Multi-conjugate adaptive optics (MCAO) has been proved to obtain the high resolution images with a large field of view in solar observation. A solar MCAO experiment system had been successfully developed and tested at the 1-meter New Vacuum Solar Telescope (NVST) of Fuxian Solar Observatory. It consists of two deformable mirrors (DMs), a multidirection Shack-Hartmann wavefront sensor (MD-WFS), and a real-time controller. In order to command the two DMs, five guide regions were selected from the MD-WFS to retrieve a three-dimensional measurement of the turbulent volume based on atmospheric tomography. This system saw the first light in October, 2017, and a series of MCAO-corrected high resolution sunspots images were acquired. In this presentation, the MCAO experiment system is introduced, and the observation results are presented. Furthermore, a new MCAO system based on our proposed MCAO configuration with a high order ground layer adaptive optics and low order high altitude correction will be developed for the NVST as a regularly operating instrument for scientific observations of the sun.
Correlating Shack-Hartmann wavefront sensor is widely used in solar adaptive optics in which the relative shift between
different subapertures by correlation algorithm is computed, and then the control voltage by wavefront
reconstruction can be estimated to use for correcting the wavefront distortion induced by atmospheric turbulence. In this
paper, several different correlation algorithms including Cross-Correlation Coefficient, Absolute Difference Function,
Absolute Difference Function-Squared and Square Difference Function are used to estimate relative shift in correlating
Shack-Hartmann wave-front sensor with the different observed solar structure such as sunspot, solar pore and solar
granulation. The measurement noise RMS error is computed to compare the performance of the correlation algorithms.
The results show the correlation algorithm precision is directly related to the solar structure. The measurement noise is
relatively small with the relatively high contrast target, and vice versa. At the same time, the size of reference image also
could influence the measurement noise, the larger size of the reference image, the smaller the measurement noise is.
In order to study some special solar activities, such as the emergence, evolution and disappearance progress of the sunspot and magnetic flux, and the key role of magnetic field, a new 1.8-meter size high-resolution solar telescope —the CLST will be built in the Institute of Optics and Electronics(IOE), Chinese Academy of Science(CAS), which locates in Chengdu, China. The CLST has a classic Gregorian configuration, alt-azimuth mount, retractable dome. Besides that, a large mechanical de-rotator will be used to cancel the image rotation, and finally it will cooperate with another kind of mechanical de-rotator to cancel both of the pupil rotation and image rotation. Φ3 arc-minute field of view will help the CLST to observe the whole solar activity region, and if necessary the FOV can be enlarged to Φ 6 arc-minute. A 1.8m primary mirror with honeycomb sandwiches structure made by using ULE material will reduce about 70% of weight. Thermal controlling system will also be equipped for the CLST, which including Heat-Stop, primary mirror, tube truss, mount and the other optics elements. An experimental system for validating thermal controlling of primary mirror and Heat-Stop has been built, and the temperature tracking results will be illustrated in this paper. Currently, we have finished the detailed design of the CLST, and some important components also have been manufactured and finished. In this paper, we describe some important progresses and the latest status of the CLST project during these two years.
Solar observation with high resolution in large field of view (FoV) is required for some solar active regions with the typical sizes of 1’ to 3’. Conventional adaptive optics (AO) could not satisfy this demand because of the atmospheric anisoplanatism. Through compensating the turbulence in different heights, multi-conjugate adaptive optics (MCAO) has been proved to obtain a larger corrected FoV. A MCAO experimental system including a conventional 151-element AO system and a 37-element MCAO part is being developed. The MCAO part contains a 37-element deformable mirror conjugated into the 2km to 5km height and a multi-direction Shack-Hartmann wavefront sensor (MD-SHWFS) with 7×7 subaperture array and 60 arcsec FoV, the frame rate of the MD-SHWFS is up to 840Hz. Three-dimensional (3-D) wavefront sensing utilizing atmospheric tomography had been validated by solar observation. Based on these results, a ground layer adaptive optics (GLAO) experimental system including a 151-element deformable mirror and the MD-SHWFS has been built at the 1m New Vacuum Solar Telescope (NVST). In this paper, the MCAO experimental system will be introduced. The preliminary experimental results of three-dimensional wavefront sensing and GLAO on the NVST of Full-shine Lake Solar Observatory are presented.
