Cubesat size estimation method and device based on RCS data

Abstract

The invention discloses a cube satellite size estimation method and device based on RCS data, and the method comprises the steps: processing the spatial position data of a cube satellite, and calculating the attitude angle data of the satellite; correcting the attitude angle data obtained by calculation by using RCS (Radar Cross-Section) data of the cubesat; and calculating two side lengths of the cubesat by using the cubesat size estimation method in the three-axis stable state provided by the invention, thereby realizing size estimation of the cubesat. The device is used for implementing the method. According to the method, the accuracy of cube satellite size estimation based on RCS data is improved, and a new scheme is provided for satellite size estimation.

Description

Technical Field

[0001] The present invention relates to the field of using RCS data to carry out on-orbit satellite size estimation, and in particular to a cube satellite size estimation method and device based on RCS data. Background Art

[0002] When using RCS data to estimate the size of an in-orbit satellite, the traditional method is to treat the satellite as an ellipsoid and then use the ellipsoid structure characteristics to estimate the size of the satellite. This estimation method is relatively simple and crude, and does not take into account the structural characteristics of the satellite itself. It is mainly applicable to satellites whose shape is close to an ellipsoid or a sphere. Therefore, this method has great limitations in practical applications. Summary of the invention

[0003] The object of the present invention is to provide a method and device for estimating the size of a cube satellite based on RCS data.

[0004] The technical solution to achieve the purpose of the present invention is: a cube satellite size estimation method based on RCS data, comprising the following steps:

[0005] Step 1: Process the spatial position data of the cube satellite and calculate the satellite's attitude angle data;

[0006] Step 2: Use the CubeSat RCS data to correct the calculated attitude angle data;

[0007] Step 3: Utilize the cube satellite size estimation method under the three-axis stable state to calculate the two side lengths of the cube satellite, thereby realizing the size estimation of the cube satellite.

[0008] Step 1 processes the spatial position data of the cube satellite and calculates the satellite's attitude angle data, which involves converting the satellite's spatial position data into the satellite's attitude angle data. The specific algorithm is as follows:

[0009] Let (x, y, z) be the position coordinates of the satellite in the J2000 mean equatorial geocentric coordinate system measured by the measuring device at time t, (dx, dy, dz) be the velocity vector coordinates of the satellite in the J2000 mean equatorial geocentric coordinate system measured by the measuring device at time t, (x r ,y r , z r ) is the coordinate of the measuring device in the J2000 mean equatorial geocentric coordinate system at time t.

[0010] The satellite axis to the earth is the Z axis, the satellite motion direction is the X axis, and the other direction determined by the right-hand rule is the Y axis. The satellite body coordinate system is constructed. The satellite body coordinate system at time t can be expressed as follows under J2000:

[0011]

[0012] Among them, Axis x Represents the unit vector direction of the X-axis of the satellite's coordinate system, Axis y Represents the unit vector direction of the Y axis of the satellite body coordinate system, Axis z Represents the unit vector direction of the Z axis of the satellite body coordinate system;

[0013] The vector D of the direction from the satellite reflecting the electromagnetic wave to the measuring device r It can be expressed as:

[0014] D r =(x r -x,x r -y,x r -z)

[0015] The attitude angle (θ, φ) of the satellite measuring the observation direction of the device at time t can be expressed as:

[0016]

[0017] In this way, the satellite attitude angle data at each observation moment can be calculated in sequence.

[0018] This step converts the satellite's in-orbit position data into satellite attitude angle data, which makes it easier to associate features with the satellite's RCS data, facilitating the implementation of subsequent steps.

[0019] Step 2 uses the cube satellite RCS data to correct the calculated attitude angle data, which involves the process of correcting the satellite attitude angle data using the satellite RCS data characteristics. The specific method is as follows:

[0020] The position where the cube satellite obtains the maximum RCS value should be the direction where a certain plane of the cube satellite faces the measurement device, and the pitch angle corresponding to this position should be 0°. When correcting the attitude angle data, first find the pitch angle θ0 corresponding to the RCS maximum value in the RCS sequence, and then reduce the pitch angle sequence values ​​calculated in the previous step by θ0, so that the pitch angle corresponding to the RCS maximum value position is 0°.

