Spatial VLBI signal enhancement method based on weighted full spectrum synthesis method

Abstract

The present invention relates to a method for enhancing space VLBI signals based on a weighted full spectrum synthesis method, comprising the steps of: S1: performing a first correlation process on signals received by a space telescope and n ground telescopes to obtain a first cross-correlation power spectrum; S2: obtaining the residual time delay and residual time delay rate to be compensated between the signals of the n ground telescopes participating in the synthesis; S3: obtaining the phase to be compensated; S4: synchronizing the signals received by the telescopes participating in the synthesis to the same wavefront; S5: searching for the best weighting coefficient, and performing weighted synthesis on the telescopes participating in the synthesis to form a virtual telescope; S6: performing VLBI interference processing on the virtual telescope and the space telescope. The method for enhancing space VLBI signals based on a weighted full spectrum synthesis method of the present invention improves the baseline sensitivity by synthesizing the signals of multiple ground telescopes to form a virtual telescope and then performing VLBI with the space telescope.

Description

Technical Field

[0001] The present invention relates to the field of astronomical observation, and more specifically to a spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method. Background Art

[0002] Astronomical observations ultimately need to pursue sensitivity or spatial resolution. Very Long Baseline Interferometry (VLBI) technology has extremely high angular resolution and sensitivity, and has been widely used in astrophysics, astrometry, and astro-geodynamics. According to the basic principles of electromagnetism, the angular resolution of a telescope is approximately equal to the observation wavelength divided by the effective aperture. For VLBI, its highest angular resolution is approximately equal to the observation wavelength divided by the baseline length (that is, the distance between the two radio telescopes). At present, the VLBI facility with the highest ground-based baseline angular resolution is the Black Hole Event Horizon Telescope, and its largest equivalent aperture is close to the diameter of the earth. Astronomers have long realized that the maximum baseline length of ground-based VLBI cannot exceed the diameter of the earth. If a radio telescope is launched into space and forms a space-to-ground or space-to-space VLBI array with ground-based or space-based radio telescopes, the baseline length can exceed the diameter of the earth, thereby obtaining a higher angular resolution. This is space VLBI (Space VLBI) or space-to-ground VLBI (Space-Earth VLBI).

[0003] Technical and cost factors limit the aperture size of space telescopes, resulting in the sensitivity of the space-ground baseline being often lower than that of the ground baseline. In addition, although the space VLBI baseline is longer and has a higher angular resolution than the ground-based VLBI baseline, it will also cause most of the target source structure to be decomposed, resulting in a very low detected source flux, which leads to low sensitivity. Therefore, how to improve the sensitivity of the space VLBI telescope is a technical problem that needs to be solved.

[0004] The current common method is to increase the diameter of the space telescope as much as possible, while at the same time increasing the effective area of ​​the ground-based telescope as much as possible. In order to increase the effective area of ​​the ground-based telescope, the current method is to use super-large-aperture ground-based telescopes or use ground-based interferometer telescope arrays to participate in space VLBI network observations.

[0005] At present, researchers have proposed a spatial VLBI signal enhancement technology based on VLBI cross-correlation spectrum synthesis. It synthesizes the cross-correlation spectrum after VLBI correlation processing, so that multiple ground-based telescopes can be combined into a telescope with a larger equivalent aperture, thereby enhancing the sensitivity of VLBI space and ground baselines. However, this technology does not use weighted synthesis, and when the apertures of the telescopes involved in the synthesis are different, the best synthesis effect cannot be achieved. Summary of the invention

[0006] The object of the present invention is to provide a spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method, which uses the weighted full spectrum synthesis method to synthesize multiple ground-based telescopes to achieve the best synthesis effect.

