CN106200697A - A kind of radio telescope points to real-time correcting method - Google Patents

Abstract

The invention discloses a method for correcting the pointing of a radio telescope in real time, comprising the following steps: controlling the radio telescope to scan a radio source at least once in the direction of right ascension and in the direction of declination to obtain scanning data of right ascension and scanning data of declination; A linear function and a Gaussian function are used to construct a parametric model for describing the right ascension scan data and the declination scan data, and the parameter model includes parameters describing pointing errors; the right ascension scan data and the declination scan data are substituted into the parameters Using a fitting algorithm to obtain the pointing errors in the right ascension and declination directions, and then obtain the pointing errors in the azimuth and elevation directions through coordinate conversion; based on the pointing errors, control the radio telescope to correct the pointing to eliminate the pointing errors. The radio telescope pointing real-time correction method disclosed by the invention can be used for real-time correction of the radio telescope pointing to eliminate pointing errors in real time, and can solve the problem of too fast azimuth operation during high-elevation-angle scanning under the azimuth and pitch coordinate systems.

Description

A Real-time Correction Method of Radio Telescope Pointing

technical field

The invention relates to a radio telescope pointing correction method, in particular to a radio telescope pointing correction method in real time.

Background technique

The deviation of the actual pointing position of the radio telescope when observing the target relative to the theoretical position of the observed target is called pointing error. The electrical axis and mechanical axis of radio telescopes have strict orthogonality and consistency requirements, but due to the influence of various factors such as atmospheric refraction, manufacturing and assembly errors of the telescope, gravity, wind load and temperature load effects, the telescope pointing error will be caused . Pointing accuracy is one of the important indicators to measure the performance of radio telescopes. Its advantages and disadvantages not only affect the single-point observation efficiency of the telescope, but also affect the accuracy of imaging observations. Among the factors that affect the pointing accuracy of the telescope, most of them have special regularity and repeatability, which can be corrected by using the established pointing model, but there are also some factors that have the characteristics of random changes, such as backlash and hysteresis in the structure, temperature Such factors as wind and wind cannot be accurately described by parameter models, and such factors will produce large pointing errors, which greatly affect the performance of the telescope.

At present, there are also methods for correcting the pointing of the telescope to eliminate pointing errors in the prior art, for example:

[1] Ott M, Witzel A, Quirenbach A, et al.An updated list of radio fluxdensity calibrators[J].Astronomy&Astrophysics,1994,284:331-339;

[2]Kong Deqing,Wang Songgen,Wang Jinqing,et al.A new calibration model for pointing a radio telescope that considers nonlinear errors in the azimuth axis[J].Research in Astronomy and Astrophysics,2014,14(6):733-740.4 ;

[3] Zhang Juyong. Structural Mechanics Analysis and Error Research of Large Radio Antennas [D]. Beijing: National Astronomical Observatory of Chinese Academy of Sciences, 2006;

[4] Jiang Zhengyang, Kong Deqing, Zhang Hongbo, et al. Pointing Correction Method of Radio Telescope Considering Orbital Roughness [J]. Astronomical Research and Technology, 2015,12(4):417-423;

[5] Yu Linfeng, Wang Jinqing, Zhao Rongbing, et al. Establishment of pointing model for TM65m radio telescope [J]. Acta Astronomical Scientia, 2015, 56(2): 165-177.

Yet these methods in the prior art still have following shortcoming:

(1) Scanning in the azimuth and elevation coordinate system results in too fast azimuth operation at high elevation angles, which affects the calculation of pointing errors, and does not support real-time correction.

(2) The pointing model established on the full pitch and all directions is a fitting result, and there are large errors in some azimuth and pitch angles.

(3) Only the pointing error caused by the azimuth axis and orbital roughness is considered, and the influence of other factors on the pointing error is not considered.

(4) Only the antenna pointing error model based on the least squares vector machine is proposed. This model needs further research in terms of kernel function and control parameter selection, and experimental verification of comprehensive environmental factors.

For this reason, it is desired to obtain a method for correcting the pointing of a radio telescope in real time, so as to correct the pointing error of the radio telescope in real time, while overcoming most of the above shortcomings.

