VLBI station neutral atmosphere time delay error correction method and system

Abstract

The invention belongs to the technical field of deep space exploration, and discloses a VLBI station neutral atmosphere time delay error correction method and system. The method comprises the following steps: calculating elevation angle and azimuth angle information from a VLBI station to a detector and elevation angle and azimuth angle information from the VLBI station to a radio power supply; fusing to generate a guide file according to the observation time sequence; the sampled neutral atmosphere time delay is obtained; calculating a neutral atmosphere time delay rate according to the neutral atmosphere time delay set of the VLBI station; and based on the observation outline, decomposing neutral atmosphere time delays and time delay rates of corresponding observation moments of the detector and the radio power source, and respectively outputting the neutral atmosphere time delays and time delay rates to different files. The method can effectively improve the real-time correction of the neutral atmosphere time delay result of the VLBI observation station.

Description

Technical Field

[0001] The invention belongs to the technical field of deep space detection, and in particular relates to a method and system for correcting neutral atmosphere delay errors of a VLBI station. Background Art

[0002] The VLBI orbit determination subsystem of the tracking and control system is an important part of China's deep space exploration. Its task is to use the Very Long Baseline Interferometry (VLBI) technology to determine the detector's orbit. The influence of neutral atmosphere delay is the main source of error in VLBI orbit determination. The neutral atmosphere delay varies with the altitude angle. The dry neutral atmosphere delay in the zenith direction is about 2.3 meters, and the wet delay is in the decimeter level (Nilsson et al. 2013). The neutral atmosphere delay can reach 20 meters at an altitude angle of 6°. At present, the international community mainly eliminates the neutral atmosphere delay in real time through the zenith delay model and mapping function. The correction accuracy of the zenith direction is at the centimeter level, and the correction accuracy of the 10° altitude angle direction is about the decimeter level, which limits the improvement of the accuracy of VLBI technology in determining the detector's orbit. It is a key problem that needs to be solved urgently for the sustainable development of deep space exploration.

[0003] Microwave radiometers (Water Vapor Radiometer, WVR) can measure the impact of the neutral atmosphere on the propagation of radio signals in real time. Studies have shown that the accuracy of the neutral atmosphere wet delay measured by the international WVR in the zenith direction is better than 1 cm. Based on its high accuracy and high timeliness, microwave radiometers can be used to measure the neutral atmosphere delay in the observation direction from radio telescopes to detectors. However, since deep space exploration uses detectors and radio sources for alternating observations, microwave radiometers cannot be used directly at present. Summary of the invention

[0004] In order to overcome the problems existing in the related art, the embodiments disclosed in the present invention provide a method and system for correcting the neutral atmosphere delay error of a VLBI station, and more particularly, relate to a method for correcting the neutral atmosphere delay error of a VLBI station based on a microwave radiometer, and relate to a method for direct observation of a microwave radiometer that integrates a detector and a radio source.

[0005] The technical solution is as follows: A method for correcting neutral atmospheric delay errors of a VLBI station, comprising:

[0006] S1: Calculate the altitude and azimuth information from the VLBI station to the detector based on the detector's predicted ephemeris;

[0007] S2: Based on the radio source observation file, calculate the elevation angle and azimuth information from the VLBI station to the radio source;

[0008] S3: Fusing the detector elevation angle azimuth file and the radio source elevation angle azimuth file according to the radio source observation file to generate a guide file in the order of observation time;

[0009] S4: Automatically upload each station’s boot file to the specified path of the corresponding microwave radiometer through the script;

[0010] S5: Eliminate observation anomalies and observations during the rotation of the microwave radiometer, smooth and filter the microwave radiometer observation results, and obtain the sampled neutral atmosphere delay;

[0011] S6: Calculate the neutral atmosphere delay rate based on the VLBI station neutral atmosphere delay set;

[0012] S7: Based on the observation outline, decompose the neutral atmosphere delay and delay rate of the detector and radio source at the corresponding observation time, and output them to different files respectively.

