Method for calculating requirement of inter-satellite signal acquisition of lunar orbit formation satellites on measured orbit accuracy of satellites

Abstract

The invention discloses a method for calculating the requirement of signal capture among lunar orbit formation satellites on satellite orbit measurement accuracy, and belongs to the technical field of deep space exploration. The method comprises the following steps: under a ground test condition, measuring an antenna pattern, transmitting signal power and receiving sensitivity of a master satellite, measuring an antenna pattern, receiving sensitivity and a transmitting EIRP value of a slave satellite, measuring an installation error and an antenna mechanism deformation error of a high-gain directional antenna of the master satellite, and measuring attitude control precision of the master satellite. According to the main satellite antenna pointing total error requirement, the antenna installation error, the antenna mechanism deformation error and the beam pointing error caused by the attitude control precision of the main satellite, the position error requirement of the slave satellite relative to the main satellite is calculated; and determining orbit measurement precision requirements of the master satellite and the slave satellite based on the position error. According to the method, the orbit measurement requirement can be put forward to a ground measurement and control system in advance, or the proper inter-satellite distance can be selected according to the orbit measurement precision provided by the ground, and the success probability of establishing the inter-satellite link is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of deep space exploration, and in particular relates to a method for calculating the requirements of satellite orbit determination accuracy for inter-satellite signal capture of formation satellites in a lunar orbit. Background Art

[0002] In recent years, the field of lunar exploration has achieved vigorous development. Several satellites are organized into a certain formation configuration in the lunar orbit and intersatellite links are established. Each satellite in the formation works together and communicates with each other to jointly achieve detection, communication, navigation and other tasks. The satellite formation has the characteristics of low cost, good performance, high reliability and strong adaptability.

[0003] Bidirectional capture of intersatellite signals is a prerequisite for establishing intersatellite links. Bidirectional capture of intersatellite signals requires the ground master control station to accurately determine the orbit of the spacecraft. Bidirectional capture of intersatellite signals requires the ground measurement and control station to accurately determine the orbit of the satellite. The satellite adjusts the satellite attitude or antenna beam pointing according to the orbit determination results to align the two satellites with each other. If the capture is unsuccessful, it is necessary to turn on the search mode and continue to adjust the direction until the capture is completed. Compared with earth-orbiting satellites, lunar-orbiting satellites cannot use the global satellite navigation system (GNSS) to determine their orbits. The ground measurement and control resources are limited, and the satellite-to-ground link distance is longer and the signal is weaker. Therefore, the satellite's orbit determination accuracy is relatively lower. This will result in too large an uncertainty range of the satellite position in the process of establishing an intersatellite link, and the two satellites will not be able to align their antenna beams with each other, resulting in too long a two-way capture time or even capture failure.

[0004] Some researchers have switched the intersatellite link module of the coarse-orbit spacecraft to the signal large-range capture working mode, unidirectionally captured the intersatellite link signal of the Beidou satellite, calculated the precise orbit of the coarse-orbit spacecraft after unidirectional precise ranging of the Beidou satellite, and then adjusted the intersatellite link to achieve two-way capture. This method requires that the error of the initial orbit of the coarse-orbit spacecraft meet the signal capture time uncertainty capability that the baseband can achieve in the signal large-range capture working mode, but does not mention how to determine whether the initial orbit error and the precise orbit error meet the requirements of intersatellite link capture.

[0005] Some researchers have also used a simplified position-velocity recursive algorithm to solve the Ka-band intersatellite link pointing angle in real time according to the orbital elements of low-orbit satellites and medium-orbit satellites, and completed the spatial beam pointing of the intersatellite link from low-orbit satellites to medium-orbit satellites. However, they did not mention whether the solved intersatellite link pointing angle error can meet the requirements of intersatellite link capture. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for calculating the requirements for satellite orbit determination accuracy of inter-satellite signal capture of satellites in a lunar orbit formation. Under the condition that ground measurement and control resources are limited and GNSS signals cannot be used, the satellite orbit determination accuracy requirements can be calculated based on parameters such as satellite performance indicators, inter-satellite distance, and expected capture probability, so as to propose orbit determination requirements to the ground measurement and control system in advance, or select a suitable inter-satellite distance based on the orbit determination accuracy that can be provided by the ground, thereby improving the success probability of establishing an inter-satellite link.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for calculating the satellite orbit determination accuracy requirement for satellite inter-satellite signal capture in a lunar orbit formation includes the following steps:

[0009] Step 1: Under ground test conditions, measure the antenna pattern, transmit signal power, and receiving sensitivity of the master satellite, and measure the antenna pattern, receiving sensitivity, and transmit EIRP value of the slave satellite;

[0010] Step 2: Under ground test conditions, measure the installation error and antenna mechanism deformation error of the main satellite high-gain directional antenna, and calculate the beam pointing error;

[0011] Step 3: Under ground test conditions, measure the attitude control accuracy of the primary satellite and calculate the beam pointing error caused by it ;

[0012] Step 4: Determine the receiver capture threshold according to the receiving sensitivity and preset capture margin of the master satellite and the slave satellite respectively;

[0013] Step 5: Calculate the minimum antenna gain of the primary satellite corresponding to the inter-satellite distance;

[0014] Step 6: Determine the beam width of the main satellite antenna based on the minimum antenna gain and the main satellite antenna pattern;

[0015] Step 7: Determine the total pointing error requirement of the main satellite antenna according to the beam width of the main satellite antenna and the preset inter-satellite signal capture probability;

[0016] Step 8: Calculate the position error of the slave satellite relative to the master satellite due to the orbit prediction error based on the total error requirement of the master satellite antenna pointing, the antenna installation error, the antenna mechanism deformation error, and the beam pointing error caused by the attitude control accuracy of the master satellite. ;

[0017] Step 9: Based on the position error calculated in step 8, determine whether the orbit determination accuracy requirements of the master and slave satellites meet , Respectively represent the orbit determination accuracy of the master satellite and the slave satellite.

[0018] The beneficial effects of the present invention are:

[0019] The present invention calculates the orbit prediction accuracy of the master satellite and the slave satellite required for establishing an inter-satellite link based on the performance indicators of the satellite obtained in the ground test phase, the formation distance of the satellites in orbit, and the expected capture probability, and proposes the orbit measurement demand to the ground measurement and control system in advance, or selects the appropriate inter-satellite distance according to the orbit measurement accuracy that can be provided by the ground, thereby improving the success probability of establishing the inter-satellite link. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic flow chart of a method for calculating the requirements for satellite orbit determination accuracy for inter-satellite signal capture of formation satellites in a lunar orbit according to the present invention;

[0021] Figure 2 Schematic diagram of the main lobe of the main satellite antenna pattern according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] The lunar orbit formation satellites include a master satellite and a slave satellite with intersatellite communication and measurement functions. Intersatellite communication and measurement is to establish an intersatellite microwave link between the master satellite and the slave satellite, and send and receive signals and data to each other, so as to achieve intersatellite data transmission, intersatellite distance and time difference measurement. Intersatellite signal capture is that both the master satellite and the slave satellite receive each other's microwave signals and successfully lock.

[0024] The master satellite adopts a high-gain directional antenna with a narrow beam width and high gain, which is beneficial to increasing the distance of inter-satellite communication. The slave satellite adopts a low-gain wide-beam antenna, which is beneficial to reducing the difficulty of inter-satellite signal alignment. After determining the requirements for establishing an inter-satellite link, the master and slave satellites adjust the satellite attitude according to the orbit forecast and control the antenna to point to each other. The premise for inter-satellite signal capture is that the master satellite can align the narrow antenna beam with the slave satellite, that is, the slave satellite falls into the signal beam of the master satellite.

