The multi-color imaging sky survey conducted by the China Space Station Telescope(CSST)holds significant promise for advancing the development of the celestial reference frame.In this study,we focus on assessing the a...The multi-color imaging sky survey conducted by the China Space Station Telescope(CSST)holds significant promise for advancing the development of the celestial reference frame.In this study,we focus on assessing the astrometric performance of the CSST celestial reference frame(CSST-CRF)in extending the Gaia Celestial Reference Frame 3(Gaia-CRF3).First,the orientation precision of the CSST reference frame is evaluated using a simulated set of extragalactic sources with CSST g magnitudes ranging from 18 to 25 mag.The estimated orientation uncertainty caused by random error insignificantly affects the alignment between Gaia-CRF3 and the CSST-CRF.Then,the systematic effect of incomplete CSST sky coverage on the alignment between CSST-CRF and Gaia-CRF3 is discussed by analyzing the differences between the subset of Gaia-CRF3 in the CSST observation region(Gaia-CRF3′)and Gaia-CRF3 as a whole.Using the third International Celestial Reference Frame(ICRF3)S/X band as an intermediate reference frame,the orientation offset between Gaia-CRF3′and GaiaCRF3 is estimated to be 20μas.This offset is marginally larger than the orientation offset between Gaia-CRF3 and the ICRF3,approximately 15μas.The residual spin and glide rate of Gaia-CRF3′are derived from the proper motions,consistent with that of Gaia-CRF3 within the formal error.Finally,we explore the role of CSST in establishing a multi-band celestial reference frame by comparing its limiting magnitude and observation accuracy with existing catalogs in the infrared and ultraviolet bands.Thanks to its broad wavelength coverage and highprecision measurements,CSST is well-positioned to make significant contributions to the development of a multiband celestial reference frame.展开更多
For detecting exoplanets with high precision,using the angular distance between the two stars to detect the periodic motion of the star will be a better choice.This approach can avoid importing the position error of t...For detecting exoplanets with high precision,using the angular distance between the two stars to detect the periodic motion of the star will be a better choice.This approach can avoid importing the position error of the reference catalog in the process that uses a traditional photographic plate to derive the star position suffers.At the precision level of microarcseconds,the error caused by optical axis deviation is not negligible.In this paper,we evaluate the impact of the stability of the optical axis on the relative angular distance measurement from the aspects of theoretical analysis and numerical simulation.When the angular distance error limit of 1 microarcsecond is given,the upper limit of optical axis deviation is estimated to be 68 milliarcsecond.In addition,when limiting the deviation of the optical axis,we give the corresponding error allowance of angular distance measurement.Moreover,we also discuss the way to resolve the problem of CCD distortion and focal length change on the measurement of angular distance.The work in this paper is of guiding significance to the design of a telescope.展开更多
OCC(Optical Camera Communication)has been proposed in recent years as a new technique for visible light communications.This paper introduces the implementation and experimental demonstration of an OCC system.Phase unc...OCC(Optical Camera Communication)has been proposed in recent years as a new technique for visible light communications.This paper introduces the implementation and experimental demonstration of an OCC system.Phase uncertainty and phase slipping caused by camera sampling are the two major challenges for OCC.In this paper,we propose a novel modulation scheme called undersampled differential phase shift on–off keying to encode binary data bits without exhibiting any flicker to human eyes.The phase difference between two consecutive samples conveys one-bit information,which can be decoded by a low-frame-rate camera receiver.Error detection techniques are introduced to enhance the reliability of the system.We present the hardware and software design of the proposed system,which is implemented with a Xilinx FPGA and a Logitech commercial camera.Experimental results demonstrate that a bit-error rate of 10−5 can be achieved with 7.15 mW received signal power over a link distance of 15 cm.展开更多
基金funded by the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-A11and NO.CMS-CSST-2021-B10the National Natural Science Foundation of China(NSFC)under grant No.12373074。
文摘The multi-color imaging sky survey conducted by the China Space Station Telescope(CSST)holds significant promise for advancing the development of the celestial reference frame.In this study,we focus on assessing the astrometric performance of the CSST celestial reference frame(CSST-CRF)in extending the Gaia Celestial Reference Frame 3(Gaia-CRF3).First,the orientation precision of the CSST reference frame is evaluated using a simulated set of extragalactic sources with CSST g magnitudes ranging from 18 to 25 mag.The estimated orientation uncertainty caused by random error insignificantly affects the alignment between Gaia-CRF3 and the CSST-CRF.Then,the systematic effect of incomplete CSST sky coverage on the alignment between CSST-CRF and Gaia-CRF3 is discussed by analyzing the differences between the subset of Gaia-CRF3 in the CSST observation region(Gaia-CRF3′)and Gaia-CRF3 as a whole.Using the third International Celestial Reference Frame(ICRF3)S/X band as an intermediate reference frame,the orientation offset between Gaia-CRF3′and GaiaCRF3 is estimated to be 20μas.This offset is marginally larger than the orientation offset between Gaia-CRF3 and the ICRF3,approximately 15μas.The residual spin and glide rate of Gaia-CRF3′are derived from the proper motions,consistent with that of Gaia-CRF3 within the formal error.Finally,we explore the role of CSST in establishing a multi-band celestial reference frame by comparing its limiting magnitude and observation accuracy with existing catalogs in the infrared and ultraviolet bands.Thanks to its broad wavelength coverage and highprecision measurements,CSST is well-positioned to make significant contributions to the development of a multiband celestial reference frame.
基金funded by the National Natural Science Foundation of China(NSFC,Grant No.11833004)funded by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences,Grant No.XDA15020800。
文摘For detecting exoplanets with high precision,using the angular distance between the two stars to detect the periodic motion of the star will be a better choice.This approach can avoid importing the position error of the reference catalog in the process that uses a traditional photographic plate to derive the star position suffers.At the precision level of microarcseconds,the error caused by optical axis deviation is not negligible.In this paper,we evaluate the impact of the stability of the optical axis on the relative angular distance measurement from the aspects of theoretical analysis and numerical simulation.When the angular distance error limit of 1 microarcsecond is given,the upper limit of optical axis deviation is estimated to be 68 milliarcsecond.In addition,when limiting the deviation of the optical axis,we give the corresponding error allowance of angular distance measurement.Moreover,we also discuss the way to resolve the problem of CCD distortion and focal length change on the measurement of angular distance.The work in this paper is of guiding significance to the design of a telescope.
文摘OCC(Optical Camera Communication)has been proposed in recent years as a new technique for visible light communications.This paper introduces the implementation and experimental demonstration of an OCC system.Phase uncertainty and phase slipping caused by camera sampling are the two major challenges for OCC.In this paper,we propose a novel modulation scheme called undersampled differential phase shift on–off keying to encode binary data bits without exhibiting any flicker to human eyes.The phase difference between two consecutive samples conveys one-bit information,which can be decoded by a low-frame-rate camera receiver.Error detection techniques are introduced to enhance the reliability of the system.We present the hardware and software design of the proposed system,which is implemented with a Xilinx FPGA and a Logitech commercial camera.Experimental results demonstrate that a bit-error rate of 10−5 can be achieved with 7.15 mW received signal power over a link distance of 15 cm.