[0013] In step S1, the elevation angle azimuth information in the direction from the VLBI station to the detector is calculated, including:

[0014] The coordinates of the detector in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The elevation angle information from the VLBI station to the detector is calculated using the following formula:

[0015]

[0016] [N,E,U] T =H×([X S ,Y S ,Z S ] T -[X R ,Y R ,Z R ] T )

[0017]

[0018] Where Ele1 is the altitude angle between the VLBI station and the detector, a is the first tropospheric hydrostatic force, U is the first coordinated universal time, T is the observation time, N is the first latitude, E is the first longitude, H is the first rotation matrix, [N,E,U] T is the rectangular coordinate of the detector in the VLBI station center coordinate system, [X S ,Y S ,Z S ] T is the coordinate vector of the detector in the J2000 inertial coordinate system, [X R ,YR ,Z R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B and L are the first geodetic coordinates of the VLBI station.

[0019] In step S2, the elevation angle azimuth information in the direction from the VLBI station to the radio source is calculated, including:

[0020] The coordinates of the radio source in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The azimuth information from the VLBI station to the radio source is calculated using the following formula:

[0021]

[0022] [N',E',U'] T =H'×([X' S ,Y' S ,Z' S ] T -[X' R ,Y' R ,Z' R ] T )

[0023]

[0024] Where Ele2 is the elevation angle between the VLBI station and the radio source, a' is the second tropospheric hydrostatic force, U' is the second coordinated universal time, T is the observation time, N' is the second latitude, E' is the second longitude, H' is the second rotation matrix, [N', E', U'] T is the rectangular coordinate of the radio source in the VLBI station center coordinate system, [X' S ,Y' S ,Z' S ] T is the coordinate vector of the radio source in the J2000 inertial coordinate system, [X' R ,Y' R ,Z' R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B', L' are the second geodetic coordinates of the VLBI station.

[0025] In step S3, the radio source observation files are fused to generate a guide file in the order of observation time, including:

[0026] If the observation file is set to observe the radio source at time t, the elevation angle azimuth information of the radio source is entered in the guide file; if the observation file is set to observe the detector, the elevation angle azimuth information of the detector is entered in the guide file. The formula is as follows:

[0027]

[0028] In the formula, is the altitude angle azimuth in the microwave radiometer guidance file at time t, t is the observation time, t q , t s are the time in the file where the radio source and detector altitude angle and azimuth are located respectively, They are respectively the altitude and azimuth information of the radio source and the detector at time t.

[0029] In step S4, the microwave radiometer sets the automatic fuzzy tracking mode. Once the guide file is uploaded successfully, the microwave radiometer converts the guide file into a recognizable format and starts fuzzy tracking observation according to the time elevation angle azimuth angle information in the guide file, specifically including:

[0030] S401, establishing a time-elevation-azimuth output information tracking behavior attribute set: dividing the collected time-elevation-azimuth output information tracking behavior data into m time-elevation-azimuth output information tracking behavior attributes according to the time-elevation-azimuth output information tracking behavior characteristics; automatically setting the microwave radiometer observation direction according to the elevation angle azimuth output information tracking behavior attribute of each time-elevation-azimuth output information tracking behavior attribute;

[0031] S402, the microwave radiometer matches the time information of the guidance file with the local time. If the match is successful, the microwave radiometer moves the antenna to the specified direction according to the altitude and azimuth information corresponding to the guidance file time; if the match is unsuccessful, the microwave radiometer continues to wait;

[0032] S403, the microwave radiometer automatically saves the observation results in the specified format through the guide file into the machine; the file content includes time, temperature, humidity, pressure, total delay, dry delay and wet delay information, the file length is 1 minute, and the sampling rate is 1 second.

[0033] Furthermore, the 1-minute file is first averaged. In order to remove outliers, a threshold judgment is performed after averaging. If the delay data at any time point exceeds three times the average value, it is removed and then averaged again, and the process is repeated iteratively.

[0034] In step S6, the neutral atmosphere delay rate is calculated using the following formula:

[0035]

[0036] Where, TSTD Ris the TSTD rate, t1, t2 are adjacent times, are the total time delay TSTD of the neutral atmosphere observed by the microwave radiometer at times t1 and t2 respectively.