Contents of the invention

The object of the present invention is to provide a real-time correction method for radio telescope pointing, which can be used for real-time correction of radio telescope pointing to eliminate pointing errors in real time.

According to the purpose of the above invention, the present invention proposes a radio telescope pointing real-time correction method, which includes the following steps:

Control the radio telescope to scan a radio source at least once in the right ascension direction and the declination direction to obtain the right ascension scanning data and the declination scanning data, wherein the right ascension scanning data includes the right ascension data and its The corresponding radio source power data, the declination scanning data includes the declination data and the corresponding radio source power data scanned in the direction of declination;

Constructing a first parametric model for describing the right ascension scan data based on a linear function and a Gaussian function Among them, x1 is the right ascension data, _y1 is the radio source power data corresponding to x1, parameter _k1 is the baseline slope, parameter _b1 is the baseline constant, parameter _a1 is the _{amplitude of} the Gaussian function, and parameter _m1 is the red The pointing error in the warp direction, the parameter n is the Gaussian function half-power beam width;

constructing a second parametric model for describing the declination scan data based on a linear function and a Gaussian function Wherein, _x2 is the declination data, _y2 is the radio source power data corresponding to _x2 , the parameter _k2 is the baseline slope, the parameter b2 is the baseline constant, the parameter _a2 is the Gaussian function amplitude, and the parameter _{m2 is} the red Pointing error in the latitudinal direction, parameter n is Gaussian function half-power beam width;

Substituting the right ascension scan data into the first parameterized model, and specifying the initial values of k ₁ , b ₁ , a ₁ , n and m ₁ ; substituting the declination scan data into the second parameterized model, and specifying k ₂ , the initial values of b ₂ , a ₂ , n and m ₂ ; based on the first parameterized model substituted into the right ascension scan data and the second parameterized model substituted into the declination scan data, the parameter m is calculated using the least squares fitting algorithm ₁ and the parameter m ₂ to obtain the pointing error in the direction of right ascension and the pointing error in the direction of declination;

Convert the pointing error in the right ascension direction and the pointing error in the declination direction to the pointing error in the azimuth direction and the pitch direction through coordinate conversion, and then control the radio telescope based on the pointing error in the azimuth direction and the pitch direction to eliminate the pointing error.

The method for correcting the pointing of a radio telescope in real time according to the invention can be used for correcting the pointing of a radio telescope in real time, so as to eliminate pointing errors in real time. The principle is: scan a radio source in the direction of right ascension and declination respectively. When the radio telescope has a pointing error, the scanned data of right ascension and declination are different in a unified coordinate system. If this difference can be eliminated, the pointing error can be eliminated. Therefore, it is considered to construct a parametric model for describing the right ascension scan data and declination scan data based on linear functions and Gaussian functions, which contains parameters describing the pointing error in the right ascension direction and the pointing error in the declination direction . Because the difference can be eliminated by fitting the right ascension scan data and the declination scan data under the unified coordinate system, the parameters of the pointing error in the right ascension direction and the pointing error in the declination direction are obtained by using the fitting method, and then The pointing error in the right ascension direction and the pointing error in the declination direction are converted to the pointing error in the azimuth direction and the elevation direction through coordinate conversion, and this parameter characterizes the pointing error of the radio telescope. Based on this parameter, the radio telescope can be controlled to perform real-time pointing correction, so as to eliminate the pointing error in real time.

Further, in the real-time correction method of radio telescope pointing according to the present invention, data preprocessing is performed on the right ascension scan data and declination scan data after the right ascension scan data and declination scan data are acquired.

Furthermore, in the method for real-time correction of radio telescope pointing, the data preprocessing includes one or more of background removal, calibration, calibration, and interpolation.

Furthermore, in the above-mentioned method for correcting the pointing of a radio telescope in real time, the right ascension scanning data and the declination scanning data represented by the corresponding antenna pattern are obtained based on the data preprocessing.

In the above solution, the accuracy and precision of the finally obtained pointing error can be improved through data preprocessing. The antenna pattern is a graph embodied in a coordinate system obtained through data preprocessing of the right ascension scanning data and declination scanning data.

