We propose a Very Long Baseline Interferometry(VLBI)precision evaluation method for probe delay measurement,so as to investigate the error contributions from different components in the Chinese VLBI Network(CVN).This ...We propose a Very Long Baseline Interferometry(VLBI)precision evaluation method for probe delay measurement,so as to investigate the error contributions from different components in the Chinese VLBI Network(CVN).This method takes the idea of traditional closure delay analysis for distant radio sources.It focuses on the VLBI closure delay only and therefore excludes the influence of probe orbit determination,which makes it very suitable to evaluate the capability of VLBI probe delay measurement.In this paper,we first introduce the principles of closure delay analysis.Then the statistical results of typical CE5(Chinese Chang’e 5 lunar exploration mission)and HX1(Chinese Mars exploration mission)observations are presented,including the comparison of the closure delay precisions between CE5 and HX1 for four closed baseline triangles in CVN.According to the result,we realize that the precision discrepancy between CE5 and HX1 in the closure delay analysis is less than that of residual delay after orbit determination,which reflects the precision level of the VLBI delay measurement.展开更多
The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a ...The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a wide field of view of approximately 3×3 square degrees.Calibration parameters are essential to ensure the precision of astrometric observations with the WFST.These parameters are derived from geometric distortion(GD)and gaps through astrometric modeling and are subsequently validated via the Yao’An High Precision Telescope(YAHPT).The GD solutions show maximum distortions between 1.18 and 10.29 pixels for the WFST chips,with central chips exhibiting lower distortion.After applying the GD correction,the precision of the WFST reaches 4 mas.The interchip gaps of the WFST range from 1.922 mm to 7.765 mm,corresponding to 10μm/pixel,aligning with the design and measurements.The calibrated parameters guarantee that the WFST can perform highly accurate astrometric measurements.Furthermore,as the WFST undergoes updates,the parameter model remains consistently applicable.展开更多
The 80 cm azimuthal telescope has newly been mounted at Yaoan Station,Purple Mountain Observatory since2018.The astrometric performance of the telescope is tested in the following three aspects.(a)The geometric distor...The 80 cm azimuthal telescope has newly been mounted at Yaoan Station,Purple Mountain Observatory since2018.The astrometric performance of the telescope is tested in the following three aspects.(a)The geometric distortion of its CCD attached.It is stable in both a single epoch and multi epochs.Eight distortion solutions are derived over about one year.The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel.(b)The limit magnitude of stars.About 20.5 mag(Gaia-G)stars can be detected with Johnson-V filter exposured in 300 s.The astrometric error of about 20.5 mag stars is estimated at O".14 using the fitted sigmoidal function.(c)The astrometric accuracy and the precision of stacked fast-moving faint object.24 stacked frames of the potentially hazardous asteroid(99942)Apophis were derived on 2021 April 14 and 15(fainter than18 mag)based on the ephemeris shifts.During data reduction,the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis,respectively.Our results show that the mean(O-C)s(observed minus computed)of Apophis are-O".018 and O".020 in R.A.and decl.,and the dispersions are estimated at O".094 and O".085,respectively,which show the consistency of the stacked results by Astrometrica.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11973011,11573057,11903067,U1938114 and U1831137)National Science and Technology Basic Conditions Platform Project“National Basic Science Data Sharing Service Platform”(Grant No.DKA201712-02-09)Key Technical Talents of Chinese Academy of Sciences,Shanghai Outstanding Academic Leaders Plan,Lunar Exploration Project and Key Cultivation Projects of Shanghai Astronomical Observatory。
文摘We propose a Very Long Baseline Interferometry(VLBI)precision evaluation method for probe delay measurement,so as to investigate the error contributions from different components in the Chinese VLBI Network(CVN).This method takes the idea of traditional closure delay analysis for distant radio sources.It focuses on the VLBI closure delay only and therefore excludes the influence of probe orbit determination,which makes it very suitable to evaluate the capability of VLBI probe delay measurement.In this paper,we first introduce the principles of closure delay analysis.Then the statistical results of typical CE5(Chinese Chang’e 5 lunar exploration mission)and HX1(Chinese Mars exploration mission)observations are presented,including the comparison of the closure delay precisions between CE5 and HX1 for four closed baseline triangles in CVN.According to the result,we realize that the precision discrepancy between CE5 and HX1 in the closure delay analysis is less than that of residual delay after orbit determination,which reflects the precision level of the VLBI delay measurement.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0350300)the National Natural Science Foundation of China(12203105,12103091,62394351,12073008)the China Manned Space Project(CMS-CSST-2021-A12,CMS-CSST-2021-B10).
文摘The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a wide field of view of approximately 3×3 square degrees.Calibration parameters are essential to ensure the precision of astrometric observations with the WFST.These parameters are derived from geometric distortion(GD)and gaps through astrometric modeling and are subsequently validated via the Yao’An High Precision Telescope(YAHPT).The GD solutions show maximum distortions between 1.18 and 10.29 pixels for the WFST chips,with central chips exhibiting lower distortion.After applying the GD correction,the precision of the WFST reaches 4 mas.The interchip gaps of the WFST range from 1.922 mm to 7.765 mm,corresponding to 10μm/pixel,aligning with the design and measurements.The calibrated parameters guarantee that the WFST can perform highly accurate astrometric measurements.Furthermore,as the WFST undergoes updates,the parameter model remains consistently applicable.
基金supported by the National Natural Science Foundation of China(grant Nos.11873026 and 11273014)the Joint Research Fund in Astronomy(grant No.U1431227)+1 种基金the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B08Excellent Postgraduate Recommendation Scientific Research Innovative Cultivation Program of Jinan University。
文摘The 80 cm azimuthal telescope has newly been mounted at Yaoan Station,Purple Mountain Observatory since2018.The astrometric performance of the telescope is tested in the following three aspects.(a)The geometric distortion of its CCD attached.It is stable in both a single epoch and multi epochs.Eight distortion solutions are derived over about one year.The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel.(b)The limit magnitude of stars.About 20.5 mag(Gaia-G)stars can be detected with Johnson-V filter exposured in 300 s.The astrometric error of about 20.5 mag stars is estimated at O".14 using the fitted sigmoidal function.(c)The astrometric accuracy and the precision of stacked fast-moving faint object.24 stacked frames of the potentially hazardous asteroid(99942)Apophis were derived on 2021 April 14 and 15(fainter than18 mag)based on the ephemeris shifts.During data reduction,the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis,respectively.Our results show that the mean(O-C)s(observed minus computed)of Apophis are-O".018 and O".020 in R.A.and decl.,and the dispersions are estimated at O".094 and O".085,respectively,which show the consistency of the stacked results by Astrometrica.