[0037] Another object of the present invention is to provide a VLBI station neutral atmosphere delay error correction system, which implements the VLBI station neutral atmosphere delay error correction method, and the system comprises:

[0038] A detector direction elevation angle azimuth calculation module is used to calculate the elevation angle azimuth information from the VLBI station to the detector direction based on the detector predicted ephemeris;

[0039] The module for calculating the elevation angle and azimuth angle in the direction of the radio source is used to calculate the elevation angle and azimuth angle information in the direction from the VLBI station to the radio source based on the radio source observation file;

[0040] A fusion module is used to fuse the detector elevation angle azimuth angle file and the radio source elevation angle azimuth angle file according to the radio source observation file to generate a guide file in the order of observation time;

[0041] The boot file upload module is used to automatically upload the boot files of each station to the specified path of the corresponding microwave radiometer through a script;

[0042] The smoothing filter module is used to remove the observed abnormal values ​​and the observed values ​​when the microwave radiometer rotates, and smooth the microwave radiometer observation results to obtain the sampled neutral atmosphere delay;

[0043] A neutral atmosphere delay rate calculation module is used to calculate the neutral atmosphere delay rate based on the neutral atmosphere delay set of the VLBI station;

[0044] The decomposition module is used to decompose the neutral atmosphere delay and delay rate of the detector and the radio source at the corresponding observation time based on the observation outline, and output them to different files respectively.

[0045] Furthermore, the VLBI station neutral atmosphere time delay error correction system is mounted on a computer-readable storage medium, and the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the functions of the above-mentioned VLBI station neutral atmosphere time delay error correction system can be realized.

[0046] In combination with all the above-mentioned technical solutions, the beneficial effects of the present invention are as follows: the present invention can measure the neutral atmosphere delay error of the VLBI station, which is used to weaken the influence of the neutral atmosphere delay on the observation direction of the detector and the radio source. The microwave radiometer observation strategy of the present invention is more suitable for deep space exploration VLBI observations. Based on the neutral atmosphere delay correction method determined by the present invention, the measured data can be used to correct the neutral atmosphere delay observed by the detector and the radio source. Compared with the use of the neutral atmosphere delay prediction model, the real-time correction of the neutral atmosphere delay results of the VLBI station can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0048] Figure 1 is a flow chart of a method for correcting neutral atmosphere delay errors of a VLBI station provided by an embodiment of the present invention;

[0049] Figure 2 It is a schematic diagram of a neutral atmosphere delay error correction method for a VLBI station provided by an embodiment of the present invention;

[0050] Figure 3 is a diagram of a neutral atmosphere delay error correction system for a VLBI station provided by an embodiment of the present invention;

[0051] Figure 4 This is the neutral atmosphere time delay map measured by the Tianma VLBI station during the observation of the Tianwen-1 probe;

[0052] Figure 5 This is the difference diagram between the microwave radiometer neutral atmosphere delay and the zenith delay prediction + VMF3 mapping function results;

[0053] In the figure: 1. Detector direction elevation angle azimuth calculation module; 2. Radio source direction elevation angle azimuth calculation module; 3. Fusion module; 4. Guide file upload module; 5. Smoothing filter module; 6. Neutral atmosphere delay rate calculation module; 7. Decomposition module. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0055] Embodiment 1, as Figure 1As shown, the VLBI station neutral atmosphere delay error correction method provided by the embodiment of the present invention includes:

[0056] S1: Calculate the altitude and azimuth information from the VLBI station to the detector based on the detector's predicted ephemeris;

[0057] S2: Based on the radio source observation file, calculate the elevation angle and azimuth information from the VLBI station to the radio source;

[0058] S3: Fusing the detector elevation angle azimuth file and the radio source elevation angle azimuth file according to the radio source observation file to generate a guide file in the order of observation time;

[0059] S4: Automatically upload each station’s boot file to the specified path of the corresponding microwave radiometer through the script;

[0060] S5: Eliminate observation anomalies and observations during the rotation of the microwave radiometer, smooth and filter the microwave radiometer observation results, and obtain the sampled neutral atmosphere delay;

[0061] S6: Calculate the neutral atmosphere delay rate based on the VLBI station neutral atmosphere delay set;

[0062] S7: Based on the observation outline, decompose the neutral atmosphere delay and delay rate of the detector and radio source at the corresponding observation time, and output them to different files respectively.

