In this paper, wide-field adaptive optics systems for ground-based solar telescopes are discussed. The features of constructing adaptive optics systems based on layer- and object-oriented approaches are considered. It is shown that the optimal adaptive optics system for the Large Solar Vacuum Telescope (LSVT) should be created on the basis of optical conjugation of deformable mirrors with turbulent layers of the atmosphere, the system for determining wavefront aberrations should be based on the use of a set of a narrow field of view sensors conjugated with telescope aperture, as well as a multi-directional wavefront sensor for turbulence tomography, designed on the basis of an object-oriented approach (measurements of wavefront aberrations in different directions). The schemes of pupil imagers that provide optical conjugation of the LSVT wavefront sensor with heights of 3 km as well as the upper atmospheric levels are considered. Direct optical conjugation of the Shack-Hartmann sensor with a turbulent layer is limited by a height of about 3 km (due to significant vignetting).
This paper is aimed at finding suitable sites for a large ground-based millimeter/submillimeter telescopes. We discuss the most promising regions in the world in terms of low values of precipitable water vapor. A separate issue is the regions with low values of precipitable water vapor within Russia, China and Uzbekistan.
The present work focuses on an algorithm for obtaining data on the positions of the centers of gravity of subimages of sunspots from the Shack–Hartmann sensor measurements. The analysis of the positions of the centers of gravity of subimages formed by spaced subapertures is used in determining the verical profiles of optical turbulence and, specifically, the structural constant of turbulent fluctuations of the air refractive index C2n . The characteristics of optical turbulence determine the quality of astronomical images obtained on ground-based telescopes.
The paper describes the results of measuring the structural parameters of optical turbulence for different altitudes in the atmosphere above the Large Solar Vacuum Telescope of the Baikal Astrophysical Observatory. The structural parameters of optical turbulence we estimated from the measurement data of the Shack-Hartmann sensor for individual atmospheric layers by applying the analysis of wavefront distortions in crossed optical beams. To estimate the structural parameters of optical turbulence, we propose an approach based on statistical averaging normalized dimensionless characteristics of turbulence, the Fried parameter and averaged profile of optical turbulence at a given site.
The paper presents the results of studies of atmospheric turbulence in the lower part of the atmospheric boundary layer. At different heights of the atmosphere (8, 121, 301 m), the energetic loses of air flow for the generation of turbulent kinetic energy are calculated for different linear scales. It is shown that on small scales the consumption of mean kinetic energy to energy of turbulence reaches 32% in winter (at 8 m) and 34% (at 301 m) in summer. The paper also uses the WRF model, for the first time in Russia, to determine secondary atmospheric parameters (characteristics of optical turbulence). The vertical profiles of the outer scale of turbulence and the structural constant of fluctuations of the refractive index of air at the Sayan Solar Observatory were determined in case of small seeing. Estimated averaged vertical profile of C2N (z) at the Sayan solar observatory site corresponds to the Fried parameter = 12.1 cm in the atmospheric layer 100 m - 30 km at light wavelength = 500nm (from 15/07/2015 to 23/07/2015).
The quality of astronomical observations is strongly related to the quality properties of the atmosphere. The studies of the atmosphere above observing sites are important for observation planning, instrument optimization, adaptive optics development. The high-altitude distributions of wind speed over the 6-meters Big Telescope Alt-Azimuthal of Special Astrophysical Observatory of Russian Academy Science for astronomical site characterization and the development of adaptive optics techniques are study. The data used from the NCEP/NCAR and ERA-Interium reanalysis, which is widely acknowledged as being reliable. Seasonal behaviors (mean, median, quantiles) of vertical distributions of wind speed are presented. Statistical analyses of the 200-mbar wind speed used as useful parameter for ranking astronomical sites in term of their suitability for adaptive optics is performed. The long-time trend of V200 is presented.
The paper presents the first results of comparative study of the optical turbulence at the sites of the Fuxian Lake Solar Observatory (FSO) and the Baikal Astrophysical Observatory (BAO). The distributions of the probability of the Fried parameter estimated from Shack-Hartmann wavefront sensor measurements are analyzed.
