Method and device for measuring the surface deviation of the main reflector of a radio astronomy telescope

Abstract

The present application relates to a kind of face shape deviation measurement method and device of main reflecting surface of radio astronomy telescope, method includes: obtaining the observation data of radio telescope in different focal position state after being observed to target SiO spectral line source in ON-Off mode, and observation data includes the signal value of different sampling time points in ON stage, azimuth and elevation and the signal value of different sampling time points in OFF stage;Determine the local temperature spectrum of each signal value segment in ON stage of each SiO spectrum in each focal position state based on the observation data in each focal position state, and determine the equivalent spectral line intensity of each signal value segment in ON stage of each focal position state, to determine the measured far field power distribution in each focal position state, finally determine the face shape deviation of main reflecting surface of radio telescope based on the measured far field power distribution in each focal position state.

Description

Method and apparatus for measuring the surface shape deviation of the primary reflector of a radio telescope Technical Field

[0001] This invention relates to the field of radio astronomy, and more specifically to a method and apparatus for measuring the surface deviation of the primary reflecting surface of a radio telescope. Background Technology

[0002] Large-aperture radio telescopes (FATs) experience significant deformation of their primary reflector surfaces due to factors such as gravity and heat, leading to reduced performance at high frequencies. As fully steerable radio telescopes evolve towards larger apertures and higher frequencies, there is an urgent need to address the surface profile deviations caused by environmental factors in compensating for these deviations. This necessitates a rapid and highly accurate measurement method to precisely reflect these changes in antenna profile.

[0003] Existing methods for measuring the surface profile of an antenna's primary reflector include theodolite measurement, photogrammetry, and holographic measurement. Theodolite and photogrammetry, due to their slow speed, are generally used during the panel installation process in antenna construction and cannot be used for rapid measurements. According to antenna theory, the far-field pattern of a reflecting antenna is a Fourier transform of the field distribution on the antenna aperture plane, applicable to a small angular range of the far-field pattern. The antenna aperture plane is the effective receiving area of ​​the radio telescope. Holographic measurement utilizes the two-dimensional Fourier transform relationship between the antenna's far-field pattern and the current distribution on the aperture plane. The field distribution on the antenna aperture plane is obtained by inverting the measured far-field pattern, and then the deformation information of the antenna surface is obtained from the field distribution using geometric optics methods.

[0004] Holographic measurement techniques can be divided into two types: phase retrieval holography and phase correlation holography. Phase acquisition holography directly measures the amplitude and phase of the far-field radiation pattern. This technique requires a reference antenna near the antenna under test to provide a phase reference. By using an auxiliary phase reference antenna to measure the amplitude and phase of the far-field beam pattern, a simple Fourier inversion can be performed to obtain the aperture function C(i,j), thus revealing the telescope's deformation. Since the reference antenna is generally small in diameter, only satellites located at specific elevation angles can be selected as signal sources. Therefore, this technique can only measure the deformation of the primary reflector at specific elevation angles. Phase retrieval holography, on the other hand, uses a phase retrieval algorithm to obtain the current amplitude and phase distribution on the antenna aperture surface from the amplitude of the antenna's focusing and defocusing radiation patterns. This method has advantages such as requiring no additional hardware, faster measurement speed, and the ability to measure at any elevation angle, but its accuracy is slightly lower than that of phase retrieval holography. Summary of the Invention

[0005] This invention provides a method for measuring the surface shape deviation of the primary reflector of a radio telescope, in order to solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides a method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope, comprising:

[0007] The observation data were obtained by the radio telescope observing the pre-selected target SiO spectral line source in three focal positions using a preset observation method.

[0008] The measured far-field power distribution at each focal position is determined based on the observation data at that focal position.

[0009] The surface profile deviation of the primary reflector of the radio telescope is determined based on the measured far-field power distribution at each focal position.

[0010] Optionally, the three focal states include a focused state, a positive defocus state, and a negative defocus state; the preset observation method is to use an ON-OFF mode for observation, which includes an ON phase and an OFF phase. In the ON phase, the radio telescope points to the target SiO spectral line source and remains so for a period of time. In the OFF phase, the radio telescope deviates from the target SiO spectral line source to point to a sky region without strong sources and remains so for the same duration as the ON phase. In the ON phase of each focal state, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data for each focal state includes the signal values, azimuth angle, and elevation angle at different sampling time points in the ON phase and the signal values ​​at different sampling time points in the OFF phase.

[0011] The measured far-field power distribution at each focal position is determined based on the observation data, specifically including:

[0012] For each focal position state, the signal values ​​at different sampling time points in the ON and OFF phases of the observation data under that focal position state are divided into the same number of signal value segments. Each signal value segment includes the same number of signal values ​​at different sampling time points, and there is a one-to-one correspondence between the signal value segments in the ON phase and the signal value segments in the OFF phase. For each signal value segment in the ON and OFF phases, a Fast Fourier Transform is performed on the signal values ​​at each sampling time point of that signal value segment to obtain the power spectrum of that signal value segment. The time corresponding to the middle sampling time point of each signal value segment in the ON phase is taken as the absolute time of that signal value segment, and the azimuth and elevation angles at the absolute time of that signal value segment are obtained as the azimuth and elevation angles of that signal value segment.

[0013] For each focal position state, the power spectrum of each signal value segment in the ON phase of that focal position state is subtracted from the power spectrum of the corresponding signal value segment in the OFF phase to obtain the differential power spectrum of that signal value segment in the ON phase of that focal position state; combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions.

[0014] The theoretical frequencies of each signal value segment in the ON phase of each target SiO spectral line in each focal state of the pre-acquired target SiO spectral line source are corrected to obtain the observed frequencies of each signal value segment in the ON phase of the target SiO spectral line in the focal state.

[0015] For each target SiO spectral line, the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the focal position state is determined by taking the observed frequency of the absolute time of each signal value segment in the ON phase of the target SiO spectral line in the focal position state as the center and a preset bandwidth; the temperature spectrum data corresponding to the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the focal position state is extracted from the temperature spectrum of each signal value segment in the ON phase of the target SiO spectral line in the focal position state, so as to obtain the local temperature spectrum of the signal value segment in the ON phase of the target SiO spectral line in the focal position state.

[0016] The noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal state is removed to obtain the local temperature spectrum of the target SiO spectral line in the ON phase of the focal state after noise removal.

[0017] The temperature spectrum values ​​of each signal value segment in the ON phase of each target SiO spectral line in each focal position state after noise reduction are summed to obtain the temperature spectrum sum of that signal value segment in the ON phase of that target SiO spectral line in that focal position state. The temperature spectrum sums of each signal value segment in the ON phase of each target SiO spectral line in that focal position state are weighted and superimposed to obtain the equivalent spectral intensity of that signal value segment in the ON phase of that focal position state.

[0018] By using the absolute time, azimuth, and elevation angles of each signal value segment in the ON phase of each focal position state, the equivalent spectral intensity of each signal value segment in the ON phase of that focal position state is mapped onto angular coordinates to obtain the measured far-field power distribution in that focal position state.

[0019] Optionally, the radio telescope can perform a two-dimensional grid scan in the azimuth and elevation planes, specifically including:

[0020] One of the azimuth and elevation planes of the radio telescope is used as the fast scan plane, and the other is used as the slow scan plane;

[0021] Determine the scanning range of the fast scanning plane and the slow scanning plane. The scanning range of both the fast scanning plane and the slow scanning plane is a range centered on the target SiO spectral line source and covering the preset scanning width. The preset scanning width is 5-10 times the half-power beamwidth.