[0025] Based on the above theory, Figure 1 As shown, the present invention provides a method for calculating the satellite orbit prediction accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite, comprising the following steps:

[0026] Step 1: Under ground test conditions, measure the antenna pattern, transmit signal power, and receiving sensitivity of the master satellite, and measure the antenna pattern, receiving sensitivity, and transmit EIRP value of the slave satellite;

[0027] The above indicators can be obtained during the comprehensive test of satellite subsystem and whole satellite. The transmit signal power, receiving sensitivity of the master satellite, the receiving sensitivity of the slave satellite, and the transmit EIRP value are respectively , and , ;

[0028] Step 2: Under ground test conditions, measure the installation error of the main satellite's high-gain directional antenna and the deformation error of the antenna mechanism, and calculate the beam pointing error caused by them;

[0029] By accurately measuring the antenna before and after the main satellite environmental test, the installation error of the directional antenna and the deformation error of the antenna structure can be obtained, and the antenna beam pointing error caused by it ( ) are and ;

[0030] Step 3: Under ground test conditions, measure the attitude control accuracy of the primary satellite and calculate the beam pointing error caused by it;

[0031] The antenna beam pointing error caused by the attitude control accuracy of the primary satellite is ;

[0032] Step 4: Determine the receiver capture threshold according to the receiving sensitivity and preset capture margin of the master satellite and the slave satellite respectively;

[0033] The capture margins of the master and slave satellites are preset to be , then the receiver capture thresholds of the master satellite and the slave satellite are , ;

[0034] Step 5: Intersatellite link calculation, calculate the minimum antenna gain of the main satellite corresponding to the intersatellite distance;

[0035] For the master satellite transmitting and slave satellite receiving link, , for the slave-satellite transmitting-master-satellite receiving link, ,in, It is the minimum transmission gain required by the antenna of the master satellite when the receiving level of the slave satellite is the capture threshold. is the minimum receiving gain required by the main satellite antenna when the receiving level of the main satellite is the capture threshold. is the minimum gain from the star antenna within the wide beam range, , are the free space losses on the two links, , , , are the transmission signal frequencies of the master and slave satellites, is the interstellar distance;

[0036] Step 6: Determine the beam width of the main satellite antenna based on the minimum antenna gain and the main satellite antenna pattern;

[0037] According to the main satellite antenna pattern and step 5 and , get the minimum transmit beam width of the main satellite antenna and receive beamwidth , the beam width of the primary satellite at this intersatellite distance ;

[0038] Step 7: Determine the total pointing error of the main satellite antenna based on the beam width of the main satellite antenna and the preset inter-satellite signal capture probability ( )Require;

[0039] Main satellite antenna pointing total error requirements , Determined by the intersatellite signal capture probability, When , the capture probability is 0.6826, , the capture probability is 0.9545, , the capture probability is 0.9973;

[0040] Step 8: Calculate the position error of the slave satellite relative to the master satellite due to the orbit prediction error based on the total error requirement of the master satellite antenna pointing, the antenna installation error, the antenna mechanism deformation error, and the beam pointing error caused by the master satellite's attitude control accuracy. );

[0041] In order to meet the preset intersatellite signal acquisition probability, the main satellite beam pointing deviation caused by the orbit prediction error should be better than , from which we can get the position error of the slave star relative to the master star ( ) should be better than ;

[0042] Step 9: The orbit determination accuracy requirements of the master and slave satellites must meet ;

[0043] Assuming that the orbit prediction accuracy of the master satellite and the slave satellite is the same, the orbit determination accuracy of the master satellite and the slave satellite ( ) should be better than ;

[0044] The orbit prediction accuracy requirements of the master and slave satellites do not vary with the distance between the satellites. This is because when When the orbit prediction error increases, the main satellite beam pointing deviation The free space loss is relatively reduced, but the increase in free space loss leads to a narrower antenna beam angle that meets the receiving level. When the antenna beam angle that meets the receiving level is reduced, the main satellite beam pointing deviation caused by the orbit prediction error is wider. So it can be used at different inter-satellite distances. Calculate and , thereby determining the inter-satellite distance that requires the minimum orbit prediction accuracy and reducing the demand on ground measurement and control systems.