[0007] The present invention provides a spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method, comprising the following steps:

[0008] S1: Perform the first correlation processing on the signals received by the space telescope and n ground telescopes to obtain the first cross-correlation power spectrum;

[0009] S2: Perform fringe fitting on the first cross-correlation power spectrum to obtain the residual delay and residual delay rate to be compensated;

[0010] S3: performing phase alignment on the first cross-correlation power spectrum to obtain a phase to be compensated;

[0011] S4: Taking the center of the earth as the reference point, the signals received by the n ground telescopes are sequentially compensated for integer bits, fringe rotation and fractional bits according to the prior delay model, the phase to be compensated, the residual delay to be compensated and the residual delay rate, so that the signals received by the n ground telescopes are uniformly compensated to the center of the earth;

[0012] S5: using a grid search method and using the signal-to-noise ratio to determine the optimal weighting coefficients of the n ground telescopes, and performing weighted synthesis on the compensated signals of the n ground telescopes to form a virtual telescope; step S5 further includes:

[0013] S51: Assume that the weighting coefficients of n ground-based telescopes are p1, p2…p n-1 、p n And their sum is 1, the signals compensated by the n ground telescopes are multiplied by the corresponding weighting coefficients respectively, and then the signals are correlated with the signals received by the space telescope for the second time to obtain the second cross-correlation power spectrum;

[0014] S52: Set a step size, p1, p2…p n-1 、p n Taking values ​​with a step size between 0 and 1 respectively, obtaining different weighting coefficient value combinations, substituting the obtained weighting coefficient value combinations into step S51, and obtaining the corresponding second cross-correlation power spectrum;

[0015] S53: Calculate and compare the signal-to-noise ratios of the second cross-correlation power spectra corresponding to all weight coefficient value combinations, take the weight coefficient value with the highest signal-to-noise ratio as the optimal weight coefficient of the n ground telescopes, and perform weighted synthesis on the compensated signals of the n ground telescopes using the optimal weight coefficient to form a virtual telescope;

[0016] S6: Perform VLBI on the virtual telescope and the space telescope.

[0017] Furthermore, n is an integer greater than or equal to 2.

[0018] Furthermore, the n ground-based telescopes are all small and medium-aperture telescopes.

[0019] Furthermore, the virtual telescope is equivalent to the effect of a large-aperture telescope.

[0020] Furthermore, the n ground-based telescopes are all large-aperture telescopes.

[0021] Furthermore, the virtual telescope is equivalent to the effect of an extra-large aperture telescope.

[0022] Furthermore, in step S53, the calculation formula of the signal-to-noise ratio is as follows:

[0023]

[0024] Where A represents the amplitude of the sum of all frequency points within the integration time; B is the channel bandwidth; T ap is the integration period; n ap is the number of integration cycles; nlags is the number of channel frequency points.

[0025] Further, in step S52, the step size is 0.1 or 0.01.

[0026] The space VLBI signal enhancement method based on the weighted full spectrum synthesis method provided by the present invention improves the baseline sensitivity by synthesizing the signals of multiple ground telescopes to form a virtual telescope and then performing VLBI with the space telescope; through correlation processing, high-precision delay and delay rate between telescopes are found. The delay, delay rate and phase corresponding to the telescope signals are compensated, and the signals received by telescopes far apart are aligned to the same wavefront; the optimal weighting coefficient is searched according to the measured signal to obtain the optimal synthesis effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 4 is a flow chart of a spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0029] Among the common methods of telescope array formation, baseband array formation, symbol synthesis and carrier array formation techniques require known spectrum characteristics and are often used for telemetry signals. Since full spectrum synthesis (Rogstad DH, Mileant A, Pham TT. Antenna Arraying Techniques in the Deep Space Network (Rogstad / Antenna Arraying Techniques)||Appendix A: Antenna Location[J].2003:127-129.) does not rely on the characteristics of the signal spectrum, it can be used for VLBI observation signal synthesis where the signal source is the detector and the radio source.

[0030] The baseline signal-to-noise ratio of VLBI is defined as:

[0031]

[0032] Where B is the signal bandwidth; t is the integration time; ρ0 is the baseline correlation strength. For the signal synthesis of the x,y telescope, ρ0 is defined as follows:

[0033]

[0034] Where T ax ,T nx ,T ay ,T ny are the signal temperature and noise temperature of the two telescopes x and y in a VLBI observation baseline.

[0035] When performing VLBI correlation processing, let the amplitude sequence of the same wavefront effective signal received by the x and y telescopes be u ax ,u ay , the noise signal amplitude sequence is u nx ,u ny When the radio source flux density is the same, due to the differences between telescope systems, the effective signal u ax and u ay It is proportional to the noise signal and has no correlation with it. Its proportionality coefficient m xy This reflects the differences in telescope performance.

