CN110823191A - Method and system for determining ocean current measurement performance of mixed baseline dual-antenna squint interference SAR - Google Patents
Method and system for determining ocean current measurement performance of mixed baseline dual-antenna squint interference SAR Download PDFInfo
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- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
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- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C25/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING 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
- G01S13/9021—SAR image post-processing techniques
- G01S13/9023—SAR image post-processing techniques combined with interferometric techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING 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
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Abstract
The invention relates to a method for determining the ocean current measurement performance of a dual-antenna squint forward-orbit interference SAR with a mixed base line, which comprises the following steps of 1) establishing observation geometry and giving an ocean current measurement speed expression under a corresponding configuration; 2) giving an ocean current measurement sensitivity expression; 3) analyzing coherence influence factors, establishing an interference coherence expression, and solving an interference phase error; 4) and solving a total interference speed measurement error according to the ocean current measurement sensitivity expression and the errors of all the influencing factors. The configuration is that the in-orbit base line is obtained through the antenna beam squint on the basis of the long-cross-orbit base line double-antenna interference SAR system, so that the in-orbit interference flow rate is realized, the satellite working mode is increased under the condition that no other hardware is arranged and no satellite attitude maneuver is required, the satellite system efficiency is improved, and the trend that the remote sensing satellite develops to one satellite and multiple energy is met. The method provided by the invention has a good reference significance for the performance analysis of a subsequent squint forward-orbit interference SAR ocean current measuring system.
Description
Technical Field
The invention belongs to the technical field of satellite microwave remote sensing, and relates to a system integrity performance determination method of an oblique-looking and along-orbit interference SAR ocean current measurement mode based on a mixed baseline in a multi-mode satellite-borne interference SAR (interferometric synthetic Aperture radar) system.
Background
The satellite-borne Synthetic Aperture Radar (SAR) records radar backscattering intensity information of a ground resolution unit and phase information related to an inclined distance by active microwave imaging on the earth surface. The interferometric SAR (InSAR) extracts a phase difference map, i.e., an interferogram, by performing interference processing on two radar images covering the same area twice in the Cross-track/Along-track direction, can extract surface elevation information or motion information of a scene (target), and establishes a digital three-dimensional terrain model or acquires sea surface flow field information, i.e., Cross-track InSAR (Cross-track InSAR) and Along-track InSAR (Along-track InSAR).
Launched satellite systems dedicated to terrain elevation mapping are the SRTM (Shuttle RadarTopodology mission) and the TanDEM-X/TerrraSAR-X two-star system in Germany. SRTM is a topographic mapping plan developed by United states space administration (NASA) and national mapping bureau of defense (NIMA) in 2 months in 2000 and Germany and Italy, and is used for performing C/X dual-band interference imaging mapping on an area between 60 degrees north latitude and 56 degrees south latitude within 11 days, wherein the mapped area exceeds 80% of the global land area, the nominal absolute elevation precision is 10m (1 sigma), the relative elevation precision is 6m (1 sigma), the absolute plane precision is 12m (1 sigma), and the relative plane precision is 9m (1 sigma). The TanDEM-X task is a global land elevation high-precision surveying and mapping task realized by Germany by using TerrasAR-X transmitted in 2006 and TanDEM-X transmitted in 2010, the nominal absolute elevation precision is 10m, the relative elevation precision is 2m, the actual absolute elevation precision is within 2m, the relative elevation precision is within 1m, and 2 times of global land elevation measurement is completed by 2014.
At present, no interference SAR ocean current measurement satellite applied in orbit exists, but a plurality of SAR satellite systems utilize an azimuth direction multi-channel or a plurality of antennas to carry out an in-orbit interference SAR ocean current measurement test. The SRTM is tested by using a forward-orbit physical baseline with the length of 7m between the main antenna and the auxiliary antenna, and the measuring precision of a flow field on the resolution of 1km reaches 0.2 m/s. The terraSAR-X can adopt a double-aperture receiving or sub-aperture switching mode to realize the in-orbit interference measurement, and the flow field measurement precision can reach 0.1m/s under the resolution of 1 km. The length of a down-track base line of the TanDEM-X/TerrasAR-X double-star operation is 0-500 m, and the flow measurement precision achieved when the resolution is 33m is 0.1 m/s. The high-grade three-number satellite in China also develops a forward-orbit interference ocean current measurement test. In addition, with the requirement of each field for two-dimensional flow field measurement, an ocean current vector measurement satellite such as a wavemill system is also internationally demonstrated, and by using two pairs of beams in front and back view, the ocean current velocities in the front and back directions are obtained, so that the two-dimensional ocean current velocity is synthesized.
