Side-by-side multi-satellite formation method capable of realizing real-time high-precision relative measurement

Abstract

The invention provides a side-by-side multi-satellite formation method capable of realizing real-time high-precision relative measurement, and the method comprises the steps: building a formation multi-satellite relative motion model based on an orbital kinematics theory, obtaining a mathematical expression of a relation between a baseline vector and six orbital elements through derivation and simplification, and building a direct corresponding relation between a baseline requirement of a formation system and an orbital parameter; according to the method, a constraint relation of a baseline measurement system view field requirement to a baseline vector is established, and the constraint relation and a baseline expression are applied to formation satellite orbit parameter design and orbit maintenance strategy design to obtain an orbit real-time adjustment criterion, so that a formation system can realize inter-satellite measurement at any moment. The method can solve the problem of distributed multi-satellite formation system orbit and configuration design oriented to inter-satellite baseline requirements, solves the problem of baseline common-view shielding during operation of the formation system, can realize on-satellite autonomous task planning and execution in the whole process of in-orbit operation, is high in efficiency and speed, is beneficial to flexible task response, and is suitable for large-scale popularization and application. The method has practical engineering significance.

Description

Technical Field

[0001] The invention relates to a side-by-side multi-star formation method capable of real-time high-precision relative measurement, belonging to the field of space technology. Background Art

[0002] The intersatellite baseline measurement of distributed satellite formations requires simultaneous measurement of multiple baselines formed by pairs of satellites in the observation formation. The accuracy of the baseline measurement method based on GNSS measurement currently used in orbit cannot meet the requirements of three-dimensional imaging applications. On this basis, the introduction of laser / visual measurement methods can greatly improve the measurement accuracy by accurately measuring the position of the target in the line of sight direction within the field of view of the measurement system. In the face of a multi-satellite formation system with more than two stars, the formation satellites will be arranged in a collinear line during flight. Due to the occlusion of the middle satellite, the satellites at both ends will have a common view occlusion, so that the laser and visual measurement system cannot complete the baseline measurement of the two distant satellites. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a side-by-side multi-satellite formation method that can perform real-time high-precision relative measurement, to establish an inter-satellite baseline mathematical model using a space relative kinematics model, to establish a corresponding relationship between the baseline and six orbital numbers, and to use the baseline as a basis for formation configuration design and real-time adjustment of formation satellites on orbit, to provide a solution to avoid common view occlusion during multi-satellite multi-baseline measurement.

[0004] The technical solution of the present invention is: a method for parallel multi-satellite formation capable of real-time high-precision relative measurement, comprising:

[0005] Based on the orbital kinematics theory, a mathematical model of the relative motion of multiple satellites in formation is established. By simplifying the relative motion deduction, a mathematical model of the intersatellite baseline is established, the mathematical expression of the relationship between the baseline vector and the six orbital elements is obtained, and a direct correspondence between the formation system baseline requirements and orbital parameters is established.

[0006] Establish the constraint relationship between the baseline measurement system field of view requirements and the baseline vector;

[0007] When designing the formation configuration and orbit, the satellites in the multi-satellite distributed formation are grouped in pairs. The relative orbit parameters of any two satellites in the distributed formation are obtained by using the corresponding relationship according to the baseline requirements. At the same time, the relative orbit parameters of the two groups of satellites are corrected by using the constraint relationship of the baseline vector according to the field of view requirements. The initial orbit parameters are designed with one satellite as the master satellite, so that the initial orbit parameters of the remaining satellites in the formation are obtained according to the above relative orbit parameters.

[0008] During on-orbit operation, the orbit parameters are solved in real time by GNSS, and the spatial baseline formed by any two satellites in the distributed formation is obtained according to the mathematical expression. The constraint relationship between the field of view requirements and the baseline vector is used to determine whether there is common view occlusion among the multiple groups of baselines formed by multiple satellites. If common view occlusion exists, the constraint relationship between the field of view requirements and the baseline vector is used to adjust the orbit parameters of one group of formation satellites on-orbit so that any two groups of baselines satisfy the constraint relationship, thereby realizing real-time and high-precision relative measurement of multi-satellite formations side by side at any time.