[0063] Exemplarily, in step S1, calculating the elevation angle azimuth information in the direction from the VLBI station to the detector includes:

[0064] The coordinates of the detector in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The elevation angle information from the VLBI station to the detector is calculated using the following formula:

[0065]

[0066] {N,E,U] T =H×([X S ,Y S ,Z S ] T -[X R ,Y R ,Z R ] T )

[0067]

[0068] Where Ele1 is the altitude angle between the VLBI station and the detector, a is the first tropospheric hydrostatic force, U is the first coordinated universal time, T is the observation time, N is the first latitude, E is the first longitude, H is the first rotation matrix, [N,E,U] T is the rectangular coordinate of the detector in the VLBI station center coordinate system, [X S ,Y S ,Z S ] T is the coordinate vector of the detector in the J2000 inertial coordinate system, [X R ,Y R ,Z R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B and L are the first geodetic coordinates of the VLBI station.

[0069] Exemplarily, in step S2, calculating the elevation angle azimuth information in the direction from the VLBI station to the radio source includes:

[0070] The coordinates of the radio source in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The azimuth information from the VLBI station to the radio source is calculated using the following formula:

[0071]

[0072] [N',E',U'] T =H'×([X' S ,Y' S ,Z'S] T -[X' R ,Y' R ,Z' R ] T )

[0073]

[0074] Where Ele2 is the elevation angle between the VLBI station and the radio source, a' is the second tropospheric hydrostatic force, U' is the second coordinated universal time, T is the observation time, N' is the second latitude, E' is the second longitude, H' is the second rotation matrix, [N', E', U'] T is the rectangular coordinate of the radio source in the VLBI station center coordinate system, [X' S ,Y' S ,Z' S ] T is the coordinate vector of the radio source in the J2000 inertial coordinate system, [X' R ,Y' R,Z' R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B', L' are the second geodetic coordinates of the VLBI station.

[0075] In another exemplary embodiment, in step S3, the radio source observation files are fused to generate a guide file in the order of observation time, including:

[0076] If the observation file is set to observe the radio source at time t, the elevation angle azimuth information of the radio source is entered in the guide file; if the observation file is set to observe the detector, the elevation angle azimuth information of the detector is entered in the guide file. The formula is as follows:

[0077]

[0078] In the formula, is the altitude angle azimuth in the microwave radiometer guidance file at time t, t is the observation time, t q ,t s are the time in the file where the radio source and detector altitude angle and azimuth are located respectively, They are respectively the altitude and azimuth information of the radio source and the detector at time t.

[0079] In another exemplary embodiment, in step S4, the microwave radiometer sets the automatic fuzzy tracking mode. Once a guide file is successfully uploaded, the microwave radiometer converts the guide file into a recognizable format and starts fuzzy tracking observation according to the time elevation angle azimuth angle information in the guide file, specifically including:

[0080] S401, establishing a time-elevation-azimuth output information tracking behavior attribute set: dividing the collected time-elevation-azimuth output information tracking behavior data into m time-elevation-azimuth output information tracking behavior attributes according to the time-elevation-azimuth output information tracking behavior characteristics; automatically setting the microwave radiometer observation direction according to the elevation angle azimuth output information tracking behavior attribute of each time-elevation-azimuth output information tracking behavior attribute;

[0081] S402, the microwave radiometer matches the time information of the guidance file with the local time. If the match is successful, the microwave radiometer moves the antenna to the specified direction according to the altitude and azimuth information corresponding to the guidance file time; if the match is unsuccessful, the microwave radiometer continues to wait;

[0082] S403, the microwave radiometer automatically saves the observation results in the specified format through the guide file into the machine; the file content includes time, temperature, humidity, pressure, total delay, dry delay and wet delay information, the file length is 1 minute, and the sampling rate is 1 second.

[0083] The 1-minute file is first averaged. In order to remove outliers, a threshold is determined after averaging. If any time point has a delay data exceeding three times the average value, it is removed and then averaged again, and the process is repeated iteratively.

[0084] In another exemplary embodiment, in step S6, the neutral atmosphere delay rate is calculated using the following formula:

[0085]

[0086] Where, TSTD R is the TSTD rate, t1, t2 are adjacent times, are the total time delay TSTD of the neutral atmosphere observed by the microwave radiometer at times t1 and t2 respectively.