Except that the ocean current vector measurement satellite needs to work in an oblique view and forward orbit interference SAR mode, the satellite-borne and forward orbit interference SAR ocean current measurement test is developed in a front side view mode, and at present, no oblique view and forward orbit interference SAR system or working mode passes through an on-orbit test, and no interference SAR ocean current measurement performance analysis method aiming at the system under the condition of an oblique view angle and a mixed base line exists. The performance analysis method aims at a system which obtains a mixed baseline component through beam squint on the basis of an cross-orbit interference baseline so as to realize an along-orbit interference ocean current measurement.
Disclosure of Invention
The technical problem solved by the invention is as follows: the method overcomes the defects of the prior art, provides a corresponding ocean current measurement performance determination method aiming at the forward-orbit interference SAR system with mixed baseline components and squint angles, and provides reference for the analysis of the subsequent ocean current measurement performance method of the system.
The technical solution of the invention is as follows:
a method for determining ocean current measurement performance of a mixed baseline dual-antenna squint forward-orbit interference SAR comprises the following steps:
(1) establishing a squint double-antenna interference SAR imaging geometric model, and obtaining a forward-orbit baseline length expression according to the geometric model;
(2) determining an interference phase expression according to the forward-orbit baseline length expression;
(3) determining an ocean current velocity expression according to the interference phase expression;
(4) establishing an ocean current measurement sensitivity expression according to the ocean current velocity expression;
(5) establishing an interference coherence expression and solving an interference phase error;
(6) and (5) solving a total interference speed measurement error according to the ocean current measurement sensitivity expression determined in the step (4) and the interference phase error obtained in the step (5), and finishing the determination of the ocean current measurement performance of the mixed baseline dual-antenna squint along-the-track interference SAR.
Further, the establishing of the squint double-antenna interference SAR imaging geometric model specifically comprises:
establishing a local horizon coordinate system XYZ-O, wherein the origin O of the coordinate system is the projection of the position of the main antenna on the ground at the moment when the center of the main antenna beam irradiates the center of the scene, the X axis is parallel to the direction of a physical baseline, the Z axis is vertical to the local horizon and points to the inside of the earth, the Y axis is a right-hand rule, and the motion direction of the satellite is parallel to the Y axis;
establishing a target coordinate system xyz-o: wherein the origin o is the center of the imaging scene, and the directions of x, y and z are respectively parallel to the X, Y, Z axis;
the ocean current moves only in the x direction and has a velocity upsilonxThe physical base length is B, the satellite orbit height is H,namely, the positions of the antenna 1 and the antenna 2 in the XYZ-O coordinate system are (0,0, H) and (B cos α,0, H + B sin α), respectively, and the slant distance R of the imaging scene center from the main antenna iscBeam squint angle θsThe downward viewing angle of the radar line of sight in a plane perpendicular to the track is thetavThe angle theta between the projection of the radar sight line on the ground and the + X directionyHas tan (theta)y)＝tan(θs)/sin(θv)。
Further, obtaining a length expression of the down-track baseline according to the geometric model specifically includes:
the length of the down-track base line is BAT＝B·cos(α)·tan(θy)。
Further, determining an interference phase expression according to the length expression of the base line along the track, specifically:
wherein, delta phi is the interference phase between two pairs of antenna echoes in ping-pong mode, upsilonrIs the velocity of the ocean current, v, projected in a radial directionr＝υxsinθvcosθs，υorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvIs the downward viewing angle of the radar line of sight in a plane perpendicular to the flight path.
Further, the ocean current velocity expression specifically includes:
further, the sensitivity equation of the ocean current measurement speed is as follows:
wherein the content of the first and second substances,
to determine the sign of the deviation, upsilonrIs the velocity of the ocean current, v, projected in a radial directionorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvThe lower visual angle of the radar sight line in a plane vertical to the track is shown, and delta phi is the interference phase between the two pairs of antennas in the ping-pong mode.
