A rapid measurement method for multi-station multi-following prism aiming at telescope reference point

Abstract

This invention relates to a rapid measurement method for a telescope reference point using multiple stations and multiple moving prisms. Multiple prisms are fixed on the telescope, and these prisms move in sync with changes in the telescope's pointing direction. The method includes loading prior information, calculating and statistically analyzing the two-dimensional distribution of the pointing angles of each prism, and selecting the most concentrated location to update the fixed pointing angle of the prism. Based on the updated fixed pointing angles of the prisms, the telescope's pointing angle is calculated, and a centered grid expansion is performed on each pointing direction. Telescope pointing angles that meet preset conditions are then selected and retained. Given ground station coordinates, moving prism position parameters and attitude, telescope azimuth / elevation, and a time window for the observation framework, a large number of dispersed target points can be acquired within a short period. This generates a continuous observation framework that allows multiple ground stations to simultaneously observe different prisms, enabling rapid monitoring of the telescope reference point using high-precision measured data.

Description

Technical Field

[0001] This invention relates to the field of pointing and observation scheduling technology of telescopes or antennas, multiple follower prisms and multiple ground monitoring devices (total stations), specifically to a rapid measurement method for a telescope reference point using multiple stations and multiple follower prisms. Background Technology

[0002] The reference point coordinates of a VLBI telescope are a crucial element in spatial reference. The reference point is defined as the orthogonal projection point from the telescope's trailing axis to its active axis. Changes in the position of this point are a comprehensive manifestation of numerous geophysical and telescope deformation effects. However, due to the telescope's structural characteristics, this point is not visible. Currently, two methods are available for determining accurate reference point coordinates. The first method uses VLBI-connected time-delay observations to calculate the reference point coordinates. The second method relies on GNSS combined with optical measurements. By observing a target moving with the telescope and combining this with a certain centering algorithm, the reference point coordinates can also be calculated. The reference point coordinates obtained by the two methods are consistent, thus identifying multi-technical system differences. This method is commonly used for site calibration of new VLBI telescopes. Considering that traditional target measurements require manual interaction, primarily achieved by manually twisting the prism to move the spherical prism... Face-to-face observation with the total station presents challenges. If the incident angle between the total station's ranging laser and the spherical prism is greater than 40 degrees, the prism becomes invisible. If it's greater than 20 degrees, it introduces significant systematic errors into the ranging and angular measurement information. Combined with telescope rotation time, the calibration time for a single target point can take at most about one minute, allowing only one target point coordinate to be observed at a time. When multiple stations simultaneously observe multiple targets (prisms), visible candidate pointing directions need to be selected and robust timing commands generated under telescope elevation / azimuth motion constraints and occlusion constraints. Existing technologies have shortcomings in the collaborative optimization of "mutual station visibility angle thresholds," "candidate pointing expansion / screening," and "timing balance and azimuth interval constraints." Summary of the Invention

[0003] The purpose of this invention is to provide a rapid measurement method for multiple stations and multiple follow-up prisms for telescope reference points, in order to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a rapid measurement method for a multi-station, multi-follower prism for a telescope reference point, wherein multiple prisms are fixed on the telescope, and the prisms follow the telescope as its orientation changes. The method includes the following steps:

[0005] Load prior information and calculate the pointing angle of the corresponding telescope when a certain prism is face-to-face with the ground station;

[0006] Based on the pointing angle of the telescope, calculate the pointing angle that each prism needs to rotate in the corresponding prism coordinate system when it is facing other corresponding ground stations.

[0007] The two-dimensional distribution of the pointing angles of each prism is statistically analyzed, and the position with the highest concentration is selected to update the fixed pointing angle of the prism.

[0008] The telescope's pointing angle is calculated based on the updated fixed pointing angle of the prism, and a centered grid expansion is performed on each pointing angle. The telescope pointing angles that meet the preset conditions are then selected and retained.

[0009] Based on the preserved telescope pointing angle, a continuous observation framework is generated that allows multiple ground stations to be simultaneously visible to different prisms, enabling rapid multi-station collaborative monitoring of the servo prism.