[0045] Example

[0046] Step 1: Under ground test conditions, measure the antenna pattern, transmit signal power, and receiving sensitivity of the master satellite, and measure the antenna pattern, receiving sensitivity, and transmit EIRP value of the slave satellite;

[0047] The receiving / transmitting direction diagram of the main satellite antenna is as follows: Figure 2 The parameter examples are as follows:

[0048] , ;

[0049] , ;

[0050] Step 2: By accurately measuring the antenna before and after the main satellite environmental test, the installation error of the main satellite high-gain directional antenna and the deformation error of the antenna structure are measured, and the beam pointing error caused by them is calculated ( ); parameter examples are as follows:

[0051] , ;

[0052] Step 3: Under ground test conditions, measure the attitude control accuracy of the primary satellite and calculate the beam pointing error caused by it ( ); parameter examples are as follows:

[0053] ;

[0054] Step 4: Determine the receiver capture threshold based on the receiving sensitivity and the preset capture margin;

[0055] The capture margins of the master and slave satellites are preset to be , then the receiver capture thresholds of the master satellite and the slave satellite are , ; Parameter examples are as follows:

[0056] ,but: , ;

[0057] Step 5: Intersatellite link calculation, calculate the minimum antenna gain of the main satellite corresponding to the intersatellite distance;

[0058] Calculate the two links of master satellite transmitting and slave satellite receiving, and slave satellite transmitting and master satellite receiving respectively. , ,in, It is the minimum transmission gain required by the antenna of the master satellite when the receiving level of the slave satellite is the capture threshold. is the minimum receiving gain required by the main satellite antenna when the receiving level of the main satellite is the capture threshold. is the minimum gain from the star antenna within the wide beam range, , are the free space losses on the two links, , , , are the transmission signal frequencies of the master and slave satellites, is the inter-satellite distance; parameter examples are as follows:

[0059] , , , then we can calculate:

[0060] ;

[0061] ;

[0062] ;

[0063] ;

[0064] Step 6: Determine the beam width of the main satellite antenna based on the minimum antenna gain and the main satellite antenna pattern;

[0065] According to the main satellite antenna pattern, and , get the minimum transmit beam width of the main satellite antenna and receive beamwidth , the beam width of the primary satellite at this intersatellite distance ;

[0066] According to the antenna pattern data, the beam angle under this antenna gain is:

[0067] , , ;

[0068] Step 7: Determine the total pointing error of the main satellite antenna based on the beam width of the main satellite antenna and the preset inter-satellite signal capture probability ( ),Require;

[0069] The total pointing error requirement of the main satellite antenna is: , Determined by the intersatellite signal capture probability, When , the capture probability is 0.6826, , the capture probability is 0.9545, , the capture probability is 0.9973;

[0070] The intersatellite signal capture probability is preset to 0.9973, then , ;

[0071] Step 8: Calculate the position error of the slave satellite relative to the master satellite due to the orbit prediction error based on the total error requirement of the master satellite antenna pointing, the antenna installation error, the antenna mechanism deformation error, and the beam pointing error caused by the master satellite's attitude control accuracy. );

[0072] In order to meet the preset intersatellite signal acquisition probability, the main satellite beam pointing deviation caused by the orbit prediction error should be better than , from which we can get the position error of the slave star relative to the master star ( ) should be better than ; Based on the example parameters, we get:

[0073] ;

[0074] ;

[0075] Step 9: Calculate the orbit determination accuracy requirements of the master and slave satellites based on the position error of the slave satellite relative to the master satellite and the inter-satellite distance.

[0076] Assuming that the orbit prediction accuracy of the master satellite and the slave satellite is the same, the orbit determination accuracy of the master satellite and the slave satellite ( ) should be better than ; Based on the example parameters, we get:

[0077] ;

[0078] The orbit prediction accuracy requirements of the master and slave satellites do not increase or decrease monotonically with the change of the inter-satellite distance R. They can be calculated under different inter-satellite distances R. and , thereby determining the minimum inter-satellite distance for orbit prediction accuracy. According to the parameters of the above embodiment, the inter-satellite distance is calculated from 100km to 350km, and the orbit prediction accuracy ( ) are as follows:

[0079] hour, ; hour, ;

[0080] hour, ; hour, ;

[0081] hour, ;

[0082] When , there is no valid value in step 8, and the capture probability requirement can no longer be met.