Further, the interference coherence expression specifically includes:
the interference coherence expression is as follows:
γtotal＝γgeom·γSNR·γtemp·γΔfdc·γamb·γvol·γreg·γquant
wherein gamma istotalFor the total interference decorrelation coefficient, gammageomFor geometric decoherence, gammaSNRDecorrelating gamma for signal-to-noise ratiotempFor temporal decoherence, gammaΔfdcFor Doppler decoherence, gammaambFor fuzzy decoherence, gammavolDecoherence for volume scattering, gammaregFor registration decoherence, gammaquantTo quantize the decorrelation.
The interference phase error is:
wherein N isLIs the total multiview.
Further, the total interference velocity measurement error is obtained, specifically:
wherein the content of the first and second substances,
error, upsilon, is measured for total radial ocean velocityrIs the velocity of the ocean current, v, projected in a radial directionorbAs the speed of movement of the satellite, BATIs the length of the base line along the track, and delta phi is the interference phase between the two pairs of antennas, sigmaΔφIn order to interfere with the error in the phase measurement,in order to measure the error in the speed of the satellite,
the error is measured for the length of the base line along the track.
Further, the present invention also provides an ocean current measurement performance determining system, including:
a model building module: establishing a squint double-antenna interference SAR imaging geometric model, and obtaining a forward-orbit baseline length expression according to the geometric model;
an interference phase determination module: determining an interference phase expression according to the forward-orbit baseline length expression;
an ocean current velocity determination module: determining an ocean current velocity expression according to the interference phase expression;
ocean current measurement sensitivity determination module: establishing an ocean current measurement sensitivity expression according to the ocean current velocity expression;
a phase-related error determination module: establishing an interference coherence expression and solving an interference phase error;
ocean current measurement performance determination module: and solving a total interference speed measurement error according to the determined ocean current measurement sensitivity expression and the interference phase error, and finishing the determination of the ocean current measurement performance of the mixed baseline dual-antenna squint along-the-track interference SAR.
Compared with the prior art, the invention has the beneficial effects that:
(1) aiming at a forward-orbit interference SAR system with mixed baseline components and squint angles, all decoherence factors are considered, a corresponding ocean current measurement performance analysis method is provided, the blank that the ocean current measurement performance analysis method without the type of configuration system and the existing analysis do not consider all decoherence factors is filled, and an effective path is provided for parameter design and measurement performance analysis of the follow-up type of ocean current measurement system.
(2) In practical application, the design of main parameters of the squint and direct-orbit interference SAR system is firstly carried out, then the ocean current measurement performance analysis is completed according to the method, whether the performance analysis result meets the requirements or not is evaluated after the performance analysis result is obtained, if the performance analysis result does not meet the requirements, the system parameter adjustment is carried out, and then iterative analysis is carried out until the design of the system parameters meets the requirements.
Drawings
FIG. 1 is a cross-rail interference SAR squint imaging geometric model;
FIG. 2 is a flow chart of mixed baseline configuration squint forward-orbit interference SAR ocean current measurement performance analysis (dotted line frame part is required steps when applied to system parameter design)
FIG. 3 total coherence coefficient plot of a simulation example
FIG. 4 simulation example interferometric phase error for different multiview views
FIG. 5 simulation example Total error in flow measurement for different multiview views
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The invention provides a method and a system for determining ocean current measurement performance of a mixed baseline dual-antenna squint interference SAR, which are used for establishing the relation between the interference phase and the ocean current speed of a forward-orbit interference SAR system with a mixed baseline and a squint angle; obtaining a sensitivity equation of the ocean current velocity by using an expression of the ocean current velocity under the configuration; obtaining a coherence coefficient expression and an interference phase error expression under the condition of mixed base line and oblique angle; and analyzing the total ocean current measurement error according to the interference phase error and other error factors.
Specifically, the method for determining the measurement performance of the mixed baseline dual-antenna squint interference SAR ocean current comprises the following steps:
(1) imaging geometric model establishment and ocean current velocity derivation
The mixed baseline-based strabismus forward-orbit interference SAR imaging geometric model is shown in figure 1.
A local horizon coordinate system XYZ-O is established, the origin O of the coordinate system is the projection of the position of the main antenna on the ground at the moment when the center of a main antenna beam irradiates the center of a scene, the X axis is parallel to the direction of a physical baseline, the Z axis is perpendicular to the local horizon and points to the inside of the earth, the Y axis is a right-hand rule, the motion direction of the satellite is parallel to the Y axis, α is a baseline angle which is the included angle between a baseline vector and the local horizon, Y' is the flight direction of the satellite and is parallel to + Y, and the physical baseline is perpendicular to the + Y direction.