[0010] Preferably, loading prior information specifically involves: reading the prism prior information, including prism structural parameters a and b; the prism's initial pitch angle OE; and the prism's pitch and azimuth angles in the prism coordinate system. The three transformation angles from the prism coordinate system to the telescope coordinate system. Prism constant (PC), ground station information, and north orientation angle of the local control network (LCN) The telescope reference point RP, the telescope elevation range [Elmin, Elmax], and the time window required to develop the observation outline.

[0011] Preferably, the pointing angle of the telescope includes azimuth AZ and elevation EL, and the calculation of azimuth AZ and elevation EL is as follows:

[0012] Calculate the angle between the direction of a single prism and the point on the ground from that prism. :

[0013] ;

[0014] Let the included angle If the value is 0, the azimuth angle AZ and elevation EL are calculated, and the elevation EL is satisfied that it does not exceed the elevation range of the telescope [Elmin, Elmax].

[0015] Preferably, the pointing angles that the prism needs to rotate in the corresponding prism coordinate system include pitch and azimuth. Based on the telescope's pointing angle, calculate the pitch and azimuth angles that each prism needs to rotate in the corresponding prism coordinate system. Statistical analysis of the elevation and azimuth angles of each prism. Two-dimensional distribution, selecting the most concentrated location to update the corresponding prism's fixed pitch and azimuth angles. .

[0016] Preferably, the telescope's pointing angle is calculated based on the updated fixed pointing angle of the prism, a preset pitch and azimuth interval is given, and a centered grid expansion is carried out for each pointing direction within ±20°.

[0017] Preferably, the preset screening condition is that the angle between the direction of the prism and the distance from the prism to the ground station is less than 20°.

[0018] Preferably, the telescope pointing angle timing is rearranged and optimized by changing the observation sequence of the telescope azimuth angle, so that the telescope moves back and forth at a preset angle interval within a preset time, ensuring that the rotating part of the telescope is heated evenly.

[0019] More preferably, the preset angle is 180°.

[0020] Preferably, when the ground station has no observation follow-up prism at a certain moment, the ground station is used to monitor the ground fixed prism at that moment.

[0021] Beneficial effects: (1) Under the given ground station coordinates, follow-up prism position parameters and attitude, telescope azimuth / elevation and outline time window conditions, the present invention can acquire a large number of dispersed target points in a short period of time, generate a continuous observation outline that satisfies the simultaneous visibility of different prisms by multiple ground stations, and realize the rapid monitoring of telescope reference points using high-precision measured data.

[0022] (2) The present invention has significant advantages in improving the efficiency of telescope reference point measurement and data acquisition capability. Through automated calculation and scheduling, the method of the present invention can acquire a large amount of widely distributed target point data within a given time window, effectively overcoming the limitations of traditional target measurement which heavily relies on manual interaction, can only observe one target point at a time, and takes a long time (about 1 minute to measure 1 point). Experimental results show that compared with the traditional method, which theoretically has an upper limit of 300 measurement points in 5 hours, the rapid measurement mode of the present invention actually acquired 455 effective follow-up target points, greatly improving the observation efficiency and data density.

[0023] (3) In terms of ensuring measurement accuracy and controlling system errors, the present invention achieves sub-millimeter level reference point measurement accuracy through strict geometric constraints; the present invention sets screening preset conditions to ensure that the angle between the prism pointing and the ground station is less than 20 degrees, thereby avoiding the problem of significant distance and angle measurement system errors caused by excessive incident angle, or the problem of the prism being invisible due to the angle exceeding 40 degrees; in addition, the present invention also designs an "interleaving mode", that is, if there is no telescope prism to observe at a certain moment, the ground station can switch to monitoring the ground prism, thereby calibrating the motion of the ground station and correcting the system errors introduced therefrom.

