DSP-based electronic reconnaissance guiding space-borne SAR imaging method

Abstract

The application provides a DSP-based electronic reconnaissance guiding spaceborne SAR imaging method and a spaceborne SAR system. Based on a DSP processing chip, according to position, speed and attitude information of a satellite platform and target information returned by electronic reconnaissance, when the DSP receives the platform information, the imaging center time of each target in a target queue at a current spaceborne time and a corresponding side view angle are calculated. A spaceborne computer controls an antenna start-up time according to the target imaging center time, and sends the side view angle of the corresponding target to the DSP. The DSP calculates a SAR antenna corresponding wave control code to control a beam pointing direction, completes imaging processing on a target area, and realizes real-time electronic reconnaissance guiding SAR imaging cooperative work. Through the powerful floating point operation capability of the DSP, real-time electronic reconnaissance guiding spaceborne SAR imaging cooperative work is realized, and application requirements for fine imaging of different targets are met.

Description

TECHNICAL FIELD

[0001] The application relates to the field of spaceborne imaging technology, in particular to an electronic reconnaissance guided spaceborne SAR imaging method based on a DSP. BACKGROUND

[0002] With the development of spaceborne SAR technology, the ground imaging technology is increasingly mature. In the face of application requirements of remote sensing observation and target reconnaissance, more and more high requirements are put forward for fine imaging of specific targets. Through target positioning information returned by electronic reconnaissance, a target imaging center moment and a corresponding side view angle are recursively calculated, and SAR imaging is guided according to the imaging center moment and the side view angle, so that fine imaging of specific targets is realized. The time and pose calculation and beam control calculation of multiple targets are large in amount and long in time, and the prior art does not propose an implementation method of electronic reconnaissance guided spaceborne SAR imaging collaborative work. SUMMARY

[0003] The application aims to provide an electronic reconnaissance guided spaceborne SAR imaging method based on a DSP.

[0004] The application provides an electronic reconnaissance guided spaceborne SAR imaging method based on a DSP, which comprises the following steps:

[0005] In step S1, a DSP interrupt is triggered by a spaceborne computer, broadcast information output from a satellite platform and target information returned by electronic reconnaissance are acquired;

[0006] In step S2, an instantaneous inertial system is established in a WGS84 coordinate system of a spaceborne moment, and the position of the satellite, the speed of the satellite, the position of the target and the position change rate of the target are represented in the instantaneous inertial system;

[0007] In step S3, the position of the satellite platform and the speed of the satellite platform in the instantaneous inertial system are used to calculate orbit information of a satellite orbit and output a calculation result of the orbit information;

[0008] In step S4, the calculation result of the orbit information is used to calculate a conversion matrix and a change rate matrix from the instantaneous inertial system to the satellite orbit system and output a calculation result of the conversion matrix and the change rate matrix;

[0009] In step S5, the calculation result of the conversion matrix and the change rate matrix is used to calculate vector representation of the satellite platform and the target and vector change rate representation of the target in the satellite orbit system;

[0010] In step S6, the vector representation of the satellite platform and the target and the vector change rate representation of the target in the satellite orbit system are converted into the satellite body system in combination with satellite platform attitude information;

[0011] Step S7, the satellite body system under the target imaging center time and side view angle are calculated by Newton iteration method, and the calculation results of the target imaging center time and side view angle are output;

[0012] Step S8, the target information and the calculation results of the target imaging center time and side view angle are sent to the on-board computer, the on-board computer controls the antenna to start according to the target imaging center time, and sends the corresponding side view angle to the DSP;

[0013] Step S9, the corresponding wave control code is calculated according to the side view angle of the target, the phased array antenna beam pointing is controlled, and the imaging irradiation task of the specified target area is completed.

[0014] Preferably, the satellite platform output broadcast information and electronic reconnaissance returned target information are further included by triggering the DSP interrupt through the on-board computer.

[0015] The target information includes the target position in WGS84 coordinate system After receiving the target information, it is stored in the target queue;

[0016] The broadcast information includes the current on-board time, the satellite position in WGS84 coordinate system Satellite speed Satellite attitude roll angle Pitch angle θ, yaw angle ψ, after receiving the satellite platform broadcast information, the time attitude calculation of each target is started.

