CN-117550098-B - SAR satellite in-motion imaging attitude reference establishment method

CN117550098BCN 117550098 BCN117550098 BCN 117550098BCN-117550098-B

Abstract

Aiming at SAR satellite imaging in motion, the invention provides a method for establishing an SAR satellite imaging attitude reference in motion, and the proposed attitude reference establishing method can calculate a target attitude quaternion and an attitude angular speed under an orbit coordinate system in real time in the satellite imaging maneuver process, so as to ensure the accuracy of imaging reference establishment in the imaging process in motion.

Inventors

GUO SIYAN
XUE XIN
Hu Wenkun
LIU DEQING
PEI JIARUI
CHEN HAN
Zhang Zengan
CHEN XIUMEI
ZHONG JINFENG
SHI XIAOHAN

Assignees

上海航天控制技术研究所

Dates

Publication Date: 20260512
Application Date: 20231117

Claims (7)

1. A method for establishing an imaging attitude reference in a SAR satellite motion, comprising: step S1, calculating a vector r et from the earth center to the ground target; S2, calculating a conversion matrix A oi of the track coordinate system relative to the geocentric inertial coordinate system; step S3, obtaining the representation of the vector r et of the earth center to the ground target under the orbit coordinate system through the transformation matrix A oi of the orbit coordinate system relative to the earth center inertial coordinate system Step S4, representing vector r et from the earth center to the ground target in the orbit coordinate system Calculating vectors of satellites to ground targets And calculate the satellite to ground target vector A component r x in the orbit coordinate system X axis, a component r y in the orbit coordinate system Y axis, and a component r z in the orbit coordinate system Z axis, respectively; Step S5, according to the vector from the satellite to the ground target Calculating the attitude quaternion q md of the current shooting target respectively at a component r x of an orbit coordinate system X axis, a component r y of an orbit coordinate system Y axis and a component r z of an orbit coordinate system Z axis; step S6, calculating the angular velocity omega md (k) of the kth beat gesture according to the quaternion q md(k) of the kth beat target gesture.
2. The method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 1, wherein said step S1 comprises: The vector r et of the earth's center to the ground target is expressed as: Wherein [ X et_g Y et_g Z et_g ] T is the representation of the vector of the ground object in the WGS84 coordinate system, X et_g is the component of the vector of the ground object in the WGS84 coordinate system X-axis, Y et_g is the component of the vector of the ground object in the WGS84 coordinate system Y-axis, and Z et_g is the component of the vector of the ground object in the WGS84 coordinate system Z-axis; The transformation matrix R i←e is: R i←e ＝(R M ·R S ·R N ·R P ) -1 Wherein R M is a polar-shift rotation matrix, R S is a star time rotation matrix, R N is a nutation rotation matrix, and R P is a years rotation matrix.
3. The method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 2, wherein said step S2 comprises: S21, acquiring a track inclination angle i and a rising intersection point right ascent and descent omega and a latitude argument u; Step S22, calculating according to the track inclination angle i, the ascending intersection point right ascent angle omega and the latitude amplitude angle u: A oi11 =-sinucosΩ-cosucosisinΩ A oi12 =-sinusinΩ+cosucosicosΩ A oi13 =cosusini A oi21 =-sinisinΩ A oi122 =sinicosΩ A oi23 =-cosi A oi31 =-cosucosΩ+sinucosisinΩ A oi32 =-cosusinΩ-sinucosicosΩ A oi33 =-sinusini step S23, calculating a transformation matrix a oi of the track coordinate system relative to the WGS84 coordinate system:
4. A method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 3, wherein said step S3 comprises: Is a representation of a geocentric to ground target vector r et in an orbital coordinate system, where X et_o is a component of the geocentric to ground target vector in the orbital coordinate system X-axis, Y et_o is a component of the geocentric to ground target vector in the orbital coordinate system Y-axis, and Z et_o is a component of the geocentric to ground target vector in the orbital coordinate system Z-axis.
5. The method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 4, wherein said step S4 comprises: Step S41, calculating a scalar r of satellite to earth center: Wherein a is a semi-long axis of the track, e is the eccentricity of the track, and f is the true near point angle; step S42, calculating the representation of the satellite-to-earth vector in the orbital coordinate system Step S43, calculating the vector of the satellite to the ground target Wherein A (q d ) is a rotation matrix corresponding to the guide quaternion; Step S44, order Calculation to obtain the vector from satellite to ground target Component r x in the X-axis of the orbital coordinate system, component r y in the Y-axis of the orbital coordinate system, and component r z in the Z-axis of the orbital coordinate system.
6. The method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 5, wherein said step S5 comprises: Calculating a current shooting target gesture quaternion q md : Wherein, the For the current beat satellite target roll angle, For the instantaneous roll angle of the current shooting satellite, the attitude sensor measures to obtain the angle theta m as the pitch angle of the current shooting satellite target, q rot_x as the attitude quaternion of the current shooting target obtained by rotating the vector from the satellite to the ground target in the X-axis of the orbit coordinate system, and q rot_y as the attitude quaternion of the current shooting target obtained by rotating the vector from the satellite to the ground target in the Y-axis of the orbit coordinate system.
7. The method for establishing an attitude reference for imaging in motion of a SAR satellite according to claim 6, wherein said step S6 comprises: calculating the derivative of the quaternion of the kth beat target gesture with respect to time The differential mode is adopted to calculate: wherein q md(k) is the quaternion of the kth beat target gesture, For the derivative of the kth target gesture quaternion with respect to time, T s is a differential time interval, q md(k-1) is the kth-1 target gesture quaternion in the differential method, and corresponding q md(k) and q Then, the kth beat attitude angular velocity ω md (k) is calculated: Wherein omega mdx (k)、ω mdy (k)、ω mdz (k) is the kth target attitude angular velocity component of the vector of the satellite to the ground target in the X axis, Y axis and Z axis directions of the orbit coordinate system respectively.

