Observatorio del Teide, Tenerife, in autumn 2023. Here we report on the commissioning phase activities followed by the first on-sky results on LGS uplink pre-compensation. CaNaPy is developed at ESO in collaboration with ESA, Durham University, IAC, INAF, and Microgate, with scientific collaborators from ANU and the RICAM institute.
The CaNaPy project pioneers a novel configuration in Visible Wavelength Laser Guide Star Adaptive Optics (LGS-AO). Collaboratively established by ESA and ESO, it hosts a 70 W CW 589nm laser, employing upward propagation pre-compensation on sodium LGS via a pyramid wavefront sensor (Py-WFS). Operating at Teide Observatory, its aim is to demonstrate the benefits of pre-compensating the LGS upward propagation path, reducing LGS spot size in the mesosphere. This enhances Sodium optical pumping effects and significantly boosts Py-WFS sensitivity. Early on-sky experiments, using Natural Guide Stars, are underway, comparing results with simulation predictions using PASSATA. These trials mark a critical milestone in advancing visible wavelength LGS-AO, promising better resolution and sensitivity with reduced laser power requirements.
We report on the novel ALASCA (Advanced LGS AO for Satellite Communication Assessment) facility being built for ESA by a consortium of industry and national research institutes under the ScyLight program. The aim of ALASCA is to create a facility for Optical Feeder Links (OFL) field tests, as well as to demonstrate at the ESA Optical Ground Station in Tenerife, starting in 2023, 24/7 reliable operation of optimal Optical Feeder Links based on Laser Guide Star Adaptive Optics (LGS-AO) to solve the point-ahead problem on ground-space laser communications. Space optical communication represents a technological challenge due to its specific requirements and merit parameters; the consortium’s extensive experience in LGS-AO in the astronomical field allows an expert technology transfer to earth-space communication. This will enhance the review of the ALASCA’s main requirements, their implementation by a proper tailoring of the modular solutions that will be adopted by the design, facing the new challenges at system level posed by the OFL applications compared to astronomical solutions. The ALASCA project will, last but not least, provide a technology assessment and a development roadmap towards the industrial exploitation of a 24/7 operational Optical Ground Station (OGS). We will provide an overview of the ALASCA project, its goals, phases and planned timeline up to the field experiments; the presentation will then focus on the project status, including also the simulations results of LGS-AO assisted OFL.
In this paper we speak about the double-axicon unit built for the CaNaPy instrument, the LGS-AO backbone of the ESA ALASCA TRL6 facility, to demonstrate Optical Feeder Links for Satellite Communications in 2023 using Laser Guide Star Adaptive Optics technologies. The ALASCA system will co-propagate a guidestar laser (λ = 589 nm) and an infrared laser (λ = 1075 nm), using the monostatic approach through the entire 1-m Optical Ground Station (OGS) at Teide Observatory, Canary Islands (Spain). Provisions have been made to use either the full aperture or a section of the OGS primary mirror. The OGS telescope secondary mirror would introduce 30% central vignetting losses on the uplink laser beams. In order to minimise the losses, a double-axicon module shapes the gaussian beam as an annulus, thus optimises the laser profile to match the telescope pupil and nulls the losses, achieving the most efficient coupling to the OGS telescope. We present the CaNaPy axicon module design and analysis for the 589-nm laser as well as the ALASCA axicon module design for the OFL; we describe the tests done and the gain achieved in power transmission when shaping the laser compared to propagating a conventional Gaussian beam through a telescope with a non-negligible central obstruction.
The next generation of large telescopes will use segmented primary mirrors. These segments must be co-aligned to a small fraction of the optical wavelength. Any difference in piston, tip, and tilt will cause a degradation of the final image. In this paper, we investigate some methods to detect, in particular, the discontinuous optical phase steps at the edges between adjoining segments. For this experiment, we use the GHOST bench developed by the ESO Adaptive Optics Systems group. This bench includes a Spatial Light Modulator (SLM) which generates known wavefronts at high resolution and a 4-facet bulk pyramid used as a wavefront sensor. The SLM emulates physical phase plates, and specifically, misaligned segmented mirrors. The measurements of the emulated phase plates are then compared to the results when using physical phase plates. This work is performed in the context of CaNaPy, which will carry out an on-sky test of detecting misalignments of segmented mirrors.