[0022] The slow scanning surface is made to step sequentially at fixed angular intervals within its scanning range and traverse the entire scanning range of the slow scanning surface. When the slow scanning surface steps to each angle, the fast scanning surface is made to scan at a constant speed within its scanning range and traverse the entire scanning range of the fast scanning surface.

[0023] Optionally, the theoretical frequencies of each signal value segment in the ON phase of each target SiO spectral line in each focal position state of the pre-acquired target SiO spectral line source are corrected to obtain the observed frequencies of each signal value segment in the ON phase of the target SiO spectral line in that focal position state, specifically including:

[0024] Using the coordinates of the radio telescope station, the absolute time of each signal value segment in the ON phase of each focal position, and the equatorial coordinates of the target SiO spectral source, the radial velocity under the local stationary standard is calculated at the absolute time of the signal value segment in the ON phase of the focal position.

[0025] Based on the radial velocity of the signal value segment in the ON phase of each focal position state at absolute time, the theoretical frequency of the signal value segment of each target SiO spectral line in the ON phase of the focal position state at absolute time is corrected using the Doppler formula to obtain the observed frequency of the signal value segment of the target SiO spectral line in the focal position state at absolute time.

[0026] Optionally, the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal position state is removed to obtain the noise-removed local temperature spectrum of that signal value segment in the ON phase of that target SiO spectral line in that focal position state, specifically including:

[0027] From the temperature spectrum of each signal value segment in the ON phase of each focal position state, extract the temperature spectrum values ​​other than the target frequency range of the absolute time of the signal value segment in the ON phase of each target SiO spectral line in the focal position state. Use these values ​​to fit the temperature spectrum to obtain the temperature spectrum estimate of the target frequency range of the absolute time of the signal value segment in the ON phase of the focal position state of the target SiO spectral line. This estimate is used as the temperature spectrum noise floor of the signal value segment in the ON phase of the focal position state of the target SiO spectral line.

[0028] The temperature spectrum of each signal value segment of the target SiO spectral line in the ON phase of each focal state is subtracted from the temperature spectrum of that signal value segment in the ON phase of the focal state to obtain the temperature spectrum of the target SiO spectral line in the ON phase of the focal state after removing the noise floor.

[0029] Optionally, the surface profile deviation of the primary reflecting surface of the radio telescope is determined based on the measured far-field power distribution at each focal position, specifically including:

[0030] Determine the aperture field power distribution model, which includes the Zernike coefficients to be solved;

[0031] The theoretical aperture field power distribution under each focal position state is determined based on the aperture field power distribution model.

[0032] The theoretical far-field power distribution at each focal position is determined based on the theoretical aperture field power distribution at that focal position.

[0033] Based on the theoretical and measured far-field power distributions at various focal positions, an objective function is constructed with the Zernike coefficients to be solved as the optimization variables.

[0034] Solve the objective function to obtain the optimal Zernike coefficients;

[0035] Based on the optimal Zernike coefficients and the aperture field power distribution model, the phase error distribution on the aperture plane is determined;

[0036] Based on the phase error distribution on the aperture plane, the surface shape deviation of the main reflecting surface is determined.

[0037] Another aspect of the present invention provides a device for measuring the surface profile deviation of the primary reflecting surface of a radio telescope, comprising:

[0038] The acquisition module is used to acquire the observation data obtained by the radio telescope after observing the pre-selected target SiO spectral line source in three focal positions using a preset observation method.

[0039] The far-field power distribution measurement module is used to determine the measured far-field power distribution at each focal position based on the observation data at that focal position.

[0040] The determination module is used to determine the surface profile deviation of the primary reflector of the radio telescope based on the measured far-field power distribution at each focal position.

[0041] Optionally, the three focal states include a focused state, a positive defocus state, and a negative defocus state; the preset observation method is to use an ON-OFF mode for observation, which includes an ON phase and an OFF phase. In the ON phase, the radio telescope points to the target SiO spectral line source and remains so for a period of time. In the OFF phase, the radio telescope deviates from the target SiO spectral line source to point to a sky region without strong sources and remains so for the same duration as the ON phase. In the ON phase of each focal state, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data for each focal state includes the signal values, azimuth angle, and elevation angle at different sampling time points in the ON phase and the signal values ​​at different sampling time points in the OFF phase.

[0042] The far-field power distribution measurement module specifically includes:

[0043] The segmentation module is used to divide the signal values ​​of the observation data at different sampling time points in the ON and OFF phases of each focal position state into the same number of signal value segments. Each signal value segment includes the signal values ​​at the same number of sampling time points, and there is a one-to-one correspondence between the signal value segments in the ON phase and the signal value segments in the OFF phase. For each signal value segment in the ON and OFF phases, a Fast Fourier Transform is performed on the signal values ​​at each sampling time point of the signal value segment to obtain the power spectrum of the signal value segment. The time corresponding to the middle sampling time point of each signal value segment in the ON phase is taken as the absolute time of the signal value segment, and the azimuth and elevation angles at the absolute time of the signal value segment are obtained as the azimuth and elevation angles of the signal value segment.

[0044] The differential module is used to calculate the difference between the power spectrum of each signal value segment in the ON phase and the power spectrum of the corresponding signal value segment in the OFF phase for each focal position state, so as to obtain the differential power spectrum of the signal value segment in the ON phase; combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions.

[0045] The correction module is used to correct the theoretical frequency of each signal value segment in the ON phase of each target SiO spectral line in each focal state of the pre-acquired target SiO spectral line source at the absolute time, so as to obtain the observed frequency of each signal value segment in the ON phase of the target SiO spectral line in the focal state at the absolute time.

[0046] The interception module is used to determine the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state, centered on the observed frequency of the absolute time of each signal value segment in the ON phase of the focal position state, and a preset bandwidth; and to intercept the temperature spectrum data corresponding to the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of the focal position state, so as to obtain the local temperature spectrum of the signal value segment of the target SiO spectral line in the ON phase of the focal position state.

[0047] The noise reduction module is used to remove the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal position state, so as to obtain the local temperature spectrum of the target SiO spectral line in the ON phase of the focal position state after noise removal.

[0048] The superposition module is used to add the temperature spectrum values ​​of each signal value segment of each target SiO spectral line in the ON phase of each focal position state after removing the noise floor, so as to obtain the sum of the temperature spectrum of the signal value segment of the target SiO spectral line in the ON phase of the focal position state; and to perform weighted superposition of the sum of the temperature spectrum of each signal value segment of each target SiO spectral line in the ON phase of the focal position state to obtain the equivalent spectral intensity of the signal value segment in the ON phase of the focal position state.

[0049] The mapping module is used to map the equivalent spectral intensity of each signal value segment in the ON phase of each focal position state to angular coordinates (or direction cosine coordinates) using the absolute time, azimuth angle and elevation angle of each signal value segment in the ON phase of each focal position state, so as to obtain the measured far-field power distribution in that focal position state.

[0050] Optionally, the radio telescope can perform a two-dimensional grid scan in the azimuth and elevation planes, specifically including:

[0051] One of the azimuth and elevation planes of the radio telescope is used as the fast scan plane, and the other is used as the slow scan plane;

[0052] Determine the scanning range of the fast scanning plane and the slow scanning plane. The scanning range of both the fast scanning plane and the slow scanning plane is a range centered on the target SiO spectral line source and covering the preset scanning width. The preset scanning width is 5-10 times the half-power beamwidth.