Further, in the method for real-time correction of radio telescope pointing described in the present invention and above, the parameter a1 adopts the maximum value _{of y1} , and the parameter _a2 adopts the maximum value of _y2 .

_In the above scheme, the parameter a1 adopts the maximum value _{of y1} , and the parameter a2 adopts the maximum value of _y2 in order to reduce the fitting error. It is reflected in the antenna pattern that parameter a ₁ and parameter a ₂ adopt the peak value of the antenna pattern.

Further, in the real-time correction method of the radio telescope pointing described in the present invention and above, the parameter n adopts the estimated half-power beam width, and its calculation method is as follows:

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.2</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ,</span>$

Wherein, λ is the wavelength of the radio source, and D is the diameter of the radio telescope.

Furthermore, in the method for real-time pointing correction of the radio telescope described in the present invention and above, the scan length of the scan is greater than four times the width of the half-power beam.

Furthermore, in the method for real-time correction of radio telescope pointing described in the present invention and above, the scanning length in both the right ascension and declination directions is 500 arc seconds, and the scanning speed is 10 arc seconds/second.

In the above solution, the scanning length and the scanning speed can be considered at the same time, and the scanning speed should not be too fast or too slow.

The radio telescope pointing real-time correction method described in the present invention has the following advantages and beneficial effects:

(1) Pointing can be corrected in real time to eliminate pointing errors in real time.

(2) Since there is a rotation angle between the celestial coordinate system formed by right ascension and declination and the horizontal coordinate system of azimuth and elevation of the radio telescope, scanning in the direction of right ascension and declination can solve the altitude problem in the azimuth and elevation coordinate system. When scanning at an elevation angle, the azimuth running speed is too fast to improve the pointing accuracy of the radio telescope at high elevation angles.

(3) Basically applicable to pointing errors caused by all factors.

Description of drawings

FIG. 1 is a schematic flow chart of a method for real-time correction of radio telescope pointing in an embodiment of the present invention.

Fig. 2 is a schematic diagram of scanning tracks in right ascension and declination directions of the method for real-time correction of radio telescope pointing according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of the right ascension scan data and declination scan data represented by the corresponding antenna pattern before the corrected pointing of the radio telescope pointing real-time correction method according to one embodiment of the present invention.

Fig. 4 is a schematic diagram of right ascension scanning data and declination scanning data represented by corresponding antenna pattern after correcting the pointing of the radio telescope pointing real-time correction method according to one embodiment of the present invention.

detailed description

The method for real-time correction of radio telescope pointing according to the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 schematically illustrates the flow of a method for real-time correction of radio telescope pointing in an embodiment of the present invention. Fig. 2 illustrates the scanning trajectory in the direction of right ascension and the direction of declination in one embodiment of the real-time correction method of radio telescope pointing according to the present invention, wherein, the abscissa RA/arcsec represents the right ascension data, and the unit is arc second , the ordinate DEC/arcsec represents declination data, unit arc second. Fig. 3 illustrates the right ascension scan data and declination scan data represented by the corresponding antenna pattern in the correction method of the radio telescope pointing real-time correction method in one embodiment, wherein, the abscissa RA or DEC /arcsec means that right ascension data and declination data are shared, the unit is arc second, and the ordinate Ta/K means radio source power data, and the unit is Kelvin. Figure 4 illustrates the right ascension scan data and declination scan data represented by the corresponding antenna pattern after the correction method of the radio telescope pointing real-time correction method according to the present invention in one embodiment, where the abscissa RA or DEC /arcsec means that right ascension data and declination data are shared, the unit is arc second, and the ordinate Ta/K means radio source power data, and the unit is Kelvin.