A multi-cascade adaptive optical system for imaging and image stabilization for the Large Solar Vacuum Telescope is described. This system was created in 2017 by specialists of the V.E. Zuev Institute of Atmospheric Optics SB RAS, Tomsk, with the technical support of the Institute of Solar-Terrestrial Physics SB RAS, Irkutsk. The system has been tested at the Large Solar Vacuum Telescope (Baikal Astrophysical Observatory) and demonstrated its efficiency. Along with the first cascade of adaptive image stabilization by a tip-tilt corrected mirror, this system employs the second imaging cascade based on correction with a flexible mirror controlled by a specialized wavefront sensor, as well as the third cascade for real-time post-detector processing of video camera frames. Reliable experimental data confirming the efficiency of the multi-cascade adaptive system for image formation and stabilization have been obtained. Three highrate digital video cameras recording simultaneously digital images with rates from 300 to 980 frames per second were used to test the system. The mirror correcting wavefront tilts and operating in a closed optical feedback loop was controlled by the specially developed software including the fast correlation tracking algorithm. The post-detector digital imaging was performed with a special software for processing of video camera frames in real time with the use of modern high-speed parallel algorithms based on the Intel MKL and IPP libraries.
We propose the concept of the new SCIDAR-based method to determine the characteristics of the atmospheric turbulent layers including its heights and strength. In this paper we discuss the possibility of the estimating of the heights of the atmospheric turbulent layers from the vertical profiles (along line of sight) of dimensionless characteristics of turbulence. The method is based on the analysis of the scintillation in crossed optical beams (with temporal lag) on the spaced subapertures of single Shack-Hartmann sensor (with field of view of order 40 arc.sec.) conjugated with the aperture.
In the paper we discuss the results of the measurements of the nighttime optical turbulence parameters performed by the mobile astronomical telescope MEADE at the Large solar vacuum telescope of the Baykal Astrophysical Observatory site. Measurements have been performed in the clear sky, when the surface-layer wind speed < 2 m/sec. The studies of the optical turbulence in the nighttime are relevant for improving our knowledge about mechanisms of the turbulence generation and dissipation at this site. It is known that diurnal variations in the energy and momentum fluxes, turbulence strength are modulated by topography. Regional peculiarities of the energetic structure of atmospheric fluctuations (including optical turbulence) is the basis for development of the parametrization methods.
In the paper we review the widefield adaptive optics systems including GeMS, LINC-NIRVANA, MAD, `Imaka, CANARY, RAVEN, MCAO installed on such telescopes as VTT, GREGOR, NST and DST. Review is relevant for the design Russian project of the Large solar telescope LST-3. The heights of the optical conjugation of the adaptive optics elements with turbulence layers as well as peculiarities in the MCAO systems` design are compared for different sites.
The paper discusses the problem of finding solar-terrestrial relations. The features of the possible optical screen influence of the atmosphere on the propagation of solar radiation in different phases of solar activity are considered. Changes of the scattered radiation at different heights are analyzed separately. Considering the small amplitudes of fluctuations in the level of diffuse radiation due to solar activity, the possible causes of disynchronization in changes in Wolf numbers and diffuse radiation are discussed. The concept of the work is modulation of incoming solar energy may be due to changes in the optical properties of the earth's atmosphere, including its transparency.
To restore the height profiles of the atmospheric turbulence we used the analysis of the spatial crosscorrelation functions of wavefront distortions registered by the Shack-Hartmann sensor of the adaptive optics (AO) system of Large solar vacuum telescope. In the paper the results of analysis of spatial crosscorrelation function within the field of view ~35 arcsec are discussed. It is shown that the wavefront distortions formed within the field of view ~35 arcsec are not random. There are the repetitive hills of spatial crosscorrelation functions in the field of view at the same intervals for different space subapertures. It is shown that spatial crosscorrelation functions do not contain pronounced kernel for finding the exact position of the atmospheric layer contributing to significant distortions in the wavefront incident on the telescope aperture.
The spatial analysis of the wavefront distortions registered by the Shack-Hartmann sensor of the adaptive optics (AO) system of Large solar vacuum telescope have been performed. In the paper the results of analysis of spatial structure of the wavefront within the field of view ~35 arcsec are discussed. It is shown that the wavefront distortions formed within the field of view ~35 arcsec are not random. There are the repetitive hills of spatial crosscorrelation functions in the field of view at the same intervals for different space subapertures. It is shown that spatial crosscorrelation functions do not contain pronounced kernel for finding the exact position of the atmospheric layer contributing to significant distortions in the wavefront incident on the telescope aperture.