[0021] In this way, the corrected satellite attitude angle data can be obtained.

[0022] In this step, the satellite attitude angle data is corrected using the characteristic points (maximum points) of the RCS sequence, so that a more accurate association is formed between the satellite attitude angle data and the RCS sequence, which can make subsequent size estimation more accurate.

[0023] Step 3 uses the cube satellite size estimation method under the three-axis stable state to calculate the two side lengths of the cube satellite, thereby realizing the size estimation of the cube satellite, which involves the cube satellite size estimation method under the three-axis stable state. The specific method is as follows:

[0024] The cube satellite is composed of 6 rectangular plates. When the attitude angle is any θ, φ, the RCS of an ideal conductive rectangular plate can be approximately expressed as:

[0025]

[0026] Where a and b represent the length and width of the rectangular plate, λ represents the wavelength of the electromagnetic wave of the measuring device, and k = 2π / λ;

[0027] When the pitch angle θ is 0°, RCS reaches the maximum value max(RCS), that is:

[0028]

[0029] When θ and φ satisfy |aksinθcosφ|=n*π or |bksinθsinφ|=n*π (n>0), RCS obtains the lowest value point in the area; if n=1, an extreme low point is obtained on the left and right of the RCS maximum value point, and the corresponding attitude angles are recorded as (θ l ,φ l ) and (θ r ,φ r ), then one of the following formulas is satisfied:

[0030]

[0031] or

[0032]

[0033] Using formula (3), we can calculate a set of a values ​​(a1, a2), and combining it with formula (2), we can get the corresponding set of b values ​​(b1, b2), namely:

[0034]

[0035] Using formula (4), we can calculate a set of b values ​​(b3, b4), and combining it with formula (2), we can get the corresponding set of a values ​​(a3, a4), namely:

[0036]

[0037] The mean values ​​of the two groups of satellite sizes (A1, B1) and (A2, B2) calculated by formula (3) and formula (4) are:

[0038]

[0039] The standard deviation of the two sets of satellite size mean results is:

[0040]

[0041] The minimum value of the sum of the coefficients of variation is used to determine the final value. The sum of the coefficients of variation corresponding to the two sets of results is:

[0042]

[0043] Compare the sizes of C1 and C2: When the C1 value is smaller, the first set of results (A1, B1) is the final size of the CubeSat; when the C2 value is smaller, the second set of results (A2, B2) is the final size of the CubeSat;

[0044] In this way, the size estimation of the CubeSat is completed.

[0045] In this step, two minimum points on the left and right of the RCS data maximum point are selected as eigenvalue points. The formulas for selecting these two eigenvalue points are used to calculate two different sets of size estimation results. The coefficient of variation and the method of distinguishing data correlation are used to determine the better result and use it as the final satellite size estimation result. This processing method makes the estimation result more reasonable and accurate.

[0046] A cube satellite size estimation device based on RCS data, comprising:

[0047] The satellite attitude angle data calculation module is used to process the cube satellite space position data to obtain the satellite attitude angle data;

[0048] The satellite attitude angle data correction module uses the cube satellite RCS data to correct the satellite attitude angle data to obtain the corrected satellite attitude angle data;

[0049] The cube satellite size estimation module uses the cube satellite size estimation method under the three-axis stable state to calculate the two side lengths of the cube satellite and estimate the size of the cube satellite.

[0050] Compared with the prior art, the present invention has the following significant advantages: 1) a satellite attitude angle calculation module is added, so that the changes of the satellite visible surface with the viewing angle of the measuring device can be expressed through data, and the changes of the satellite attitude angle are integrated into the target size estimation process, thereby improving the effectiveness and accuracy of the size estimation; 2) the method limits the research object to cube satellites, which are also the main structural type of most of the current small and medium-sized satellites, and helps to solve the size estimation problem of most small and medium-sized satellites; 3) an in-depth study is conducted on the size estimation problem of cube satellites, and a cube satellite size estimation method is proposed based on the RCS equivalent formula of cube satellites, which can solve the cube satellite size estimation problem in a targeted manner.