[0053] The slow scanning surface is made to step sequentially at fixed angular intervals within its scanning range and traverse the entire scanning range of the slow scanning surface. When the slow scanning surface steps to each angle, the fast scanning surface is made to scan at a constant speed within its scanning range and traverse the entire scanning range of the fast scanning surface.

[0054] Optionally, the theoretical frequencies of each signal value segment in the ON phase of each target SiO spectral line in each focal position state of the pre-acquired target SiO spectral line source are corrected to obtain the observed frequencies of each signal value segment in the ON phase of the target SiO spectral line in that focal position state, specifically including:

[0055] Using the coordinates of the radio telescope station, the absolute time of each signal value segment in the ON phase of each focal position, and the equatorial coordinates of the target SiO spectral source, the radial velocity under the local stationary standard is calculated at the absolute time of the signal value segment in the ON phase of the focal position.

[0056] Based on the radial velocity of the signal value segment in the ON phase of each focal position state at absolute time, the theoretical frequency of the signal value segment of each target SiO spectral line in the ON phase of the focal position state at absolute time is corrected using the Doppler formula to obtain the observed frequency of the signal value segment of the target SiO spectral line in the focal position state at absolute time.

[0057] Optionally, the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal position state is removed to obtain the noise-removed local temperature spectrum of that signal value segment in the ON phase of that target SiO spectral line in that focal position state, specifically including:

[0058] From the temperature spectrum of each signal value segment in the ON phase of each focal position state, extract the temperature spectrum values ​​other than the target frequency range of the absolute time of the signal value segment in the ON phase of each target SiO spectral line in the focal position state. Use these values ​​to fit the temperature spectrum to obtain the temperature spectrum estimate of the target frequency range of the absolute time of the signal value segment in the ON phase of the focal position state of the target SiO spectral line. This estimate is used as the temperature spectrum noise floor of the signal value segment in the ON phase of the focal position state of the target SiO spectral line.

[0059] The temperature spectrum of each signal value segment of the target SiO spectral line in the ON phase of each focal state is subtracted from the temperature spectrum of that signal value segment in the ON phase of the focal state to obtain the temperature spectrum of the target SiO spectral line in the ON phase of the focal state after removing the noise floor.

[0060] Optionally, the surface profile deviation of the primary reflecting surface of the radio telescope can be determined based on the measured far-field power distribution at each focal position, specifically including:

[0061] Determine the aperture field power distribution model, which includes the Zernike coefficients to be solved;

[0062] The theoretical aperture field power distribution under each focal position state is determined based on the aperture field power distribution model.

[0063] The theoretical far-field power distribution at each focal position is determined based on the theoretical aperture field power distribution at that focal position.

[0064] Based on the theoretical and measured far-field power distributions at various focal positions, an objective function is constructed with the Zernike coefficients to be solved as the optimization variables.

[0065] Solve the objective function to obtain the optimal Zernike coefficients;

[0066] Based on the optimal Zernike coefficients and the aperture field power distribution model, the phase error distribution on the aperture plane is determined;

[0067] Based on the phase error distribution on the aperture plane, the surface shape deviation of the main reflecting surface is determined. Attached Figure Description

[0068] Figure 1 is a flowchart of a method for measuring the surface deviation of the main reflecting surface of a radio telescope according to an embodiment of the present invention;

[0069] Figure 2 is a structural block diagram of a surface deviation measurement device for the main reflector of a radio telescope according to an embodiment of the present invention. Detailed Implementation

[0070] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0071] As shown in Figure 1, this embodiment of the invention provides a method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope, which includes the following steps:

[0072] S100: Acquire observation data obtained by the radio telescope observing a pre-selected target SiO spectral source in three focal positions using a preset observation method. The three focal positions include a focused state, a positive defocus state, and a negative defocus state. The preset observation method is to use an ON-OFF mode, which includes an ON phase and an OFF phase. In the ON phase, the radio telescope points to the target SiO spectral source and remains so for a period of time. In the OFF phase, the radio telescope deviates from the target SiO spectral source to point to a sky region without strong sources and remains so for the same duration as the ON phase. During the ON phase of each focal position, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data for each focal position includes the signal values, azimuth angle, and elevation angle at different sampling time points in the ON phase and the signal values ​​at different sampling time points in the OFF phase.

[0073] SiO spectral line sources (such as SiO maser emission lines in red giants) refer to celestial bodies that can produce characteristic spectral line emissions of SiO (silicon monoxide) molecules. They offer the following advantages: First, SiO spectral line sources can be approximated as point sources in the radio band, avoiding systematic errors introduced by extended source models. Second, the spectral line frequencies are stable and unaffected by continuous absorption by atmospheric water vapor, maintaining a high signal-to-noise ratio even under adverse weather conditions. Third, within the same receiving bandwidth, multiple SiO emission lines (such as transitions between different vibrational energy levels like v=1 and v=2) typically exist simultaneously. These spectral lines are independent in the frequency domain, and their equivalent signal-to-noise ratio can be effectively improved through frequency domain superposition. Theoretical analysis shows that if N independent spectral lines are superimposed within the same bandwidth, the equivalent signal-to-noise ratio can be improved by approximately N. 1 / 2 This is significant for improving the robustness of surface shape measurements. The target SiO spectral source can be selected from a pre-established SiO spectral line calibration source table. This table contains multiple SiO spectral line sources, including their equatorial coordinates, spectral frequency, and spectral intensity. One or more SiO spectral line sources that are visible under the current elevation angle of the radio telescope and have sufficiently strong spectral lines are selected as the target SiO spectral source. That is, there can be one or more target SiO spectral line sources.

[0074] After identifying the target SiO spectral source, the radio telescope can be used to observe it in three different focal positions. For example, first, the radio telescope can be in a focused state (i.e., when the sub-reflector is at its normal focal position), and the target SiO spectral source can be observed using a preset observation method. Next, the radio telescope can be in a positive defocus state (i.e., when the sub-reflector is moved a predetermined distance away from the main reflector along the optical axis), and the target SiO spectral source can be observed using the preset observation method. Finally, the radio telescope can be in a negative defocus state (i.e., when the sub-reflector is moved a predetermined distance closer to the main reflector along the optical axis), and the target SiO spectral source can be observed using the preset observation method. It is understood that although the above description uses the order of the radio telescope being in a focused state, positive defocus state, and negative defocus state, in practical applications, this order is not limited. Those skilled in the art can observe in any suitable order as needed, as long as observation results can be obtained in three different focal positions.

[0075] The preset observation mode refers to observing the target SiO spectral source using an ON-OFF mode. The ON-OFF mode includes an ON phase and an OFF phase. The ON phase means that the radio telescope is pointed at the target SiO spectral source (that is, the optical axis of the primary reflector is precisely aligned with the celestial coordinates of the target SiO spectral source) and maintained at the SiO spectral source for a period of time. The OFF phase means that the radio telescope is deviated from the target SiO spectral source and pointed at a sky region without strong sources, and the pointing at the sky region is maintained for the same time as the ON phase. For example, the radio telescope can be deviated from the target SiO spectral source by shifting its azimuth or elevation direction by several times the half-power beamwidth (HPBW). During the ON phase, the radio telescope simultaneously performs a two-dimensional grid scan on the azimuth and elevation planes.

[0076] To enable the radio telescope to perform two-dimensional grid scanning in the azimuth and elevation planes, specifically including:

[0077] One of the azimuth and elevation planes of the radio telescope is used as the fast scan plane, and the other is used as the slow scan plane;

[0078] Determine the scanning range of the fast scanning plane and the slow scanning plane. The scanning range of both the fast scanning plane and the slow scanning plane is a range centered on the target SiO spectral line source and covering the preset scanning width. The preset scanning width is usually 5-10 times the HPBW.

