High-precision lunar orbit satellite laser ranging echo signal grading rapid search method

Abstract

The invention discloses a high-precision lunar orbit satellite laser ranging echo signal grading rapid search method, and belongs to the technical field of deep space laser ranging. The method comprises the following steps: a ground end laser emission system tracks and points to a target position according to a guide file; transmitting a long-pulse-width laser signal, and if a tracking target point echo is not monitored, performing target point airspace search based on an Archimedes spiral search model; after an echo signal of a tracking target point is received at the current position, Archimedes spiral search is stopped, and the current position serves as a correction original point to continue to track and forecast the trend of an orbit guide file; and if the quality of the echo signal of the tracking target point reaches a predetermined identification threshold, emitting a narrow pulse width laser signal, entering an accurate measurement mode, and obtaining high-precision laser measurement data. According to the method, the searching time of the lunar orbit satellite angle reflection echo can be effectively shortened, and the success rate of capturing the satellite angle reflection laser echo signal in a complex and deep earth-moon space environment is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser ranging, and particularly relates to a method for rapidly searching hierarchical echo signals of a high-precision lunar orbit satellite laser ranging. Background Art

[0002] The technology of lunar ranging with laser retroreflectors is a high-tech means for accurately measuring the distance between the Earth and the Moon and studying the dynamics of the Moon. By emitting laser pulses towards the laser retroreflectors on the lunar surface and receiving the reflected light, the distance between the Earth and the Moon can be calculated. This technology is of great significance for verifying the general theory of relativity, studying the physical properties and motion laws of the Moon, etc. Extending the lunar surface retroreflector to a lunar orbit satellite for laser ranging is of great significance for the precise orbit determination of satellites in the Earth-Moon space and the construction of the Earth-Moon communication, navigation, and positioning system.

[0003] The working principle of a laser retroreflector is based on the reflection characteristics of light, that is, after the incident light is reflected by three mutually perpendicular reflecting surfaces of the retroreflector, it can return along the original path. Due to the long distance between the Earth and the Moon in laser lunar ranging itself, the signal is extremely weak compared with that of near-Earth satellites. It has extremely high requirements for the laser pointing accuracy and is greatly affected by weather, atmospheric disturbances, and the positions of celestial bodies, etc., and the success probability is very low. Especially if higher-precision data is to be obtained, usually the width of the laser pulse also needs to be restricted, making the reflected signal even weaker.

[0004] To this extent, if the measurement target position changes from the lunar surface to a lunar orbit satellite, the ranging difficulty will be further increased, mainly reflected in the pointing error caused by the pointing determination orbit error and the decrease in the laser retroreflector index caused by the satellite platform.

[0005] In the traditional laser telescope system for space target ranging, the laser source is fixed. Theoretically, the success probability of lunar laser ranging is positively correlated with the intensity of the echo signal. The larger the single-pulse laser energy, the stronger its echo signal, and the greater the probability of receiving the echo signal. However, in actual engineering, due to the limitations of the laser itself, it is impossible to take into account both narrow pulse width and large energy. The larger the single-pulse laser, the more it will cause the broadening of the pulse width, resulting in a decrease in ranging accuracy. Narrow-pulse-width lasers are difficult to ensure accurate pointing and obtain effective echo signals due to their small pulse energy.

[0006] Different from the relatively fixed position of the retroreflector on the lunar surface, the current tracking and ranging of the laser retroreflector on a lunar orbit satellite more rely on long-term orbit determination by ground stations. There may be a large pointing error in the case of insufficient tracking and control resources. The transverse mode of the ranging laser beam is usually the fundamental mode, also known as the 00 mode, and its energy is distributed in a Gaussian-like manner, mainly concentrated in the center of the beam. At this time, if the laser telescope still only ranges for the designated target pointing, it is very likely that the ranging success probability will be further reduced due to the pointing deviation.

[0007] Traditional laser ranging for lunar orbit spacecraft generally generates a pointing guidance file based on the results of orbit determination and prediction, and guides the telescope's pointing azimuth tracking based on the pointing guidance file. The inspector manually adjusts the pointing error and manually adjusts and searches based on the deviation between the predicted and actual pointing. This method is largely based on the subjective judgment of the operator. When there is a pointing error or orbit prediction error, it is impossible to accurately search the area covered by the error ellipsoid near the target point.