The article proposes a design of sensor of optical distortions in a wide field of view for the adaptive optical system of the Large Solar Vacuum Telescope. The calculation of the optical scheme of the sensor based on the use of two wavefront sensors was performed. The working field of view of the adaptive system with an additional sensor for determining the distortions of the wavefront is 120 arc sec. Adjusting the field of view of each Shack-Hartmann sensor up to 30 arc sec is provided by field diaphragms. It is shown that for the used second imager, the quality of subimages remains high, the standard deviation is λ /80.
One of the approach to calculate the characteristics of the air refractive index fluctuations along line of sight for multiconjugated adaptive optics is based on the triangulating the wavefront distortions or/and scintillation amplitudes analysis. The description of the experiments aimed to measurements of the wavefront distortions and scintillation fluctuations is given. The scheme for recovering the optical distortions (wavefront) at the different heights is discussed. The results of changes of the wavefront distortions measured by Shack-Hartmann sensor in the spaced regions of images are discussed. The results obtained may be used for estimation of the real amplitudes of the wavefront distortions in crossed optical beams at the different heights using such method as SDimm+[ 5].
The Baikal Astrophysical Observatory of Institute Solar- Terrestrial Physics of Siberian Branch of Russian Academy Sciences is located at an altitude of about 700 meter above sea level on the shore of Lake Baikal, Russian Federation. Large Solar Vacuum Telescope (LSVT) is the main telescope of the Baikal Astrophysical Observatory. We develop models of vertical profile of atmospheric turbulence (the refractive-index structure constant) and wind speed at the BAO for adaptive optical system design of LSVT. We also presented vertical profile wind speed and the refractive-index structure constant is obtained from NCEP/NCAR Reanalysis base.
This paper describes the features of the two-mirror adaptive system for correcting atmospheric disturbances of the Large Solar Vacuum Telescope, developed with allowance for the correction of instrumental vibrations of telescopes in a wide amplitude-frequency range with an open siderostat supply mirror. Correction of the general slopes of the light wave front and its deformations is carried out separately. The adaptive optical system is designed to work with extended light sources (the Sun), which have a low contrast of image details.
We study seasonal variations of the vertical distribution of wind speed at the Baikal Astrophysical Observatory (BAO) using NCEP/NCAR Reanalysis data base for development of adaptive optical system of Large Solar Vacuum Telescope (LSVT). The statistics of wind speed including mean and median profile, the first and third quartiles are calculated. Also we analyzed seasonal variations of wind speed on the pressure level 200-mbar, as parameter for estimation of suitable of the site for adaptive optics and level of atmospheric optical turbulence.
The work discusses the optical turbulence structure and dynamics at the Baykal Astrophysical Observatory (BAO) site. The characteristics of the optical turbulence including Fried radius, isoplanatic angle are analyzed. Estimates of the variations of the height profiles of the air refraction index turbulent fluctuations at the Baykal Astrophysical Observatory are given. Using the mean height profile of the structure characteristic of the air refraction index turbulent fluctuations, diurnal variations of the Fried radius at the BAO site are estimated.
The optical turbulence characteristics statistics including "seeing", Fried radius, wind speed height profiles are discussed. Distribution of the mean Fried radius obtained from the data of image motion measurements by the Brandt sensor is given. Also, the Fried radius values calculated from the Shack-Hartmann data are given. Using the height profile of the structure characteristic of air refractive index fluctuations obtained from spectral multiscale turbulence model the results of the Fried radius simulations from micrometeorological mast measurement data given.
The work discusses the spatial scales of atmospheric optical distortions including the outer scale of turbulence and the Fried radius. It is assumed that the energy spectrum of atmospheric turbulence is not limited strictly [6] and the outer scale is considered in application to astronomical telescopes. In the case when the telescope diameter is larger or comparable with the outer scale the optical distortions substantially differ from the results of the Kolmogorov model. For a given diameter it is possible to introduce a certain spatial scale at distances larger than the size of which the refractive index fluctuations no longer have a significant effect on the quality of astronomical images. Estimates of the outer scale of turbulence are reported for both a atmospheric layer from 0 up to 20 km and surface layer.