[0024] (4) This invention also solves the problem of observation scheduling under complex conditions through a multi-station collaborative and optimized operation strategy; it can automatically generate continuous observation outlines that satisfy the simultaneous visibility of multiple ground stations to different prisms based on prior information and occlusion constraints, thus solving the shortcomings of existing technologies in mutual station visibility judgment and pointing selection. At the same time, this method fully considers the impact of environmental factors on the equipment. By rearranging and optimizing the timing of the telescope pointing angle, the telescope moves back and forth at large intervals of azimuth angles in a short period of time, ensuring that the rotating part is heated evenly, thereby effectively reducing the impact of thermal deformation on measurement accuracy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating whether the ground station and the prism of the present invention can be synchronously aligned;

[0026] Figure 2 This is a flowchart of the rapid measurement method for multi-station, multi-follower prisms at a telescope reference point according to the present invention. Detailed Implementation

[0027] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0028] like Figure 1 As shown, the telescope is in a certain state The three prisms were positioned precisely at the three ground monitoring stations. Figure 1 In the middle (a) diagram, after the telescope is switched to a different orientation, only one prism is aligned with the ground station. Figure 1 As shown in Figure (b), this invention aims to determine the direction of the telescope and adjust the direction of each prism, enabling the switching of the telescope's direction. Upon arrival, there will be two or more prisms aligned with the ground station (the angle between the prism's pointing direction and its distance from the ground station is less than 20 degrees). (See reference.) Figure 2 As shown, a rapid measurement method for multiple stations and multiple follower prisms at a telescope reference point is provided, as detailed below:

[0029] Step 1: Load prior information, including: reading prism prior information including prism structural parameters a and b, in meters; prism initial pitch angle OE, in deg / rad; and prism pitch and azimuth angles in the prism coordinate system. The unit is deg|rad; the three transformation angles from the prism coordinate system to the telescope coordinate system. (Unit: deg | rad), prism constant PC (unit: m), ground station information, north orientation angle of the local control network (LCN) (Units are deg | rad), telescope reference point RP, telescope elevation range [Elmin, Elmax], and time window required for compiling the observation outline, etc.;

[0030] Each telescope is equipped with a fixed prism, and the prism moves with the corresponding telescope as its direction changes. Determine whether the prism's direction needs to be adjusted. If adjustment is needed, proceed to step 2.

[0031] Step 2: Perform a double loop for both the station and the prism to calculate the required pointing angle of the telescope when one of the prisms is "face-to-face" with a ground monitoring station. This includes the azimuth angle AZ and the elevation angle EL (in deg / rad). Determine the optimal pointing angle of the telescope, i.e., the pointing angle of the telescope when a certain prism is exactly "face-to-face" with the ground station. Details are as follows:

[0032] The orientation u of the prism in the local coordinate system can be expressed as:

[0033] ;

[0034] in, These are the geometric / assembly parameters of the prism relative to the telescope; the three transformation angles from the prism coordinate system to the telescope coordinate system; Represents a rotation matrix about the z-axis or the third axis; Represents a rotation matrix about the y-axis or the second axis. The unit length can be set to 1;

[0035] The vector v from the prism pointing to the total station can be expressed by the following formula:

[0036] ;

[0037] in, These are the prior coordinates of the reference point in the local system, in meters. Let be the rotation matrix about the 1st, 2nd, and 3rd axes. These are the coordinates of the ground monitoring station (total station) in the local coordinate system.

[0038] ;

[0039] To obtain high-precision target ranging and angle measurement observations, it is necessary to ensure that:

[0040] ;

[0041] Based on the above formula, It can be represented as the following function:

[0042] ;

[0043] In the formula, These are the coordinate components of the ground monitoring station in the local coordinate system, in meters (m). Together These four parameters need to be determined in advance, along with the ground station coordinates. It is also in a fixed position, and the angle between the direction of a single follower prism and the point on the ground is... , can be represented as:

[0044] ;

[0045] At this point, the included angle can be set =0, Determined by the angle of the prior input, a set of partial derivatives of the above equation can be calculated. , such as the calculated If the telescope's design parameters [Elmin, Elmax] are exceeded (in deg / rad), adjustments can be made. We need to recalculate the azimuth AZ and elevation EL from the angle of reference.

