A calculation method for the requirements of satellite determination and orbit accuracy for inter-satellite signal acquisition of satellites in lunar orbit formation

Abstract

The present invention discloses a calculation method for the requirements of satellite determination and orbit determination accuracy for inter-satellite signal acquisition in a lunar orbit formation, belonging to the technical field of deep space exploration. The method includes measuring the antenna pattern, transmitted signal power, and receiving sensitivity of the main satellite, measuring the antenna pattern, receiving sensitivity, and transmitted EIRP value of the slave satellite, measuring the installation error and antenna mechanism deformation error of the high-gain directional antenna of the main satellite, measuring the attitude control accuracy of the main satellite, and calculating the position error requirement of the slave satellite relative to the main satellite according to the total error requirement of the main satellite antenna pointing, the installation error of the antenna, the antenna mechanism deformation error, and the beam pointing error caused by the attitude control accuracy of the main satellite; determining the requirements for the determination and orbit determination accuracy of the main satellite and the slave satellite based on the position error. The present invention can put forward the requirements for determination and orbit determination to the ground TT&C system in advance, or select an appropriate inter-satellite distance according to the determination and orbit determination accuracy that can be provided by the ground, improving the success probability of establishing an inter-satellite link.

Description

Technical Field

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

[0002] In recent years, the field of lunar exploration has witnessed vigorous development. In a lunar orbit, several satellites are formed into a certain formation configuration and an inter-satellite link is established. Each satellite in the formation collaborates and communicates with each other to jointly achieve tasks such as exploration, communication, and navigation. The satellite formation has the characteristics of low cost, good performance, high reliability, and strong adaptability.

[0003] The two-way acquisition of inter-satellite signals is a prerequisite for establishing an inter-satellite link. The two-way acquisition of inter-satellite signals requires precise orbit determination of the spacecraft by the ground master control station and precise orbit determination of the satellite by the ground TT&C station. The satellite adjusts its attitude or the pointing direction of the antenna beam according to the orbit determination result to align the two satellites with each other. If the acquisition fails, the search mode needs to be activated and the direction is continuously adjusted until the acquisition is completed. Compared with Earth orbit satellites, lunar orbit satellites cannot use the Global Navigation Satellite System (GNSS) for orbit determination, the ground TT&C resources are limited, and the signal of the space-ground link is weaker due to the longer distance. Therefore, the orbit determination accuracy of the satellite is relatively lower. This will lead to an overly large uncertain range of the satellite position during the establishment of the inter-satellite link, and the two satellites cannot align the antenna beams with each other, resulting in an overly long two-way acquisition time or even acquisition failure.

[0004] Some research scholars switch the inter-satellite link module of the rough orbit spacecraft to the large-range signal acquisition working mode, unidirectionally acquire the inter-satellite link signal of the Beidou satellite, calculate the precise orbit of the rough orbit spacecraft after unidirectionally precisely ranging the Beidou satellite, and then adjust the inter-satellite link to achieve two-way acquisition. This method requires that the error of the initial orbit of the rough orbit spacecraft meets the signal acquisition time uncertainty ability that the baseband can achieve in the large-range signal acquisition working mode, but does not mention how to determine whether the initial orbit error and the precise orbit error meet the requirements of inter-satellite link acquisition.

[0005] There are also research scholars who adopt a simplified position and velocity recurrence algorithm to real-time solve the pointing angle of the Ka-band inter-satellite link according to the orbital elements of the low-orbit satellite and the medium-orbit satellite, and complete the spatial beam pointing of the inter-satellite link from the low-orbit satellite to the medium-orbit satellite, but do not mention whether the pointing angle error of the solved inter-satellite link can meet the requirements of inter-satellite link acquisition. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a calculation method for the requirements of satellite orbit determination accuracy for inter-satellite signal acquisition of satellites in a lunar orbit formation. Under the condition of limited ground measurement and control resources and the inability to use GNSS signals, the requirements for satellite orbit determination accuracy can be calculated based on parameters such as the performance indicators of the satellites, the inter-satellite distance, and the expected acquisition probability, so as to advance the orbit determination requirements to the ground measurement and control system in advance, or select an appropriate inter-satellite distance according to the orbit determination accuracy that the ground can provide, thereby improving the success probability of establishing an inter-satellite link.

