CN103675760B  A kind of spaceborne geostationary orbit syntheticaperture radar attitude guidance method  Google Patents
A kind of spaceborne geostationary orbit syntheticaperture radar attitude guidance method Download PDFInfo
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 CN103675760B CN103675760B CN201310651459.3A CN201310651459A CN103675760B CN 103675760 B CN103675760 B CN 103675760B CN 201310651459 A CN201310651459 A CN 201310651459A CN 103675760 B CN103675760 B CN 103675760B
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Classifications

 G—PHYSICS
 G01—MEASURING; TESTING
 G01S—RADIO DIRECTIONFINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCEDETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
 G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
 G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00

 G—PHYSICS
 G01—MEASURING; TESTING
 G01S—RADIO DIRECTIONFINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCEDETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
 G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
 G01S13/88—Radar or analogous systems specially adapted for specific applications
 G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
 G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
Abstract
Description
Technical field
The present invention relates to Synthetic Aperture Radar Technique field, be specifically related to a kind of spaceborne geostationary orbit syntheticaperture radar attitude guidance method.
Background technology
Synthetic aperture radar (SAR) is a kind of roundtheclock, roundtheclock highresolution microwave remote sensing imaging radar, can be arranged on the flying platforms such as aircraft, satellite, spaceship.Application in environmental monitoring, oceanographic observation, resource exploration, Crop Estimation, mapping and military affairs etc. has unique advantage, the effect that other remote sensings are difficult to play can be played.Apply so widely for SAR, its application quality quality generally depends on the image resolution ratio of SAR.
Spaceborne geostationary orbit (GEO) syntheticaperture radar refer to be positioned at geostationary orbit, take satellite as the syntheticaperture radar of carrier.Spaceborne geostationary orbit syntheticaperture radar (GEOSAR) has the advantages such as overlay area is wide, revisit time is short.In the orbital period of a GEOSAR, the direction variation range that earth center rotates (ECR) coordinate system speed is large.When GEOSAR is positioned at equator, ECR velocity reversal is close to range direction.Now, ambiguity function is projected in the twodimentional secondary lobe on ground will be no longer orthogonal.This causes orientation to ground range resolution much larger than orientation to slant range resolution, ground range resolution severe exacerbation.
Syntheticaperture radar can improve range resolution by improving transmitted bandwidth, can improve azimuth resolution by extending the synthetic aperture time.But because distance is no longer orthogonal to bidimensional to, orientation, even may overlap, thus only by raising transmitted bandwidth with extend the synthetic aperture time and be difficult to effectively improve resolution.
Syntheticaperture radar can also change beam position by attitude guiding, and then improves ground range resolution.Attitude guiding refers to the adjustment for reaching the attitude of satellite that certain ideal behavior is carried out.In earth low orbit (LEO) syntheticaperture radar, the object of attitude guiding normally reduces Doppler frequency.The attitude guidance method that current LEOSAR is conventional has one dimension Yaw steering and complete zero Doppler to guide, and the former can reduce Doppler frequency, and the latter can make Doppler frequency be zero.In GEOSAR, Yaw steering effectively can reduce the deterioration of ground range resolution, but required guiding angle is large, high to the requirement of platform stance control system.Complete zero Doppler's guiding not only needs larger guiding angle, and can not reduce the deterioration of ground range resolution.
Summary of the invention
In view of this, the invention provides a kind of spaceborne geostationary orbit syntheticaperture radar attitude guidance method, less attitude guiding angle can be utilized to realize optimum ground range resolution.
Spaceborne geostationary orbit syntheticaperture radar attitude guidance method of the present invention, comprises the following steps:
Step 1, definitely apart from differentiating ellipse area:
Wherein, S is the area of3dB ground range resolution ellipse, ρ _{a}for oblique distance azimuth resolution; ρ _{r}for oblique distance range resolution; α is the angle of pitch of radar; β is the downwards angle of visibility of radar; for the position angle of radar;
Wherein,
Wherein, ω _{s}for orbit angular velocity, ω _{e}for rotationalangular velocity of the earth, R _{s}for the height in satellite distance the earth's core, for R _{s}to the derivative of time, i is orbit inclination, and u is latitude argument, and μ is Gravitational coefficient of the Earth, and a is semimajor axis of orbit, and e is orbital eccentricity, and ω is argument of perigee;
Step 2, base area is apart from resolution ellipse area determination top optimization direction angle:
Solve draw top optimization direction angle for
Wherein, positive sign represents that right side is looked, and negative sign represents that left side is looked;
Step 3, determines attitude guiding angle according to top optimization direction angle, carries out attitude guiding:
According to the guidance mode of pitching after first roll, then roll guiding angle θ _{r}, pitching guiding angle θ _{p}be respectively
According to the guidance mode of roll after first pitching, then roll guiding angle θ _{r}, pitching guiding angle θ _{p}be respectively
Wherein,
Beneficial effect:
When the present invention utilizes distance resolution ellipse area minimum, ground range resolution is optimum, calculate the top optimization direction angle of optimum ground range resolution, then guided by pitching roll or roll pitching guiding make direction, place, beam position top optimization direction angle, complete the guiding of optimal resolution attitude, attitude steering angle is little.
Accompanying drawing explanation
Fig. 1 is process flow diagram of the present invention.
Fig. 2 is coordinate angle schematic diagram of the present invention.
Fig. 3 is that the attitude guiding roll angle of pitching guidance mode after adopting first roll changes.
Fig. 4 is that the attitude guiding angle of pitch of pitching guidance mode after adopting first roll changes.
Fig. 5 is distance ambiguity function after attitude guiding.