[0036]

[0037] Therefore, the following relationship exists:

[0038]

[0039] In full spectrum synthesis, the synthesized signal is the weighted sum of the original signal amplitudes. The noise temperature T of the virtual telescope s nsThere is the following relationship with the noise temperature T of telescope x nx as follows:

[0040]

[0041] where p is the weighting coefficient of the first observation station in the full-spectrum synthesis, and 0 < p < 1. At this time, the weighting coefficient of the second signal is (1 - p).

[0042] Since:

[0043] T ns ~(pu nx +(1 - p)u ny ) 2 (6)

[0044] T ns ~(pu nx ) 2 +[(1 - p)u ny ) 2 +2p(1 - p)u nx *u ny (7)

[0045] where u nx , u ny are two independent white noise signals with the following characteristics:

[0046] u nx *u ny = 0 (8)

[0047] Therefore, the noise temperature T ns of the synthesized virtual telescope s is obtained as follows:

[0048] T ns = p 2 T nx +(1 - p) 2 T ny (9)

[0049] According to Equation (5), the effective signal temperature T as of the virtual telescope s can be obtained as follows:

[0050] T as = (p+(1 - p)m xy ) 2 T ax = (p / m xy +1 - p) 2 T ay (10)

[0051] In the full-spectrum synthesis, the correlation intensity ρ szRewrite (3) as:

[0052]

[0053] where h s =T ns / T as ,h z =T nz / T az Substituting equations (9) and (10) into (11), we obtain:

[0054]

[0055] When full spectrum synthesis is not performed, the correlation strengths of the telescope x and telescope z baselines, and the telescope y and telescope z baselines are:

[0056]

[0057]

[0058] where h x =T nx / T ax ,h y =T ny / T ay .

[0059] According to formula (12), we can know that only when the following two conditions are satisfied at the same time:

[0060]

[0061]

[0062] Only then there is ρ sz Greater than ρ xz and ρ yz , the synthesized signal baseline SNR will be higher than the non-synthesized signal baseline SNR, which can be simplified to:

[0063]

[0064] It can be seen that when the full spectrum is synthesized, the weighting coefficients of the two station signals need to be adjusted to satisfy the above formula in order to improve the baseline SNR compared with the previous one. According to (12), if the correlation strength of the synthesized baseline is to be maximized, the following formula should be minimized:

[0065]

[0066] Among them, 0<a<1, h x >0,h y >0,m xy > 0. After deduction, when y takes the minimum value, the following conditions are met:

[0067]

[0068] At this time, the synthetic baseline SNR is the largest. Substituting equation (19) into equation (17), we can see that equation (17) always holds true. x =T nx / T ax ,h y =T ny / T ay , combined with formula (4), we get:

[0069]

[0070] in, It represents the weighting coefficient ratio of the two telescopes, which can be used as the weighting coefficient of the synthetic signal to adjust so that the synthetic baseline SNR reaches the maximum. At this time, the SNR of the synthesized virtual telescope under the optimal weighting coefficient can always be higher than the SNR before synthesis. It can be seen that the ratio of the weighting coefficients of the synthetic signal of the two telescopes when the synthetic baseline SNR reaches the highest is related to the performance between the two telescopes.

[0071] Next, we try to calculate the noise temperature T n and signal temperature T a It is expressed by the relevant parameters of the telescope. In radio astronomy, the system equivalent flux density (SEFD) is generally used to describe the performance of a radio telescope. The smaller the SEFD, the lower the flux density corresponding to the system noise, that is, the higher the sensitivity of the telescope. Noise temperature T n The relationship between (in K) and SEFD (in Jy) is as follows:

[0072]

[0073] Where k is the Boltzmann constant; η is the telescope efficiency; and A is the telescope aperture area.