[0051] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Flowchart of the CubeSat size estimation method based on RCS data;

[0053] Figure 2 A CubeSat built for simulation in one example;

[0054] Figure 3 is an RCS sequence curve and attitude angle change curve of the cube satellite in the example. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0056] In one embodiment, in combination Figure 1 A specific implementation flow chart of a cube satellite size estimation method based on RCS data is provided, comprising the following steps:

[0057] Step 1: Process the spatial position data of the cube satellite and calculate the satellite's attitude angle data;

[0058] Step 2: Use the CubeSat RCS data to correct the calculated attitude angle data;

[0059] Step 3: Utilize the cube satellite size estimation method under the three-axis stable state to calculate the two side lengths of the cube satellite, thereby realizing the size estimation of the cube satellite.

[0060] Further, in one of the embodiments, in step 1, the spatial position data of the cube satellite detected and acquired by the measuring device is processed, and the attitude angle data of the satellite passing through the airspace of the measuring device is calculated. The STK satellite analysis tool can be used to simulate the spatial position data of a cube satellite (size 0.3m*0.3m*0.3m) measured by a certain device, and the corresponding satellite attitude angle data is calculated. The spatial position data of the satellite includes the transit time scale, the position (x, y, z) and the velocity (dx, dy, dz) in the J2000 mean equatorial geocentric coordinate system, and the pitch angle and roll angle of the satellite attitude in the direction of the measuring device's viewing angle can be calculated using a vector analysis method. Figure 2 The structural model of the cube satellite is shown. Figure 3 The satellite RCS change curve and the satellite attitude angle data (pitch angle and roll angle) obtained through steps 1 and 2 are shown.

[0061] Further, in one of the embodiments, the calculated attitude angle data is corrected using the cube satellite RCS data detected and acquired by the measuring equipment in step 2, mainly the pitch angle in the attitude angle is corrected. First, the maximum value point in the RCS data is found, which theoretically corresponds to the position where the pitch angle is 0°. If the pitch angle corresponding to the RCS maximum value point is θ, the pitch angle sequence values ​​calculated in the previous step are reduced by θ in sequence, thereby obtaining the corrected attitude angle data.

[0062] Furthermore, in one embodiment, a cube satellite size estimation method under a three-axis stable state is used to calculate two side lengths of the cube satellite, thereby realizing the size estimation of the cube satellite. The cube satellite size estimation method is explained as follows:

[0063] The cube satellite is composed of 6 rectangular plates. When the attitude angle is any θ, φ, the RCS of an ideal conductive rectangular plate can be approximately expressed as:

[0064]

[0065] In the above formula, a and b represent the length and width of the rectangular plate, λ represents the wavelength of the electromagnetic wave, and k = 2π / λ.

[0066] When the pitch angle θ is 0°, RCS reaches the maximum value max(RCS), that is:

[0067]

[0068] When θ and φ satisfy |aksinθcosφ|=n*π or |bksinθsinφ|=n*π (n>0), RCS obtains the lowest value point in the area; if n=1, an extreme low point is obtained on the left and right of the RCS maximum value point, and the corresponding attitude angles are recorded as (θl ,φ l ) and (θ r ,φ r ), then one of the following formulas is satisfied:

[0069]

[0070] or

[0071]

[0072] Using formula (3), we can calculate a set of a values ​​(a1, a2), and combining it with formula (2), we can get the corresponding set of b values ​​(b1, b2), namely:

[0073]

[0074] Using formula (4), we can calculate a set of b values ​​(b3, b4), and combining it with formula (2), we can get the corresponding set of a values ​​(a3, a4), namely:

[0075]

[0076] The mean values ​​of the two groups of satellite sizes (A1, B1) and (A2, B2) calculated by formula (3) and formula (4) are:

[0077]

[0078] The standard deviation of the two sets of satellite size mean results is:

[0079]

[0080]

[0081] The minimum value of the sum of the coefficients of variation is used to determine the final value. The sum of the coefficients of variation corresponding to the two sets of results is:

[0082]

[0083] Compare the sizes of C1 and C2: When the C1 value is smaller, the first set of results (A1, B1) is the final size of the CubeSat; when the C2 value is smaller, the second set of results (A2, B2) is the final size of the CubeSat;

[0084] In this way, the size estimation of the CubeSat can be achieved.

