Daytime optical turbulence profiling with a profiler of the differential solar limb

2020 ◽  
Vol 499 (2) ◽  
pp. 1909-1917
Author(s):  
Tengfei Song ◽  
Zhanchuan Cai ◽  
Yu Liu ◽  
Mingyu Zhao ◽  
Yuliang Fang ◽  
...  
Keyword(s):  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Solar Limb ◽  
Coefficient Matrix ◽  
Image Motion ◽  
Index Structure ◽  
Test Results ◽  
Optical Turbulence ◽  
Optical Telescopes ◽  
Turbulence Parameters

ABSTRACT Atmospheric turbulence reduces the image quality and resolution of ground-based optical telescopes. Future large solar telescopes (e.g. the CGST, China Giant Solar Telescope) should be equipped with adaptive optics (AO) systems. The design of AO systems is associated with atmospheric optical turbulence parameters, especially the profile of the refractive index structure $C_{n}^{2}(h)$. With the solar differential image motion monitor (S-DIMM) and the profiler of the moon limb (PML), a simplified version of a PML, termed a profiler of the differential solar limb (PDSL), was built in order to determine the daytime $C_{n}^{2}(h)$ and other atmospheric turbulence parameters. A PDSL with differential solar limb fluctuations was used to determine the turbulence profiling, and the extended solar limb extends the range of separation angles for a higher resolution of the height profile. The PDSL structure and its performance are described. In addition, numerical simulations were conducted to verify the effectiveness of the method. As revealed from the simulation results, the layered integral coefficient matrix is capable of solving the discretization error and enhancing the inversion accuracy of the turbulence contour. The first test results at Mt Wumingshan (a candidate site for the CGST) are presented.

scholarly journals Forecasting seeing for the Maunakea Observatories

2020 ◽  
Vol 496 (4) ◽  
pp. 4734-4748
Author(s):  
Ryan Lyman ◽  
Tiziana Cherubini ◽  
Steven Businger
Keyword(s):  
Adaptive Optics ◽  
Atmospheric Stability ◽  
Weather Conditions ◽  
Image Resolution ◽  
Image Motion ◽  
Optical Turbulence ◽  
Observational Measures ◽  
Weather Model ◽  
Operational Forecasting

ABSTRACT Optical turbulence greatly impacts the range and quality of astronomical observations. Advanced knowledge of the expected atmospheric optical turbulence provides important guidance that helps astronomers decide which instrument to schedule and enables them to optimize the adaptive optics technology that improves image resolution. Along with forecasts of weather conditions, prediction of the optical observing quality on the Maunakea summit has been a goal for the Maunakea Weather Center (MKWC) since its inception more than 20 yr ago. Forecasting optical turbulence, and its derivative, ‘seeing’, has proven to be quite challenging because optical turbulence is too small and complex to directly capture with a regional weather model. Fortunately, the permanent installation of a Differential Image Motion Monitor (DIMM) and Multi-Aperture Scintillation Sensor (MASS) at the summit of Maunakea has made seeing observations available during the last decade, providing valuable feedback to the MKWC. This paper summarizes the experience at MKWC in anticipating optical turbulence for the summit of Maunakea accrued through years of daily operational forecasting, and continuous comparison between MKWC official forecasts, model guidance, and observational measures of seeing. Access to a decade seeing observations has allowed quantification the factors that impact seeing, including wind shear, atmospheric stability patterns, and optical turbulence, and to document the seasonal and intra-seasonal variations in seeing. Consequently, the combination of experience gained, and custom model guidance has led to more accurate seeing forecasts (rms errors averaging <0.25 arcsec since 2012) for the Maunakea astronomical observatories.

Two-telescope-based solar seeing profile measurement simulation

2022 ◽  
Vol 21 (12) ◽  
pp. 298
Author(s):  
Zi-Yue Wang ◽  
De-Qing Ren ◽  
Raffi Saadetian
Keyword(s):  
Numerical Simulations ◽  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Solar Observatory ◽  
Performance Estimation ◽  
Image Motion ◽  
Profile Measurement ◽  
Solar Telescope ◽  
National Solar Observatory ◽  
Bear Lake

Abstract Measurements of the daytime seeing profile of the atmospheric turbulence are crucial for evaluating a solar astronomical site so that research on the profile of the atmospheric turbulence as a function of altitude C n 2 ( h n ) becomes more and more critical for performance estimation and optimization of future adaptive optics (AO) including the multi-conjugate adaptive optics (MCAO) systems. Recently, the S-DIMM+ method has been successfully used to measure daytime turbulence profiles above the New Solar Telescope (NST) on Big Bear Lake. However, such techniques are limited by the requirement of using a large solar telescope which is not realistic for a new potential astronomical site. Meanwhile, the A-MASP (advanced multiple-aperture seeing profiler) method is more portable and has been proved that can reliably retrieve the seeing profile up to 16 km with the Dunn Solar Telescope (DST) on the National Solar Observatory (Townson, Kellerer et al.). But the turbulence of the ground layer is calculated by combining A-MASP and S-DIMM+ (Solar Differential Image Motion Monitor+) due to the limitation of the two-individual-telescopes structure. To solve these problems, we introduce the two-telescope seeing profiler (TTSP) which consists of two portable individual telescopes. Numerical simulations have been conducted to evaluate the performance of TTSP. We find our TTSP can effectively retrieve seeing profiles of four turbulence layers with a relative error of less than 4% and is dependable for actual seeing measurement.