[0017] Preferably, the instantaneous inertial system is established in the WGS84 coordinate system of the on-board time, and in the instantaneous inertial system, the position of the satellite, the speed of the satellite, the position of the target and the position change rate of the target are further included.

[0018] Combined with the earth rotation angular velocity, according to the conversion formula of the position of the satellite platform and the speed of the satellite platform, the position of the target and the position change rate of the target, the obtained satellite platform position, satellite speed, target position are converted into the position of the satellite platform, the speed of the satellite platform, the position of the target and the position change rate of the target represented in the instantaneous inertial system;

[0019] The conversion formula of the position of the satellite platform represented in the instantaneous inertial system And the speed of the satellite platform The conversion formula is:

[0020]

[0021]

[0022] Wherein, The position of the satellite platform The component in x axis direction, is the position of the satellite platform, is the component of the position of the satellite platform in the y-axis direction, is the velocity of the satellite, ω e is the angular velocity of the earth rotation, is the position of the satellite platform in the instantaneous inertial system, is the velocity of the satellite platform in the instantaneous inertial system;

[0023] is the position of the target, is the rate of change of the position of the target, The conversion formula is:

[0024]

[0025]

[0026] wherein X et0 is the position of the target in the x-axis direction, is the component of the position of the target in the x-axis direction, Y et0 is the position of the target in the y-axis direction, is the component of the position of the target in the y-axis direction, Z et0 is the position of the target in the z-axis direction. is the component of the position of the target in the z-axis direction.

[0027] Preferably, the calculating the orbital information of the satellite orbit according to the position of the satellite platform in the instantaneous inertial system and the velocity of the satellite platform further comprises:

[0028] The orbital information comprises the position of the satellite platform the velocity of the satellite platform calculating the inclination i, the ascending node right ascension Ω, the orbital angular velocity ω, and the orbital amplitude μ of the satellite orbit;

[0029] According to the calculation formula of the orbital inclination i, the inclination of the satellite orbit is calculated, and the formula is as follows:

[0030]

[0031]

[0032] wherein H is the orbital angular momentum,

[0033] According to the calculation formula of the ascending node right ascension Ω, the ascending node right ascension is calculated, and the formula is as follows:

[0034]

[0035] i z = I x × N, I x = [1 0 0] T ,

[0036] Ω = sign(i z (3))arccos(N · I x ),

[0037] where N is the unit vector of the orbit nodal line, I i (i = x, y, z) is the moment of inertia of the satellite corresponding to the axis of rotation, is the sign function;

[0038] According to the calculation formula of the orbit angular velocity ω, the orbit angular velocity is calculated, and the formula is as follows:

[0039]

[0040] According to the calculation formula of the initial orbit amplitude angle μ0 and the orbit amplitude angle μ, the orbit amplitude angle is calculated, and the formula is as follows:

[0041]

[0042] μ(t) = μ0 + ωt,

[0043] where μ is a function of time t, is the component in the z-axis direction.

[0044] Preferably, the calculation of the instantaneous inertial system to the satellite orbit system conversion matrix and the rate matrix according to the calculation result of the orbit information and outputting the calculation result of the conversion matrix and the rate matrix further comprises:

[0045] According to the calculated orbit inclination i, the ascending node right ascension Ω, the orbit angular velocity ω and the orbit amplitude angle μ, the instantaneous inertial system is converted to the satellite orbit system according to the geometric relationship between the instantaneous inertial system and the satellite orbit system, and the conversion matrix A oi from the instantaneous inertial system to the satellite orbit system is calculated according to the conversion matrix expression; and the rate matrix is calculated according to the conversion rate conversion matrix expression from the instantaneous inertial system to the satellite orbit system.