[0009] The method of establishing a mathematical model of relative motion of multiple satellites in formation based on orbital kinematics theory, simplifying and establishing an intersatellite baseline mathematical model through relative motion deduction, obtaining a mathematical expression of the relationship between the baseline vector and the six orbital elements, and establishing a direct correspondence between the formation system baseline requirements and the orbital parameters includes:

[0010] Establish the RTN coordinate system of the spacecraft master satellite; then the relative motion expression of the slave satellite relative to the master satellite in the RTN coordinate system is:

[0011] Δr R =a a -a c +a c [-(e a cosω a -e c cosω c )cosu c -(e a sinω a -e c sinω c )sinu c ]

[0012]

[0013] Δr N =a c [-(Ω a -Ω c )sini c cosu c +(i a -i c )sinu c ]

[0014] Among them, u c is the mean latitude argument of the primary star, u c =ω c +M c , M c is the mean anomaly, Ω c and r c are the right ascension of the ascending node and the distance from the center of the Earth, ic is the inclination of the primary star, e c is the eccentricity of the primary star, a c is the semi-major axis of the primary star; a a 、e a 、u a 、M a ,Ω a 、i a and r a The physical meaning of the orbital variables of the slave star corresponds to that of the master star mentioned above;

[0015] Let a a -a c =0,u a -u c = 0, with virtual star O as the main star, the main star is a circular orbit, e c = 0, simplify the relative motion expression of the slave star relative to the master star, and we get

[0016] Δr R =-a c e a cos(u c -ω a )

[0017] Δr T =2a c e a sin(u c -ω a )

[0018]

[0019] in,

[0020] According to the intersatellite baseline requirements of the formation system, the baseline component in the normal N direction is not considered. The two satellites M1 and S2 of each baseline are at the two ends of the same straight line with the virtual star O, and the distances between the two satellites and the virtual star O are equal. At this time, the eccentricities of the two satellites are required to be equal, that is, e a1 =e a2 , and the perigee arguments of the two satellites differ by 180°, that is, ω a1 =ω a2 -180°; the subscripts 1 and 2 represent satellites M1 and S2 in the formation respectively;

[0021] The component expressions of the inter-satellite baseline in the RT plane in the RTN coordinate system are calculated to obtain the baseline length and baseline inclination.

[0022] The expressions of the baseline length and the baseline inclination are:

[0023] Radial R direction baseline length Bz :

[0024] B z =2Δr R =-2a c e a1 cps(u c -ω a1 ),

[0025] Flight direction T direction baseline length B x :

[0026] B x =2Δr T =4a c e a1 sin(u c -ω a1 )

[0027] Baseline inclination α:

[0028]

[0029] α=arctan(-0.5cot(u c -ω a1 )).

[0030] The establishment of the spacecraft master satellite RTN coordinate system includes: the formation flying relative motion coordinate system is defined as: the origin of the coordinate system is the master satellite spacecraft, the R direction is the direction of the earth's center of mass pointing to the master satellite, the T direction is the motion direction of the master satellite, and the N direction is the normal direction perpendicular to the orbital plane determined by the right-hand system.

[0031] The establishment of the constraint relationship between the baseline measurement system field of view requirement and the baseline vector includes:

[0032] Establishing the constraint relationship of the baseline vector required by the field of view of the baseline measurement system, with the virtual star O as the center, the formation satellites M1, M3... are located on the same side of the center O, and the formation satellites S2, S4... are located on the other side of the center O, where M1 and S2 form a group to form the space baseline MS1, M3 and S4 form a group to form the space baseline MS2... and so on; where the expression of the baseline inclination difference between the baseline MS1 and the baseline MS2 is as follows:

[0033] Δα=arctan(-0.5cot(u c -ω a3 ))-arctan(-0.5cot(u c -ω a1 )) According to the above rules, the range of the baseline inclination difference Δα is Where Δω=ω a3 -ω a1, subscripts 1 and 3 represent satellite M1 and satellite M3 respectively;

[0034] Δα≥θ

[0035] Where θ represents the maximum field of view of the baseline measurement system;

[0036] but,

[0037] Δω=ω a3 -ω a1 ≥2θ;

[0038] That is, the difference in perigee argument angle between satellite M3 and satellite M1 is required to be greater than 2 times the field of view angle.