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

[0008] A calculation method for the requirements of satellite orbit determination accuracy for inter-satellite signal acquisition of satellites in a lunar orbit formation, comprising the following steps:

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

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

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

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

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

[0014] Step 6: Determine the beam width of the master satellite antenna according to the minimum antenna gain of the master satellite and the antenna pattern of the master satellite;

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

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

[0017] Step 9: Determine that the orbit determination accuracy requirements of the master satellite and the slave satellite are met based on the position error calculated in Step 8 , respectively representing the orbit determination accuracies of the master satellite and the slave satellite.

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

[0019] Based on the performance indicators obtained during the ground test phase of the satellite, the formation distance in orbit of the satellite, and the expected capture probability, the present invention calculates and establishes the orbit prediction accuracies of the master satellite and the slave satellite required for establishing an inter-satellite link, and advances the orbit determination requirements to the ground TT&C system in advance, or selects an appropriate inter-satellite distance according to the orbit determination accuracy that can be provided by the ground, thereby increasing the success probability of establishing an inter-satellite link. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 It is a schematic diagram of the main lobe of the master satellite antenna pattern in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0023] The lunar orbit formation satellite includes a master satellite and a slave satellite with inter-satellite communication and measurement functions. Inter-satellite communication and measurement is to establish an inter-satellite microwave link between the master satellite and the slave satellite, mutually transmit and receive signals and data, so as to realize inter-satellite data transmission, measurement of inter-satellite distance and time difference. Inter-satellite signal capture means that both the master satellite and the slave satellite receive the microwave signals of each other and successfully lock them.

[0024] The master satellite uses 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 uses a low-gain wide-beam antenna, which is beneficial to reducing the difficulty of aligning inter-satellite signals; after determining the requirements for establishing an inter-satellite link, the master satellite and the slave satellite adjust the satellite attitude according to the orbit prediction and control the antenna to point to each other. The prerequisite 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 within the signal beam of the master satellite.

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

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

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

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

[0029] By precisely 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 mechanism can be obtained, and the antenna beam pointing errors caused thereby ( ) are respectively and ;

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

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

[0032] Step 4: Determine the receiver capture threshold according to the respective receiving sensitivities of the main satellite and the slave satellite and the preset capture margin;

[0033] The preset capture margins of the main satellite and the slave satellite are both , then the receiver capture thresholds of the main satellite and the slave satellite are respectively , ;

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

[0035] For the main satellite transmitting and the slave satellite receiving link, , for the slave satellite transmitting and the main satellite receiving link, , where is the minimum transmit gain required by the main satellite antenna under the condition that the received level of the slave satellite is the capture threshold, is the minimum receive gain required by the main satellite antenna under the condition that the received level of the main satellite is the capture threshold, is the minimum gain of the slave satellite antenna within the wide beam range, , are the free space losses on the two links respectively, , , , are the transmit signal frequencies of the main satellite and the slave satellite respectively, is the inter-satellite distance;

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

[0037] According to the main satellite antenna pattern and those in Step 5 and , the minimum transmitting beam width and receiving beam width of the main satellite antenna are obtained, and the beam width of the main satellite at this inter-satellite distance;

[0038] Step 7: Determine the requirement for the total pointing error ( ) of the main satellite antenna according to the beam width of the main satellite antenna and the preset inter-satellite signal acquisition probability;

[0039] The requirement for the total pointing error of the main satellite antenna , is determined by the inter-satellite signal acquisition probability. When , the acquisition probability is 0.6826. When , the acquisition probability is 0.9545. When , the acquisition probability is 0.9973;

[0040] Step 8: Calculate the position error ( ) of the slave satellite relative to the main satellite caused by the orbit prediction error according to the requirement for the total pointing error of the main satellite antenna, the installation error of the antenna, the deformation error of the antenna mechanism, and the beam pointing error caused by the attitude control accuracy of the main satellite;

[0041] To meet the preset inter-satellite signal acquisition probability, the beam pointing deviation of the main satellite caused by the orbit prediction error should be better than . From this, it can be obtained that the position error ( ) of the slave satellite relative to the main satellite should be better than ;

[0042] Step 9: The requirements for the orbit determination accuracy of the main satellite and the slave satellite need to meet ;

[0043] Assume that the orbit prediction accuracies of the main satellite and the slave satellite on the ground are equivalent. Then, the orbit determination accuracies ( ) of the main satellite and the slave satellite should be better than ;

[0044] The requirements for the orbit prediction accuracies of the main satellite and the slave satellite do not monotonically increase or decrease with the change of the inter-satellite distance . This is because when increases, the beam pointing deviation of the main satellite caused by the orbit prediction error relatively decreases, but the free space loss increases, resulting in a narrower antenna beam angle to meet the received level. When decreases, the antenna beam angle to meet the received level is wider, but the beam pointing deviation of the main satellite caused by the orbit prediction error is also larger. Therefore, at different inter-satellite distances Downward calculation and , so as to determine the minimum inter-satellite distance required for orbit prediction accuracy and reduce the demand for ground measurement and control systems.

