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Study on the pointing model of a slant-axis terahertz antenna

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Research in Astronomy and Astrophysics 2020年第4期20卷 115-122页

作者： Yu Wang Zheng Lou Ying-Xi Zuo Hao-Ran Kang Ming-Zhu Zhang Purple Mountain Observatory Chinese Academy of SciencesNanjing 210034China Key Laboratory for Radio Astronomy Chinese Academy of SciencesNanjing 210034China Shanghai Normal University Shanghai 201400China University of Science and Technology of China Hefei 230026China

This paper describes the establishment and verification of an accurate pointing model for a1.2 m aperture slant-axis terahertz antenna.A new analytical pointing model for the slant-axis antenna is presented based on an analogy to that of the alt-azimuth antennas.Furthermore,extra error terms are added to the pointing model based on the structure and mechanical analysis of the slant-axis antenna.To verify the pointing model experimentally,a pointing error measurement method based on photogrammetric techniques is proposed.Using this method,pointing behaviors of the antenna are accurately measured without the aid of astronomical observations,and major sources of the pointing errors are measured individually by photogrammetry and their respective coefficients are compared with those in the analytical pointing model.The results show that an extended pointing model consisting 21 error terms can significantly reduce the residual systematic errors compared with the traditional model,more details are given in the following sections.

关键词： telescopes slant-axis antenna photogrammetry pointing models

Insight-HXMT on-orbit thermal control status and thermal deformation impact analysis

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Radiation Detection Technology and Methods 2023年第3期7卷 337-349页

作者： Ai-Mei Zhang Yi-Fan Zhang Jin-Yuan Liao Yu-Peng Xu Yu-Sa Wang Wen-Bo Luo Yu-Peng Zhou Zhi-Ying Qian Xiao-Bo Li Fang-Jun Lu Shuang-Nan Zhang Li-Ming Song Cong-Zhan Liu Fan Zhang Jian-Yin Nie Juan Wang Sheng Yang Tong Zhang Xiao-Jing Liu Rui-Jie Wang Xu-Fang Li Yi-Fei Zhang Zheng-Wei Li Xue-Feng Lu He Xu Di Wu Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing 100049China Beijing Institute of Spacecraft System Engineering CASTBeijing 100094China

Purpose The Hard X-ray Modulation Telescope is China’s first X-ray astronomy satellite launched on June 15,2017,dubbed Insight-HXMT.Active and passive thermal control measures are employed to keep devices at suitable temperatures.In this paper,we analyzed the on-orbit thermal monitoring data of the first 5 years and investigated the effect of thermal deformation on the point spread function(PSF)of the telescopes.Methods We examined the data of the on-orbit temperatures measured using 157 thermistors placed on the collimators,detectors and their support structures and compared the results with the thermal control requirements.The thermal deformation was evaluated by the relative orientation of the two star sensors installed on the main support structure.Its effect was estimated with evolution of the PSF obtained with calibration scanning observations of the Crab nebula.Conclusion The on-orbit temperatures met the thermal control requirements thus far,and the effect of thermal deformation on the PSF was negligible after the on-orbit pointing calibration.

关键词： X-ray Insight-HXMT Thermal control Temperature Star sensor data pointing PSF

A Precise Calibration Method on Phase Center of Uplink Antenna Array Considering Its Actual pointing

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Journal of Geodesy and Geoinformation Science 2020年第1期3卷 93-101页

作者： Zongchun LI Zhiyong LU Guanyu ZHANG Bo LIU Qiqiang FENG Yinggang GUO Hua HE PLA Strategic Support Force Information Engineering University Zhengzhou 450001China CETC Key Laboratory of Aerospace Information Applications Shijiazhuang 050081China

With regard to the inferior techniques and low accuracy of phase center calibration of an antenna array, this paper proposes a new calibration method considering the actual antenna pointing by introducing a precise engineering surveying technique to measure the real state of antennas. First, an industrial photogrammetric system is utilized to obtain the coordinates of points on antenna panels in different postures, and the actual pointing of the mechanical axis is obtained via least-squares fitting. Then, based on this, the coordinates of antenna rotation center are obtained by seeking the intersection of mechanical axes via using the matrix method. Finally, the mechanical axis in arbitrary postures is estimated based on the inverse-angle weighting interpolation method, and the reliable phase center is obtained by moving a fixed length from the projective center along the mechanical axis. An uplink antenna array including three ? 3 m antennas is taken as experimental object, and all photogrammetric coordinate systems are unified by the engineering control network, with each antenna phase center precisely calibrated via the proposed method. The results of electrical signal synthesis indicate that this method can effectively overcome the influence of gravity deformation and mechanical installation error, and enhance the synthetic signal magnitude of the uplink antenna array.