[0039] The method of obtaining the relative orbital parameters of any two satellites in the distributed formation satellites by using the corresponding relationship according to the baseline requirements, and correcting the relative orbital parameters of the two groups of satellites by using the constraint relationship of the baseline vectors according to the field of view requirements, and designing the initial orbital parameters with one satellite as the master satellite, thereby obtaining the initial orbital parameters of the remaining satellites in the formation according to the relative orbital parameters, includes:

[0040] According to the regression characteristics of remote sensing satellites and the observation efficiency requirements, the semi-major axis a c The size of is given by mission calculation, and the orbital inclination and ascending node right ascension are also given by mission calculation; for any set of two satellites constituting the baseline, the maximum length B of the baseline in the radial R direction is given by mission requirements z , that is, the eccentricity of the two satellites e a1 and e a2 represents the eccentricity of satellite M1 and satellite S2; similarly, the eccentricity e of satellite M3 and satellite S4 can be obtained a3 and e a4 ;

[0041] The baseline of multiple satellites in parallel is given to reach the maximum length B according to the mission requirements z The corresponding u c The value u0 of satellite M1 is obtained, and then the latitude argument ω is obtained. a1 =u0, the latitude argument of satellite S2 satisfies ω a2 =ω a1 +180°;

[0042] According to the field of view constraint of the measurement system, the constraint of the baseline inclination difference Δα between the baselines MS1 and MS2 formed by the two pairs of satellites is Δα≥2θ, θ is given by the mission requirements, and Δω≥2θ can be determined. Since the smaller the double baseline angle Δα, the better the observation effect, Δω=2θ, ω a3 =ω a1 +2θ,ω a4 =ω a3 -180°; through condition ua -u c = 0, obtain the initial mean anomaly angle M of each satellite a =u a -ω a ; At this point, the initial orbital parameters of the formation satellites are obtained.

[0043] If there is common view occlusion, the constraint relationship between the field of view requirements and the baseline vector is used to adjust the orbit parameters of one group of formation satellites on-orbit so that any two groups of baselines meet the constraint relationship, including: realizing real-time measurement of inter-satellite baselines MS1 and MS2 through GNSS navigation, obtaining the difference Δα between the directions of the MS1 and MS2 baselines, and specifically adjusting the perigee arguments ω of the four satellites by using the constraint relationship criterion of the field of view requirements of the baseline measurement system on the baseline vector. a1 ,ω a2 ,ω a3 ,ω a4 , thereby achieving on-board autonomous avoidance of multi-satellite common viewing obstruction in the formation system.

[0044] The specific adjustment of the perigee argument ω of the four stars a1 ,ω a2 ,ω a3 ,ω a4 , including: the latitude argument ω of satellite M1 a1 For reference, the latitude argument of satellite S2 satisfies ω a2 =ω a1 +180°; using the relationship Δω=2θ, adjust ω a3 =ω a1 +2θ,ω a4 =ω a3 -180°.

[0045] The advantages of the present invention compared with the prior art are:

[0046] (1) The present invention establishes a mathematical relationship model between the intersatellite baseline and orbital parameters of a distributed formation satellite system, providing a theoretical method for the orbital parameter design of the formation system for three-dimensional imaging observation tasks.

[0047] (2) The present invention establishes a constraint relationship between the field of view requirements of the baseline measurement system and the inter-satellite baseline vector, which is applied to the theoretical design of orbital parameters of distributed formation satellites and real-time orbit adjustment on-orbit.

[0048] (3) During actual on-orbit operation, the present invention determines whether there is common view occlusion among multiple satellites through orbital parameters calculated in real time through GNSS information, thereby completing the adjustment of orbital parameters to meet the requirements of real-time baseline measurement among multiple satellites.

[0049] (4) The method constructed by the present invention can solve the baseline design problem of the distributed multi-satellite system formation configuration, and at the same time solve the baseline common view occlusion problem during operation. During the on-orbit operation, the satellite can independently plan and execute tasks, which is efficient and fast, helps to flexibly respond to tasks, and has practical engineering significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the distributed parallel multi-satellite formation system and configuration;

[0051] Figure 2 This is a schematic diagram of the baseline measurement system field of view and intersatellite baseline;

[0052] Figure 3 This is the satellite formation configuration diagram;

[0053] Figure 4 Satellite baseline distribution. DETAILED DESCRIPTION

[0054] The present invention will be further explained and illustrated below in conjunction with the accompanying drawings and specific implementation methods.