[0087] Figure 2 This is a schematic diagram of a method for correcting neutral atmosphere delay errors at a VLBI station provided by an embodiment of the present invention. The present invention fuses the detector altitude angle azimuth angle file and the radio source altitude angle azimuth angle file according to the radio source observation file to generate a guide file in the order of observation time, which provides sufficient guarantee conditions for the microwave radiometer to obtain the sampled neutral atmosphere delay.

[0088] The fuzzy comprehensive evaluation system proposed in the present invention calculates the relationship between the time-elevation-azimuth output information tracking behavior and the level set to obtain the time-elevation-azimuth output information tracking behavior membership matrix, which not only describes the uncertainty and fuzziness of the time-elevation-azimuth output information tracking behavior through the time-elevation-azimuth output information tracking behavior, but also reflects the membership of the time-elevation-azimuth output information tracking behavior attributes to different levels through the association relationship between the time-elevation-azimuth output information tracking behavior and the level set. This method is more in line with objective facts. In addition, since the present invention adopts the "weight method" to adaptively assign attribute weights, different weights are assigned according to the different contributions of each time-elevation-azimuth output information tracking behavior attribute to the evaluation result, which further reduces subjectivity. Improve the accuracy of the evaluation results.

[0089] Embodiment 2, as Figure 3 As shown, the VLBI station neutral atmosphere delay error correction system provided by the embodiment of the present invention includes:

[0090] The detector direction elevation angle azimuth calculation module 1 is used to calculate the elevation angle azimuth information from the VLBI station to the detector direction based on the detector predicted ephemeris;

[0091] A radio source direction elevation angle azimuth calculation module 2 is used to calculate the elevation angle azimuth information from the VLBI station to the radio source direction based on the radio source observation file;

[0092] Fusion module 3, used to fuse the detector elevation angle azimuth angle file and the radio source elevation angle azimuth angle file according to the radio source observation file, and generate a guide file in the order of observation time;

[0093] The boot file upload module 4 is used to automatically upload the boot files of each station to the designated path of the corresponding microwave radiometer through a script;

[0094] Smoothing filter module 5, used to remove observation abnormal values ​​and observation quantities when the microwave radiometer rotates, and smooth the microwave radiometer observation results to obtain the sampled neutral atmosphere delay;

[0095] A neutral atmosphere delay rate calculation module 6, used to calculate the neutral atmosphere delay rate according to the neutral atmosphere delay set of the VLBI station;

[0096] The decomposition module 7 is used to decompose the neutral atmosphere delay and delay rate of the detector and the radio source at the corresponding observation time based on the observation outline, and output them to different files respectively.

[0097] In order to further illustrate the relevant effects of the embodiments of the present invention, the following experiment was conducted: The present invention selected the observation data of a VLBI station in a certain area on May 15, 2021 for experiment.

[0098] Get the altitude and azimuth: first write a program to read the predicted ephemeris and observation outline data of the Tianwen-1 probe, and then calculate the altitude and azimuth from the station to the probe and the radio source based on the Tianma station coordinates, the Earth's rotation parameter file, etc., and output the results to files respectively.

[0099] Merge elevation and azimuth file: Since the calculated detector elevation and azimuth are complete data covering the 1-minute sampling of the observation arc, the detector and the radio source are observed alternately during real-time observation. Therefore, the detector and radio source elevation and azimuth are merged into one file as the guide file for microwave radiometer observation.

[0100] Automatically upload the guide file and observe: Write a program to automatically upload the guide file and start it before the real-time observation begins. The microwave radiometer is set to automatic fuzzy tracking mode. Once a guide file is successfully uploaded, the microwave radiometer converts the guide file into a recognizable format and starts fuzzy tracking observation according to the time altitude angle azimuth information in the guide file.

[0101] Microwave radiometer observation delay processing: The microwave radiometer samples for 1 second. In order to obtain the neutral atmosphere delay of 1 minute sampling, the observation data is preprocessed by smoothing filtering. Outliers and observations when the microwave radiometer is rotating are eliminated.

[0102] Calculate the neutral atmosphere delay rate: Calculate the delay rate by taking the difference between the delay rate sets and dividing it by the time difference.