Description

SAR satellite in-motion imaging attitude reference establishment method Technical Field The invention relates to the technical field of spacecraft attitude control, in particular to a control technology for establishing an attitude reference of an SAR satellite in a maneuvering process. Background Compared with the traditional push-broom and agile maneuvering modes, the SAR (SYNTHETIC APERTURE RADAR ) satellite in-motion imaging mode has great efficiency improvement and various novel imaging modes, but brings great difficulty and challenges to the establishment of satellite imaging attitude references. The attitude control accuracy of the satellite mainly depends on the establishment of an attitude reference, and the accuracy of the establishment of an imaging attitude reference directly influences the imaging quality of SAR load. Particularly, the low orbit spacecraft is more easily influenced by external interference such as atmospheric resistance, the dependence on the attitude reference of imaging in motion is stronger, and the quality of imaging can be seriously influenced by smaller attitude reference deviation, and even the serious result of imaging failure is caused. The currently disclosed method for establishing the imaging attitude reference in motion is basically an algorithm level, and a complete flow of the SAR satellite from an imaging ground target point to a target attitude quaternion and an angular speed under an orbit coordinate system is not formed. Disclosure of Invention The invention aims to provide a method for establishing an SAR satellite in-motion imaging attitude reference, which comprises the following steps of S1, calculating a vector r et from a ground center to a ground target, S2, calculating a transformation matrix A oi of an orbit coordinate system relative to a ground center inertial coordinate system, and S3, obtaining the representation of a vector r et from the ground center to the ground target under the orbit coordinate system through the transformation matrix A oi of the orbit coordinate system relative to the ground center inertial coordinate systemStep S4, representing vector r et from the earth center to the ground target in the orbit coordinate systemCalculating vectors of satellites to ground targetsAnd calculate the satellite to ground target vectorThe component r x in the X axis of the orbit coordinate system, the component r y in the Y axis of the orbit coordinate system and the component r z in the Z axis of the orbit coordinate system respectively, and the step S5 is based on the vector of the satellite to the ground targetCalculating a current beat target attitude quaternion q md according to the component r x on the X axis of the orbit coordinate system, the component r y on the Y axis of the orbit coordinate system and the component r z on the Z axis of the orbit coordinate system, and calculating a kth beat attitude angular velocity omega md (k) according to the kth beat target attitude quaternion q md (k) in the step S6 Preferably, the step S1 includes the step of expressing a vector r et of the earth' S center to the ground target as: Wherein [ X et_g Yet_g Zet_g]T is the representation of the vector of the ground object in the WGS84 coordinate system, X et_g is the component of the vector of the ground object in the WGS84 coordinate system X-axis, Y et_g is the component of the vector of the ground object in the WGS84 coordinate system Y-axis, Z et_g is the component of the vector of the ground object in the WGS84 coordinate system Z-axis, the transformation matrix R i←e is: Ri←e＝(RM·RS·RN·RP)-1 Wherein R M is a polar-shift rotation matrix, R S is a star time rotation matrix, R N is a nutation rotation matrix, and R P is a years rotation matrix. Preferably, the step S2 includes the step S21 of obtaining the track inclination angle i, the ascending intersection point right ascent and descent angle omega and the latitude amplitude angle u, and the step S22 of calculating according to the track inclination angle i, the ascending intersection point right ascent and descent angle omega and the latitude amplitude angle u: Aoi11=-sinucosΩ-cosucosisinΩ Aoi12=-sinusinΩ+cosucosicosΩ Aoi13=cosusini Aoi21=-sinisinΩ Aoi122=sinicosΩ Aoi23=-cosi Aoi31=-cosucosΩ+sinucosisinΩ Aoi32=-cosusinΩ-sinucosicosΩ Aoi33=-sinusini step S23, calculating a transformation matrix a oi of the track coordinate system relative to the WGS84 coordinate system: preferably, the step S3 includes: Is a representation of a geocentric to ground target vector r et in an orbital coordinate system, where X et_o is a component of the geocentric to ground target vector in the orbital coordinate system X-axis, Y et_o is a component of the geocentric to ground target vector in the orbital coordinate system Y-axis, and Z et_o is a component of the geocentric to ground target vector in the orbital coordinate system Z-axis. Preferably, the step S4 includes a step S41 of calculating a satellite-to-eart