According to the work plan for the RSF project, during 2016 measurements were taken in all seasons of the year: February, April, May, August and October. With the use of the whole set of equipment of the stand on the BSVT, the task was set to work out methods for recording and correcting the distortions of the phase of optical radiation passing through a layer of turbulent atmosphere. Complex on-site meteorological observations were organized and conducted at the site of the BSVT. Observations were carried out with the aim of developing and improving the local computational model of turbulent characteristics in the entire thickness of the active atmosphere in the "optical turbulence" range, including the surface layer. As the initial meteorological information for calculations, the model uses two-level data of pulsating observations of temperature and wind speed at the BSVT site, as well as current NCEP/NCAR archival data for the period from 1948 to 2015.
The dynamics of turbulent characteristics including air index refraction vertical variations as well as effective turbulent velocity important for the functioning of the Large solar vacuum telescope (LSVT) adaptive optics system is considered. Long-term changes of the effective turbulent velocity and Fried radius in the atmospheric layer from 0 to 20 km are estimated using model of turbulence taking into account the shape of the energy spectrum over a wide range of spatial and temporal scales. The possible experimental local model of Fried radius changes is discussed for the Large solar vacuum telescope site.
The problem of selection of sites for modern telescopes which are characterized by favorable conditions for astronomical observations is discussed. A number of new sites to telescope construct with separate mountain peaks (above 2 km) as well as high image quality (astronomical seeing) and low level of cloud are pointed.
The features of air index refraction vertical variations up to 20 km at the Large solar vacuum telescope site are discussed. The possible local model of air index refraction fluctuations are supposed at the Large solar vacuum telescope site.
The results of optical measurements of the quality of astronomical seeing on the Large solar vacuum telescope (LSVT) in spring and summer are shown. It is noticed that in the summer measurements, the quality of vision is higher on average 2.5 times than in the spring. Information on the seasonal variability of the astronomical quality of vision can be useful in the planning of scientific experiments for the LSVT, as well as to improve the performance of existing adaptive system
In this article, we describe the development of the newest adaptive optics system for the Big Solar Vacuum Telescope of the Baikal Astrophysical Observatory. This system is a result of collaboration between VE Zuev Institute of Atmospheric Optics SB RAS, Tomsk, and Institute of Solar-Terrestrial Physics SB RAS, Irkutsk. The system includes two active mirrors for the correction: domestic tip-tilt and bimorph deformable (Active Optics NightN Ltd.), and separate wavefront sensors (WFS). A correlation S-H wave-front sensor is based on a Allies Prosilica GX-1050 GigE camera with speed of 309 Hz and frame size of 1248x1248 pixels. A personal computer is used for bimorph deformable mirror image processing. The mirror was successfully used during the 2010–2014 observing seasons. The system developed is capable of correcting up to 35 modes, thus providing diffraction limited images at visible wavelengths.
The estimations of the Fried parameter according to micrometeorological and optical measurements in the atmospheric surface layer in the area of l. Baikal, Baikal astrophysical Observatory (BAO). According to the archive of NCEP/NCAR Reanalysis data obtained vertical distribution of temperature pulsations, and revealed the most pronounced atmospheric layers with high turbulence. It is established that the values of the fried parameter at the location of the BAO are in the range from 1.5 to 5.5 cm in inter, the atmospheric coherence radius is characterized by low values of the Fried parameter. Turbulyzed atmospheric layers of the atmosphere located at an altitude of about 2.5 km and 11.5 km above the observatory, respectively. The average values of the fried radius is 4.6 cm.
The estimations of the fried parameter according to micrometeorological and optical measurements in the atmospheric surface layer in the area of lake Baikal, Baikal astrophysical Observatory. According to the archive of NCEP/NCAR Reanalysis data obtained vertical distribution of temperature pulsations, and revealed the most pronounced atmospheric layers with high turbulence. A comparison of astronomical conditions vision in winter and in summer. By the registration of optical radiation of the Sun with telescopes, ground-based there is a need to compensate for the effects of atmospheric turbulence. Atmospheric turbulence reduces the angular resolution of the observed objects and distorts the structure of the obtained images. To improve image quality, and ideally closer to angular resolution, limited only by diffraction, it is necessary to implement and use adaptive optics system. The specificity of image correction using adaptive optics is that it is necessary not only to compensate for the random jitter of the image as a whole, but also adjust the geometry of the individual parts of the image. Evaluation of atmospheric radius of coherence (Fried parameter) are of interest not only for site-testing research space, but also are the basis for the efficient operation of adaptive optical systems 1 .