[0046] The conversion relationship from the instantaneous inertial system to the orbit system is as follows, and after the conversion, the coordinate system is converted from XYZ to X'Y'Z':

[0047]

[0048] In actual cases, the satellite center of mass pointing coordinate system origin is often defined as the Z-axis, the satellite flight direction is defined as the X-axis, and the Y-axis points to the right-hand screw law. After the coordinate axis transformation, the conversion matrix expression is:

[0049]

[0050] The transformation rate conversion matrix from the instantaneous inertial system to the orbital system is expressed as:

[0051]

[0052] Preferably, the calculation of the satellite platform and target vector in the satellite orbital system and the target vector change rate according to the calculation results of the conversion matrix and the change rate matrix further comprises:

[0053] According to the target position in the instantaneous inertial system Target position change rate Satellite platform position The conversion matrix A from the instantaneous inertial system to the orbital system oi And the change rate matrix Calculate the satellite platform and target vector in the orbital system And the target vector change rate

[0054] In the orbital system, after coordinate axis conversion, the position of the satellite The expression is:

[0055]

[0056] The expression of the satellite platform and target vector is:

[0057]

[0058] The expression of the satellite platform and target vector change rate is:

[0059]

[0060] Preferably, the conversion of the satellite platform and target vector in the satellite orbital system and the target vector change rate to the satellite body system in combination with the satellite platform attitude information further comprises:

[0061] The attitude information includes the satellite platform attitude roll angle Pitch angle θ, yaw angle ψ, according to the attitude information, calculate the conversion matrix A from the satellite orbital system to the satellite body system bo And convert the satellite platform and target vector in the satellite orbital system And the change rate To the satellite platform and target vector in the satellite body system And the target vector change rate

[0062] According to the satellite attitude angle, the conversion matrix A of the satellite platform from the orbital system to the body system is: bo ​

[0063]

[0064] The vector between the satellite platform and the target in the satellite body system is represented as:

[0065] The vector between the satellite platform and the target in the satellite body system is represented as:

[0066]

[0067]

[0068] Preferably, the calculation of the imaging center time and the side-looking angle of the target in the satellite body system by the Newton iteration method and the output of the calculation result of the imaging center time and the side-looking angle of the target further comprise:

[0069] According to the geometric relationship, a geometric model is established, and the imaging center time T of the target in the satellite body system is obtained by the Newton iteration method center and the side-looking angle Angle at this time.

[0070] In the satellite body system, the vector between the target and the satellite is determined, and the vector OP between the target and the satellite is The following geometric relationship expression is established:

[0071]

[0072] Let

[0073]

[0074] The Newton iteration equation is established:

[0075]

[0076] The iteration calculation time t is obtained, that is,

[0077]

[0078] The imaging center time T satisfying the constraint condition is finally obtained center ;

[0079] The side-looking angle Angle is obtained by the following formula:

[0080]

[0081] ​​​Preferably, the sending the target information and the calculation results of the target imaging center time and the side view angle to the on-board computer, and the on-board computer controlling the antenna to start up according to the target imaging center time and sending the corresponding side view angle to the DSP further comprises:

[0082] The time and position of all targets in the target queue are calculated by the DSP;

[0083] The target information and the corresponding calculation results are transmitted to the on-board computer;

[0084] The on-board computer controls the antenna to start up according to the target imaging center time and sends the side view angle to the DSP.

[0085] Preferably, the calculating the corresponding wave control code according to the side view angle of the target, controlling the phased array antenna beam pointing, and completing the imaging irradiation task of the specified target area further comprises:

[0086] The corresponding wave control code is calculated according to the received side view angle and azimuth angle;

[0087] After the calculation, the wave control code data group is sent to the wave control FPGA;

[0088] The wave control data is distributed to each exciter of the phased array antenna by the wave control FPGA, so as to control the phased array antenna beam pointing and complete the imaging irradiation task of the specified target area.

[0089] For the prior art, the present application has the following beneficial effects: the present application is based on the real-time electronic reconnaissance guiding spaceborne SAR imaging cooperative work implementation method based on DSP. For the spaceborne SAR system, due to the powerful floating point operation capability of the DSP processing chip, the imaging center time and the side view angle of the target can be quickly calculated, real-time and accurate guidance and beam control are performed, and the method is suitable for satellite platform application. Real-time electronic reconnaissance guiding spaceborne SAR imaging cooperative work is realized, and the application requirements of fine imaging of different targets are met. BRIEF DESCRIPTION OF DRAWINGS

[0090] Figure 1 is the method step schematic diagram of the electronic reconnaissance guiding spaceborne SAR imaging method based on DSP in the embodiment of the present application;

[0091] Figure 2 is the work flow chart of the electronic reconnaissance guiding spaceborne SAR imaging method based on DSP in the embodiment of the present application;

[0092] Figure 3 is the geometric relationship schematic diagram of the instantaneous inertial system and the orbit system in the embodiment of the present application;

[0093] Figure 4 is the geometric relationship schematic diagram of the satellite and the target in the satellite system in the embodiment of the present application. Detailed Implementation

[0094] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0095] like Figure 1 , 2 As shown, this invention provides a method for DSP-based electronic reconnaissance-guided spaceborne SAR imaging, comprising:

[0096] Step S1: Trigger a DSP interrupt via the onboard computer to acquire broadcast information output from the satellite platform and target information returned by electronic reconnaissance.