[0079] The slow scanning surface is made to step sequentially at fixed angular intervals within its scanning range and traverse the entire scanning range of the slow scanning surface. When the slow scanning surface steps to each angle, the fast scanning surface is made to scan at a constant speed within its scanning range and traverse the entire scanning range of the fast scanning surface.

[0080] During observations at each focal position, the radio telescope's receiver samples the molecular spectral signal (usually voltage) at a preset sampling rate, obtaining signal values ​​at different sampling times, i.e., a signal value-time series. Since the radio telescope operates in ON-OFF mode at each focal position, both the ON and OFF phases of the signal value-time series can be obtained. The lengths of the ON and OFF phase signal value-time series are the same, depending on the ON and OFF phase times and the sampling rate. In the ON phase, the radio telescope performs a two-dimensional grid scan, causing its azimuth and elevation angles to change over time. During the observation phase, the azimuth and elevation angles at different sampling time points can be acquired simultaneously, i.e., azimuth-time series and elevation-time series. The observation data for each focal position includes the signal values, azimuth and elevation angles at different sampling time points in the ON phase and the signal values ​​at different sampling time points in the OFF phase within that focal position.

[0081] S200: For each focal position state, the signal values ​​at different sampling time points in the ON and OFF phases of the observation data under that focal position state are divided into the same number of signal value segments. Each signal value segment includes the same number of signal values ​​at different sampling time points. The signal value segments in the ON phase correspond one-to-one with the signal value segments in the OFF phase. For each signal value segment in the ON and OFF phases, a Fast Fourier Transform is performed on the signal values ​​at each sampling time point of that signal value segment to obtain the power spectrum of that signal value segment. The time corresponding to the middle sampling time point of each signal value segment in the ON phase is taken as the absolute time of that signal value segment. The azimuth and elevation angles at the absolute time of that signal value segment are obtained and used as the azimuth and elevation angles of that signal value segment.

[0082] At each focal position, the observed data were processed as follows:

[0083] The signal values ​​at each sampling time point in the ON phase are evenly divided into multiple signal value segments, which are sequentially connected. Each signal value segment includes the same number of signal values ​​at each sampling time point, meaning that the length of each signal value segment is the same. A Fast Fourier Transform (FFT) is performed on each signal value segment in the ON phase to obtain its spectrum. The power spectrum of the signal value segment can be obtained from the spectrum, meaning that each signal value segment in the ON phase has a corresponding power spectrum. Similarly, the above operation is performed on the OFF phase to obtain multiple signal value segments in the OFF phase, as well as the power spectrum of each signal value segment. The number of signal value segments in the OFF phase and the length of each signal value segment are the same as in the ON phase, and there is a one-to-one correspondence between each signal value segment in the OFF phase and each signal value segment in the ON phase. Then, for each signal value segment in the ON phase, the time corresponding to its intermediate sampling time point can be extracted as the absolute time of the signal value segment. The azimuth and elevation angles at this absolute time are then obtained as the azimuth and elevation angles of the signal value segment.

[0084] For ease of understanding, let's take an example where both the ON and OFF phases include 100 sampling points. That is, both the ON and OFF phases include 100 signal values. The signal values ​​at sampling points 1-10 of the ON phase are taken as the first signal value segment of the ON phase, the signal values ​​at sampling points 11-20 of the ON phase are taken as the second signal value segment, and so on, to obtain the third to tenth signal value segments of the ON phase. Then, using the same method as the ON phase, the first to tenth signal value segments of the OFF phase are obtained. The m-th signal value segment of the ON phase corresponds to the m-th signal value segment of the OFF phase, where m = 1-10. For the ON phase and... Performing an FFT on each signal value segment in the OFF phase yields its spectrum, from which its power spectrum can be obtained. Thus, each signal value segment in both the ON and OFF phases has a corresponding power spectrum. The time corresponding to the intermediate sampling time point of the first signal value segment in the ON phase (e.g., the 5th, 6th, or the average of the 5th and 6th sampling time points) is taken as the absolute time of the first signal value segment in the ON phase. Then, the azimuth and elevation angles at this absolute time are obtained as the azimuth and elevation angles of the first signal value segment in the ON phase. In this way, the correspondence between each signal value segment, absolute time, azimuth angle, and elevation angle in both the ON and OFF phases can be established.

[0085] S300: For each focal position state, the power spectrum of each signal value segment in the ON phase of that focal position state is subtracted from the power spectrum of the corresponding signal value segment in the OFF phase to obtain the differential power spectrum of that signal value segment in the ON phase; combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions.

[0086] Assume the power spectrum of the signal value segment in the ON phase is The power spectrum of the corresponding signal value segment in the OFF phase is Where t represents the absolute time of a signal value segment, then the differential power spectrum of that signal value segment is... for:

[0087] (1)

[0088] By combining the noise tube calibration file, the differential power spectrum of each dimensionless signal value segment can be converted into a temperature spectrum with temperature dimensions for that signal value segment. The temperature spectrum can be denoted as... The unit is K, which ensures that the data in subsequent steps has a clear physical meaning and facilitates the removal of abnormal data.

[0089] Since the above operation is performed on the observation data for each focal position state, the temperature spectrum of each signal value segment in the ON stage of each focal position state can be obtained through step S300.

[0090] S400: Correct the theoretical frequency of each signal value segment in the ON phase of each target SiO spectral line in each focal state of the pre-acquired target SiO spectral line source at the absolute time, and obtain the observed frequency of the absolute time of each signal value segment in the ON phase of the target SiO spectral line in the focal state.

[0091] Once the target SiO spectral source is determined, the theoretical frequencies of each target SiO spectral line at different times can be obtained. As described in step S200, each signal value segment in the ON phase of each focal position corresponds to an absolute time. Therefore, based on the theoretical frequencies of each target SiO spectral line at different times, the theoretical frequency of each signal value segment in the ON phase of each focal position can be obtained at the absolute time. That is, for each SiO spectral line, each signal value segment in the ON phase of each focal position corresponds to a theoretical frequency of that SiO spectral line. After the theoretical frequency is corrected, it becomes the observation frequency. Therefore, each signal value segment in the ON phase of each focal position also corresponds to an observation frequency of that SiO spectral line.

[0092] In some embodiments, the radial velocity under the local rest standard (LSR) can be calculated using information such as the coordinates of the radio telescope station, the observation time (UTC) (i.e., the absolute time of each signal value segment in the ON phase of each focal position state), and the equatorial coordinates of the target SiO spectral source. Since line-of-sight velocity is time-dependent, each signal value segment corresponds to a line-of-sight velocity, where t is the absolute time corresponding to the signal value segment. The theoretical frequency is corrected to the observation frequency using the Doppler formula.

[0093] (2)

[0094] Where k = 1, 2, ..., N represents the number of each target SiO spectral line within the same bandwidth, and c is the speed of light. Let be the observed frequency of the k-th target SiO spectral line at absolute time t. Let be the theoretical frequency of the k-th target SiO spectral line at absolute time t.

[0095] S500: For each target SiO spectral line, the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the ON phase of the focal position is determined by taking the observed frequency of the absolute time of each signal value segment in the ON phase of the focal position as the center and the preset bandwidth; the temperature spectrum data corresponding to the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the focal position is extracted from the temperature spectrum of each signal value segment in the ON phase of the focal position to obtain the local temperature spectrum of the signal value segment in the ON phase of the target SiO spectral line in the focal position.