[0046] Step 3: Based on the pointing angle of the telescope, calculate the pointing angles that each prism needs to rotate in its corresponding prism coordinate system when facing other ground stations; including elevation and azimuth angles. By fixing the azimuth angle AZ and the elevation angle EL, the elevation and azimuth angles can be solved. Thus, corresponding to the telescope pointing direction calculated in step 2, each prism has a set of [properties] relative to each ground station. angle;

[0047] Step 4: Calculate the optimal pointing angle for each prism based on visibility. In this embodiment, the pitch and azimuth angles that each prism needs to rotate in the corresponding prism coordinate system are calculated based on the telescope's pointing angle. Statistical analysis of the elevation and azimuth angles of each prism. Two-dimensional distribution, selecting the most concentrated location to update the corresponding prism's fixed pitch and azimuth angles. .

[0048] Based on the updated prism pointing information, the telescope pointing information is calculated in step 2; it is determined whether the prism pointing needs to be adjusted, and if no adjustment is needed, step 5 is executed.

[0049] Step 5: Perform a double loop for the station and the prism to calculate the pointing angle that the telescope needs to rotate when one of the prisms is "face to face" with a ground monitoring station;

[0050] Step 6: Based on the pointing angle in Step 5, give a certain azimuth and elevation interval, and expand the telescope pointing into a grid within ±20 degrees;

[0051] Step 7: Perform centering grid expansion for each of the above pointing angles. The purpose is to obtain target scatter points with certain spatial distribution characteristics, such as using Δ =10°、Δ =10°, nstep=1. Re-expand and calculate to obtain the orientation of prism 1 and the angle between prism 1 and ground station 1. The angle between the direction of prism 2 and the distance from prism 2 to ground station 2. wait;

[0052] Step 8: Based on the included angle calculated in Step 7, apply... <20° The <20° double constraint means that the angle between the prism's pointing direction and the prism's distance from the ground station is less than 20°, and these telescope pointing angles that meet the conditions are retained; based on the retained telescope pointing angles, a continuous observation outline is generated that allows multiple ground stations to be simultaneously visible to different prisms, so as to realize multi-station collaborative and rapid monitoring of the servo prism.

[0053] In one embodiment, considering the uniform thermal deformation of the telescope, the telescope pointing angle timing can be rearranged and optimized. By changing the observation sequence of the telescope azimuth angle, the telescope can move back and forth at a preset large interval of azimuth angle within a short period of time, for example, moving back and forth at an interval of about 180 degrees, to ensure that the rotating part of the telescope is heated uniformly.

[0054] In one embodiment, if the ground station has no observation follow-up prism at a certain moment, the ground station can monitor the ground fixed prism at that moment, i.e., in an interleaved mode, to further calibrate the motion of the ground station and correct the systematic error introduced by the motion of the ground station.

[0055] This application also provides a specific embodiment that comprehensively analyzes the rapid measurement method for multi-station, multi-follower prisms for telescope reference points provided above, as follows:

[0056] The actual reference settings used the following parameters:

[0057] First expansion: ΔAZ = ΔEL = 5°, nStep = 0 (center point).

[0058] Second extension: ΔAZ=ΔEL=6°, nStep=3 (7×7 grid).

[0059] Angle threshold: 20° for initial screening, and approximately 18° for secondary screening.

[0060] Timing parameters: TIMEGAP = 60 s; UTC = Beijing time − 8h.

[0061] From 20:00 on September 16, 2025 to 01:00 on September 17, 2025 (Beijing Time), a rapid measurement experiment was conducted around the Shanghai Tianma VGOS station using a stop-and-go mode. Using the traditional method, measuring one homing target point per minute theoretically limits the number of monitoring points for each homing target point to 300. However, using the rapid measurement method, a total of 455 homing target points were actually obtained, and 417 target points were actually used in the centering calculation. The table below shows the calculated telescope reference point, axis parameters, and their mean square error. The results indicate that a 5-hour rapid measurement experiment can achieve sub-millimeter accuracy for determining the telescope reference point.

[0062] Table 1. Coordinates of the telescope reference point and axis parameters calculated in rapid measurement mode.