[0055] like Figure 1 As shown in the figure, when designing the orbital parameters of the formation satellite, multiple satellites are required to fly in the same plane and are symmetrically distributed around the virtual center O. Two satellites form a group (M1, S2) (M3, S4) around the virtual center point in an elliptical relative motion. Each pair of satellites is defined as a group of main and auxiliary satellites flying forward together. The space connection between the main and auxiliary satellites is called the space baseline MS1 and MS2. The two groups of inter-satellite baselines form a baseline angle Δα in space. When the baseline angle Δα is smaller than the field of view angle, the field of view is blocked, resulting in the unmeasurable baseline between the two satellites at the far end. When designing the formation system, it is necessary to avoid the situation where the baseline angle Δα is smaller than the field of view angle. When the formation system is in orbit, it is necessary to adjust the orbital parameters in orbit so that the baseline angle Δα is smaller than the field of view angle. Through the formation satellite orbit design and orbital parameter adjustment, the problem of multi-satellite common view blockage in the formation satellite system can be avoided.

[0056] A design of a parallel multi-satellite formation capable of real-time high-precision relative measurement includes the following steps:

[0057] Step 1: Based on the orbital kinematics theory, a mathematical model of the relative motion of multiple satellites in the formation is established. The mathematical model of establishing the intersatellite baseline is simplified by deducing the relative motion, the mathematical expression of the relationship between the baseline vector and the six orbital elements is obtained, and a direct correspondence between the baseline requirements of the formation system and the orbital parameters is established.

[0058] Further, the specific steps of step 1 are:

[0059] Step 1.1, establish the coordinates of the slave satellite relative to the master satellite in the RTN coordinate system, and simplify it to obtain the relative motion expression of the slave satellite relative to the master satellite:

[0060] Δr R =a a -a c +a c [-(e a cosω a -e c cosω c )cosu c -(e a sinω a -e c sinω c )sinu c ] (1)

[0061]

[0062] Δr N =a c [-(Ω a -Ω c )sini c cosu c +(i a -i c )sinu c ] (3)

[0063] where u c is the mean latitude argument of the primary star, u c =ω c +M c , M c is the mean anomaly, Ω c (h c ) and r c are the right ascension of the ascending node and the distance from the center of the Earth, i c is the inclination of the primary star, e c is the eccentricity of the primary star, a c is the semi-major axis of the primary star. a 、e a 、u a 、M a ,Ω a 、i a and r a From the orbital variables of the star, its physical meaning is the same as above.

[0064] Step 1.2, simplify the formula in step 1.1 and let a a -a c =0,u a -u c= 0, with virtual star O as the main star, the main star is a circular orbit, e c =0, simplify the above formula, and we get:

[0065] Δr R =-a c e a cos(u c -ω a ) (4)

[0066] Δr T =2a c e a sin(u c -ω a ) (5)

[0067]

[0068] in, The remaining variables are the same as the above formula.

[0069] like Figure 2 As shown, according to the intersatellite baseline requirements of the formation system, the baseline component in the normal N direction is not considered here. The satellites at both ends of each baseline are in the same straight line with the virtual star O, and the distances between the two satellites and the virtual star O are equal. At this time, the eccentricities of the two satellites are required to be equal, that is, e a1 =e a2 , and the perigee arguments of the two satellites differ by 180°, that is, ω a1 =ω a2 -180°.

[0070] Step 1.3: According to the formula in step 1.2, the component expressions of the intersatellite baseline in the RT plane are twice the relative motion of a single satellite, that is,

[0071] Radial R direction baseline length B z :

[0072] B z =2Δr R =-2a c e a1 cos(u c -ω a1 ), (7)

[0073] Flight direction T direction baseline length B x :

[0074] B x =2Δr T =4a c e a1 sin(u c -ω a1 ) (8)

[0075] Baseline inclination α:

[0076]

[0077] α=arctan(-0.5cot(u c -ω a1 )) (10)

[0078] Step 2, such as Figure 1 and Figure 2 As shown in the figure, the field of view of the baseline measurement system requires the constraint relationship on the baseline vector. With the virtual star O as the center, the two satellites of each baseline group are located on both sides of the center O. Taking the figure as an example, M1 and S2 are a group, and M3 and S4 are a group. The expression of the difference in the inclination angle of the two groups of satellite baselines is as follows:

[0079] Δα=arctan(-0.5cot(u c -ω a3 ))-arctan(-0.5cot(u c -ω a1 )) (11)

[0080] According to the above formula, the range of Δα is Δω=ω a3 -ω a1 This constraint relationship is applied to the theoretical design of orbital parameters and the basis for on-orbit real-time orbit adjustment.