Adaptive Optics (AO) has become the requisite equipment of the ground-based large solar telescope to correct the wavefront aberration induced by the atmospheric turbulence. Two generation solar AO systems, one is the 37-element loworder AO system with 2100Hz frame rate and the other is 151-element high-order AO system with 3500Hz frame rate, were successfully developed in 2013 and 2015 respectively. In this presentation, the development of the two AO systems for 1-m New Vacuum Solar Telescope (NVST) at Fuxian Solar Observatory (FSO) will be introduced and the solar high resolution observational results are presented.
The AO progresses for astronomy in the Key Laboratory of Adaptive Optics, Chinese Academy of Sciences are reported in this presentation. For night-time astronomical observations, the recent AO technological developments, such as Laser Guide Star, Pyramid Sensor and Deformable Secondary Mirror, are introduced. The solar AO researches are also presented for day-time astronomical observations. Furthermore, we will show the on-sky high resolution observational results in the 1.8m telescope at Gaomeigu site, Yunnan Observatory and the 1-m New Vacuum Solar Telescope (NVST) at Fuxian Lake Solar Observatory respectively.
For better understanding and forecasting of solar activity, high resolution observations for the Sun are needed. Therefore, the Chinese Large Solar Telescope (CLST) with a 1.8-m aperture is being built. The CLST is a classic Gregorian configuration telescope with an open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with an all reflective design has a field of view of larger than 3 arc-min. The 1.8-m primary mirror is a honeycomb sandwich fused silica lightweight mirror with an ultra lower expansion material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction-limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012, respectively. We plan for the CLST’s start of commission to be in 2017. A multiwavelength tomographic imaging system, ranging from visible to near-infrared, is considered as the first light scientific instrument. The main system configuration and the corresponding postfocal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.
For better understanding and forecasting of the solar activity and the corresponding impacts human technologies and life on earth, the high resolution observations for Sun are needed. The Chinese Large Solar Telescope (CLST) with 1.8 m aperture is being built. The CLST is a classic Gregorian configuration telescope with open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with all reflective design has the field of view of larger than 3 arc-minute. The 1.8 m primary mirror is a honeycomb sandwiches fused silica lightweight mirror with ULE material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012 respectively. We plan for the CLST’s starting of commission in 2017. A multi-wavelength tomographic imaging system with seven wavelengths range from visible to near-infrared wavelength is considered as the first light scientific instruments. In this paper the main system configuration and the corresponding post focal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.
A low-order solar adaptive optics (AO) system, which consists of a fine tracking loop with a tip/tilt mirror and a
correlation tracker, and a high-order correction loop with a 37-element deformable mirror, a correlating Shack-Hartmann
wavefront sensor and a high-order wavefront correction controller, had been successfully developed and installed at 1-m
New Vacuum Solar Telescope of Full-shine Lake (also called Fuxian Lake) Solar Observatory. This system is an update
of the 37-element solar AO system designed for the 26-cm Solar Fine Structure Telescope at Yunnan Astronomical
Observatory in 2009. The arrangement of subapertures of the Shack-Hartmann wavefront sensor was changed from
square to hexagon to achieve better compensation performance. Moreover, the imaging channel of the updated system
was designed to observe the Sun at 710nm and 1555nm simultaneously. The AO system was integrated into the solar
telescope in 2011, and AO-corrected high resolution sunspots and granulation images were obtained. The observational
results show that the contrast and resolution of the solar images are improved evidently after the correction by the AO