Embodiment
To develop simultaneously embodiment below in conjunction with accompanying drawing, describe the present invention.
The invention provides a kind of spaceborne geostationary orbit syntheticaperture radar attitude guidance method, first differentiate the expression formula of ellipse area according to the condition acquisition satellite velocities directions such as known orbit parameter, downwards angle of visibility and distance.Then base area is apart from the expression formula differentiating ellipse area, solves the top optimization direction angle realized needed for minimum resolution ellipse area.Finally, guided by pitching roll or roll pitching guiding make direction, place, beam position abovementioned top optimization direction angle, as shown in Figure 1.Concrete steps are as follows.
Step 1, differentiates ellipse area according to orbit parameter and downwards angle of visibility determination satellite velocities direction and distance.
Step 1.1, determines satellite velocities direction.
The velocity reversal of satellite in earth fixed coordinate system is determined according to semimajor axis of orbit a, orbit inclination i, orbital eccentricity e, argument of perigee ω, latitude argument u.Wherein, earth fixed coordinate system initial point is positioned at earth centroid, and xaxis points to Greenwich meridian in earth equatorial plane, and zaxis is along the sensing arctic, earth rotation direction, and yaxis and xaxis, zaxis form right hand rectangular coordinate system.
Under earth fixed coordinate system, the direction of satellite velocities can use crab angle φ and angle of pitch α to represent, crab angle φ and angle of pitch α computing formula as follows:
Wherein, ω _{e}for rotationalangular velocity of the earth, ω _{s}for orbit angular velocity, R _{s}for the height in satellite distance the earth's core, for R _{s}to the derivative of time, can be expressed as
Wherein, μ is Gravitational coefficient of the Earth, and numerical value is 398600.5km ^{3}/ s ^{2}; Sign () is sign function, can be expressed as
Step 1.2, definitely apart from differentiating ellipse area
Ground range resolution can use the cartographic represenation of area of3dB resolution ellipse, and its formula is
Wherein, S is the area of3dB resolution ellipse, ρ _{a}for oblique distance azimuth resolution, ρ _{r}for oblique distance range resolution.Angle of squint γ is the angle of beam position and ECR velocity reversal, position angle for beam position is at the projection of surface level and the angle of ECR speed between the projection of surface level, β is downwards angle of visibility, position angle determine according to the beam position of reality with downwards angle of visibility β.
As shown in Figure 2, wherein V is ECR speed to abovementioned angle, and R is beam position, and O point is the earth's core.
Angle of squint γ and position angle between there is following relation:
Thus, ground range resolution area can be expressed as
Step 2, base area is apart from resolution ellipse area determination top optimization direction angle.
If ground range resolution area is minimum, demand fulfillment equation
Solving equation (7), can obtain the top optimization direction angle corresponding to optimum ground range resolution:
Wherein, be top optimization direction angle, positive sign represents that right side is looked, and negative sign represents that left side is looked.
Step 3, determines attitude guiding angle according to top optimization direction angle.
In initial time beam position substar, position, beam position top optimization direction angle after attitude guiding.Attitude guiding strategy is the guiding of roll pitching two dimension.Beam position before attitude guiding can represent
u'＝[0,0,1] ^{T}(9)
Beam position after attitude guiding can be expressed as
Attitude guided procedure can be expressed as
u'＝Au(11)
Wherein, A is the rotation matrix of attitude guiding correspondence.
According to the strategy of pitching after first roll, rotation matrix can be expressed as
Wherein, θ _{r}for roll guiding angle, θ _{p}for pitching guiding angle.Rotation matrix is substituted into equation (11), solving equation (11) can obtain attitude steering angle and be
According to the strategy of roll after first pitching, rotation matrix can be expressed as
Rotation matrix substitutes into equation (11), and solving equation (11) can obtain attitude steering angle and be
Since then, a kind of satelliteborne synthetic aperture radar attitude guidance method is just achieved.
Satellite transit on elliptical orbit, shown in each parameter of track is specific as follows: earth radius is 6371.004km; Semimajor axis of orbit is 42100km; Orbit inclination is 50 °; Orbital eccentricity is 0.1; Perigee of orbit argument is 90 °; Downwards angle of visibility is 7 °; Slant range resolution is 1m; Rotationalangular velocity of the earth is 7.292115 × 10 ^{5}rads.The mode of pitching after the first roll of attitude guiding employing.As shown in Figure 3, the angle of pitch as shown in Figure 4 for roll angle needed for attitude guiding.Ground range resolution ambiguity function after attitude guides as shown in Figure 5.From Fig. 3, Fig. 4, the attitude steering angle needed for geostationary orbit syntheticaperture radar optimal resolution attitude guidance method is less.As shown in Figure 5, after carrying out the guiding of geostationary orbit syntheticaperture radar optimal resolution attitude, it is vertical that distance differentiates two secondary lobes, and ground range resolution is optimum.
In sum, these are only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
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CN109001762A (en) *  20180608  20181214  上海微小卫星工程中心  A kind of the gas light suppressing method and system of synchronous belt objective optics observation satellite 
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CN104597446B (en) *  20141010  20170215  北京理工大学  Spaceborne synthetic aperture radar ground range resolution representation and parameter design method 
CN104375511A (en) *  20141028  20150225  上海卫星工程研究所  Geosynchronous orbit SAR satellite offcourse guide method based on wave beam cooperative control 
CN104765023B (en) *  20150320  20170329  北京理工大学  A kind of satelliteborne synthetic aperture radar height resolution computational methods 
CN105403888A (en) *  20151230  20160316  中国科学院电子学研究所  Geosynchronous orbit circular track SAR imaging method using beam pointing control 
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