[0103] Among them, the global mapping function (GMF) is used to map the microwave radiometer zenith calibration to the inclined aiming direction, which is one of the accurate mapping functions in real time. The GMF formula is:

[0104]

[0105] The parameters a, b and c of the hydrostatic and wet components of the troposphere are different. These parameters are calculated using a 15°×15° global grid of the monthly average profiles of pressure, temperature and humidity from the 40-year reanalysis data of the European Centre for Medium-Range Weather Forecasts (ECMWF). According to the observation outline, the neutral atmosphere delay and delay rate corresponding to the Tianwen-1 probe and the radio source in the observation arc on May 15, 2021 are decomposed and output to different files.

[0106] in, Figure 4 This is the neutral atmosphere delay map measured by the Tianma VLBI station during the observation of the Tianwen-1 probe. The brown color is the altitude angle sequence, the black color is based on the microwave radiometer result, and the green color is the zenith delay prediction + VMF3 mapping function result; Figure 5 This is a difference diagram between the neutral atmosphere delay based on the microwave radiometer and the zenith delay prediction + VMF3 mapping function results; it shows that the results of direct observations by the microwave radiometer can be used in real time to correct the neutral atmosphere delay of the measuring station.

[0107] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for correcting neutral atmosphere delay error of a VLBI station, characterized in that: The method includes: S1: Calculate the altitude and azimuth information from the VLBI station to the detector based on the detector's predicted ephemeris; S2: Based on the radio source observation file, calculate the elevation angle and azimuth information from the VLBI station to the radio source; S3: Fusing the detector elevation angle azimuth file and the radio source elevation angle azimuth file according to the radio source observation file to generate a guide file in the order of observation time; S4: Automatically upload each station’s boot file to the specified path of the corresponding microwave radiometer through the script; S5: Eliminate observation anomalies and observations during the rotation of the microwave radiometer, smooth and filter the microwave radiometer observation results, and obtain the sampled neutral atmosphere delay; S6: Calculate the neutral atmosphere delay rate based on the VLBI station neutral atmosphere delay set; S7: Based on the observation outline, decompose the neutral atmosphere delay and delay rate of the detector and radio source at the corresponding observation time, and output them to different files respectively.

2. The method for correcting neutral atmosphere delay error of a VLBI station according to claim 1, characterized in that: In step S1, the elevation angle azimuth information in the direction from the VLBI station to the detector is calculated, including: The coordinates of the detector in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The elevation angle information from the VLBI station to the detector is calculated using the following formula: [N,E,U] T =H×([X S ,Y S ,Z S ] T -[X R ,Y R ,Z R ] T ) Where Ele1 is the altitude angle between the VLBI station and the detector, a is the first tropospheric hydrostatic force, U is the first coordinated universal time, T is the observation time, N is the first latitude, E is the first longitude, H is the first rotation matrix, [N,E,U] T is the rectangular coordinate of the detector in the VLBI station center coordinate system, [X S ,Y S ,Z S ] T is the coordinate vector of the detector in the J2000 inertial coordinate system, [X R ,Y R ,Z R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B and L are the first geodetic coordinates of the VLBI station.

3. The VLBI station neutral atmosphere delay error correction method according to claim 1, characterized in that: In step S2, the elevation angle azimuth information in the direction from the VLBI station to the radio source is calculated, including: The coordinates of the radio source in the J2000 inertial coordinate system are converted into rectangular coordinates in the station center coordinate system, the earth rotation parameters are corrected, and the Doppler and aberration are corrected using the model recommended by IERS2010. The azimuth information from the VLBI station to the radio source is calculated using the following formula: Where Ele2 is the elevation angle between the VLBI station and the radio source, a' is the second tropospheric hydrostatic force, U' is the second coordinated universal time, T is the observation time, N' is the second latitude, E' is the second longitude, H' is the second rotation matrix, [N', E', U'] T is the rectangular coordinate of the radio source in the VLBI station center coordinate system, [X' S ,Y' S ,Z' S ] T is the coordinate vector of the radio source in the J2000 inertial coordinate system, [X' R ,Y' R ,Z' R ] T is the coordinate vector of the VLBI station in the J2000 inertial coordinate system, and B', L' are the second geodetic coordinates of the VLBI station.