[0008] Therefore, how to improve the success rate of laser ranging from the Earth to the Moon orbit spacecraft corner reflector has become an important technical problem to be solved urgently in this technical field. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a high-precision lunar-orbit satellite laser ranging echo signal hierarchical rapid search method, which significantly improves the capture success rate of the Earth-Moon laser ranging echo signal by improving the laser signal search method.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0011] A high-precision lunar orbit satellite laser ranging echo signal hierarchical rapid search method comprises the following steps:

[0012] Step 1: The ground-side laser launch system tracks and points to the target location according to the guidance file;

[0013] Step 2: Enter the rough measurement search phase and switch the laser light source of the ground laser transmission system to transmit long pulse width laser signals;

[0014] Step 3: In the coarse search phase, if the echo of the tracking target point is not detected, the target point airspace search is performed based on the Archimedean spiral search model;

[0015] Step 4: After receiving the tracking target point echo signal at the current position, stop the Archimedean spiral search and continue to track the trend of the predicted orbit guidance file with the current position as the origin;

[0016] Step 5: If it is confirmed that the quality of the echo signal of the tracking target point reaches the predetermined threshold, the control system switches to emitting a narrow pulse width laser signal, enters the precision measurement mode, and obtains high-precision laser measurement data.

[0017] In a second aspect, the present invention provides an electronic device comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned high-precision lunar-orbit satellite laser ranging echo signal hierarchical rapid search method.

[0018] In a third aspect, the present invention provides a computer-readable storage medium storing executable instructions that, when executed by a processor, enable the processor to implement the foregoing method for hierarchical and rapid search of echo signals of high-precision lunar orbit satellite laser ranging.

[0019] The beneficial effects of the present invention are as follows:

[0020] By switching laser light sources with multiple different pulse widths at the ground end, the present invention preferentially uses long-pulse-width and high-energy laser signals in the early target search stage, in combination with the Archimedes spiral search method, to enhance the intensity of transmitted and reflected signals and the laser search coverage, thereby improving the success rate of signal capture in the complex and far-reaching earth-moon space environment.

[0021] After successfully capturing the target echo, the system switches to a narrow-pulse-width and high-precision laser signal to improve the ranging accuracy. This pulse-width switching mechanism enables the system to search for the accurate laser pointing more quickly and efficiently.

[0022] The Archimedes spiral method is used to search the airspace of the target point. This spiral search mode can systematically cover the target area, reduce the search blind area, and optimize the search efficiency.

[0023] In summary, the present invention can effectively improve the success rate of ground-based laser ranging to lunar orbit satellites, especially in the complex and far-reaching earth-moon space environment. The switching of multi-pulse-width laser light sources and the application of the Archimedes spiral search mode enable the system to capture target signals more efficiently, thereby providing more reliable ranging support for earth-moon space exploration. This search method can be used not only for laser retroreflection of lunar orbit satellites, but also can be extended to include lunar surfaces, earth-moon space, or other deep space orbit spacecraft that are far from the earth. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flowchart of a method for hierarchical and rapid search of echo signals of high-precision lunar orbit satellite laser ranging according to the present invention;

[0025] Figure 2 is a ranging emission optical path diagram of a dual-laser under the condition of realizing dual-laser switching through a beam splitting prism;

[0026] Figure 3 is a ranging emission optical path diagram of a dual-laser under the condition of realizing dual-laser switching through the rotation of a fast steering mirror;

[0027] Figure 4 is a ranging emission optical path diagram of a laser for realizing laser switching by Q-switching a single laser;

[0028] Figure 5 is a schematic diagram of an Archimedes spiral. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] As Figure 1 shown, the present invention provides a high-precision hierarchical fast search method for lunar orbit satellite laser ranging echo signals. This method divides the search process into two stages: rough measurement search and fine measurement search. By switching laser light sources with different pulse widths on the ground end, the laser pulse energy, pulse width, and frequency are adjusted. Its main purpose is that in the early stage of the experiment, a long pulse width laser is used in the rough measurement search. Its single pulse laser energy is large, but the pulse frequency is relatively low, the pulse width time is long, and the relative ranging accuracy will decrease to a certain extent. However, due to the increase in signal energy, its echo signal is relatively enhanced, and the echo capture probability is greater. At the same time, to avoid errors caused by inaccurate pointing and guiding files, the Archimedes spiral method is used to search the target point airspace to improve the success rate of signal capture. After successfully capturing the rough measurement search target signal, it can be confirmed that the current laser pointing is accurate. At this time, it switches to the fine measurement search stage. On the premise of maintaining the pointing, it switches to a narrow pulse width laser. Its single pulse laser energy is small, but the pulse frequency is relatively high, the pulse width time is short, and the relative ranging accuracy will be maintained at a high level. The specific steps are as follows:

[0031] Step 1: The ground laser emission system tracks and points to the target position according to the guiding file.