[0063] parameter Meaning (unit) Value and Precision The x-component (m) of the telescope reference point's coordinates in the local frame. -70.903939 +- 0.000118 The y-component (m) of the telescope reference point in the local frame. 69.685964 +- 0.000112 The z-component (m) of the telescope reference point's coordinates in the local frame. 10.778628 +- 0.000512 𝛂 Eastward tilt of the azimuth axis (as, arcseconds) -224.657040 +- 14.037959 Azimuth axis southward tilt (as, arcseconds) 76.141645 +- 11.120297 Pitch axis tilt angle (as, arcseconds) 9.956289 +- 39.060332 Telescope axis deviation (m, arcseconds) 0.000534 +- 0.000509 Local north orientation angle (am, arcminutes) 125.215603 +- 0.010709

[0064] The embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above embodiments. For those skilled in the art, after learning the contents described in the present invention, several equivalent changes and substitutions can be made without departing from the principle of the present invention. These equivalent changes and substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A rapid measurement method for a multi-station, multi-follower prism for a telescope reference point, wherein multiple prisms are fixed on the telescope, and the prisms follow the telescope as its orientation changes, characterized in that: The method includes the following steps: Load prior information and calculate the pointing angle of the corresponding telescope when a certain prism is face-to-face with the ground station; Based on the pointing angle of the telescope, calculate the pointing angle that each prism needs to rotate in the corresponding prism coordinate system when it is facing other corresponding ground stations. The two-dimensional distribution of the pointing angles of each prism is statistically analyzed, and the position with the highest concentration is selected to update the fixed pointing angle of the prism. The telescope's pointing angle is calculated based on the updated fixed pointing angle of the prism, and a centered grid expansion is performed on each pointing angle. The telescope pointing angles that meet the preset conditions are then selected and retained. Based on the preserved telescope pointing angle, a continuous observation framework is generated that allows multiple ground stations to be simultaneously visible to different prisms, enabling rapid multi-station collaborative monitoring of the servo prism.

2. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 1, characterized in that: Loading prior information specifically involves: reading the prism's prior information, including prism structural parameters a and b; the prism's initial pitch angle OE; and the prism's pitch and azimuth angles in the prism coordinate system. The three transformation angles from the prism coordinate system to the telescope coordinate system. Prism constant (PC), ground station information, and north orientation angle of the local control network (LCN) The telescope reference point RP, the telescope elevation range [Elmin, Elmax], and the time window required to develop the observation outline.

3. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 2, characterized in that: The telescope's pointing angle includes azimuth AZ and elevation EL. The specific calculation of azimuth AZ and elevation EL is as follows: Calculate the angle between the direction of a single prism and the point on the ground from that prism. : ； Let the included angle If the value is 0, the azimuth angle AZ and elevation EL are calculated, and the elevation EL is satisfied that it does not exceed the elevation range of the telescope [Elmin, Elmax].

4. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 3, characterized in that: The prism needs to be rotated in the corresponding prism coordinate system by the pointing angles including pitch and azimuth. Based on the telescope's pointing angle, calculate the pitch and azimuth angles that each prism needs to rotate in the corresponding prism coordinate system. Statistical analysis of the elevation and azimuth angles of each prism. Two-dimensional distribution, selecting the most concentrated location to update the corresponding prism's fixed pitch and azimuth angles. .

5. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 4, characterized in that: The telescope's pointing angle is calculated based on the updated fixed pointing angle of the prism, and the preset pitch and azimuth intervals are given. The center grid expansion is carried out for each pointing direction within ±20°.

6. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 5, characterized in that: The preset screening condition is that the angle between the prism's direction and the angle between the prism and the ground station is less than 20°.

7. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 1, characterized in that: The telescope pointing angle timing was rearranged and optimized by changing the observation sequence of the telescope azimuth angle, so that the telescope moves back and forth at a preset angle interval within a preset time, ensuring that the rotating parts of the telescope are heated evenly.

8. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 7, characterized in that: The preset angle is 180°.

9. The rapid measurement method for multi-station, multi-follower prisms of a telescope reference point according to claim 1, characterized in that: When there is no servo prism to observe at a certain moment, the ground station is used to monitor the fixed ground prism at that moment.

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