[0096] Since the S300 acquires a full-band temperature spectrum, and the effective bandwidth of the target SiO spectral line only occupies a portion of that spectrum, to simplify calculations, temperature spectrum data within the effective bandwidth of the target SiO spectral line can be extracted for subsequent calculations. Specifically, for each target SiO spectral line, its observation frequency at each absolute time is used... Centered on a target frequency, with a preset bandwidth, the target frequency range of the target SiO spectral line at a given absolute time is determined. Temperature spectrum data corresponding to the target frequency range of the signal value segment at that absolute time is then extracted from this target frequency range, yielding a local temperature spectrum. This local temperature spectrum represents the local temperature spectrum of the signal value segment of the target SiO spectral line during the ON phase at a specific focal position. In each focal position, each SiO spectral line has multiple local temperature spectra, and each local temperature spectrum corresponds one-to-one with each signal value segment during the ON phase at that focal position.

[0097] Assume the local temperature spectrum of the k-th SiO spectral line at absolute time t is as follows: The calculation formula is as follows:

[0098] (3)

[0099] in, Let be the target frequency range of the k-th SiO spectral line at absolute time t.

[0100] S600: Remove the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal state, so as to obtain the local temperature spectrum of the target SiO spectral line in the ON phase of the focal state after noise removal.

[0101] In some embodiments, a piecewise fitting method can be used to estimate the local temperature spectrum noise floor of each signal value segment in the ON phase of each target SiO spectral line in each focal position state, in order to suppress the slowly varying baseline noise introduced by the high-frequency link and receiver. Specifically, from the temperature spectrum of each signal value segment in the ON phase of each focal position state, the temperature spectrum values ​​other than the target frequency range of the absolute time of the signal value segment in the ON phase of each target SiO spectral line in that focal position state can be extracted. These values ​​are then used for fitting to obtain the estimated temperature spectrum value of the target frequency range of the absolute time of the signal value segment in the ON phase of that target SiO spectral line in that focal position state. This estimated value is the temperature spectrum noise floor of the signal value segment in the ON phase of that target SiO spectral line in that focal position state. Subtracting the temperature spectrum noise floor of the signal value segment in the ON phase of that target SiO spectral line in that focal position state from the temperature spectrum of that signal value segment in that focal position state yields the noise-removed temperature spectrum of the signal value segment in the ON phase of that target SiO spectral line in that focal position state. The noise-removed temperature spectrum of the signal value segment corresponding to the absolute time t of the ON phase of the k-th target SiO spectral line is denoted as... .

[0102] S700: Add the temperature spectrum values ​​of each signal value segment of each target SiO spectral line in the ON phase of each focal state after removing the noise floor, to obtain the sum of the temperature spectrum values ​​of that signal value segment of the target SiO spectral line in the ON phase of each focal state; and perform a weighted superposition of the sums of the temperature spectra values ​​of each signal value segment of each target SiO spectral line in the ON phase of each focal state to obtain the equivalent spectral intensity of that signal value segment in the ON phase of each focal state.

[0103] For example, for By summing the temperature spectrum values ​​at each frequency point, we can obtain the temperature spectrum of the signal value segment corresponding to the absolute time t of the ON phase of the k-th target SiO spectral line. The specific calculation formula is as follows:

[0104] (4)

[0105] in, For frequency points, It represents the frequency difference between two adjacent frequency points.

[0106] Subsequently, by weighted superposition of the N target SiO spectral lines, the equivalent spectral intensity of each signal value segment in the ON phase at each focal position state can be obtained:

[0107] (5)

[0108] in, The equivalent spectral intensity is the signal value segment corresponding to the absolute time t during the ON phase. Let k be the weight of the k-th target SiO spectral line, where k = 1, 2, ..., N. For example, the weight of all spectral lines can be set to 1.

[0109] By summing the temperature spectra of each target SiO spectral line, it is theoretically possible to obtain approximately [a certain value] while maintaining the isosource characteristics of the spectral lines. Signal-to-noise ratio gain on the order of magnitude.

[0110] S800: Using the absolute time, azimuth, and elevation angles of each signal value segment in the ON phase of each focal position state, the equivalent spectral intensity of each signal value segment in the ON phase of that focal position state is mapped onto angular coordinates (or direction cosine coordinates) through interpolation or resampling to obtain the measured far-field power distribution in that focal position state.

[0111] The specific method of mapping the equivalent spectral intensity of each signal value segment in the ON phase of each focal position state to angular coordinates using the absolute time, azimuth angle, and elevation angle of each signal value segment in the ON phase of each focal position state is a conventional technique in this field and will not be elaborated here.

[0112] The far-field power distribution under different focal positions can be denoted as:

[0113] (6)

[0114] in, Indicates a focused state. Indicates the state of being out of focus. This indicates a negative defocus state.

[0115] S900: Determine the surface profile deviation of the primary reflector of the radio telescope based on the measured far-field power distribution at each focal position.

[0116] In some embodiments, step S900 specifically includes:

[0117] S910: Determine the aperture field power distribution model, which includes the Zernike coefficients to be solved.

[0118] The aperture field power distribution model is as follows:

[0119] (7)

[0120] in, For aperture field power distribution, The aperture illuminance distribution includes factors such as feed Gaussian illumination and central obstruction. The aperture phase distribution is caused by the deformation of the primary reflector. dz represents the additional defocus phase introduced by the movement of the sub-reflector along the optical axis, where dz is the distance between the actual position of the sub-reflector and the normal focal position. When the radio telescope is in focus, dz = 0; when the radio telescope is in positive defocus, dz is positive; and when the radio telescope is in negative defocus, dz is negative.

[0121] To describe large-scale surface errors, low-order Zernike polynomials can be used to... Expanding on this:

[0122] (8)

[0123] in, For a Zernike polynomial defined on a normalized caliber, Let be the Zernike coefficients to be solved, where n is the radial order and l is the angular order. Zernike polynomials are approximately orthogonal on the unit circle and can effectively represent low-order aberrations and large-scale deformations on the aperture plane.

[0124] S920: Determine the theoretical aperture field power distribution for each focal position based on the aperture field power distribution model.

[0125] Given an illuminance model Under these conditions, the theoretical aperture field power distribution for each focal position is as follows:

[0126] (9)

[0127] S930: Determine the theoretical far-field power distribution at each focal position based on the theoretical aperture field power distribution at that focal position.

[0128] According to antenna theory, the far-field complex electric field of a reflector antenna and the complex aperture field on the aperture plane satisfy a two-dimensional Fourier transform relationship. The relationship between the far-field power distribution and the aperture field power distribution is as follows:

[0129] (10)

[0130] Based on formulas (9) and (10), the theoretical far-field power distribution for each focal position can be determined:

[0131] (11)

[0132] in, This represents the theoretical far-field power distribution under focal position state j. The imaginary unit, This is the additional defocus phase in the focal position state j, which is determined by the structure of the radio telescope and the displacement geometry of the sub-reflector. λ is the wavelength.

[0133] S940: Construct an objective function with the Zernike coefficients to be solved as optimization variables based on the theoretical and measured far-field power distributions at various focal positions.

[0134] The objective function is constructed as follows:

[0135] (12)

[0136] in, The angular region where the main lobe and some of the side lobes are located. This is the weighting function for the out-of-focus state j, used to balance the data contributions at different focal positions and angles.

[0137] 950: Solve the objective function to obtain the optimal Zernike coefficients.