关键词： uplink array phase center rotation center actual antenna pointing three-dimension control network precise calibration

A Magnetically Levitated Precise pointing Mechanism for Application to Optical Communication Terminals

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Optics and Photonics Journal 2012年第2期2卷 85-97页

作者： Thomas Edward Donaldson Frame Alexandre Alexandre Pechev Surrey Space Centre University of Surrey Guildford UK

Increasing data bandwidth requirements from spacecraft systems is beginning to pressure existing microwave communications systems. Free-Space optical communications allows for larger bandwidths for lower relative power consumption, smaller size and weight when compared to the microwave equivalent. However optical communication does have a formidable challenge that needs to be overcome before the advantages of the technology can be fully utilized. In order for the communication to be successful the transmitter and receiver terminals need to be pointed with a high accuracy (generally in the order of ≤10 μradians) for the duration of communication. In this paper we present a new concept for the precise pointing of optical communications terminals (termed the Precise pointing Mechanism). In this new concept we combine the separate pointing mechanisms of a conventional optical terminal into a single mechanism, reducing the complexity and cost of the optical bench. This is achieved by electromagnetically actuating the whole telescope assembly in 6 degrees-of-freedom with an angular resolution of less than ±3 μradians within a 10 (Az. El.) field of view and linear resolution of ±2 μm. This paper presents the new pointing mechanism and discusses the modelling, simulation and experimental work undertaken using the bespoke engineering model developed.

关键词： Optical Communications Magnetic Levitation Control pointing Active Anti-Vibration

Normalized point source sensitivity analysis in GSSM prototype

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Chinese Optics Letters 2017年第11期15卷 46-49页

作者：安其昌张景旭杨飞赵宏超 Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130033 China Graduate University of Chinese Academy of Sciences Beijing 100039 China

The Giant Steerable Science Mirror（GSSM） is the tertiary mirror of the Thirty Meter Telescope（TMT）.To evaluate the performance of GSSM,normalized point source sensitivity（PSSn） is investigated.Calibration and metrology allow the estimation of telescope performance at different zenith angles.PSSn also realizes the prediction of the TMT main mirror assembly optical performance.The relationship between PSSn and slope root mean square（RMS） is analyzed theoretically when evaluating the performance of GSSM.First and foremost,the pointing performance of the GSSM prototype（GSSMP） is specified by PSSn and calibrated by a laser tracker.Then,the tracking performance influence on PSSn is taken into consideration.The jitter of the GSSMP also contributes to the degradation of PSSn,and it is also discussed.Lastly,the interaction between GSSM and the main mirror unit is also revealed by PSSn.

关键词： prototype mirror metrology pointing jitter Giant normalized tracker evaluating Mirror

Performance of Free Space Optical Communication System Based on M-ary PPM Modulation over Double Generalized Gamma Channel

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China Communications 2020年第4期17卷 19-30页

作者： Mohamed Maalej Hichem Besbes Higher School of Communications of Tunis University of Carthage2083 El Ghazala ArianaTunisia

In this paper, we provide analytical results on average Symbol Error Probability(SEP) of a Free Space Optics(FSO) link employing M-ary Pulse Position Modulation(PPM), subjected to turbulent atmosphere modeled with Double Generalized Gamma(DGG) distribution. FSO link is generally impaired by turbulent atmosphere and pointing errors. As far as we know, results are presented in previous works by considering the atmosphere turbulence modeled with a Gamma-Gamma distribution. In our work, we also give asymptotic results on average SEP in order to approximate its evolution at high Signal-to-Noise-Ratio(SNR). Numerical results showed that FSO link performance is enhanced when PPM-modulation index is increased, for both strong and moderate turbulence regimes, and for both strong and weak pointing error jitter. Monte-Carlo simulations were presented to corroborate our analytical expressions.

关键词： FSO DGG atmospheric turbulence PPM modulation SEP pointing error

The SDG Project:A Long-Term Project under Technological Uncertainty

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Engineering 2020年第6期6卷 600-603页

作者： Fred Phillips University of New Mexico AlbuquerqueNM 87131USA

1.Introduction A second"Warning to Humanity"issued by 15000 scientists from across the globe[1],the"disappointing"COP25 meeting(25th Conference of the Parties to the United Nations Framework Convention on Climate Change)[2],and a"grim"United Nations report[3]imply that the ability of Earth's environment to support human life will persist for a much shorter time than the 200 years predicted by physicist Stephen Hawking.

关键词： shorter issued pointing

A note on the role of foreign experts in the long-term development of China

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国际人才交流 2022年第12期 29-30页

作者： [墨西哥]阿尔伯托·科内霍·纳瓦北京科技大学冶金与生态工程学院

On October 16th,2022,President Xi Jinping made a report to the 20th CPC National Congress outlining the strategies to attract high-quality talent for“the longterm development of China and the Chinese nation,”pointing out that“No effort should be spared and no rigid boundaries drawn in the endeavor to bring together the best a nd the brightest m i nds f rom all over.”What supports his words is the actions taken by the Chinese government in the last decades.

关键词： pointing bright development

北京天文台兴隆观测站2.16米望远镜对星模式

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紫金山天文台台刊 1994年第1期 88-90页

作者：高震东

The pointing accuracy of a telescope is influenced by its encoder system, by the alignments of the mounting relative to the earth’s axis of rotation, by the alignment of the optics, by mechanical effects like the flexture of the tube and by systemtic errors of the drive system. As to the 2.16m telescope, it is necessary to establish a pointing model to make normal obsercation easier. In this paper, an empirical approach to set up the pointing model for the 2.16m telescope was reported together with a physical interpretation of most of the individual parameters of this model.

关键词：北京天文台兴隆观 pointing interpretation alignment encoder rotation telescope optics iterative