As shown in Figure 1, with reference to Figures 2-3, the real-time correction method for radio telescope pointing in this embodiment includes the following steps:

Step 110: To implement this step, Ku-band receivers and continuum astronomy terminals need to be prepared (usually radio telescopes are equipped with high-performance Ku-band receivers and continuum terminals). In order to eliminate the gain fluctuation of the receiver and the system temperature change, the Ku-band receiver in this step has a periodic calibration signal injection function. Select a strong flow (greater than 3 Jansky) and dense continuum point source as the radio source, turn on the periodic calibration signal of the Ku-band receiver under fine weather conditions, and control the radio telescope according to the trajectory shown in Figure 1 Carry out a scanning observation of a radio source in the right ascension direction (line segment A in Figure 1) and declination direction (line segment B in Figure 1) and record the scanned right ascension data and declination data, and use the Ku-band receiver to receive The scanned radio signal, and the power value of the radio signal is recorded by the astronomical terminal, so that the right ascension scanning data and the declination scanning data are obtained, where the right ascension scanning data includes the right ascension data and its corresponding The radio source power data, the declination scanning data include the declination data and the corresponding radio source power data scanned in the direction of declination. In this step, the scanning length in the direction of right ascension and the direction of declination is 500 arc seconds, the scanning speed is 10 arc seconds/second, the integration time of the continuum terminal is 0.2 seconds, and the scanning in the direction of right ascension and declination The total completion time is about 1 minute. The observation frequency in this step is 15.75GHz, and the observation bandwidth is 500MHz.

Step 120: After the right ascension scan data and the declination scan data are acquired, data preprocessing is performed on the right ascension scan data and the declination scan data, and the data preprocessing includes background removal, calibration, calibration and interpolation processing. As shown in FIG. 2 , the right ascension scanning data (curve C in FIG. 2 ) and declination scanning data (curve D in FIG. 2 ) characterized by the corresponding antenna pattern are obtained based on the data preprocessing. It can be seen from Figure 2 that the antenna patterns scanned along the right ascension and declination directions are quite different, indicating that there is an error in the pointing of the radio telescope, and this pointing error is mainly caused by the error of the temperature and the pointing model.

Step 130: Construct a first parametric model for describing the right ascension scan data based on linear functions and Gaussian functions Among them, x1 is the right ascension data, _y1 is the radio source power data corresponding to x1, parameter _k1 is the baseline slope, parameter _b1 is the baseline constant, parameter _a1 is the _{amplitude of} the Gaussian function, and parameter _m1 is the red The pointing error in the warp direction, the parameter n is the Gaussian function half-power beam width;

constructing a second parametric model for describing the declination scan data based on a linear function and a Gaussian function Wherein, _x2 is the declination data, _y2 is the radio source power data corresponding to _x2 , the parameter _k2 is the baseline slope, the parameter b2 is the baseline constant, the parameter _a2 is the Gaussian function amplitude, and the parameter _{m2 is} the red Pointing error in the latitudinal direction, parameter n is Gaussian function half-power beamwidth;

Substituting the right ascension scan data into the first parameterized model, and specifying the initial values of k ₁ , b ₁ , a ₁ , n and m ₁ ; substituting the declination scan data into the second parameterized model, and specifying k ₂ , the initial values of b ₂ , a ₂ , n and m ₂ ; based on the first parameterized model substituted into the right ascension scan data and the second parameterized model substituted into the declination scan data, the parameter m is calculated using the least squares fitting algorithm ₁ and the parameter m ₂ to obtain the pointing error in the direction of right ascension and the pointing error in the direction of declination;

_In this step, the parameters a1 and a2 use the peak value _of the corresponding antenna pattern, and the parameter n uses the estimated half-power beamwidth, and its calculation method is as follows:

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.2</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ,</span>$

Wherein, λ is the wavelength of the radio source, and D is the diameter of the radio telescope.

Step 140: Control the radio telescope to correct the pointing based on the pointing error in the right ascension direction and the pointing error in the declination direction, so as to eliminate the pointing error. In this step, the pointing errors in the right ascension and declination directions are first converted into pointing errors in the azimuth and elevation directions, and then the pointing errors in the azimuth and elevation directions are substituted into the parameters of the corresponding pointing correction program in the radio telescope control software In , the radio telescope is controlled to correct the pointing to eliminate the pointing error.