[0032] Step 2: Enter the rough measurement search stage, and switch the laser light source of the ground laser emission system to emit long pulse width and high energy laser signals. Usually, the single pulse energy of the long pulse width is generally not less than 3J, the pulse width is not more than 10ns, and the pulse frequency is not less than 1Hz;

[0033] Step 3: In the case where there is no obvious echo when tracking the target point in the rough measurement search stage, use the Archimedes spiral search and set parameters. The ground laser control system adjusts the laser emission direction according to the preset Archimedes spiral model to search the target point airspace. The Archimedes spiral model is designed according to the divergence angle of the laser itself and the orbit projection parameters. If no echo signal is detected, taking the current predicted position as the origin, combined with the theoretical orbit determination error of the guiding file, adjust the Archimedes spiral, including parameters such as pitch, number of scanning circles, and rotation period. Ensure that the scanning range covers the pointing error range.

[0034] Step 4: Monitor the echo signal. After receiving the wide beam laser echo at the current position, stop the Archimedes spiral search form and continue to track the trend of the guiding file of the predicted orbit with the current position as the origin. At this time, the ranging accuracy is poor, but the accurate pointing can be quickly obtained.

[0035] Step 5: Perform pulse width switching: Once it is confirmed that the signal quality reaches the predetermined threshold, the control system switches to a narrow pulse width and high-precision laser signal and enters the fine measurement mode. At this time, a high-precision laser signal can be obtained. The single-pulse energy of the narrow pulse width laser is generally not less than 300 mJ, the pulse width is not more than 100 ps, and the pulse frequency is not less than 100 Hz.

[0036] Furthermore, a long pulse width and high-energy laser is selected as the main light source during the coarse measurement search stage to enhance the signal energy and improve the capture probability. After the ground receiving device receives the echo signal and successfully captures the target echo, it switches to a narrow pulse width and high-precision laser signal to improve the ranging accuracy.

[0037] In the said Step 2, two laser light sources with different pulse widths are used, including a long pulse width (selecting a wavelength of 562 nm, a single-pulse energy of 3 J, a pulse frequency of 10 Hz, and a pulse width of 7 ns) and a narrow pulse width laser (selecting a wavelength of 1064 nm, a single-pulse energy of 300 mJ, a pulse frequency of 1000 Hz, and a pulse width of 75 ps).

[0038] As Figure 2 shown, for the two groups of lasers with long and narrow pulse widths, the double-laser laser common path is realized through a beam splitting prism, and the light source switching is realized by controlling the lasers not to emit light simultaneously. Or as Figure 3 shown, the light source switching is realized through a fast steering mirror. A fast steering mirror is a lens that can quickly and accurately change the direction of the reflected light beam. It usually consists of a high-precision reflecting mirror surface and a fast-response driving mechanism. Through the control of the driving mechanism, the reflecting mirror can rotate around one or two axes, thereby realizing the rapid adjustment of the light beam direction. By adjusting the rotation position of the fast steering mirror, the light sources of lasers with different pulse widths enter the telescope optical path, thereby realizing the rapid switching of lasers with different pulse widths.

[0039] Preferably, a single laser can also be used, and the pulse width and pulse energy of the single laser are adjusted through the acousto-optic or electro-optic Q-switching technology generated by a modulator to achieve an effect similar to the switching of different pulse widths and energies of a double laser. As Figure 4 shown.

[0040] The signal receiving system is used to detect the laser echo signal reflected from the moon. The signal receiving system includes a high-sensitivity photodetector and a signal processing unit, such as a superconducting nanowire detector, etc.

[0041] For the Archimedes spiral search, a mathematical model is used to generate an Archimedes spiral path. This path can systematically cover the target airspace, reduce the search blind area, and improve the search efficiency and measurement accuracy. The Archimedes spiral is a spiral with special properties, such as Figure 5As shown in the figure. Assume that point A starts from point O at the center of the cross and moves along the straight line OA at a constant speed, while rotating around point O at a fixed angular speed in a spiral motion. When viewed from above, the trajectory of point A is spiral-shaped, and this spiral is named the "Archimedes spiral". Since it is a uniform motion during the movement process, it can also be defined as an "equiangular spiral". The curve equation of the Archimedes spiral in the plane polar coordinate system:

[0042] r(θ) = a + b(θ)

[0043] Where: b is the spiral coefficient, with the unit of km / °, representing the change in the curve diameter when the curve changes by 1°; θ is the rotation angle, with the unit of degree, representing the total number of degrees the curve has rotated; a is the polar radius when θ = 0°, with the unit of km.

[0044] The generation of the Archimedes spiral search path is based on pre-set parameters, such as the pitch and the starting radius. During the actual search process, dynamic adjustments can be made, such as adjustments in the suspected echo area or the key focus area. The selection of the Archimedes spiral parameters matches the orbit determination error and the laser divergence angle. Assume a laser with an aperture of 1m and a laser divergence angle of 0.6 arcseconds (half angle). When the satellite-to-ground distance is approximately 380,000 km, the diameter of the light spot is approximately 2.2 km after reaching the lunar orbit satellite. Assume the orbit determination error of the guidance file obtained by radio orbit determination is 10 km. Then the number of scanning circles is selected as 5 circles, the pitch is 0.01 arcminute, and the total scanning radius is 0.05 arcminute, covering a range of approximately 11 km. The target airspace can be completely covered.