[0074] Similarly, there is a signal temperature T a Relationship with radio source flux density S:

[0075]

[0076] When observing radio sources, since both radio source signals and noise signals are considered white noise, only when the radio source signal obtained by the telescope is compensated to a certain accuracy can it be considered as an effective signal, otherwise it is considered as a noise signal. Therefore, different telescopes are considered to obtain the same radio source flux density S, and we get:

[0077]

[0078]

[0079] Substituting formula (4) into formula (24), we get:

[0080]

[0081] Substituting equation (23) and equation (25) into equation (20), we can obtain:

[0082]

[0083] w x and w y are the optimal weighting coefficients of station x and station y during synthesis. It can be seen that the ratio of the weighting coefficients of the synthetic signals of the two observation stations when the synthetic baseline SNR reaches the highest is related to the performance of the telescope SEFD, telescope efficiency and telescope aperture. The above theoretical analysis shows that the purpose of enhancing the signal-to-noise ratio of the synthetic signal can be achieved by selecting appropriate weighting coefficients. Considering the influence of telescope pointing error, phase noise introduced by the atmosphere, thermal noise of the equipment and noise introduced during data processing, the theoretical analysis can be used as a reference, and the weighting coefficient needs to be calculated through the measured signal.

[0084] In order to obtain the best weighting coefficient and the best synthesis effect, Figure 1 As shown, the present invention provides a spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method, comprising the following steps:

[0085] S1: Perform the first correlation processing on the signals received by the space telescope and n ground telescopes to obtain the first cross-correlation power spectrum;

[0086] In this embodiment, n is a positive integer greater than or equal to 2, that is, there are at least two ground telescopes.

[0087] Correlation processing can be completed in the VLBI correlation processor (FX type). The input of the VLBI correlation processor is the time domain signal obtained by the stations at both ends of the baseline, and the output is the cross-correlation power spectrum between the stations (called the visibility function). A cross-correlation power spectrum can be obtained between every two telescopes. After the two signals enter the FX type correlation processor, they are first decoded according to the frequency channel; then integer bit delay compensation is performed according to the pre-calculated delay model; after fringe rotation and fast Fourier transform, the signal is transformed from the time domain to the frequency domain, and fractional bit delay compensation is completed; finally, the two signals are conjugate multiplied and accumulated and integrated to obtain visibility data.

[0088] Due to the finite speed of light, the signal wavefront emitted by the radio source reaches the two telescopes at different times. The time difference between the two is called the VLBI delay, which can be expressed as:

[0089]

[0090] Where τ is the total delay, τ0 and is the theoretical delay and delay rate at the moment calculated according to the delay model. The correlation processor corrects the delay and delay rate according to the theoretical model, specifically aligning the two signals in the time domain and frequency domain through integer bit compensation, fringe rotation and fractional bit compensation. Due to the limited accuracy of the delay model, the output visibility data still has residual delay and residual delay rate, that is, the slope of the interference fringe "frequency-phase" function is not zero, and changes with time.

[0091] S2: Perform fringe fitting on the first cross-correlation power spectrum to obtain the residual delay and residual delay rate to be compensated;

[0092] In the FX-type VLBI software correlation processor, after the signal is compensated by the priori delay model, there is often a residual delay and a residual delay rate. Therefore, it is necessary to perform fringe fitting to obtain the residual delay and residual delay rate that need to be compensated.

[0093] S3: performing phase alignment on the first cross-correlation power spectrum (i.e., flattening the stripes to the same horizontal line) to obtain the phase to be compensated;

[0094] S4: using a correlation processor, taking the center of the earth as a reference point (it may also be replaced by other reference points), and performing integer bit compensation, fringe rotation and fractional bit compensation on the signals received by the n ground telescopes in sequence according to the priori delay model, the phase to be compensated, the residual delay to be compensated and the residual delay rate, so that the signals received by the n ground telescopes are uniformly compensated to the center of the earth;

[0095] After compensating for the residual delay and delay rate, the signals received by each telescope may also have phase misalignment, which will affect the effect of full spectrum synthesis. Therefore, in step S3, that is, before compensating for the residual delay and delay rate, it is necessary to flatten the phase spectrum fringes of multiple baseline cross-power spectra to the same horizontal line, so that the delay and phase errors of each telescope are minimized. For the VLBI full spectrum synthesis combination of two ground telescopes and one space telescope, the flattening equation is as follows:

[0096]

[0097]

[0098] is the coherent addition of the cross power spectra of baseline YZ and baseline XY. is the coherent addition of the cross power spectra of baselines YZ and XZ, where X and Y represent two ground-based telescopes, Z represents the space telescope, and V xy ,V xz and Vyz Respectively represent the cross-power spectrum data (ie, the first cross-correlation power spectrum) of baseline XY, baseline XZ, and baseline YZ. They are the phases that need to be compensated when the baseline XY and baseline XZ are leveled to the baseline YZ. and Make the Q1 and Q2 functions reach their maximum, and the three baseline stripes of XY, XZ, and YZ are basically flat. The signal phase compensation is as follows:

[0099]

[0100]

[0101] Will and Compensate to telescope X and telescope Z respectively. At this time, it is considered that the baselines XY, ZX, and YZ are phase-aligned and the fringes are flattened.

[0102] S5: searching for the best weighting coefficients of n ground telescopes, and performing weighted synthesis on the compensated signals of the n ground telescopes to form a virtual telescope;

[0103] Step S5 adopts a grid search method and uses the signal-to-noise ratio to determine the optimal weighting coefficient, which further includes:

[0104] S51: Assume that the weighting coefficients of n ground-based telescopes are p1, p2…p n-1 、p n And their sum is 1, the signals compensated by the n ground telescopes are multiplied by the corresponding weighting coefficients in the time domain, and then the signals are correlated with the signals received by the space telescope for the second time to obtain the second cross-correlation power spectrum;

[0105] S52: Set a step size, p1, p2…p n-1 、p n Taking values ​​with a step size between 0 and 1 respectively, obtaining different weighting coefficient value combinations, substituting the obtained weighting coefficient value combinations into step S51, and obtaining the corresponding second cross-correlation power spectrum;

[0106] The step value can be set as needed, such as 0.1, 0.01 or other values. It can be understood that the smaller the value, the more weighting coefficient value combinations there are, and the more accurate the optimal weighting coefficient obtained in the end.

[0107] S53: Calculate the signal-to-noise ratio of the second cross-correlation power spectrum corresponding to all weight coefficient value combinations and compare them, take the weight coefficient value with the highest signal-to-noise ratio as the optimal weight coefficient of the n ground telescopes, and use the optimal weight coefficient to weightedly synthesize the compensated signals of the n ground telescopes to form a virtual telescope.

[0108] In this embodiment, the signal-to-noise ratio SNR is calculated as follows:

[0109]

[0110] Where A is the amplitude of the sum of all frequency points within the integration time; B is the channel bandwidth; T ap is the integration period; n ap is the number of integration cycles; nlags is the number of channel frequency points.

[0111] Taking n=2 as an example, the method for determining the optimal weighting coefficient of the present invention is specifically described below:

[0112] When n=2, the weighting coefficients of the two ground telescopes are p1 and p2 respectively. Assuming the step size s=0.1, p1 takes values ​​from 0 to 1 with a step size of 0.1, with a total of 11 values. The corresponding p2 also has 11 values. Therefore, (p1, p2) has a total of 11 value combinations, including (0, 1), (0.1, 0.9), (0.2, 0.8), (0.3, 0.7), (0.4, 0.6), (0.5, 0.5), (0.6, 0.4), (0.7, 0.3), (0.8, 0.2), (0.9, 0.1) and (1, 0). These 11 value combinations are substituted into step 51 to calculate the corresponding second cross-correlation power spectra respectively, and then the signal-to-noise ratios of the 11 groups of second cross-correlation power spectra are calculated. The weighting coefficient value combination corresponding to the highest signal-to-noise ratio is the optimal weighting coefficient, and then the two ground telescopes are combined into a virtual telescope with the optimal weighting coefficient.

[0113] When n=3 or a larger value, the calculation method is the same as when n=2, except that there are more value combinations and the amount of calculation is larger, which will not be repeated here.

[0114] Before synthesis, the compensated signals of the n ground telescopes need to be transformed from the frequency domain to the time domain through a fast Fourier transform, and the synthesized virtual telescope signal is then transformed from the time domain to the frequency domain through a second fast Fourier transform, so as to facilitate VLBI with the space telescope. Fast Fourier transform is a conventional method in the field and will not be described here.