Establishing a target coordinate system xyz-o: the origin o is the center of the imaging scene, and the directions x, y and z are respectively parallel to the X, Y, Z axis.
Assuming that the ocean current moves only in the x-direction, the velocity is upsilonxThe physical base line length is B, the satellite orbit height is H, namely the positions of the antenna 1 and the antenna 2 in an XYZ-O coordinate system are (0,0, H) and (B cos α,0, H + B sin α), respectively, and the slant distance R from the center of the imaging scene to the main antenna iscBeam squint angle θsThe downward viewing angle of the radar line of sight in a plane perpendicular to the track is thetavThe angle theta between the projection of the radar sight line on the ground and the + X directionyThen, there is tan (theta)y)＝tan(θs)/sin(θv)。
According to the basic principle of squint forward-orbit interference SAR under mixed baseline configuration, when the SAR works in a ping-pong mode
Wherein, BATIs a base line in the direction of orbit, upsilonrTarget (ocean current) velocity, upsilon, in the direction of the line of sightorbIs the orbital velocity of the satellite. According to the definition of the in-orbit interference SAR, in a coordinate system XYZ-O, the length of the in-orbit base line is BAT＝B cosα·tan(θy)＝Bcosα·tan(θs)/sin(θv)，
In summary, the estimated ocean current velocity is expressed as follows:
(2) obtaining sensitivity equation of ocean current measurement speed
Theoretically, the ocean current measurement speed error has a relationship with a satellite platform speed error, an interference phase error, a base line length error, a sea surface height error and a satellite orbit determination error, but according to data processing experience and the proportion of each error factor, the interference phase error, the platform speed error and the base line error are main error factors, and generally the three error terms are mainly considered, so that the sensitivity equation of the ocean current measurement speed in the claim 2 is as follows:
the platform speed error and the baseline measurement error are respectively determined by the precision of the on-satellite orbit determination and baseline measurement equipment, and the interference phase error is mainly determined by the coherence of the system and the multi-view of the SAR image.
(3) Obtaining the coherence coefficient of a mixed baseline interference SAR along-orbit ocean current velocity measurement system
The coherence coefficient for such a system is expressed as follows:
γtotal＝γgeom·γSNR·γtemp·γΔfdc·γamb·γvol·γreg·γquant
wherein gamma isgeomFor geometric decoherence, gammaSNRDecorrelating gamma for signal-to-noise ratiotempFor temporal decoherence, gammaΔfdcFor Doppler decoherence, gammaambFor fuzzy decoherence, gammavolDecoherence for volume scattering, gammaregFor registration decoherence, gammaquantTo quantize the decorrelation.
The expression of each coherence coefficient is as follows:
(3.1)
wherein, B⊥CIs taken as a limit baseline for the test,
r is the distance from the target point to the phase center of the radar antenna, BrIs the SAR system signal bandwidth.
Wherein the SNR1And SNR2SNR for two antenna images, respectively, is common for ping-pong mode1≈SNR2。
Wherein, Δ t ═ BAT/υorbFor interference time delay between front and rear antennas, tcIs the sea coherence time. Empirical formula according to coherence time:
u is sea surface wind speed and ρ is the average geometric resolution of the image.
(3.4)
Wherein, Δ fdcIs the difference in Doppler center frequency of the two antenna images, BdIs the doppler bandwidth.
(3.5)
Where RASR and AASR represent range and azimuth ambiguities, respectively.
(3.6)
Wherein σhStandard deviation of sea surface wave height, BxIs the length of the base line perpendicular to the track direction and parallel to the X-axis.
γregAnd gammaquantCan be estimated based on the registration accuracy and the number of quantization bits.
Further, the multi-view post-theoretical interference phase error can be obtained as follows.
Wherein N isLIs the total multiview.
(4) Obtaining total ocean current velocity measurement error
According to the sensitivity coefficient of the ocean current velocity to each factor and the corresponding error term, the total ocean current velocity measurement error is as follows.
The invention provides a corresponding ocean current measurement performance analysis method by considering all decoherence factors aiming at a forward-orbit interference SAR system with mixed baseline components and squint angles, fills the blank that the ocean current measurement performance analysis method without the type of configuration system and the existing analysis do not consider all decoherence factors, and provides an effective path for parameter design and measurement performance analysis of the follow-up type of ocean current measurement system.