It is shown that atmospheric turbulence is not suppressed completely in strongly stably stratified conditions when Richardson's number exceeds its critical value. It is worth to note that airflow is laminar according classical ideas of the turbulence theory when Richardson's number values are supercritical. It is shown that in the stably stratified atmospheric surface layer under conditions of large vertical temperature gradients and low wind speeds, atmospheric turbulence is often characterized by intermittent structure and in some parts of space intensity of fluctuations can reach high values. The results of experimental investigations of optical instability conducted out along the horizontal path in the stably stratified atmospheric surface layer are discussed.
Last results of experimental researches of the decrease of the light fluctuations in coherent turbulence are presented. Measurements were executed in the autumn of 2013 in a high-mountainous Sayan solar observatory. It is found that astronomical observations are accompanied by periodical transition from the Kolmogorov’s turbulence to coherent turbulence. Such a change of the turbulence type gives intermittency in jitter of the astronomical images.
The results of investigations of vertical profile of turbulent inhomogeneities of the air refractive index using NCEP / NCAR Reanalysis data are discussed in this paper. Model used for calculations is based on the spectral features of atmospheric turbulence characteristics in a wide range of scales. The differences of the shapes of small-scale atmospheric turbulence spectra in the free atmosphere and the boundary layer are in the focus of the paper. The obtained results may allow us to estimate characteristics of turbulent and, thus, parameters of adaptive optics systems.
The hypothesis to explain observed warming climate is proposed. It is assumed that land existed in the past at the location of the Arctic Ocean, which lowered under the weight of the Arctic ice sheet. As a result of the lowering the altitude of the land, ocean began to wash the glacier, which led to its melting. Nowadays, the final stage of the process is observed. Melting of outer polar regions of the Northern Hemisphere ice is the main cause of the observed warming. The details of the proposed mechanism and a number of additional effects are discussed.
The results of investigations of small-scale atmospheric turbulence are discussed. The differences of the shapes of smallscale atmospheric turbulence spectra in the free atmosphere and the boundary layer are in the focus of the paper. The obtained results may allow us to estimate the characteristics of small-scale (optical) atmospheric turbulence parameters and adaptive optics systems.
Energy spectra of wind speed fluctuations and temperature fluctuations are calculated at altitudes between 2 and 301 m
for the period from January 1, 2008 to 31 December, 2008 by using results of numerical analysis of high-altitude
meteorological mast data. Comparison of the shape of the calculated spectra with known shapes has confirmed presence
of two basic regions of wavenumbers with an approximate "-3" dependence and "-5/3" dependence. The result obtained
has been used for estimating of high-frequency characteristics of atmospheric turbulence using network meteorological
data.
The devices and components of adaptive optical system ANGARA, which is developed for image correction in the Big
solar vacuum telescope (BSVT) at Baykal astrophysical observatory are described. It is shown that the use of
modernized adaptive system on BSVT not only reduces the turbulent atmospheric distortions of image, but also gives a
possibility to improve the telescope developing new methods of solar observations. A high precision Shack-Hartmann
wavefront (WF) sensor has been developed on the basis of a low-aperture off-axis diffraction lens array. The device is
capable of measuring WF slopes at array sub-apertures of size 640X640 μm with an error not exceeding 4.80 arc.sec.
Also the modification of this sensor for adaptive system of solar telescope using extended scenes as tracking objects,
such as sunspot, pores, solar granulation and limb, is presented. The software package developed for the proposed WF
sensors includes three algorithms of local WF slopes estimation (modified centroids, normalized cross-correlation and
fast Fourier-demodulation), as well as three methods of WF reconstruction (modal Zernike polynomials expansion,
deformable mirror response functions expansion and phase unwrapping), that can be selected during operation with
accordance to the application.
This paper summarizes results received by authors for last decade on the problem of the atmospheric coherence turbulence. Also shows some new results of the unpublished researches. According to our data the coherent turbulence is the result of the self-organizing non-linear processes in continuous media, including in the atmospheric air. New theoretical and experimental data are considered, it confirm the effect of the decreasing of the optical waves fluctuations in the coherence turbulence.