4. The VLBI station neutral atmosphere delay error correction method according to claim 1, characterized in that: In step S3, the radio source observation files are fused to generate a guide file in the order of observation time, including: If the observation file is set to observe the radio source at time t, the elevation angle azimuth information of the radio source is entered in the guide file; if the observation file is set to observe the detector, the elevation angle azimuth information of the detector is entered in the guide file. The formula is as follows: In the formula, is the altitude angle azimuth in the microwave radiometer guidance file at time t, t is the observation time, t q ,t s are the time in the file where the radio source and detector altitude angle and azimuth are located respectively, They are respectively the altitude and azimuth information of the radio source and the detector at time t.

5. The VLBI station neutral atmosphere delay error correction method according to claim 1, characterized in that: In step S4, the microwave radiometer sets the automatic fuzzy tracking mode. Once a guide file is uploaded successfully, the microwave radiometer converts the guide file into a recognizable format and starts fuzzy tracking observation according to the time elevation angle and azimuth angle information in the guide file.

6. The method for correcting neutral atmosphere delay error of a VLBI station according to claim 5, characterized in that: Start fuzzy tracking observation according to the time elevation angle and azimuth angle information in the guide file, including: S401, establishing a time-elevation-azimuth output information tracking behavior attribute set: dividing the collected time-elevation-azimuth output information tracking behavior data into m time-elevation-azimuth output information tracking behavior attributes according to the time-elevation-azimuth output information tracking behavior characteristics; automatically setting the microwave radiometer observation direction according to the elevation angle azimuth output information tracking behavior attribute of each time-elevation-azimuth output information tracking behavior attribute; S402, the microwave radiometer matches the time information of the guidance file with the local time. If the match is successful, the microwave radiometer moves the antenna to the specified direction according to the altitude and azimuth information corresponding to the guidance file time; if the match is unsuccessful, the microwave radiometer continues to wait; S403, the microwave radiometer automatically saves the observation results in the specified format through the guide file into the machine; the file content includes time, temperature, humidity, pressure, total delay, dry delay and wet delay information, the file length is 1 minute, and the sampling rate is 1 second.

7. The neutral atmosphere delay error correction method for a VLBI station according to claim 6, wherein in step S403, the 1-minute file is first averaged, and in order to remove outliers, a threshold judgment is performed after averaging. If the delay data of any time point exceeds three times the average value, it is removed and then averaged, and the process is repeated iteratively.

8. The VLBI station neutral atmosphere delay error correction method according to claim 1, characterized in that: In step S6, the neutral atmosphere delay rate is calculated using the following formula: Where, TSTD R is the TSTD rate, t1, t2 are adjacent times, are the total time delay TSTD of the neutral atmosphere observed by the microwave radiometer at times t1 and t2 respectively.

9. A VLBI station neutral atmosphere delay error correction system, characterized in that: The system implements the VLBI station neutral atmosphere delay error correction method as claimed in any one of claims 1 to 8, and the system comprises: A detector direction elevation angle azimuth angle calculation module (1) is used to calculate the elevation angle azimuth angle information from the VLBI station to the detector direction based on the detector predicted ephemeris; A radio source direction elevation angle azimuth calculation module (2) is used to calculate the elevation angle azimuth information from the VLBI station to the radio source direction based on the radio source observation file; A fusion module (3) is used to fuse the detector elevation angle azimuth angle file and the radio source elevation angle azimuth angle file according to the radio source observation file to generate a guide file in the order of observation time; A boot file upload module (4), used to automatically upload the boot file of each station to the designated path of the corresponding microwave radiometer through a script; A smoothing filter module (5) is used to remove abnormal observation values ​​and observation quantities when the microwave radiometer rotates, and to perform smoothing filtering on the observation results of the microwave radiometer to obtain a sampled neutral atmosphere delay; A neutral atmosphere delay rate calculation module (6), used for calculating the neutral atmosphere delay rate according to the neutral atmosphere delay set of the VLBI station; The decomposition module (7) is used to decompose the neutral atmosphere delay and delay rate of the detector and the radio source at the corresponding observation time based on the observation outline, and output them to different files respectively.

10. The VLBI station neutral atmosphere delay error correction system according to claim 9, characterized in that: The VLBI station neutral atmosphere time delay error correction system is mounted on a computer-readable storage medium, and the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the functions of the VLBI station neutral atmosphere time delay error correction system are realized.

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