Examples
The interference SAR system configured by the invention is provided with the system parameters shown in the following table 1, and the ocean current measurement precision analysis under the system parameters is completed under the assumption that the interference SAR works in a ping-pong mode.
TABLE 1 squint interference SAR system simulation parameter setup
| Height of platform track | 450km |
| Error in platform velocity | 0.05m/s |
| Base line length error | 0.8mm |
| Base length | 100m |
| Range of viewing angles | 20～50° |
| Oblique angle | 4° |
| Carrier frequency | X wave band |
| Bandwidth of signal | 90MHz |
| Single sided Pulse Repetition Frequency (PRF) | 2600Hz |
| SAR average power | 1330W |
| Single view image resolution | 4～5m |
The other parameters related to the coherence coefficient are set as follows: RASR-AASR-18 dB, gammareg0.973 (this can be achieved with distance and azimuth registration accuracy of 0.1 pixels), γquant0.989 (determined essentially by the number of quantization bits), γΔfdc0.98, five other coherence factors, γgeom、γSNR、γtemp、γambAnd gammavolThe total coherent coefficient and the interference phase error can be calculated according to a formula.
According to simulation parameters, fig. 2 is a mixed baseline configuration squint along-the-rail interference SAR ocean current measurement performance analysis flow, wherein a dotted line frame part is required steps applied to system parameter design. The results of the overall coherence coefficient are shown in FIG. 3. The interference phase errors under different multi-view conditions are shown in figure 4, the total ocean current velocity measurement errors under different multi-view conditions are shown in figure 5, and the requirement that the ocean current velocity measurement accuracy is less than 0.2m/s, which is required by general application, can be met when the viewing angle is below 35 degrees.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. The method for determining the measurement performance of the mixed baseline double-antenna squint forward-orbit interference SAR ocean current is characterized by comprising the following steps of:
(1) establishing a squint double-antenna interference SAR imaging geometric model, and obtaining a forward-orbit baseline length expression according to the geometric model;
(2) determining an interference phase expression according to the forward-orbit baseline length expression;
(3) determining an ocean current velocity expression according to the interference phase expression;
(4) establishing an ocean current measurement sensitivity expression according to the ocean current velocity expression;
(5) establishing an interference coherence expression and solving an interference phase error;
(6) and (5) solving a total interference speed measurement error according to the ocean current measurement sensitivity expression determined in the step (4) and the interference phase error obtained in the step (5), and finishing the determination of the ocean current measurement performance of the mixed baseline dual-antenna squint along-the-track interference SAR.
2. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: the method for establishing the squint double-antenna interference SAR imaging geometric model specifically comprises the following steps:
establishing a local horizon coordinate system XYZ-O, wherein the origin O of the coordinate system is the projection of the position of the main antenna on the ground at the moment when the center of the main antenna beam irradiates the center of the scene, the X axis is parallel to the direction of a physical baseline, the Z axis is vertical to the local horizon and points to the inside of the earth, the Y axis is a right-hand rule, and the motion direction of the satellite is parallel to the Y axis;
establishing a target coordinate system xyz-o: wherein the origin o is the center of the imaging scene, and the directions of x, y and z are respectively parallel to the X, Y, Z axis;
the ocean current moves only in the x direction and has a velocity upsilonxThe physical base line length is B, the satellite orbit height is H, namely the positions of the antenna 1 and the antenna 2 in an XYZ-O coordinate system are (0,0, H) and (Bcos α,0, H + Bsin α), respectively, and the slant distance R from the center of the imaging scene to the main antenna is RcBeam squint angle θsThe downward viewing angle of the radar line of sight in a plane perpendicular to the track is thetavThe angle theta between the projection of the radar sight line on the ground and the + X directionyHas tan (theta)y)＝tan(θs)/sin(θv)。
3. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 2, characterized in that: obtaining a length expression of the down-track base line according to the geometric model, specifically:
the length of the down-track base line is BAT＝B·cos(α)·tan(θy)。
4. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: determining an interference phase expression according to the base line length expression along the track in the step (2), wherein the step specifically comprises the following steps:
wherein, delta phi is the interference phase between two pairs of antenna echoes in ping-pong mode, upsilonrIs the velocity of the ocean current, v, projected in a radial directionr＝υxsinθvcosθs，υorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvIs the downward viewing angle of the radar line of sight in a plane perpendicular to the flight path.
5. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: step (3), expressing the ocean current velocity, specifically:
wherein upsilon isrIs the velocity of the ocean current, v, projected in a radial directionr＝υxsinθvcosθs，υorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvThe lower visual angle of the radar sight line in a plane vertical to the track is shown, and delta phi is the interference phase between the two pairs of antennas in the ping-pong mode.
6. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: the sensitivity equation of the ocean current measurement speed is as follows:
wherein the content of the first and second substances,
to determine the sign of the deviation, upsilonrIs the velocity of the ocean current, v, projected in a radial directionorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvThe lower visual angle of the radar sight line in a plane vertical to the track is shown, and delta phi is the interference phase between the two pairs of antennas in the ping-pong mode.
7. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: the step (5) of establishing the interference coherence expression specifically comprises the following steps:
the interference coherence expression is as follows:
γtotal＝γgeom·γSNR·γtemp·γΔfdc·γamb·γvol·γreg·γquant
wherein gamma istotalFor the total interference decorrelation coefficient, gammageomFor geometric decoherence, gammaSNRDecorrelating gamma for signal-to-noise ratiotempFor temporal decoherence, gammaΔfdcFor Doppler decoherence, gammaambFor fuzzy decoherence, gammavolDecoherence for volume scattering, gammaregFor registration decoherence, gammaquantTo quantize the decorrelation.
The interference phase error is:
wherein N isLIs the total multiview.
8. The hybrid baseline dual-antenna squint forward-orbit interference SAR ocean current measurement performance determination method according to claim 1, characterized in that: and (6) solving a total interference speed measurement error, which specifically comprises the following steps:
wherein the content of the first and second substances,
error, upsilon, is measured for total radial ocean velocityrIs the velocity of the ocean current, v, projected in a radial directionorbAs the speed of movement of the satellite, BATIs the length of the base line along the track, and delta phi is the interference phase between the two pairs of antennas, sigmaΔφIn order to interfere with the error in the phase measurement,
in order to measure the error in the speed of the satellite,the error is measured for the length of the base line along the track.
9. An ocean current measurement performance determination system based on the interferometric SAR ocean current measurement performance determination method of claim 1, characterized by comprising:
a model building module: establishing a squint double-antenna interference SAR imaging geometric model, and obtaining a forward-orbit baseline length expression according to the geometric model;
an interference phase determination module: determining an interference phase expression according to the forward-orbit baseline length expression;
an ocean current velocity determination module: determining an ocean current velocity expression according to the interference phase expression;
ocean current measurement sensitivity determination module: establishing an ocean current measurement sensitivity expression according to the ocean current velocity expression;
a phase-related error determination module: establishing an interference coherence expression and solving an interference phase error;
ocean current measurement performance determination module: and solving a total interference speed measurement error according to the determined ocean current measurement sensitivity expression and the interference phase error, and finishing the determination of the ocean current measurement performance of the mixed baseline dual-antenna squint along-the-track interference SAR.
10. The ocean current survey performance determining system of claim 9, wherein:
obtaining a length expression of the down-track base line according to the geometric model, specifically:
the length of the down-track base line is BAT＝B·cos(α)·tan(θy)；
The interference phase expression specifically includes:
the ocean current velocity expression specifically comprises:
wherein upsilon isrIs the velocity of the ocean current, v, projected in a radial directionr＝υxsinθvcosθs，υorbAs the speed of movement of the satellite, BATIs the base length along the rail, lambda is the load operating wavelength, B is the physical base length, α is the base angle, thetasFor beam squint angle, θvThe lower visual angle of the radar sight line in a plane vertical to the track is shown, and delta phi is the interference phase between the two pairs of antennas in the ping-pong mode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN115267780A (en) * | 2022-09-26 | 2022-11-01 | 中国电子科技集团公司第十四研究所 | Multi-channel polarized SAR system and method for simultaneously realizing along-track and tangential-track interference |
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| CN114002666A (en) * | 2021-10-26 | 2022-02-01 | 南京航空航天大学 | Method and equipment for extracting satellite-borne ATI-SAR ocean current flow velocity under any antenna configuration |
| CN114002666B (en) * | 2021-10-26 | 2024-04-12 | 南京航空航天大学 | Method and equipment for extracting satellite-borne ATI-SAR ocean current flow velocity under any antenna configuration |
| CN115267780A (en) * | 2022-09-26 | 2022-11-01 | 中国电子科技集团公司第十四研究所 | Multi-channel polarized SAR system and method for simultaneously realizing along-track and tangential-track interference |
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