The paper describes the results of the measurements of telescope actroclimate characteristics in the mountains on the lake Baikal shore and in the Sayan foothills. For the measurements a mobile ultrasonic meteorological system was used. It is shown that the place of arrangement of telescopes on the lake Baikal shore is favorable to daytime observations, the quality of astronomical images during daytime observations (in summer and in the autumn) will be higher than during night observations. It is demonstrated that in the mountain conditions the turbulence is of not Kolmogorov character and
has marked characteristics of the coherent structure.
Processes of Benard cell origination and disintegration in air are studied experimentally. It is shown that temperature
gradients cause a Benard cell. Our data confirm the main scenarios of turbulence origination (Landau-Hopf, Ruelle-Takens, Feigenbaum, and Pomeau-Menneville stochastic scenarios). It is ascertained that a Benard cell disintegrates according to the Feigenbaum scenario. In this case, the main vortex in the Benard cell is decomposed into smaller ones as a result of ten period-doubling bifurcations. It is shown that the resulting turbulence is coherent and determinate; the
fractal character (local self-similarity) of its spectrum is found.
These results allow the definition of a coherent structure as a compact formation containing a long-lived threedimensional
hydrodynamic cell (originating from long-term action of thermodynamic gradients) and products of its discrete coherent cascade disintegration. The coherent structure answers all the signs of chaos occurrence (turbulence) in typical thermodynamic structures. On the base of the results, presented in this work, a coherent structure can be considered as a key turbulence element. It is shown that the real atmospheric turbulence is the result of mixing of different coherent structures.
Based on the results of repeated measurements of under dome airstreams parameters of the AZT-33 telescope, some conclusions have been drawn, allowing improvement in quality of astronomic images in the telescope. After fulfillment of a part of recommended works, changes of under dome climate were compared with the measurements of 2005. New measurements verify the results obtained in 2005. Mixing of warm and cold air is observed inside the telescope after dome opening as well as one-order-of-magnitude increase of turbulence intensity in front of the input telescope mirror after dome opening. A changed pattern of under dome airstreams has been constructed. Further measures on qualitative thermal insulation of the under dome room are recommended. Astronomic observations are to be carried out only after
ending of transient processes concerned with dome opening.
High-altitude profiles of the parameters of atmospheric air currents in the lower surface layer were measured with the
use of a meteorological mast of 32 m in height. A mobile ultrasonic meteosystem was used for the measurements. The
theory of similarity for turbulence in anisotropic boundary layer has been verified. The measured vertical profiles of
main turbulence parameters have an oscillating character. High-altitude profiles of vertical outer scale are given,
reconstructed from measurements by two independent techniques. An equation for the outer turbulence scale is given,
determined by the departure from the 2/3-law in the structure temperature function. This scale depends on temperature
dispersion and structural characteristic of temperature fluctuations. A satisfactory agreement between values of such
outer scale and those of the Tatarskii outer scale is observed.
The possibility of applying adaptive correction to ground-based solar astronomy is considered. Several experimental
systems for image stabilization are described along with the results of their tests. As a result of the installation of the first
order adaptive-optics system, the Big Solar Vacuum Telescope (BSVT) acquired the new quality. Different ways of
development of an adaptive correction to be used in the BSVT of the Baikal Astrophysical Observatory are discussed.
Tests of the modified correlation sensor (MCS) at BSVT have shown that at a proper choice of the filtering function
parameters, the MCS reliably measures shifts of the solar granulation image in the telescope first focus under good
visibility conditions. The MCS, as a part of the adaptive optical system, was intended for measuring the image shift in
the telescope second focus. It turned out that the image quality becomes noticeably worse at image transfer to the second
focus. The MCS measures the image shift of solar granulation in the second focus only under extremely good visibility
conditions and certain granulation structure. Reduction of the telescope entrance aperture to 170 mm insignificantly
affects the image quality and, therefore, the MCS operation.