So far, the steps of the method for real-time correction of the radio telescope pointing in the above-mentioned embodiments are completed. After the above steps are completed, the radio telescope is controlled to repeat steps 110 and 120 to check the effect of pointing error elimination. The scanning result is as shown in Figure 3, and the antenna pattern (curve E in Figure 3) representing the right ascension scanning data is basically consistent with the antenna pattern (curve F in Figure 3) representing the declination scanning data, indicating that the method of the above-mentioned embodiment The pointing of the radio telescope is corrected in real time, and pointing errors are effectively eliminated in real time.

It should be noted that the above examples are only specific embodiments of the present invention, and obviously the present invention is not limited to the above embodiments, and there are many similar changes accordingly. All modifications directly derived or associated by those skilled in the art from the content disclosed in the present invention shall belong to the protection scope of the present invention.

Claims (8)

1. a radio telescope points to real-time correcting method, it is characterised in that comprise the following steps:

Control radio telescope to scan the most at least one times to obtain right ascension in right ascension direction and declination direction to a radio source Scan data and declination scan data, right ascension data under wherein right ascension scan data is included in right ascension scanning direction and corresponding Radio source power data, declination data that declination scan data is included under declination scanning direction and corresponding radio source merit thereof Rate data；

The first parameterized model for describing described right ascension scan data is built based on linear function and Gaussian functionWherein, x₁For described right ascension data, y₁For x₁Penetrate accordingly Power data, parameter k₁For baseline slope, parameter b₁For baseline constant, parameter a₁For Gaussian function amplitude, parameter m₁For red Through the error in pointing in direction, parameter n is Gaussian function half-power beam width；

The second parameterized model for describing described declination scan data is built based on linear function and Gaussian functionWherein, x₂For described declination data, y₂For x₂Penetrate accordingly Power data, parameter k₂For baseline slope, parameter b₂For baseline constant, parameter a₂For Gaussian function amplitude, parameter m₂For red The error in pointing in latitude direction, parameter n is Gaussian function half-power beam width；

Right ascension scan data is substituted into described first parameterized model, and specifies k₁、b₁、a₁, n and m₁Initial value；Declination is swept Retouch data and substitute into described second parameterized model, and specify k₂、b₂、a₂, n and m₂Initial value；Based on substituting into right ascension scan data The first parameterized model and substitute into declination scan data second parameterized model use least square fitting algorithm calculate ginseng Number m₁With parameter m₂, to obtain error in pointing and the error in pointing in declination direction in right ascension direction；

By Coordinate Conversion, the error in pointing in right ascension direction and the error in pointing in declination direction are converted to azimuth direction and pitching The error in pointing in direction, then control radio telescope based on the error in pointing on azimuth direction and pitch orientation, to eliminate The error in pointing stated.

2. radio telescope as claimed in claim 1 points to real-time correcting method, it is characterised in that obtaining right ascension scanning number Also this right ascension scan data and declination scan data are carried out data prediction according to after declination scan data.

3. radio telescope as claimed in claim 2 points to real-time correcting method, it is characterised in that described data prediction bag Include background, calibrate, calibrate, one or more in interpolation process.

4. radio telescope as claimed in claim 3 points to real-time correcting method, it is characterised in that locate in advance based on described data Reason obtains right ascension scan data and the declination scan data characterized with corresponding antenna radiation pattern.

5. the radio telescope as described in any one in claim 1-4 points to real-time correcting method, it is characterised in that parameter a₁Use y₁Maximum, parameter a₂Use y₂Maximum.

6. the radio telescope as described in any one in claim 1-4 points to real-time correcting method, it is characterised in that parameter N uses the half-power beam width estimated, its computational methods such as following formula:

$n=1.2\&times;\frac{\mathrm{\&lambda;}}{D},$

Wherein, λ is the wavelength of described radio source, and D is the diameter of described radio telescope.

7. the radio telescope as described in any one in claim 1-4 points to real-time correcting method, it is characterised in that described The sweep length of scanning is more than four times of half-power beam width.

8. the radio telescope as described in any one in claim 1-4 points to real-time correcting method, it is characterised in that described Sweep length on right ascension direction and declination direction is 500 rads, and scanning speed is 10 rads/second.