[0045] Embodiment

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

[0047] An example of the receiving / transmitting direction diagram of the master satellite antenna is as Figure 2 shown. Parameter examples are as follows:

[0048] , ;

[0049] , ;

[0050] Step 2: By precisely measuring the antenna before and after the environmental test of the master satellite, measure the installation error of the high-gain directional antenna of the master satellite and the deformation error of the antenna mechanism, and calculate the beam pointing error caused by them ( ); Parameter examples are as follows:

[0051] , ;

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

[0053] ;

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

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

[0056] , then: , ;

[0057] Step 5: Inter-satellite link calculation, calculate the minimum antenna gain of the master satellite corresponding to the inter-satellite distance;

[0058] Calculate the two links of the master satellite transmitting and the slave satellite receiving, and the slave satellite transmitting and the master satellite receiving respectively, , , where is the minimum transmit gain required for the main satellite antenna when the received level of the slave satellite is the acquisition threshold condition, is the minimum receive gain required for the main satellite antenna when the received level of the main satellite is the acquisition threshold condition, is the minimum gain of the slave satellite antenna within the wide beam range, and are the free space losses on the two links respectively, , , and are the transmit signal frequencies of the main satellite and the slave satellite respectively, is the inter-satellite distance; parameter examples are as follows:

[0059] , , , then it can be calculated that:

[0060] ;

[0061] ;

[0062] ;

[0063] ;

[0064] Step Six: Determine the beam width of the main satellite antenna according to the minimum antenna gain of the main satellite and the main satellite antenna pattern;

[0065] According to the main satellite antenna pattern, and , obtain the minimum transmit beam width and receive beam width of the main satellite antenna. The beam width of the main satellite at this inter-satellite distance;

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

[0067] , , ;

[0068] Step Seven: Determine the total pointing error of the main satellite antenna ( ) according to the beam width of the main satellite antenna and the preset inter-satellite signal acquisition probability, requirement;

[0069] Total pointing error requirement of the main satellite antenna, , is determined by the inter-satellite signal acquisition probability, When the capture probability is 0.6826, the capture probability is 0.9545, and the capture probability is 0.9973;

[0070] If the preset inter-satellite signal capture probability is 0.9973, then , ;

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

[0072] To meet the preset inter-satellite signal capture probability, the deviation of the master satellite beam pointing caused by the orbit prediction error should be better than , from which the position error of the slave satellite relative to the master satellite ( ) should be better than ; According to the example parameters, it is obtained that:

[0073] ;

[0074] ;

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

[0076] Assume that the orbit prediction accuracies of the master satellite and the slave satellite on the ground are equivalent, then the orbit determination accuracies of the master satellite and the slave satellite ( ) should be better than ; According to the example parameters, it is obtained that:

[0077] ;

[0078] The requirements for the orbit prediction accuracies of the master satellite and the slave satellite do not increase or decrease monotonically with the change of the inter-satellite distance R. The and can be calculated at different inter-satellite distances R to determine the inter-satellite distance with the minimum requirement for the orbit prediction accuracy. According to the parameters of the above embodiments, calculate the requirements for the orbit prediction accuracy ( ) in the range of the inter-satellite distance from 100 km to 350 km as follows:

[0079] When ; When ;

[0080] When ; When ;

[0081] When ;

[0082] In step eight, no valid value can be obtained, and at this time, the capture probability requirement can no longer be met.

[0083] From the above solution values, the minimum inter-satellite distance with the lowest requirement for orbit prediction can be obtained as 200 - 250 km. If the ground orbit determination resources are poor, this inter-satellite distance can be preferentially selected to establish an inter-satellite link.

[0084] In the above-described specific embodiments, the object, technical solution, and beneficial effects of the present invention have been further described in detail. 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 replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope 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 lunar orbit formation satellites 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 .

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