The possibility of applying adaptive correction to ground-based solar astronomy is considered. Several experimental
systems for image stabilization are described along with the results of their tests. Using our work along several years and
world experience in solar adaptive optics (AO) we are assuming to obtain first light to the end of 2008 for the first
Russian low order ANGARA solar AO system on the Big Solar Vacuum Telescope (BSVT) with 37 subapertures
Shack-Hartmann wavefront sensor based of our modified correlation tracker algorithm, DALSTAR video camera, 37
elements deformable bimorph mirror, home made fast tip-tip mirror with separate correlation tracker. Too strong daytime
turbulence is on the BSVT site and we are planning to obtain a partial correction for part of Sun surface image.
The paper presents the results of measurements of characteristics of local astroclimate in special production areas of the
Large solar vacuum telescope (the Baikal astrophysical observatory of the Institute of Solar-Terrestrial Physics SB
RAS). It is demonstrated that the temperature gradients in the telescope rooms are the cause of the initiation of the
Benard cell and originating (incipient) turbulence in the pavilion of the astronomical spectrograph. The characteristics of
the originating turbulence were studied in detail. It has been found that the measurements date have supported the basic
scenarios of stochastization (Landau-Hopf, Ruelle-Takens, Feigenbaum, Pomeau-Menneville scenarios). The
Feigenbaum bifurcation diagram has experimentally been supported. It is shown that the basic vortex in Benard cell
breaks down into smaller vortices as the result of ten bifurcations of the period duplication. It has been found that the
originating turbulence introduced large errors in the data of spectral measurements, even at the path of small length. The
horizontal random displacements of spectral lines, appearing due to the pavilion effects, in the horizontal Ebert scheme
can reach 1 second of arc. In this case the line displacements occur slowly, at the frequency about 0.01 Hz. Because of
low frequencies of line displacements the originating turbulence by its optical characteristics approximated the regular
refraction.
The paper presents the results of measurements of characteristics of local astroclimate in special production areas of the
Large solar vacuum telescope (the Baikal astrophysical observatory of the Institute of Solar-Terrestrial Physics SB
RAS). It is demonstrated that the temperature gradients in the telescope rooms are the cause of the initiation of the
Benard cell and originating (incipient) turbulence in the pavilion of the astronomical spectrograph. The characteristics of
the originating turbulence were studied in detail. It has been found that the measurements date have supported the basic
scenarios of stochastization (Landau-Hopf, Ruelle-Takens, Feigenbaum, Pomeau-Menneville scenarios). The
Feigenbaum bifurcation diagram has experimentally been supported. It is shown that the basic vortex in Benard cell
breaks down into smaller vortices as the result of ten bifurcations of the period duplication. It has been found that the
originating turbulence introduced large errors in the data of spectral measurements, even at the path of small length. The
horizontal random displacements of spectral lines, appearing due to the pavilion effects, in the horizontal Ebert scheme
can reach 1 second of arc. In this case the line displacements occur slowly, at the frequency about 0.01 Hz. Because of
low frequencies of line displacements the originating turbulence by its optical characteristics approximated the regular
refraction.
This work presents the results of measurements of intradome astroclimate parameters of the AZT-14 telescope of Sayan
solar observatory of the ISTP SB. The picture of airflows concerned with the warm air run-out though leaky connections
and air mixing inside the telescope after dome opening is obtained. It is shown that the value of the structure
characteristic of the refractive index Cn2 in closed and open dome can 1.5-2 times differ. Essential turbulence
intensification in front of the entrance telescope mirror when dome opening is ascertained. Strongly unstable
stratification near the receiver is observable, caused by the stair opening in the concrete floor of the dome, which can
result in intensification of the refractive index fluctuations in the presence of even small heat sources. Conclusions are
drawn from the measurements, which can be related to all telescope of the considered class. It is necessary to prevent
foreign heat sources in the dome and block warmer airflows from the stair opening; astronomical observations are to be
carried out after completion of transient processes related to the dome opening.
The main purpose of this investigation was to estimate the influence of local natural condition on behavior of electric
field of the atmosphere. Observations were conducted nearby Listvyanka settlement at a south-west coast of the Lake
Baikal at three sites with different natural conditions and with minimal anthropogenic influence. The main permanent
observation site was organized at the territory of Baikal Astrophysical observatory (BAO) - at one of coastal hills about
220 meters above lake level. Temporally measurements were conducted (synchrony with the main site): in September -
inside the narrow and deep stream valley, at the distance about 2 km from the main observation site; in March - at the
lake ice, at the distance 5 km from the shore. Observations at the main site were conducted also at two levels: near
ground surface and at the top of solar telescope tower (26 meters above the ground).