[0085] In one embodiment, the electromagnetic frequency emitted by the measuring device is 1 GHz, and a cube satellite (size is 0.3m*0.3m*0.3m) is detected. The satellite RCS maximum value is calculated to be 0.9850㎡, the attitude angle of the extreme low point on the left side of the RCS maximum value is (44.24°, -62.45°), and the attitude angle of the extreme low point on the right side of the RCS maximum value is (-28.77°, 74.68°). Using the RCS maximum value and two sets of attitude angle data, the target size estimation results corresponding to formula (5) and formula (6) are calculated, as shown in the following table:

[0086]

[0087] Since the value of the coefficient of variation and the value of the result calculated by formula (6) are the smallest, the mean satellite size calculated by formula (6) (i.e., the size is 0.283m*0.303m) is determined as the final estimated satellite size result. This result is consistent with the actual size of a single surface of the satellite (0.3m*0.3m).

[0088] In addition, the traditional ellipsoid model size estimation method is used to process this data, and the satellite size is calculated to be 0.171m*0.488m. Compared with the estimation result (0.283m*0.303m) in this paper, the size estimation result obtained by the traditional ellipsoid model size estimation method is poor, indicating that the cube satellite size estimation method proposed in this paper is more effective.

[0089] In one embodiment, a device for estimating the size of a cube satellite based on RCS data is provided, the device comprising:

[0090] The satellite attitude angle calculation module can process and calculate the satellite space position data to obtain the attitude angle data of the satellite when it passes;

[0091] The attitude angle correction module can correct the attitude angle data according to the RCS data characteristics;

[0092] The cube satellite size estimation method can estimate the size of the satellite's visible surface based on the RCS data characteristics and attitude angle data, thereby realizing the cube satellite size estimation.

[0093] For the specific definition of a cube satellite size estimation device based on RCS data, please refer to the definition of a cube satellite size estimation method based on RCS data above, which will not be repeated here. Each module in the above-mentioned cube satellite size estimation device based on RCS data can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0094] The present invention provides a cube satellite size estimation method and device based on RCS data, which realizes the function of estimating the size of a cube satellite using RCS data, can calculate the satellite attitude angle according to the satellite motion data and RCS data, and use the cube satellite size estimation method to estimate the satellite size, thereby obtaining the cube satellite size estimation result. The present invention provides a cube satellite size estimation method, which effectively improves the accuracy of the cube satellite size estimation result and provides a new idea for space satellite size estimation.

[0095] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cube satellite size estimation method based on RCS data, characterized in that: The following steps are involved: Step 1: Process the spatial position data of the cube satellite to obtain the attitude angle data of the satellite; Step 2: Using the cube satellite RCS data, the satellite attitude angle data obtained in step 1 is corrected to obtain corrected satellite attitude angle data; Step 3: Using the cube satellite size estimation method under the three-axis stable state, calculate the two side lengths of the cube satellite to complete the size estimation of the cube satellite.