[0138] In some embodiments, the objective function can be evaluated using a nonlinear least squares algorithm (e.g., the Levenberg-Marquardt algorithm). Perform iterative optimization:

[0139] 1) Initialize the maximum radial order M of Zernike (e.g., 5th or 6th order), and then... Set the initial value to zero;

[0140] 2) Continuously update during the iteration process. Each iteration calculates a new theoretical far-field power distribution. and ;

[0141] 3) When Reduced to below a preset threshold, or between two adjacent iterations When the change is below a given tolerance, convergence is determined, and the optimal set of Zernike coefficients is output. .

[0142] Because this invention significantly improves the signal-to-noise ratio of the far-field radiation pattern by weighted superposition of multiple spectral lines in the frequency domain during the data preprocessing stage, the iterative optimization process has better convergence and robustness, and can effectively avoid getting trapped in local minima.

[0143] S960: Based on the optimal Zernike coefficients and aperture field power distribution model, determine the phase error distribution on the aperture plane.

[0144] After obtaining the optimal Zernike coefficients, the phase error distribution on the aperture plane can be recovered:

[0145] (13)

[0146] S970: Determine the surface profile deviation of the primary reflector based on the phase error distribution on the aperture plane.

[0147] Then, based on the optical geometry of the radio telescope, the phase error is converted into the geometric displacement of the principal reflecting surface. Its general form can be written as:

[0148] (14)

[0149] in, It is a geometric scaling factor determined by the specific optical path and the incident / reflection angle of the primary reflecting surface.

[0150] That is, the surface shape deviation of the main reflecting surface, through the analysis of... Statistical analysis can yield information such as the RMS surface shape error of the main reflector, large-scale gravity deformation mode, and thermal deformation mode, providing a basis for active surface control and deformation compensation.

[0151] The method for measuring the surface deviation of the primary reflector of a radio telescope, as described in this invention, utilizes a natural SiO spectral line source as a stable point source signal for defocused observation to obtain the beam response map of the radio telescope. The observation data is converted from the time domain to the frequency domain, and the local temperature spectra of multiple target SiO spectral lines after noise removal are extracted in the frequency domain. The temperature spectra of each target SiO spectral line are then superimposed to synthesize the spectrum, effectively improving the signal-to-noise ratio and measurement reliability. Because the spectral line source itself possesses point source characteristics, errors caused by non-ideal source models are avoided. Based on the frequency stability and high-resolution characteristics of the spectral line point source, this invention enhances the holographic measurement accuracy of radio telescopes in the high-frequency band. It has advantages such as requiring no additional hardware support, low dependence on weather conditions, and applicability to multi-frequency band measurements, providing an efficient and reliable technical means for radio telescope surface maintenance and performance calibration.

[0152] As shown in Figure 2, this embodiment of the invention provides a surface deviation measurement device for the main reflector of a radio telescope, which includes an acquisition module 10, a segmentation module 20, a difference module 30, a correction module 40, a truncation module 50, a noise reduction module 60, a superposition module 70, a mapping module 80, and a determination module 90.

[0153] The acquisition module 10 is used to acquire observation data obtained by the radio telescope after observing a pre-selected target SiO spectral source in three focal positions using a preset observation method. The three focal positions include a focused state, a positive defocus state, and a negative defocus state. The preset observation method is to use an ON-OFF mode, which includes an ON phase and an OFF phase. In the ON phase, the radio telescope points to the target SiO spectral source and remains so for a period of time. In the OFF phase, the radio telescope deviates from the target SiO spectral source to point to a sky region without strong sources and remains so for the same duration as the ON phase. In the ON phase of each focal position, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data in each focal position includes the signal value, azimuth angle, and elevation angle at different sampling time points in the ON phase and the signal value at different sampling time points in the OFF phase.

[0154] The segmentation module 20 is used to divide the signal values ​​of the observation data in the ON and OFF phases of each focal position state into the same number of signal value segments at different sampling time points. Each signal value segment includes the same number of signal values ​​at sampling time points, and the signal value segments in the ON phase and the signal value segments in the OFF phase correspond one-to-one. For each signal value segment in the ON and OFF phases, a fast Fourier transform is performed on the signal values ​​at each sampling time point of the signal value segment to obtain the power spectrum of the signal value segment. The time corresponding to the middle sampling time point of each signal value segment in the ON phase is taken as the absolute time of the signal value segment, and the azimuth and elevation angles at the absolute time of the signal value segment are obtained as the azimuth and elevation angles of the signal value segment.

[0155] The differential module 30 is used to subtract the power spectrum of each signal value segment in the ON phase of each focal position state from the power spectrum of the corresponding signal value segment in the OFF phase for each focal position state, so as to obtain the differential power spectrum of the signal value segment in the ON phase; combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions.

[0156] The correction module 40 is used to correct the theoretical frequency of each signal value segment in the ON phase of each target SiO spectral line in each focal state of the pre-acquired target SiO spectral line source at the absolute time, so as to obtain the observed frequency of each signal value segment in the ON phase of the target SiO spectral line in the focal state at the absolute time.

[0157] The interception module 50 is used to determine the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state, centered on the observed frequency of the absolute time of each signal value segment in the ON phase of the focal position state, and a preset bandwidth for each target SiO spectral line; and to intercept the temperature spectrum data corresponding to the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of the focal position state, so as to obtain the local temperature spectrum of the signal value segment of the target SiO spectral line in the ON phase of the focal position state.

[0158] The noise reduction module 60 is used to remove the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line in each focal state, so as to obtain the local temperature spectrum of the target SiO spectral line in the ON phase of the focal state after noise removal.

[0159] The superposition module 70 is used to add the temperature spectrum values ​​of each signal value segment of each target SiO spectral line in the ON phase of each focal position state after removing the noise floor, to obtain the sum of the temperature spectrum of the signal value segment of the target SiO spectral line in the ON phase of the focal position state; and to perform weighted superposition of the sum of the temperature spectrum of each signal value segment of each target SiO spectral line in the ON phase of the focal position state to obtain the equivalent spectral intensity of the signal value segment in the ON phase of the focal position state.

[0160] The mapping module 80 is used to map the equivalent spectral intensity of each signal value segment in the ON phase of each focal position state to angular coordinates (or direction cosine coordinates) using the absolute time, azimuth angle and elevation angle of each signal value segment in the ON phase of each focal position state, so as to obtain the measured far-field power distribution in the focal position state.

[0161] The determination module 90 is used to determine the surface profile deviation of the main reflector of the radio telescope based on the measured far-field power distribution under each focal position.

[0162] The acquisition module 10, the segmentation module 20, the difference module 30, the correction module 40, the truncation module 50, the noise reduction module 60, the superposition module 70, the mapping module 80, and the determination module 90 are the functional modules of the virtual device corresponding to steps S100-S900 in the method embodiment. Their specific implementation methods can be referred to the description in the method embodiment, and will not be repeated here.

[0163] The surface deviation measurement device for the primary reflector of a radio telescope in this embodiment of the invention utilizes a natural SiO spectral line source as a stable point source signal for defocus observation to obtain the beam response map of the radio telescope. The observation data is converted from the time domain to the frequency domain, and the local temperature spectra of multiple target SiO spectral lines after noise removal are extracted in the frequency domain. The temperature spectra of each target SiO spectral line are then superimposed and synthesized, effectively improving the signal-to-noise ratio and measurement reliability. Since the spectral line source itself possesses point source characteristics, errors caused by non-ideal source models are avoided.