[0097] Here, the satellite platform and electronic reconnaissance broadcast platform information and return target information at a set rhythm, respectively, and the onboard computer triggers a DSP interrupt to send the corresponding data. The target information includes the target position in the WGS84 coordinate system. Upon receiving target information, it is stored in the target queue. Satellite platform broadcast information includes the current onboard time and the satellite's position in the WGS84 coordinate system. satellite speed Satellite attitude roll angle Pitch angle θ and yaw angle ψ are calculated for each target after receiving the broadcast information from the satellite platform.

[0098] Step S2, using the satellite time T GPS An instantaneous inertial frame is established using the WGS84 coordinate system. In this instantaneous inertial frame, the satellite's position, velocity, target's position, and rate of change of target's position are represented.

[0099] Here, based on the obtained satellite platform location satellite speed Target location Combined with the Earth's rotational angular velocity ω e The position of the satellite platform in the instantaneous inertial frame. Satellite platform speed Target location and the rate of change of the target's position

[0100] and The conversion formula is:

[0101]

[0102]

[0103] wherein, is the component in the x-axis direction, is the component in the y-axis direction.

[0104] and the conversion formula is:

[0105]

[0106]

[0107] wherein, X et0 is the component in the x-axis direction, Y et0 is the component in the y-axis direction, Z et0 is the component in the z-axis direction.

[0108] Step S3, according to the position of the satellite platform in the instantaneous inertial system and the speed of the satellite platform, the orbit information of the satellite orbit is calculated and the calculation result of the orbit information is outputted;

[0109] Here, in the instantaneous inertial system, according to the position of the satellite platform the speed of the satellite platform the inclination i, the ascending node right ascension Ω, the orbit angular velocity ω, the orbit amplitude angle μ and other orbit information of the satellite orbit are calculated;

[0110] The calculation formula of the orbit inclination i is:

[0111]

[0112]

[0113] wherein H is the orbit angular momentum,

[0114] The calculation formula of the ascending node right ascension Ω is:

[0115]

[0116] i z = I x × N, I x = [1 0 0] T ,

[0117] Ω = sign(i z(3))arccos(N·I x ),

[0118] where N is the unit vector of the orbit nodal line, I i (i=x, y, z) is the moment of inertia of the satellite corresponding to the axis of rotation, is the sign function.

[0119] The formula for calculating the orbital angular velocity ω is:

[0120]

[0121] The formula for calculating the initial orbit amplitude μ0and the orbit amplitude μ is:

[0122]

[0123] μ(t) = μ0+ ωt,

[0124] where μ is a function of time t, is the sign function. The component in the z-axis direction.

[0125] Step S4, according to the calculation result of the orbit information, calculating the conversion matrix and the rate of change matrix of the instantaneous inertial system to the satellite orbit system and outputting the calculation result of the conversion matrix and the rate of change matrix;

[0126] Here, according to the calculated orbit inclination i, the ascending node right ascension Ω, the orbit angular velocity ω and the orbit amplitude μ, the conversion matrix A oi and the rate of change matrix

[0127] The geometric relationship between the instantaneous inertial system and the orbit system is shown in Figure 3 The conversion relationship from the instantaneous inertial system to the orbit system is as follows, and after the conversion is completed, the coordinate system is converted from XYZ to X'Y'Z':

[0128]

[0129] In actual situations, the satellite center of mass pointing coordinate system origin is often defined as the Z-axis, the satellite flight direction is defined as the X-axis, and the Y-axis points to the right-hand screw law. After the coordinate axis transformation, the conversion matrix expression is:

[0130]

[0131] The rate of change conversion matrix expression from the instantaneous inertial system to the orbit system is:

[0132]

[0133] Step S5, according to the calculation results of the conversion matrix and the rate of change matrix, the vector of the satellite platform and the target in the satellite orbit system and the rate of change of the target vector are calculated;

[0134] Here, according to the target position in the instantaneous inertial system Target position rate of change Satellite platform position Conversion matrix A from the instantaneous inertial system to the orbit system oi And the rate of change matrix The vector of the satellite platform and the target in the orbit system is calculated And the rate of change

[0135] In the orbit system, after the coordinate axis conversion in step 4, the position of the satellite The expression is:

[0136]

[0137] The vector of the satellite platform and the target is expressed as:

[0138]

[0139] The rate of change of the vector of the satellite platform and the target is expressed as:

[0140]

[0141] Step S6, combined with the satellite platform attitude information, the vector of the satellite platform and the target in the satellite orbit system and the rate of change of the target vector are converted to the satellite body system;

[0142] Here, in the orbit system, the satellite is regarded as a mass point, and in the actual situation, the phased array antenna is installed in the satellite body system, and the attitude of the satellite body affects the beam control angle of the phased array antenna, so combined with the satellite platform attitude roll angle Pitch angle θ, yaw angle ψ, the conversion matrix A from the satellite orbit system to the satellite body system is calculated bo And the vector of the satellite platform and the target in the satellite orbit system And the rate of change Is converted to the vector of the satellite platform and the target in the satellite body system And the rate of change

[0143] According to the satellite attitude angle, the conversion matrix A of the satellite platform from the orbit system to the body system is bo :

[0144]

[0145] The vector of the satellite platform and the target in the satellite body system is expressed as:

[0146]

[0147] The vector transformation rate of the satellite platform and the target under the satellite body system is is expressed as:

[0148]

[0149] Step S7, the satellite body system under the target imaging center time and the side view angle are calculated by Newton iteration method, and the calculation results of the target imaging center time and the side view angle are output.

[0150] Here, a geometric model is established according to the geometric relationship, and the satellite body system under the target imaging center time T center and the side view angle Angle at this time are obtained by Newton iteration method.

[0151] Under the body system, as shown in Figure 4 , the vector OP between the target and the satellite is The following geometric relationship expression can be established:

[0152]

[0153] Let :

[0154]

[0155] The Newton iteration equation is established as follows:

[0156]

[0157]

[0158] The iteration calculation time t is

[0159]

[0160] The imaging center time T center that satisfies the constraint condition is finally obtained.

[0161] The side view angle Angle at this time is

[0162]

[0163] Step S8, the target information and the calculation results of the target imaging center time and the side view angle are sent to the on-board computer, the on-board computer controls the antenna to start according to the target imaging center time, and the corresponding side view angle is sent to the DSP.

[0164] Here, the DSP completes the time attitude calculation of all targets in the target queue, and transmits the target information and the corresponding calculation results to the on-board computer. The on-board computer controls the antenna to start according to the imaging center time of the target, and sends the side view angle to the DSP.

[0165] Step S9, according to the side view angle of the target, the corresponding wave control code is calculated, the phased array antenna beam pointing is controlled, and the imaging irradiation task of the specified target area is completed.

[0166] Here, the DSP calculates the corresponding wave control code according to the received side view angle and azimuth angle θ1. After the calculation is completed, the wave control code data group is sent to the wave control FPGA. The wave control FPGA distributes the wave control data to each exciter of the phased array antenna, so as to control the phased array antenna beam pointing, and complete the imaging irradiation task of the specified target area.

[0167] According to the above-mentioned electronic reconnaissance guiding spaceborne SAR imaging cooperative work implementation method, due to the strong floating point operation ability of the DSP, the imaging center time and the side view angle of the target can be quickly calculated, and real-time and accurate guidance and beam control can be realized, which is suitable for satellite platform application.

[0168] In various embodiments of the present application, the present application also provides a DSP-based electronic reconnaissance guiding spaceborne SAR imaging device / system / equipment. The functions and principles of each module / component are realized as described in the method, and will not be repeated here.