This conference presentation was prepared for the Ground-based and Airborne Telescopes IX conference at SPIE Astronomical Telescopes + Instrumentation, 2022.
We report on the visible LGS-AO experimental facility which we are building to be installed at the 1m ESA Optical Ground Station at Observatorio del Teide, Tenerife, Canary Islands. We focus on the system aspects related to optics. The instrument will be a novel facility to perform strategic LGS-AO technology R&D in future years, demonstrating a 50+ W CW 589nm laser, uplink laser beam pre-compensation on sodium LGS in pulsed laser operation. The rationale for the LGS-AO facility is to have a synergy between astronomical and space awareness adaptive optics, to technologies for astrophysics and optical communication with satellites (Optical Feeder Links), including daytime LGS-AO, for future OGS systems.
Imaging system design is not limited to circular aperture shapes. However, non-circular apertures require a different set of polynomials, because broadly used Zernike polynomials are not orthogonal over non-circular shapes. Applying the Gram-Schmidt orthogonalization process provide the adopted set of orthogonal polynomials over selected non-circular aperture shape. However, when the aperture shape is complicated, non-symmetrical, the resulting set of polynomials can be very complex. In the case of odd-sided polygons is the analytical form of the polynomials inappropriate due to their complexity and these polynomials have to be expressed in their numerical form. Concerning the laborious complexity of some non-circular polynomials, we analyze the desired accuracy of such polynomials and their performance of the wavefront modeling according to classical circular Zernike polynomials.
A new generation of the WILLIAM (WIde-field aLL-sky Image Analyzing Monitoring system) camera includes new features such as monitoring of rain and storm clouds during the day observation. Development of the new generation of weather monitoring cameras responds to the demand for monitoring of sudden weather changes. However, new WILLIAM cameras are ready to process acquired image data immediately, release warning against sudden torrential rains, and send it to user's cell phone and email. Actual weather conditions are determined from image data, and results of image processing are complemented by data from sensors of temperature, humidity, and atmospheric pressure. In this paper, we present the architecture, image data processing algorithms of mentioned monitoring camera and spatially-variant model of imaging system aberrations based on Zernike polynomials.
KEYWORDS: Systems modeling, Imaging systems, Zernike polynomials, Point spread functions, Cameras, Wavefront aberrations, RGB color model, Sensors, Data modeling, Stars
Extremely wide-field imaging systems have many advantages regarding large display scenes whether for use in
microscopy, all sky cameras, or in security technologies. The Large viewing angle is paid by the amount of aberrations,
which are included with these imaging systems. Modeling wavefront aberrations using the Zernike polynomials is
known a longer time and is widely used. Our method does not model system aberrations in a way of modeling
wavefront, but directly modeling of aberration Point Spread Function of used imaging system. This is a very complicated
task, and with conventional methods, it was difficult to achieve the desired accuracy. Our optimization techniques of
searching coefficients space-variant Zernike polynomials can be described as a comprehensive model for ultra-wide-field
imaging systems. The advantage of this model is that the model describes the whole space-variant system, unlike the
majority models which are partly invariant systems. The issue that this model is the attempt to equalize the size of the
modeled Point Spread Function, which is comparable to the pixel size. Issues associated with sampling, pixel size, pixel
sensitivity profile must be taken into account in the design. The model was verified in a series of laboratory test patterns,
test images of laboratory light sources and consequently on real images obtained by an extremely wide-field imaging
system WILLIAM. Results of modeling of this system are listed in this article.
Color grading of archive films is a very particular task in the process of their restoration. The ultimate goal of color grading here is to achieve the same look of the movie as intended at the time of its first presentation. The role of the expert restorer, expert group and a digital colorist in this complicated process is to find the optimal settings of the digital color grading system so that the resulting image look is as close as possible to the estimate of the original reference release print adjusted by the expert group of cinematographers. A methodology for subjective assessment of perceived differences between the outcomes of color grading is introduced, and results of a subjective study are presented. Techniques for objective assessment of perceived differences are discussed, and their performance is evaluated using ground truth obtained from the subjective experiment. In particular, a solution based on calibrated digital single-lens reflex camera and subsequent analysis of image features captured from the projection screen is described. The system based on our previous work is further developed so that it can be used for the analysis of projected images. It allows assessing color differences in these images and predict their impact on the perceived difference in image look.