[0164] Another embodiment of the present invention provides a readable storage medium storing a computer program that, when executed in a computer, causes the computer to perform the steps of the method for measuring the surface deviation of the primary reflector of a radio telescope in the above embodiments of the present invention.

[0165] Another embodiment of the present invention provides an electronic device, which includes a memory and a processor. The memory stores executable code. When the processor executes the executable code, it performs the steps of the surface deviation measurement method of the main reflecting surface of the radio telescope in the above embodiments of the present invention.

[0166] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0167] For ease of description, the above apparatus is described by dividing it into various functional units. Of course, in implementing this invention, the functions of each unit can be implemented in one or more software and / or hardware components.

[0168] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0169] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0170] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0171] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0172] In a typical configuration, an electronic device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0173] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0174] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by electronic devices. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0175] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0176] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0177] This invention can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0178] The various embodiments in this invention are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0179] The foregoing has described specific embodiments of the invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0180] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope, characterized in that, include: The observation data were obtained by the radio telescope observing the pre-selected target SiO spectral line source in three focal positions using a preset observation method. The measured far-field power distribution under each focal position is determined based on the observation data; the surface shape deviation of the radio telescope's main reflector is determined based on the measured far-field power distribution under each focal position; the three focal positions include the focused state, the positive defocus state, and the negative defocus state. The preset observation mode is to use the ON-OFF mode, which includes an ON phase and an OFF phase. In the ON phase, the radio telescope points to the target SiO spectral line source and remains so for a period of time. In the OFF phase, the radio telescope deviates from the target SiO spectral line source to point to a sky region without strong sources and remains so for the same duration as the ON phase. During the ON phase of each focal position, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data for each focal position includes the signal values, azimuth and elevation angles at different sampling time points in the ON phase and the signal values ​​at different sampling time points in the OFF phase. The measured far-field power distribution under each focal position is determined based on the observation data. Specifically, this includes: for each focal position, dividing the signal values ​​at different sampling time points in both the ON and OFF phases of the observation data into an equal number of signal value segments. Each signal value segment includes the same number of signal values ​​at different sampling time points, with a one-to-one correspondence between the signal value segments in the ON phase and the signal value segments in the OFF phase; for each signal value segment in both the ON and OFF phases, performing a Fast Fourier Transform on the signal values ​​at each sampling time point to obtain the power spectrum of that signal value segment; and using the time corresponding to the intermediate sampling time point of each signal value segment in the ON phase as the power spectrum of that signal value segment. The absolute time of the signal value segment is used to obtain the azimuth and elevation angles at that absolute time, which are then used as the azimuth and elevation angles of the signal value segment. For each focal position state, the power spectrum of each signal value segment in the ON phase of that focal position state is subtracted from the power spectrum of the corresponding signal value segment in the OFF phase to obtain the differential power spectrum of that signal value segment in the ON phase of that focal position state. Combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions. The theoretical frequencies of each target SiO spectral line of the pre-acquired target SiO spectral line source at the absolute time of each signal value segment in the ON phase of each focal position state are corrected to obtain the... The observation frequencies of the absolute time of each signal value segment in the ON phase of the target SiO spectral line under the focal position state are determined. For each target SiO spectral line, the target frequency range of the absolute time of that signal value segment in the ON phase of the target SiO spectral line under the focal position state is determined with the observation frequency of the absolute time of each signal value segment in the ON phase of the target SiO spectral line under the focal position state as the center and a preset bandwidth. The temperature spectrum data corresponding to the target frequency range of the absolute time of that signal value segment in the ON phase of the target SiO spectral line under the focal position state is extracted from the temperature spectrum of each signal value segment in the ON phase of the target SiO spectral line under the focal position state to obtain the local temperature of that signal value segment in the ON phase of the target SiO spectral line under the focal position state. The local temperature spectrum of each target SiO spectral line in the ON phase of each signal value segment under each focal state is noise-removed to obtain the noise-removed local temperature spectrum of that target SiO spectral line in the ON phase of the focal state. The temperature spectrum values ​​of each signal value segment in the ON phase of each target SiO spectral line under each focal state are summed to obtain the sum of the temperature spectra of that target SiO spectral line in the ON phase of the focal state. The sums of the temperature spectra of each signal value segment in the ON phase of each target SiO spectral line under each focal state are weighted and superimposed to obtain the equivalent spectral intensity of that signal value segment in the ON phase of the focal state.By using the absolute time, azimuth, and elevation angles of each signal value segment during the ON phase in each focal position state, the equivalent spectral intensity of each signal value segment during the ON phase in that focal position state is mapped onto angular coordinates to obtain the measured far-field power distribution in that focal position state.

2. The method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope according to claim 1, characterized in that, The radio telescope performs a two-dimensional grid scan in both the azimuth and elevation planes. Specifically, this involves: designating one of the azimuth and elevation planes as a fast scan plane and the other as a slow scan plane; determining the scanning ranges of both the fast and slow scan planes, each centered on the target SiO spectral line source and covering a predetermined scan width (5-10 times the half-power beamwidth); sequentially stepping within the slow scan plane's range at fixed angular intervals and traversing its entire range, while simultaneously scanning at a uniform speed within the fast scan plane's range at each step angle, traversing its entire range; and removing the local temperature spectrum noise floor of each signal value segment in the ON phase of each target SiO spectral line at each focal position, to obtain the noise-reduced signal value segment of that target SiO spectral line in the ON phase at that focal position. The local temperature spectrum after noise removal specifically includes: extracting temperature spectrum values ​​other than the target frequency range of the absolute time of the signal value segment of the ON phase of each target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of each focal position state; fitting these values ​​to obtain the temperature spectrum estimate of the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state, which serves as the temperature spectrum noise floor of the signal value segment of the ON phase of the target SiO spectral line in the focal position state; subtracting the temperature spectrum noise floor of the signal value segment of the ON phase of each target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of each focal position state to obtain the noise-removed temperature spectrum of the signal value segment of the ON phase of the target SiO spectral line in the focal position state.

3. The method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope according to claim 1, characterized in that, The theoretical frequencies of each target SiO spectral line from a pre-acquired target SiO spectral line in the ON phase at each focal position are corrected for the absolute time of each signal value segment, thus obtaining the observed frequencies of that target SiO spectral line in the ON phase at that focal position. Specifically, this involves: calculating the radial velocity of the signal value segment in the ON phase at that focal position under local stationary standards using the coordinates of the radio telescope station, the absolute time of each signal value segment in the ON phase at each focal position, and the equatorial coordinates of the target SiO spectral line source; and, based on the radial velocity of the signal value segment in the ON phase at each focal position, correcting the theoretical frequencies of each target SiO spectral line in the ON phase at that focal position using the Doppler formula, thereby obtaining the observed frequencies of that target SiO spectral line in the absolute time of that signal value segment at that focal position.

4. The method for measuring the surface shape deviation of the primary reflecting surface of a radio telescope according to claim 1, characterized in that, The surface profile deviation of the radio telescope's primary reflector is determined based on the measured far-field power distribution at each focal position. Specifically, this involves: determining the aperture field power distribution model, which includes the Zernike coefficients to be solved; determining the theoretical aperture field power distribution at each focal position based on the aperture field power distribution model; determining the theoretical far-field power distribution at each focal position based on the theoretical aperture field power distribution at that focal position; constructing an objective function with the Zernike coefficients to be solved as the optimization variable based on the theoretical and measured far-field power distributions at each focal position; solving the objective function to obtain the optimal Zernike coefficients; determining the phase error distribution on the aperture plane based on the optimal Zernike coefficients and the aperture field power distribution model; and determining the surface profile deviation of the primary reflector based on the phase error distribution on the aperture plane.