2. The method for estimating the size of a cube satellite based on RCS data according to claim 1, characterized in that: In step 1, the cube satellite spatial position data is processed to calculate the satellite's attitude angle data, including: Let (x, y, z) be the position coordinates of the satellite in the J2000 mean equatorial geocentric coordinate system measured by the measuring device at time t, (dx, dy, dz) be the velocity vector coordinates of the satellite in the J2000 mean equatorial geocentric coordinate system measured by the measuring device at time t, (x r ,y r , z r ) is the coordinate of the measuring device at time t in the J2000 mean equatorial geocentric coordinate system; The satellite axis to the earth is the Z axis, the satellite motion direction is the X axis, and the other direction determined by the right-hand rule is the Y axis. The satellite body coordinate system is constructed. The satellite body coordinate system at time t is expressed as follows under J2000: Among them, Axis x Represents the unit vector direction of the X-axis of the satellite's coordinate system, Axis y Represents the unit vector direction of the Y axis of the satellite body coordinate system, Axis z Represents the unit vector direction of the Z axis of the satellite body coordinate system; The vector D of the direction from the satellite reflecting the electromagnetic wave to the measuring device r It is expressed as: D r =(x r -x,x r -y,x r -z) The attitude angle (θ, φ) of the satellite measuring the observation direction of the device at time t is expressed as: Calculate the satellite attitude angle data at each observation moment; The satellite attitude angle data at each observation time forms the satellite attitude angle data.

3. The method for estimating the size of a cube satellite based on RCS data according to claim 1, characterized in that: In step 2, the attitude angle data of the satellite obtained in step 1 is corrected using the cube satellite RCS data, specifically including: In the CubeSat RCS data, the position of the RCS maximum is the direction in which a plane of the CubeSat faces the measurement equipment, and the corresponding pitch angle at this position should be 0°; When correcting the attitude angle data, first find the pitch angle θ0 corresponding to the RCS maximum value in the cube satellite RCS data, and then reduce the pitch angle in the satellite attitude angle data obtained in step 1 by θ0, so that the pitch angle corresponding to the RCS maximum position is 0°, and obtain the corrected satellite attitude angle data.

4. The method for estimating the size of a cube satellite based on RCS data according to claim 1, characterized in that: In step 3, the cube satellite size estimation method under the three-axis stable state is used to calculate the two side lengths of the cube satellite to complete the size estimation of the cube satellite, which specifically includes: The cube satellite is composed of 6 rectangular plates. When the attitude angle is arbitrary θ, φ, the RCS of an ideal conductive rectangular plate is approximately expressed as: Where a and b represent the length and width of the rectangular plate, λ represents the wavelength of the electromagnetic wave of the measuring device, and k = 2π / λ; When the pitch angle θ is 0°, RCS reaches the maximum value max(RCS), that is: When θ and φ satisfy |aksinθcosφ|=n*π or |bksinθsinφ|=n*π (n>0), RCS obtains the lowest value point in the area; if n=1, an extreme low point is obtained on the left and right of the RCS maximum value point, and the corresponding attitude angles are recorded as (θ l ,φ l ) and (θ r ,φ r ), then one of the following formulas is satisfied: or Formula (3) is used to calculate a set of a values ​​(a1, a2), and combined with formula (2) to obtain a corresponding set of b values ​​(b1, b2), namely: Using formula (4) to calculate a set of b values ​​(b3, b4), combined with formula (2) to obtain a corresponding set of a values ​​(a3, a4), namely: The mean values ​​of the two groups of satellite sizes (A1, B1) and (A2, B2) calculated by formula (3) and formula (4) are: The standard deviation of the two sets of satellite size mean results is: The minimum value of the sum of the coefficients of variation is used to determine the final value. The sum of the coefficients of variation corresponding to the two sets of results is: Compare the sizes of C1 and C2: When the C1 value is smaller, the first set of results (A1, B1) is the final size of the CubeSat; when the C2 value is smaller, the second set of results (A2, B2) is the final size of the CubeSat; In this way, the size estimation of the CubeSat is completed.

5. A cube satellite size estimation device based on RCS data, characterized in that: include: The satellite attitude angle data calculation module is used to process the cube satellite space position data to obtain the satellite attitude angle data; The satellite attitude angle data correction module uses the cube satellite RCS data to correct the satellite attitude angle data to obtain the corrected satellite attitude angle data; The cube satellite size estimation module uses the cube satellite size estimation method under the three-axis stable state to calculate the two side lengths of the cube satellite and estimate the size of the cube satellite.

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