4-aperture differential image motion monitor as a new approach for estimating atmospheric turbulence parameters

2019 ◽  
Vol 66 (7) ◽  
pp. 753-763 ◽  
Author(s):  
B. Dibaee ◽  
R. Shomali ◽  
J. Khalilzadeh ◽  
A. Jafari ◽  
M. Amniat-Talab
Keyword(s):  
Atmospheric Turbulence ◽  
Image Motion ◽  
New Approach ◽  
Turbulence Parameters

H∞ controller design for the mitigation of atmospheric effects on the laser beam pointing

2021 ◽  
pp. 014233122199846
Author(s):  
Özgenç Subaşı ◽  
Bilal Erol ◽  
Berk Altıner ◽  
Harun Turan ◽  
Nurdan Baci
Keyword(s):  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Controller Design ◽  
Index Structure ◽  
Atmospheric Effects ◽  
Core Element ◽  
Turbulence Data ◽  
Fixed Order ◽  
Implementation Problems ◽  
Low Order

In this paper, the control of a fast steering mirror, which is the core element of an adaptive optics system, is investigated to suppress the beam jitter. The main source of the jitter is taken as the atmospheric turbulence. The effect of the atmospheric turbulence on the beam jitter is experimentally determined with respect to the two different refractive index structure parameters. The mathematical model of the fast steering mirror based on the atmoshperic turbulence data is obtained using the system identification. In order to overcome implementation problems, the low order proportional-integral-derivative (PID) type controllers, which minimize the [Formula: see text] norm of the closed loop system, are designed in the centralized and the decentralized settings. In addition to this, the fixed order weighted [Formula: see text] controller is based on the frequency characteristics of the atmospheric turbulence that is determined experimentally. Then, in order to show the effectiveness of the proposed low order PID type controller, the designed controllers are compared on the experimental setup. Finally, the simulation and the experimental results are presented. Comparison of advantageous and disadvantageous of centralized and decentralized controller architectures are discussed.

scholarly journals Remote Sensing of Atmospheric Turbulence Profiles by Laser Guide Stars

2020 ◽  
Vol 237 ◽  
pp. 06014
Author(s):  
Xiwen Qiang
Keyword(s):  
Remote Sensing ◽  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Image Motion ◽  
Inversion Algorithm ◽  
Laser Guide Stars ◽  
Atmospheric Structure ◽  
Structure Constants ◽  
Laser Guide ◽  
Motion Method

Ranged-resolved profiles of atmospheric turbulence are necessary and important for many applications in astronomical and adaptive optics communities. In order to characterize the vertical atmospheric structure in field, a technique is put forward to remote sensing ranged-resolved profiles of atmospheric turbulence by combined with laser guide stars and differential image motion method. Laser guide stars are formed at several successive altitudes by projecting pulsed laser, returned signals of images are received by a optical system with two receiving telescopes, and variance of centroids′ distance is derived from the images with two spots at the same altitude. So, based on a inversion algorithm, atmospheric turbulence profiles are retrieved from differential image motion variance of distance of centroids at various altitudes. The structure constants of refractive index of atmosphere range from 10-14m-2/3 at lower altitudes to 10-16m-2/3 at higher altitudes are remote sensed experimentally. The results show it is a effective method that combined laser guide stars with differential image motion method and could sense atmospheric turbulence profiles remotely in real time.

scholarly journals Re-Visiting Acoustic Sounding to Advance the Measurement of Optical Turbulence

2021 ◽  
Vol 11 (16) ◽  
pp. 7658
Author(s):  
Steven Fiorino ◽  
Santasri Bose-Pillai ◽  
Kevin Keefer
Keyword(s):  
Large Scale ◽  
Velocity Structure ◽  
Sonic Anemometer ◽  
Structure Constant ◽  
Vertical Wind Shear ◽  
Index Of Refraction ◽  
Image Motion ◽  
Index Structure ◽  
Temperature Structure ◽  
Optical Turbulence