[0045] By increasing the pulse energy and pulse width of the laser light source and combining with the Archimedes spiral search method, the ranging success probability of the ground laser station for the laser corner reflector on the lunar orbit satellite can be effectively improved. This search method can be used not only for lunar orbit laser corner reflectors, but also for lunar surfaces, the Earth-Moon space, or other deep space orbit spacecraft that are far from the Earth.

[0046] In a second aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the foregoing high-precision lunar orbit satellite laser ranging echo signal hierarchical fast search method.

[0047] In a third aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the foregoing high-precision lunar orbit satellite laser ranging echo signal hierarchical fast search method.

[0048] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hierarchical fast search method for lunar orbit satellite laser ranging echo signals with high precision, characterized in that, It includes the following steps: Step 1: The ground-based laser emission system tracks and points to the target position according to the guidance file; Step 2: Enter the rough measurement and search stage, and switch the laser light source of the ground laser emission system to emit a long pulse-width laser signal; Step 3: In the rough measurement and search stage, if the echo of the tracking target point is not detected, based on the Archimedes spiral search model, conduct an airspace search for the target point; Step 4: After receiving the echo signal of the tracking target point at the current position, stop the Archimedes spiral search, and continue to track and predict the trend of the guidance file with the current position as the origin; Step 5: If it is confirmed that the quality of the echo signal of the tracking target point reaches the predetermined recognition threshold, the control system switches to emit a narrow pulse-width laser signal and enters the fine measurement mode. At this time, high-precision laser measurement data can be obtained.

2. A hierarchical fast search method for the echo signal of lunar orbit satellite laser ranging with high precision according to claim 1, characterized in that In Step 2, two lasers with different pulse widths are used as the laser light source of the emission system.

3. A method for hierarchical fast search of lunar orbit satellite laser ranging echo signals with high precision according to claim 2, characterized in that, For the two lasers with different pulse widths, the light source switching is realized through a beam splitter prism or a fast steering mirror.

4. A method for hierarchical fast search of laser ranging echo signals of a high-precision lunar orbit satellite according to claim 1, characterized in that, A single laser can also be used, and the switching between the long pulse-width laser signal and the narrow pulse-width laser signal is realized through acousto-optic modulation or electro-optic Q-switching technology.

5. A method for hierarchical fast search of lunar orbit satellite laser ranging echo signals with high precision according to claim 2, characterized in that, The two lasers with different pulse widths include a long pulse-width laser and a narrow pulse-width laser. The single pulse energy of the long pulse-width is not less than 3J, the pulse width is not more than 10ns, and the pulse frequency is not less than 1Hz; the single pulse energy of the narrow pulse-width laser is not less than 300mJ, the pulse width is not more than 100ps, and the pulse frequency is not less than 100Hz.

6. A method for fast hierarchical search of laser ranging echo signals of a high-precision lunar orbit satellite according to claim 1, characterized in that In Step 3, if the echo of the tracking target point is still not detected, with the current predicted position as the origin, combined with the theoretical orbit determination error of the guidance file, adjust the Archimedes spiral to ensure that the scanning range covers the pointing error range.

7. A method for fast hierarchical search of laser ranging echo signals of a high-precision lunar orbit satellite according to claim 6, characterized in that The adjustment of the Archimedes spiral includes the pitch, the number of scanning circles, and the rotation period.

8. A method for fast hierarchical search of echo signals of lunar orbit satellite laser ranging with high precision according to claim 1, characterized in that, During the search process, the laser pointing adopts an Archimedes spiral. The curve equation of the Archimedes spiral in the plane polar coordinate system is: r(θ) = a + b(θ), where b is the spiral coefficient, with the unit of km / °, representing the change in the curve diameter when the curve changes by 1°; θ is the rotation angle, with the unit of degree, representing the total number of degrees the curve has turned; a is the polar radius when θ = 0°, with the unit of km.

9. An electronic device, characterized in that, It includes: One or more processors; A memory for storing one or more programs; Among them, when the one or more programs are executed by the one or more processors, the one or more processors implement a high-precision lunar orbit satellite laser ranging echo signal hierarchical fast search method according to any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, An executable instruction is stored thereon, and when the instruction is executed by the processor, the processor can implement a high-precision lunar orbit satellite laser ranging echo signal hierarchical fast search method according to any one of claims 1-8.

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