5. A device for measuring the surface deviation of the primary reflecting surface of a radio telescope, characterized in that, include: The acquisition module is used to acquire observation data obtained by the radio telescope observing a pre-selected target SiO spectral line source in three focal positions using a preset observation method; the far-field power distribution measurement module is used to determine the measured far-field power distribution in each focal position based on the observation data; the determination module is used to determine the surface shape deviation of the radio telescope's main reflector based on the measured far-field power distribution in each focal position; the three focal positions include the focused state, the positive defocus state, and the negative defocus state. The preset observation mode is an ON-OFF mode, which includes an ON phase and an OFF phase. During the ON phase, the radio telescope points to the target SiO spectral source for a period of time. During the OFF phase, the radio telescope deviates from the target SiO spectral source to point to a region of the sky without a strong source, and this deviates for the same duration as the ON phase. During the ON phase at each focal position, the radio telescope performs a two-dimensional grid scan on the azimuth and elevation planes. The observation data for each focal position includes the signal values, azimuth and elevation angles at different sampling time points during the ON phase, and the signal values ​​at different sampling time points during the OFF phase. The far-field power distribution measurement module specifically includes a segmentation module. For each focal position state, the signal values ​​at different sampling time points in both the ON and OFF phases of the observed data under that focal position state are divided into an equal number of signal value segments. Each signal value segment includes signal values ​​at the same number of sampling time points, with a one-to-one correspondence between the signal value segments in the ON phase and the signal value segments in the OFF phase. For each signal value segment in both the ON and OFF phases, a Fast Fourier Transform is performed on the signal values ​​at each sampling time point of that signal value segment to obtain the power spectrum of that signal value segment. The time corresponding to the middle sampling time point of each signal value segment in the ON phase is taken as the absolute time of that signal value segment, and the azimuth angle and sum of the values ​​at that absolute time are obtained. The pitch angle serves as the azimuth and pitch angle of the signal value segment. The differential module, for each focal position state, calculates the difference between the power spectrum of each signal value segment in the ON phase and the power spectrum of the corresponding signal value segment in the OFF phase, obtaining the differential power spectrum of the signal value segment in the ON phase. Combined with the noise tube calibration file, the differential power spectrum of each signal value segment in the ON phase of each focal position state is converted into a temperature spectrum with temperature dimensions. The correction module corrects the theoretical frequency of each target SiO spectral line from the pre-acquired target SiO spectral line source at the absolute time of each signal value segment in the ON phase of each focal position state, obtaining the frequency of that target SiO spectral line in that focal position state. The observation frequency of the absolute time of each signal value segment in the ON phase; the extraction module, for each target SiO spectral line, uses the observation frequency of the absolute time of each signal value segment in the ON phase of each focal position state as the center and a preset bandwidth to determine the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the focal position state; extracts the temperature spectrum data corresponding to the target frequency range of the absolute time of the signal value segment in the ON phase of the target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of each focal position state, so as to obtain the local temperature spectrum of the signal value segment in the ON phase of the target SiO spectral line in the focal position state.The system comprises the following modules: a denoising module to remove the noise floor of the local temperature spectrum of each signal value segment in the ON phase of each target SiO spectral line at each focal position, thus obtaining the noise-free local temperature spectrum of that signal value segment in the ON phase of the target SiO spectral line at that focal position; a superposition module to sum the noise-free temperature spectrum values ​​of each signal value segment in the ON phase of each target SiO spectral line at each focal position, thus obtaining the sum of the temperature spectra of that signal value segment in the ON phase of the target SiO spectral line at that focal position; a weighted superposition of the sums of the temperature spectra of each signal value segment in the ON phase of each target SiO spectral line at that focal position, thus obtaining the equivalent spectral intensity of that signal value segment in the ON phase of the focal position; and a mapping module to map the equivalent spectral intensity of each signal value segment in the ON phase of each focal position onto angular coordinates using the absolute time, azimuth, and elevation angles of each signal value segment in the ON phase of each focal position, thus obtaining the measured far-field power distribution at that focal position.

6. The device for measuring the surface deviation of the primary reflecting surface of a radio telescope according to claim 5, characterized in that, The radio telescope performs a two-dimensional grid scan in both the azimuth and elevation planes. Specifically, this involves: designating one of the azimuth and elevation planes as a fast scan plane and the other as a slow scan plane; determining the scanning ranges of both the fast and slow scan planes, each centered on the target SiO spectral line source and covering a predetermined scan width (5-10 times the half-power beamwidth); sequentially stepping within the slow scan plane's range at fixed angular intervals and traversing its entire range, while simultaneously scanning at a uniform speed within the fast scan plane's range at each step angle, traversing its entire range; and removing the local temperature spectrum noise floor of each signal value segment in the ON phase of each target SiO spectral line at each focal position, to obtain the noise-reduced signal value segment of that target SiO spectral line in the ON phase at that focal position. The local temperature spectrum after noise removal specifically includes: extracting temperature spectrum values ​​other than the target frequency range of the absolute time of the signal value segment of the ON phase of each target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of each focal position state; fitting these values ​​to obtain the temperature spectrum estimate of the target frequency range of the absolute time of the signal value segment of the ON phase of the target SiO spectral line in the focal position state, which serves as the temperature spectrum noise floor of the signal value segment of the ON phase of the target SiO spectral line in the focal position state; subtracting the temperature spectrum noise floor of the signal value segment of the ON phase of each target SiO spectral line in the focal position state from the temperature spectrum of each signal value segment in the ON phase of each focal position state to obtain the noise-removed temperature spectrum of the signal value segment of the ON phase of the target SiO spectral line in the focal position state.

7. The device for measuring the surface deviation of the primary reflecting surface of a radio telescope according to claim 5, characterized in that, The theoretical frequencies of each target SiO spectral line from a pre-acquired target SiO spectral line in the ON phase at each focal position are corrected for the absolute time of each signal value segment, thus obtaining the observed frequencies of that target SiO spectral line in the ON phase at that focal position. Specifically, this involves: calculating the radial velocity of the signal value segment in the ON phase at that focal position under local stationary standards using the coordinates of the radio telescope station, the absolute time of each signal value segment in the ON phase at each focal position, and the equatorial coordinates of the target SiO spectral line source; and, based on the radial velocity of the signal value segment in the ON phase at each focal position, correcting the theoretical frequencies of each target SiO spectral line in the ON phase at that focal position using the Doppler formula, thereby obtaining the observed frequencies of that target SiO spectral line in the absolute time of that signal value segment at that focal position.

8. The device for measuring the surface deviation of the primary reflecting surface of a radio telescope according to claim 5, characterized in that, The surface profile deviation of the radio telescope's primary reflector is determined based on the measured far-field power distribution at each focal position. Specifically, this involves: determining the aperture field power distribution model, which includes the Zernike coefficients to be solved; determining the theoretical aperture field power distribution at each focal position based on the aperture field power distribution model; determining the theoretical far-field power distribution at each focal position based on the theoretical aperture field power distribution at that focal position; constructing an objective function with the Zernike coefficients to be solved as the optimization variable based on the theoretical and measured far-field power distributions at each focal position; solving the objective function to obtain the optimal Zernike coefficients; determining the phase error distribution on the aperture plane based on the optimal Zernike coefficients and the aperture field power distribution model; and determining the surface profile deviation of the primary reflector based on the phase error distribution on the aperture plane.

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