[0169] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A DSP-based electronic reconnaissance steered satellite-borne SAR imaging method, characterized in that, The method comprises the following steps: Step S1, triggering a DSP interrupt by a satellite computer, obtaining broadcast information output from a satellite platform and target information returned by electronic reconnaissance; Step S2, establishing an instantaneous inertial system in a WGS84 coordinate system at a satellite time, in the instantaneous inertial system, representing a position of the satellite, a speed of the satellite, a position of the target and a position change rate of the target; Step S3, calculating orbit information of a satellite orbit according to the position of the satellite platform and the speed of the satellite platform in the instantaneous inertial system and outputting a calculation result of the orbit information; Step S4, calculating a conversion matrix and a change rate matrix from the instantaneous inertial system to the satellite orbit system according to the calculation result of the orbit information and outputting a calculation result of the conversion matrix and the change rate matrix; Step S5, calculating vector representations of the satellite platform and the target and a vector change rate representation of the target in the satellite orbit system according to the calculation result of the conversion matrix and the change rate matrix; Step S6, converting the vector representations of the satellite platform and the target and the vector change rate representation of the target in the satellite orbit system to a satellite body system in combination with satellite platform attitude information; Step S7, calculating a target imaging center time and a side view angle in the satellite body system by a Newton iteration method and outputting a calculation result of the target imaging center time and the side view angle; Step S8, sending the target information and the calculation result of the target imaging center time and the side view angle to the satellite computer, the satellite computer controlling an antenna to be turned on according to the target imaging center time and sending a corresponding side view angle to the DSP; Step S9, calculating a corresponding wave control code according to the side view angle of the target, controlling a phased array antenna beam to be pointed, and completing an imaging irradiation task of a specified target area.

2. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The method of triggering the DSP interrupt by the satellite computer, obtaining the broadcast information output from the satellite platform and the target information returned by the electronic reconnaissance further comprises: The target information includes a target position under a WGS84 coordinate system The target information is stored in a target queue after being received. The broadcast information includes current on-board time, satellite position in WGS84 coordinate system Satellite velocity Satellite attitude roll angle Pitch angle θ, yaw angle ψ, start time and attitude calculation of each target after receiving satellite platform broadcast information.

3. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The method of establishing the instantaneous inertial system in the WGS84 coordinate system at the satellite time, in the instantaneous inertial system, representing the position of the satellite, the speed of the satellite, the position of the target and the position change rate of the target further comprises: In combination with an angular velocity of the earth rotation, converting the satellite platform position, the satellite speed and the target position into the position of the satellite platform, the speed of the satellite platform, the position of the target and the position change rate of the target represented in the instantaneous inertial system according to conversion formulas of the position of the satellite platform and the speed of the satellite platform, the position of the target and the position change rate of the target; The conversion formula for representing the position of the satellite platform in the instantaneous inertial system and the velocity of the satellite platform is: wherein, is the satellite platform position is the component in the x-axis direction, is the satellite platform position is the component in the y-axis direction, is the satellite velocity, ω e is the earth rotation angular velocity, is the position of the satellite platform in the instantaneous inertial system, is the velocity of the satellite platform in the instantaneous inertial system; Position of the target and the rate of change of the position of the target The conversion formula is: wherein X et0 is the target position in the x-axis component, Y et0 is the target position in the y-axis component, Z et0 is the target position in the z-axis component.

4. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The method of calculating the orbit information of the satellite orbit according to the position of the satellite platform and the speed of the satellite platform in the instantaneous inertial system further comprises: The orbital information includes a position of the satellite platform A velocity of the satellite platform An inclination i, an ascending node right ascension Ω, an orbital angular velocity ω, and an orbital argument μ of the satellite orbit are calculated. According to a calculation formula of an orbit inclination i, calculating the orbit inclination of the satellite orbit, the formula being as follows: where H is the orbital angular momentum, According to a calculation formula of an ascending node right ascension Ω, calculating the ascending node right ascension, the formula being as follows: i z = I x × N, I x = [1 0 0] T , Ω = sign(i z (3)) arccos(N · I x ), where N is the unit vector of the orbit nodal line, I i (i = x, y, z) is the moment of inertia of the satellite corresponding to the axis of rotation of the maneuver, is a sign function; According to a calculation formula of an orbit angular velocity ω, calculating the orbit angular velocity, the formula being as follows: According to calculation formulas of an initial orbit amplitude angle μ0 and an orbit amplitude angle μ, calculating the orbit amplitude angle, the formulas being as follows: μ(t) = μ0 + ωt, where μ is a function of time t, for in the z-axis direction.

5. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The method of calculating the conversion matrix and the change rate matrix from the instantaneous inertial system to the satellite orbit system according to the calculation result of the orbit information and outputting the calculation result of the conversion matrix and the change rate matrix further comprises: According to the calculated orbit inclination i, the ascending node right ascension Ω, the orbit angular velocity ω and the orbit amplitude μ, the conversion matrix A from the instantaneous inertial system to the satellite orbit system is calculated according to the conversion matrix expression in the geometric relationship between the instantaneous inertial system and the satellite orbit system oi According to the conversion rate conversion matrix expression from the instantaneous inertial system to the satellite orbit system, the change rate matrix is calculated The conversion relationship from the instantaneous inertial system to the orbital system is as follows, and the coordinate system is converted from XYZ to X'Y'Z' after conversion: In actual cases, the satellite center of mass pointing coordinate system origin is often defined as the Z axis, the satellite flight direction is defined as the X, the Y axis points to the right-hand screw law, and the coordinate axis conversion is as follows: The transformation rate conversion matrix expression from the instantaneous inertial system to the orbital system is as follows:

6. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The calculation result of the conversion matrix and the change rate matrix is calculated to calculate the satellite platform and the target vector in the satellite orbital system and the target vector change rate, and the expression further comprises: Target position in instantaneous inertial frame Target position rate Satellite platform position Conversion matrix A from instantaneous inertial frame to orbital frame oi and rate matrix Compute satellite platform and target vectors in orbital frame and target vector rate Under the orbit system, after the coordinate axis conversion, the satellite position The expression is: The satellite platform and the target vector expression is as follows: The satellite platform and the target vector change rate expression is as follows:

7. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The satellite platform and the target vector in the satellite orbital system and the target vector change rate are converted to the satellite body system further comprising: The attitude information includes a satellite platform attitude roll angle The pitch angle θ and the yaw angle ψ are calculated according to the attitude information, and a conversion matrix A of a satellite orbit system to a satellite body system is calculated bo The satellite platform and the target vector in the satellite orbit system And the change rate The satellite platform and the target vector in the satellite orbit system And the change rate of the target vector The conversion matrix A of the satellite platform from the orbital system to the body system according to the satellite attitude angle is: bo is: Under the satellite system, the satellite platform and the target vector is represented as: Under the satellite system, the satellite platform and target vector transformation rate is represented as:

8. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The target imaging center time and the side view angle of the satellite body system are calculated by the Newton iteration method, and the calculation result of the target imaging center time and the side view angle is output further comprising: According to geometric relationship, a geometric model is established, and the target imaging center time T and the side view angle Angle at this time are obtained by Newton iteration method under the satellite body system center and the satellite body system Under the satellite body system, the target vector is between the satellite and the target, and the target vector OP between the satellite and the target is The following geometric relationship expressions are established: Let be: The Newton iteration equation is established: The iteration time t is calculated as The imaging center time T satisfying the constraint condition is finally obtained center ; The side view angle Angle is obtained by the following formula:

9. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The target information and the calculation result of the target imaging center time and the side view angle are sent to the on-board computer, the on-board computer controls the antenna to start according to the target imaging center time, and the corresponding side view angle is sent to the DSP further comprising: The time and attitude of all targets in the target queue are calculated by the DSP; The target information and the corresponding calculation result are transmitted to the on-board computer; The on-board computer controls the antenna to start according to the target imaging center time, and the side view angle is sent to the DSP.

10. The DSP-based electronic reconnaissance steered satellite-borne SAR imaging method according to claim 1, characterized in that, The corresponding wave control code is calculated according to the side view angle of the target, the phased array antenna beam pointing direction is controlled, and the imaging irradiation task of the specified target area is completed further comprising: The corresponding wave control code is calculated according to the received side view angle and azimuth angle; After calculation, the wave control code data group is packaged and sent to the wave control FPGA; The wave control data is distributed to each exciter of the phased array antenna by the wave control FPGA, so as to control the phased array antenna beam pointing direction, and complete the imaging irradiation task of the specified target area.

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