[0081] Δα≥θ (12)

[0082] That is,

[0083] Δω=ω a3 -ω a1 ≥2θ (13)

[0084] Step 3, formation configuration design step Based on the formulas and constraints derived in steps 1 and 2, the formation configuration can be designed according to the specific baseline constraints.

[0085] Further, the specific steps of step 3 are:

[0086] Step 3.1, through the regression characteristics of remote sensing satellites and observation efficiency requirements, the semi-major axis a c The size of is given by mission calculation, and the orbital inclination and ascending node right ascension are also given by mission calculation; for any set of two satellites constituting the baseline, the maximum length B of the baseline in the radial R direction is given by mission requirements z , that is, the eccentricity of the two satellites e a1 and e a2Indicates the eccentricity of satellite M1 and satellite S2"; Similarly, the eccentricity of satellite M3 and satellite S4 can be obtained a3 and e a4 ;

[0087] Step 3.2: According to the mission requirements, the baseline of multiple satellites in parallel is given to reach the maximum length B z The corresponding u c The value u0 of satellite M1 is obtained, and then the latitude argument ω is obtained. a1 =u0, the latitude argument of satellite S2 satisfies ω a2 =ω a1 +180°;

[0088] Step 3.3, according to the field of view constraint of the measurement system, the constraint of the baseline inclination difference Δα between the baselines MS1 and MS2 formed by the two pairs of satellites, that is, Δα≥θ, θ is given by the mission requirements, and Δω≥2θ can be determined. Since the smaller the double baseline angle Δα, the better the observation effect, then Δω=2θ, ω a3 =ω a1 +2θ,ω a4 =ω a3 -180°; through condition u a -u c = 0, obtain the initial mean anomaly angle M of each satellite a =u a -ω a . So far, the initial orbital parameters of the formation satellites are obtained.

[0089] Step 4, such as Figure 1 In this process, the intersatellite baselines MS1 and MS2 are measured in real time through GNSS navigation to obtain the difference Δα between the baseline directions of MS1 and MS2. The perigee arguments ω of the four satellites are adjusted using the criterion of step 2. a1 ,ω a2 ,ω a3 ,ω a4 . Realize on-board autonomous avoidance of multi-satellite common viewing obstruction in the formation system.

[0090] The effects of the present invention are briefly introduced and described below in conjunction with specific examples.

[0091] The mission requires the design of a four-star formation with a semi-major axis of 6873.68 km. The four stars are approximately evenly distributed side by side. The maximum value of the long baseline is 1 km, and the maximum value of the short baseline is 0.33 km. The latitude argument u c The baseline length reaches the maximum near the equator, and the included angle between the two sets of intersatellite baselines MS1 and MS2 must be no less than 3°. The overall formation parameters can be obtained through the following process:

[0092] 1. Eccentricity of the outer stars M1 and S2 The eccentricity of the inner stars M3 and S4

[0093] 2. The baseline reaches its maximum near the equator, that is, u0 = 0, ω a1 =0, and ω a2 =ω a1 -180°=180°.

[0094] 3. The included angle between the two sets of intersatellite baselines MS1 and MS2 is Δα≥3°, θ=3°, Δω=2θ=6°, ω a3 =ω a1 -2θ=6°,ω a4 =ω a3 +180°=186°. When the baseline design in the normal N direction is not considered, the right ascension Ω of the ascending nodes of all slave satellites and the virtual master satellite can be kept consistent. The following formation design parameters can be obtained:

[0095]

[0096] The above design formation is simulated by simulation software, and the following results are obtained: Figure 3 The satellite formation configuration diagram shown in Figure 1 shows the distribution of the spatial baseline formed under this design configuration. Figure 4 shown.

[0097] 4. When the formation satellites are in orbit, if the intersatellite baselines MS1 and MS2 measured by GNSS navigation are blocked, the perigee arguments ω of the four satellites are adjusted. a1 ,ω a2 ,ω a3 ,ω a4 , which can meet the needs of the formation system to avoid autonomous tasks on board when there is common visual obstruction on orbit.

[0098] The design method of the parallel multi-satellite distributed formation configuration proposed in the present invention can solve the common view occlusion problem of multi-satellite inter-satellite baselines from both theoretical design and actual on-orbit operation, and can achieve high-precision measurement of inter-satellite baselines at any time.