There are various deconvolution methods for suppression of blur in images. In this paper a survey of image deconvolution techniques is presented with focus on methods designed to handle images acquired with wide-field astronomical imaging systems. Image blur present in such images is space-variant especially due to space-variant point spread function (PSF) of the lens. The imaging system can contain also nonlinear electro-optical elements. Analysis of nonlinear and space-variant imaging systems is usually simplified so that the system is considered as linear and space-invariant (LSI) under specific constraints. Performance analysis of selected image deconvolution methods is presented in this paper, while considering space-variant nature of wide-field astronomical imaging system. Impact of nonlinearity on the overall performance of image deconvolution technique is also analyzed. Test images with characteristics obtained from the real system with space-variant wide-field input lens and nonlinear image intensifier are used for the performance analysis.
This paper deals with evaluation and processing of astronomical image data, which are obtained by a wide-field all-sky image analyzing monitoring system (WILLIAM). The WILLIAM is an additional experimental camera for project MAIA equipped with wide field lens. The system can detect stellar objects as faint as 6th magnitude. Acquired image data are processed by an algorithm for stellar object detection and identification which is based on coordinates transfer function. Cartesian coordinates at the image data are transformed to horizontal coordinate system. This coordinate system allows searching in astronomical catalogues of stellar objects. This paper presents the components of WILLIAM, its measured electro-optical characteristics and some results of identification.
Additional monitoring equipment is commonly used in astronomical imaging. This electro-optical system usually complements the main telescope during acquisition of astronomical phenomena or supports its operation e.g. evaluating the weather conditions. Typically it is a wide-field imaging system, which consists of a digital camera equipped with fish-eye lens. The wide-field imaging system cannot be considered as a space-invariant because of space-variant nature of its input lens. In our previous research efforts we have focused on measurement and analysis of images obtained from the subsidiary all-sky monitor WILLIAM (WIde-field aLL-sky Images Analyzing Monitoring system). Space-variant part of this imaging system consists of input lens with 180 fi angle of view in horizontal and 154 fi in vertical direction. For a precise astronomical measurement over the entire field of view, it is very important to know how the optical aberrations affect characteristics of the imaging system, especially its PSF (Point Spread Function). Two methods were used for characterization of the space-variant PSF, i.e. measurement in the optical laboratory and estimation using acquired images and Zernike polynomials. Analysis of results obtained using these two methods is presented in the paper. Accuracy of astronomical measurements is also discussed while considering the space-variant PSF of the system.
Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe. They are produced during the collapse of massive stellar-sized objects, which create a black hole and eject material at ultra-relativistic speeds. They are unique tools to study the evolution of our Universe, as they are the only objects that, thanks to their extraordinary luminosity, can be observed during the complete history of star formation, from the era of reionisation to our days.
One of the main tools to obtain information from GRBs and their environment is optical and near-infrared spectroscopy. After 17 years of studies spectroscopic data for around 300 events that have been collected. However, spectra were obtained by many groups, at different observatories, and using instruments of very different types, making data difficult to access, process and compare.
Here we present GRBspec: A collaborative database that includes processed GRB spectra from multiple observatories and makes them available to the community. The website provides access to the datasets, allowing queries based not only on the observation characteristics but also on the properties of the GRB that was observed. Furthermore, the website provides visualisation and analysis tools, that allow the user to asses the quality of the data before downloading and even make data analysis online.
Most of the classical approaches to the measurement and modeling of electro-optical imaging systems rely on the principles of linearity and space invariance (LSI). In our previous research efforts we have focused on measurement and analysis of images obtained from a double station video observation system MAIA (Meteor Automatic Imager and Analyzer). The video acquisition module of this system contains wide-field input lens which contributes to space-variability of the imaging system. For a precise astronomical measurement over the entire field of view, it is very important to comprehend how the characteristics of the imaging system can affect astrometric and photometric outputs. This paper presents an analysis of how the space-variance of the imaging system can affect precision of astrometric and photometric results. This analysis is based on image data acquired in laboratory experiments and astronomical observations with the wide-field system. Methods for efficient calibration of this system to obtain precise astrometric and photometric measurements are also proposed.
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