[0083] From the above solution, it can be obtained that the minimum inter-satellite distance for orbit prediction is 200~250km. If the ground orbit determination resources are not good, it can be preferred to establish an inter-satellite link at this inter-satellite distance.

[0084] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for calculating the satellite orbit determination accuracy requirements for inter-satellite signal capture of a lunar orbit formation satellite, characterized in that: The steps include: Step 1: Under ground test conditions, measure the antenna pattern, transmit signal power, and receiving sensitivity of the master satellite, and measure the antenna pattern, receiving sensitivity, and transmit EIRP value of the slave satellite; Step 2: Under ground test conditions, measure the installation error and antenna mechanism deformation error of the main satellite high-gain directional antenna, and calculate the beam pointing error; Step 3: Under ground test conditions, measure the attitude control accuracy of the primary satellite and calculate the beam pointing error caused by it ; Step 4: Determine the receiver capture threshold according to the receiving sensitivity and preset capture margin of the master satellite and the slave satellite respectively; Step 5: Calculate the minimum antenna gain of the primary satellite corresponding to the inter-satellite distance; Step 6: Determine the beam width of the main satellite antenna based on the minimum antenna gain and the main satellite antenna pattern; Step 7: Determine the total pointing error requirement of the main satellite antenna according to the beam width of the main satellite antenna and the preset inter-satellite signal capture probability; Step 8: Calculate the position error of the slave satellite relative to the master satellite due to the orbit prediction error based on the total error requirement of the master satellite antenna pointing, the antenna installation error, the antenna mechanism deformation error, and the beam pointing error caused by the attitude control accuracy of the master satellite. ; Step 9: Based on the position error calculated in step 8, determine whether the orbit determination accuracy requirements of the master and slave satellites meet , Respectively represent the orbit determination accuracy of the master satellite and the slave satellite.

2. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 1, characterized in that: In step 2, the antenna is precisely measured before and after the host satellite environmental test to obtain the installation error of the directional antenna and the deformation error of the antenna mechanism. The antenna beam pointing errors caused are and .

3. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 2, characterized in that: In step 4, the capture margins of the master satellite and the slave satellite are preset to be , then the receiver capture thresholds of the master satellite and the slave satellite are , ; and They are the receiving sensitivities of the master satellite and the slave satellite respectively.

4. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 3, characterized in that: In step 5, for the master satellite to transmit the slave satellite receiving link, , for the slave-satellite transmitting-master-satellite receiving link, ,in, is the minimum transmission gain required by the antenna of the master satellite when the receiver level of the slave satellite is at the capture threshold. It is the minimum receiving gain required by the main satellite antenna when the receiver level of the main satellite is at the capture threshold. is the minimum gain from the star antenna within the wide beam range, , They are the free space losses on the link between the master satellite transmitting and the slave satellite receiving, and the link between the slave satellite transmitting and the master satellite receiving. is the transmitting signal power of the main satellite, is the emission EIRP value from the satellite.

5. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 4, characterized in that: In step 6, the minimum transmit beam width of the main satellite antenna is obtained according to the minimum antenna gain of the main satellite and the antenna pattern of the main satellite. and minimum receive beamwidth , the beam width of the primary satellite at this intersatellite distance .

6. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 5, characterized in that: In step 7, the total pointing error of the main satellite antenna is required to be , Determined by the probability of capturing intersatellite signals.

7. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of a lunar orbit formation satellite according to claim 6, characterized in that: In step eight, the main satellite beam pointing deviation caused by orbit prediction error , the position error of the slave satellite relative to the master satellite , is the distance between stars.

8. The method for calculating the satellite orbit determination accuracy requirement for inter-satellite signal capture of lunar orbit formation satellites according to claim 7, characterized in that: When the orbit prediction accuracy of the master satellite and the slave satellite is equal, the orbit determination accuracy of the master satellite and the slave satellite meets .

Images