Optical turbulence, as determined by the widely accepted practice of profiling the temperature structure constant, CT2, via the measurement of ambient atmospheric temperature gradients, can be found to differ quite significantly when characterizing such gradients via thermal-couple differential temperature sensors as compared to doing so with acoustic probes such as those commonly used in sonic anemometry. Similar inconsistencies are observed when comparing optical turbulence strength derived via CT2 as compared to those through direct optical or imaging measurements of small fluctuations of the index of refraction of air (i.e., scintillation). These irregularities are especially apparent in stable atmospheric layers and during diurnal quiescent periods. Our research demonstrates that when care is taken to properly remove large-scale index of refraction gradients, the sonic anemometer-derived velocity structure constant, Cv2, coupled with the similarly derived turbulence-driven index of refraction and vertical wind shear gradients, provides a refractive index structure constant, Cn2, that can more closely match the optical turbulence strengths inferred by more direct means such as scintillometers or differential image motion techniques. The research also illustrates the utility and robustness of quantifying Cn2 from CT2 at a point using a single sonic anemometer and establishes a clear set of equations to calculate volumetric Cn2 data using instrumentation that measures wind velocities with more spatial/temporal fidelity than temperature.

scholarly journals Determination of the optical turbulence parameters from the adaptive optics telemetry: critical analysis and on-sky validation

2018 ◽  
Vol 57 (27) ◽  
pp. 7837 ◽  
Author(s):  
Laurent Jolissaint ◽  
Sam Ragland ◽  
Julian Christou ◽  
Peter Wizinowich
Keyword(s):  
Adaptive Optics ◽  
Critical Analysis ◽  
Optical Turbulence ◽  
Turbulence Parameters

Measurement of Atmospheric Turbulence Parameters on Airborne Platform Based on Differential Image Motion Method

2017 ◽  
Vol 44 (3) ◽  
pp. 0304002
Author(s):  
张 雷 Zhang Lei ◽  
赵 馨 Zhao Xin ◽  
佟首峰 Tong Shoufeng ◽  
李 勃 Li Bo ◽  
姜会林 Jiang Huilin
Keyword(s):  
Atmospheric Turbulence ◽  
Image Motion ◽  
Turbulence Parameters ◽  
Motion Method

scholarly journals Method of Estimation of Turbulence Integral Parameters

2021 ◽  
Vol 11 (9) ◽  
pp. 4157
Author(s):  
Hong Shen ◽  
Longkun Yu ◽  
Xu Jing ◽  
Fengfu Tan
Keyword(s):  
Refractive Index ◽  
Linear Combination ◽  
Adaptive Optics ◽  
Structure Constant ◽  
Index Structure ◽  
Angle Of Arrival ◽  
Weighting Functions ◽  
Optical Effects ◽  
Finite Distance ◽  
Turbulence Parameters

The optical effects of turbulence are directly related to turbulence integral parameters, which are integrals of the refractive index structure constant over a whole path with different path-weighting functions (PWFs). We describe a method that utilizes measurable turbulence integral parameters, such as angle-of-arrival fluctuations and scintillation, to estimate turbulence integral parameters that cannot be measured directly. The estimates of the turbulence integral parameters are based on the linear combination of the PWFs of those measurable quantities. New measurable quantities and their PWFs under different propagation conditions were studied. Some interesting and meaningful results have been obtained. This method shows the prospect of characterizing anisoplanatism in adaptive optics and allows for the estimation of some optical turbulence parameters under non-ideal conditions, such as an isoplanatic angle in a finite distance.

Review on Remote Sensing of Atmospheric Turbulence Profiles by Laser Guide Stars

2013 ◽  
Vol 303-306 ◽  
pp. 823-826
Author(s):  
Xi Wen Qiang ◽  
Jun Wei Zhao ◽  
Shuang Lian Feng ◽  
Min Wu ◽  
Jing Yong Chang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Image Motion ◽  
Inversion Algorithm ◽  
Laser Guide Stars ◽  
Atmospheric Structure ◽  
Structure Constants ◽  
Laser Guide ◽  
Motion Method

Ranged-resolved profiles of atmospheric turbulence are necessary and important for many applications in astronomical and adaptive optics communities. In order to characterize the vertical atmospheric structure in field, a technique is put forward to remote sensing ranged-resolved profiles of atmospheric turbulence by combined with laser guide stars and differential image motion method. Laser guide stars are formed at several successive altitudes by projecting pulsed laser, returned signals of images are received by a optical system with two receiving telescopes, and variance of centroids distance is derived from the images with two spots at the same altitude. So, based on a inversion algorithm, atmospheric turbulence profiles are retrieved from differential image motion variance of distance of centroids at various altitudes. The structure constants of refractive index of atmosphere range from 10-14m-2/3 at lower altitudes to 10-16m-2/3 at higher altitudes are remote sensed experimentally. The results show it is a effective method that combined laser guide stars with differential image motion method and could sense atmospheric turbulence profiles remotely in real time.

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