[0099] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for parallel multi-satellite formation capable of real-time high-precision relative measurement, characterized in that: include: Based on the orbital kinematics theory, a mathematical model of the relative motion of multiple satellites in formation is established. By simplifying the relative motion deduction, a mathematical model of the intersatellite baseline is established, the mathematical expression of the relationship between the baseline vector and the six orbital elements is obtained, and a direct correspondence between the formation system baseline requirements and orbital parameters is established. Establish the constraint relationship between the baseline measurement system field of view requirements and the baseline vector; When designing the formation configuration and orbit, the satellites in the multi-satellite distributed formation are grouped in pairs. The relative orbit parameters of any two satellites in the distributed formation are obtained by using the corresponding relationship according to the baseline requirements. At the same time, the relative orbit parameters of the two groups of satellites are corrected by using the constraint relationship of the baseline vector according to the field of view requirements. The initial orbit parameters are designed with one satellite as the master satellite, so that the initial orbit parameters of the remaining satellites in the formation are obtained according to the above relative orbit parameters. During on-orbit operation, the orbit parameters are solved in real time by GNSS, and the spatial baseline formed by any two satellites in the distributed formation is obtained according to the mathematical expression. The constraint relationship between the field of view requirements and the baseline vector is used to determine whether there is common view occlusion among the multiple groups of baselines formed by multiple satellites. If common view occlusion exists, the constraint relationship between the field of view requirements and the baseline vector is used to adjust the orbit parameters of one group of formation satellites on-orbit so that any two groups of baselines satisfy the constraint relationship, thereby realizing real-time and high-precision relative measurement of multi-satellite formations side by side at any time.

2. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 1, characterized in that: The method of establishing a mathematical model of relative motion of multiple satellites in formation based on orbital kinematics theory, simplifying and establishing an intersatellite baseline mathematical model through relative motion deduction, obtaining a mathematical expression of the relationship between the baseline vector and the six orbital elements, and establishing a direct correspondence between the formation system baseline requirements and the orbital parameters includes: Establish the RTN coordinate system of the spacecraft master satellite; then the relative motion expression of the slave satellite relative to the master satellite in the RTN coordinate system is: Δr R =a a -a c +a c [-(e a so a -e c so c )this c -(and a yes a -e c yes c )sinus c ] Δr N =a c [-(Ω a -Ω c )breasts c something c +(i a -i c )sinus c ] Among them, u c is the mean latitude argument of the primary star, u c =ω c +M c , M c is the mean anomaly, Ω c and r c are the right ascension of the ascending node and the distance from the center of the Earth, i c is the inclination of the primary star, e c is the eccentricity of the primary star, a c is the semi-major axis of the primary star; a a 、e a 、u a 、M a ,Ω a 、i a and r a The physical meaning of the orbital variables of the slave star corresponds to that of the master star mentioned above; Let a a -a c =0,u a -u c = 0, with virtual star O as the main star, the main star is a circular orbit, e c = 0, simplify the relative motion expression of the slave star relative to the master star, and we get Δr R =-a c e a cos(u c -oh a ) Δr T 2a c and a sin(u c -ω a ) in, According to the intersatellite baseline requirements of the formation system, the baseline component in the normal N direction is not considered. The two satellites M1 and S2 of each baseline are at the two ends of the same straight line with the virtual star O, and the distances between the two satellites and the virtual star O are equal. At this time, the eccentricities of the two satellites are required to be equal, that is, e a1 =e a2 , and the perigee arguments of the two satellites differ by 180°, that is, ω a1 =ω a2 -180°; the subscripts 1 and 2 represent satellites M1 and S2 in the formation respectively; The component expressions of the inter-satellite baseline in the RT plane in the RTN coordinate system are calculated to obtain the baseline length and baseline inclination.

3. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 2, characterized in that: The expressions of the baseline length and the baseline inclination are: Radial R direction baseline length B z : B z =2Δr R =-2a c e a1 cos(u c -ω a1 ), Flight direction T direction baseline length B x : B x =2Δr T =4a c e a1 sin(u c -oh a1 ) Baseline inclination α: α=arctan(-0.5cot(u c -oh a1 ))。 4. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 2, characterized in that: The establishment of the spacecraft master satellite RTN coordinate system includes: the formation flying relative motion coordinate system is defined as: the origin of the coordinate system is the master satellite spacecraft, the R direction is the direction of the earth's center of mass pointing to the master satellite, the T direction is the motion direction of the master satellite, and the N direction is the normal direction perpendicular to the orbital plane determined by the right-hand system.

5. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 4, characterized in that: The establishment of the constraint relationship between the baseline measurement system field of view requirement and the baseline vector includes: Establishing the constraint relationship of the baseline vector required by the field of view of the baseline measurement system, with the virtual star O as the center, the formation satellites M1, M3... are located on the same side of the center O, and the formation satellites S2, S4... are located on the other side of the center O, where M1 and S2 form a group to form the space baseline MS1, M3 and S4 form a group to form the space baseline MS2... and so on; where the expression of the baseline inclination difference between the baseline MS1 and the baseline MS2 is as follows: Δα=arctan(-0.5cot(u c -ω a3 ))-arctan(-0.5cot(u c -ω a1 )) According to the above rules, the range of the baseline inclination difference Δα is Where Δω=ω a3 -ω a1 , subscripts 1 and 3 represent satellite M1 and satellite M3 respectively; Δα≥θ Where θ represents the maximum field of view of the baseline measurement system; but, Give = oh a3 -oh a1 ≥2θ; That is, the difference in perigee argument angle between satellite M3 and satellite M1 is required to be greater than 2 times the field of view angle.

6. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 5, characterized in that: The method of obtaining the relative orbital parameters of any two satellites in the distributed formation satellites by using the corresponding relationship according to the baseline requirements, and correcting the relative orbital parameters of the two groups of satellites by using the constraint relationship of the baseline vectors according to the field of view requirements, and designing the initial orbital parameters with one satellite as the master satellite, thereby obtaining the initial orbital parameters of the remaining satellites in the formation according to the relative orbital parameters, includes: According to the regression characteristics of remote sensing satellites and the observation efficiency requirements, the semi-major axis a c The size of is given by mission calculation, and the orbital inclination and ascending node right ascension are also given by mission calculation; for any set of two satellites constituting the baseline, the maximum length B of the baseline in the radial R direction is given by mission requirements z , that is, the eccentricity of the two satellites e a1 and e a2 represents the eccentricity of satellite M1 and satellite S2; similarly, the eccentricity e of satellite M3 and satellite S4 can be obtained a3 and e a4 ; The baseline of multiple satellites in parallel is given to reach the maximum length B according to the mission requirements z The corresponding u c The value u0 of satellite M1 is obtained, and then the latitude argument ω is obtained. a1 =u0, the latitude argument of satellite S2 satisfies ω a2 =ω a1 +180°; According to the field of view constraint of the measurement system, the constraint of the baseline inclination difference Δα between the baselines MS1 and MS2 formed by the two pairs of satellites, that is, Δα≥θ, θ is given by the mission requirements, and Δω≥2θ can be determined. Since the smaller the double baseline angle Δα, the better the observation effect, then Δv=2θ, ω a3 =ω a1 +2θ,ω a4 =ω a3 -180°; through condition u a -u c = 0, obtain the initial mean anomaly angle M of each satellite a =u a -ω a ; At this point, the initial orbital parameters of the formation satellites are obtained.

7. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 1, characterized in that: If there is common view occlusion, the constraint relationship between the field of view requirements and the baseline vector is used to adjust the orbit parameters of one group of formation satellites on-orbit so that any two groups of baselines meet the constraint relationship, including: realizing real-time measurement of inter-satellite baselines MS1 and MS2 through GNSS navigation, obtaining the difference Δα between the directions of the MS1 and MS2 baselines, and specifically adjusting the perigee arguments ω of the four satellites by using the constraint relationship criterion of the field of view requirements of the baseline measurement system on the baseline vector. a1 ,ω a2 ,ω a3 ,ω a4 , thereby achieving on-board autonomous avoidance of multi-satellite common viewing obstruction in the formation system.

8. The method for parallel multi-satellite formation capable of real-time high-precision relative measurement according to claim 7, characterized in that: The specific adjustment of the perigee argument ω of the four stars a1 ,ω a2 ,ω a3 ,ω a4 , including: the latitude argument ω of satellite M1 a1 For reference, the latitude argument of satellite S2 satisfies ω a2 =ω a1 +180°; using the relationship Δω=2θ, adjust ω a3 =ω a1 +2θ,ω a4 =ω a3 -180°.

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