The work presents the results of measuring the characteristics of local astroclimate near the Large Solar Vacuum
Telescope (LSVT, located in the Listvyanka village of Irkutsk region). For measurements we used a mobile ultrasonic
meteorological system "Meteo2M" designed at the Institute of Atmospheric Optics. The measurements were performed
near the telescope
and on the telescope siderostat platform near the dome and the mirror. Then we are measuring the high-altitude profiles
of the fluctuations of the refractive index (structure constant) Cn2 along the telescope tower. It has been established that
the profiles of the Cn2, the averaged temperature and other parameters do not coincide with the results of the similarity
theory for a flat underlying surface. In our measurements the oscillating behaviour of high-altitude profiles is observed.
On the basis of the results obtained we can explain the oscillating character by the presence of periodic inhomogeneities
of the underlying surface near the telescope, as the surface has various degrees of heating.
The AZT-33 astronomic telescope has been testes at Sayan solar observatory (Institute of Solar-Terrestrial Physics SB
RAS) with respect to the characteristics of intradome airflows, affecting the image quality. From the results of testing
the airflows in the telescope, some conclusions have been drawn, which allow the quality of astronomic images in
telescopes similar to AZT-33 to be improved. For example, there should be no foreign heat sources inside the telescope
dome during measurements. This means that measures should be undertaken to remove open slits in the concrete floor
and to block out warm airflows from the stair well. In addition, measurements should be carried out only after the
transient processes associated with the opening of the dome slit are fully accomplished.
The possibility of applying adaptive correction to ground-based solar astronomy is considered. Several experimental
systems for image stabilization are described along with the results of their tests. As a result of the installation of the
first order adaptive-optics system, the Big Solar Vacuum Telescope (BSVT) acquired the new quality. Different ways of
development of an adaptive correction to be used in the BSVT of the Baikal Astrophysical Observatory are discussed.
The possibility of applying adaptive-optics devices to ground-based solar astronomy and high-resolution spectroscopy is considered [1]. The several experimental adaptive-optics systems for image stabilization are described, as well as the results of its tests. Different ways of the development of the adaptive-optics system for use in the Big Solar Vacuum Telescope (BSVT) of the Baikal Astrophysical Observatory are discussed.
The possibility of applying adaptive-optics devices to ground-based solar astronomy and high-resolution spectroscopy is considered. Due to atmospheric turbulence the resolution of ground-based solar telescopes are limited to 1 arcsec on the average with short period of suarcsecond resolution at good sites. Application of adaptive correction is a ground-based telescope to improve image quality is possible to improve whole performance of telescope to obtain images with resolution about 0,3" and to improve resolution for spectral measurements of the Sun. Adaptive Optics represent a visible tool for increasing the resolution of ground-based telescopes to the level that will be needed to understand the physical processes occurring on the Sun. An experimental adaptive-optics system for image stabilization is described, as well as the results of its tests. Different ways of the further development of the adaptive-optics system for use in the Big Solar Vacuum Telescope (BSVT) of the Baikal Astrophysical Observatory are discussed.
Leonid Antoshkin, A. Borovik, Nina Botygina, Alexei Bulatov, Oleg Emaleev, N. Firstova, Boris Fortes, Victor Grigoryev, P. Kovadlo, Lidia Lavrinova, Vladimir Lukin, A. Petrov, Valery Skomorovsky, Alexander Yankov
The possibility of applying adaptive-optics devices to ground- based solar astronomy and high-resolution spectroscopy is considered. Due to atmospheric turbulence the resolution of ground-based solar telescopes are limited to 1 arcsec on the average with short period of subarcsecond resolution at good sites. Application of adaptive correction is a ground-based telescope to improve image quality is possible to improve whole performance of telescope to obtain images with resolution about 0.3' and to improve resolution for spectral measurements of the Sun. Adaptive Optics represent a visible tool for increasing the resolution of ground-based telescopes to the level that will be needed to understand the physical processes occurring on the Sun. An experimental adaptive- optics system for image stabilization is described, as well as the results of its tests. Different ways of the further development of the adaptive-optics system for use in the Big Solar Vacuum Telescope (BSVT) of the Baikal Astrophysical Observatory are discussed.
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