[0115] S6: Use the virtual telescope to perform VLBI with the space telescope.

[0116] The method of using a virtual telescope and a space telescope to perform VLBI is common knowledge in the art and will not be described in detail here.

[0117] In practical applications, the n ground telescopes can be small and medium-sized telescopes, and the effect of the synthesized virtual telescope is equivalent to that of a large-aperture telescope, which can avoid the construction of large-aperture telescopes and save construction and maintenance costs. This method can also be extended to the synthesis of large-aperture telescopes, and the effect is equivalent to the observation effect of super-large-aperture telescopes.

[0118] The space VLBI signal enhancement method based on the weighted full spectrum synthesis method provided by the present invention improves the baseline sensitivity by synthesizing the signals of multiple ground telescopes to form a virtual telescope and then performing VLBI with the space telescope; through correlation processing, high-precision delay and delay rate between telescopes are found. The delay, delay rate and phase corresponding to the telescope signals are compensated, and the signals received by telescopes far apart are aligned to the same wavefront; the optimal weighting coefficient is searched according to the measured signal to obtain the optimal synthesis effect.

[0119] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A spatial VLBI signal enhancement method based on a weighted full spectrum synthesis method, characterized in that: The following steps are involved: S1: Perform the first correlation processing on the signals received by the space telescope and n ground telescopes to obtain the first cross-correlation power spectrum; S2: Perform fringe fitting on the first cross-correlation power spectrum to obtain the residual delay and residual delay rate to be compensated; S3: performing phase alignment on the first cross-correlation power spectrum to obtain a phase to be compensated; S4: Taking the center of the earth as the reference point, the signals received by the n ground telescopes are sequentially compensated for integer bits, fringe rotation and fractional bits according to the prior delay model, the phase to be compensated, the residual delay to be compensated and the residual delay rate, so that the signals received by the n ground telescopes are uniformly compensated to the center of the earth; S5: using a grid search method and using the signal-to-noise ratio to determine the optimal weighting coefficients of the n ground telescopes, and performing weighted synthesis on the compensated signals of the n ground telescopes to form a virtual telescope; step S5 further includes: S51: Assume that the weighting coefficients of n ground-based telescopes are p1, p2, ... n-1 、p n And their sum is 1, the signals compensated by the n ground telescopes are multiplied by the corresponding weighting coefficients respectively, and then the signals are correlated with the signals received by the space telescope for the second time to obtain the second cross-correlation power spectrum; S52: Set a step size, p1, p2…p n-1 、p n Taking values ​​with a step size between 0 and 1 respectively, obtaining different weighting coefficient value combinations, substituting the obtained weighting coefficient value combinations into step S51, and obtaining the corresponding second cross-correlation power spectrum; S53: Calculate and compare the signal-to-noise ratios of the second cross-correlation power spectra corresponding to all weight coefficient value combinations, take the weight coefficient value with the highest signal-to-noise ratio as the optimal weight coefficient of the n ground telescopes, and perform weighted synthesis on the compensated signals of the n ground telescopes using the optimal weight coefficient to form a virtual telescope; S6: Perform VLBI on the virtual telescope and the space telescope.

2. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 1, characterized in that: n is an integer greater than or equal to 2.

3. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 1, characterized in that: The n ground-based telescopes are all small and medium-aperture telescopes.

4. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 3, characterized in that: The virtual telescope is equivalent to the effect of a large-aperture telescope.

5. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 1, characterized in that: The n ground-based telescopes are all large-aperture telescopes.

6. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 5, characterized in that: The virtual telescope is equivalent to the effect of a super-large aperture telescope.

7. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 1, characterized in that: In step S53, the calculation formula of the signal-to-noise ratio is as follows: Where A represents the amplitude of the sum of all frequency points within the integration time; B is the channel bandwidth; T ap is the integration period; n ap is the number of integration cycles; nlags is the number of channel frequency points.

8. The spatial VLBI signal enhancement method based on weighted full spectrum synthesis method according to claim 1, characterized in that: In step S52, the step size is 0.1 or 0.01.

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