Measuring and Correcting Wind-Induced Pointing Errors of the Green Bank Telescope Using an Optical Quadrant Detector

Ries, Paul; Hunter, T. R.; Constantikes, Kim T.; Brandt, Joe; Ghigo, F. D.; Mason, B. S.; Prestage, Richard; Ray, Jason; Schwab, Friedrich

doi:10.1086/660677

Cited by 10 publications

(6 citation statements)

References 20 publications

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“…Adjusting the sub-reflector position by an active surface control system is the main method to improve electrical performance [ 2 , 3 , 4 ]. In this approach, the position and altitude of a deformed sub-reflector support structure must be accurately obtained first in order to provide an accurate input to the active surface control system.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the research on the deformation of the sub-reflector support structure under environmental loads has practical significance for maintaining the electrical performance of a radio telescope. Adjusting the sub-reflector position by an active surface control system is the main method to improve electrical performance [2][3][4]. In this approach, the position and alti tude of a deformed sub-reflector support structure must be accurately obtained first in order to provide an accurate input to the active surface control system.…”

Section: Introductionmentioning

confidence: 99%

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An Online Measurement and Calibration Method for a Radio Telescope Sub-Reflector Support Structure Using Fiber Bragg Grating

Bao

2023

Micromachines

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The position and altitude of a sub-reflector have an important influence on the pointing accuracy of a radio telescope. With the increase of the antenna aperture, the stiffness of the support structure for the sub-reflector decreases. This causes deformation of the support structure when environmental loads, such as gravity, temperature, and wind load, are applied to the sub-reflector, which will seriously influence antenna pointing accuracy. This paper proposes an online measurement and calibration method for assessing the deformation of the sub-reflector support structure based on the Fiber Bragg Grating (FBG) sensors. Firstly, a reconstruction model between the strain measurements and the deformation displacements of a sub-reflector support structure is established based on the inverse finite element method (iFEM). In addition, a temperature-compensating device with an FBG sensor is designed to eliminate the effects of temperature variations on strain measurements. Considering the lack of the trained original correction, a non-uniform rational B spline (NURBS) curve is built to extend the sample data set. Next, a self-structuring fuzzy network (SSFN) is designed for calibrating the reconstruction model, which can further improve the displacement reconstruction accuracy of the support structure. Finally, a full-day experiment was carried out using a sub-reflector support model to verify the effectiveness of the proposed method.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Online Measurement and Calibration Method for a Radio Telescope Sub-Reflector Support Structure Using Fiber Bragg Grating

Bao

2023

Micromachines

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“…are modeled for many telescopes, including the Green Bank Telescope (GBT) (Brandt 2000;Constantikes 2008;White et al 2022), the NRAO Very Large Array Sky Survey (NVSS) (Condon & Yin 2001), the Atacama Submillimeter Telescope Experiment (ASTE) 10 m antenna (Stark et al 2001), the Hamburg Robotic Telescope (HRT) (Mittag et al 2008), the 50 m Large Millimeter Telescope (LMT) (Blecher et al 2016), the 40 m Thai National Radio Telescope (Phakam et al 2019) and the 40 m Radio Telescope of Yunnan Observatory (Wang et al 2020). Other factors that generate optical pointing errors have also been included in the optical pointing models of many telescopes in recent years, e.g., the temperature dependence (Antebi et al 1998;Mittag et al 2008), the wind-induced pointing errors (Ukita et al 2010;Ries et al 2011;Xu et al 2021) and the nonlinear error terms (Kong et al 2014). Operation and observation of these telescopes show that these additional terms may be very helpful in reducing the optical pointing errors.…”

Section: Introductionmentioning

confidence: 99%

An Improved Radio Pointing Model for SHARC II of the Caltech Submillimeter Observatory Telescope

Chen¹,

Wang²,

Zhou³

2022

PASP

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In this research, we develop a new method of upgrading the radio pointing model of an important instrument of the Caltech Submillimeter Observatory (CSO) telescope, i.e., the Submillimeter High Angular Resolution Camera II (SHARC II), by making three types of structural reconstruction of its existing model. First, the axial displacement of the secondary reflector of the telescope is introduced to the radio pointing model for SHARC II. Second, the multi-layer perceptron is applied for better describing higher-order terms in the radio pointing model, which are hard to be mathematically formulated. Third, a receding horizon modeling method is proposed to replace the time-dependent term in the existing model, for better reducing the negative impact of the time drift on the model’s accuracy. Results of numerical experiments and statistical significance analysis based on the real pointing data of SHARC II show that the reconstructed radio pointing model can improve the accuracy of estimating the pointing error, and the proposed method of upgrading the radio pointing model is effective. Considering that the CSO telescope will be moved from the old site at Maunakea, Hawaii to the new site at the Chajnantor Plateau in Chile, the proposed methods of upgrading the radio pointing model are expected to be employed for pointing correction after the telescope is refurbished at the new site.

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“…In a series of three papers, the active control system has been widely used for adjusting the position and orientation of the sub-reflector [1,2,3]. In order to provide the exact input for the active control system, the position and orientation of the sub-reflector must be firstly and accurately obtained.…”

Section: Introductionmentioning

confidence: 99%

Real-Time Monitoring of the Position and Orientation of a Radio Telescope Sub-Reflector with Fiber Bragg Grating Sensors

Zhao

et al. 2019

Sensors

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Environmental loads linked with pointing errors, such as gravity, thermal gradients, and wind disturbances, are a serious concern for large-aperture high-frequency radio telescopes. For the purpose of maintaining the pointing performance of a telescope, a contact measurement scheme is proposed on basis of fiber Bragg grating (FBG) strain sensors that can monitor the sub-reflector shift in real time as the input data of the adjustment system. In this scheme, the relationship between the in situ strain measurement and the deformation of the supporting structure, which is the main cause of sub-reflector shift, is deduced using the inverse Finite Element Method (iFEM). Finally, experimental studies are carried out on a simple physical structure model to validate the effectiveness and accuracy of the contact measurement scheme.

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Measuring and Correcting Wind-Induced Pointing Errors of the Green Bank Telescope Using an Optical Quadrant Detector

Cited by 10 publications

References 20 publications

An Online Measurement and Calibration Method for a Radio Telescope Sub-Reflector Support Structure Using Fiber Bragg Grating

An Online Measurement and Calibration Method for a Radio Telescope Sub-Reflector Support Structure Using Fiber Bragg Grating

An Improved Radio Pointing Model for SHARC II of the Caltech Submillimeter Observatory Telescope

Real-Time Monitoring of the Position and Orientation of a Radio Telescope Sub-Reflector with Fiber Bragg Grating Sensors

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