CN114814909B - Ground track tracking method - Google Patents

Abstract

The present invention provides a ground track tracking method, which comprises: obtaining satellite ground tracking control points at different times by controlling the scanning attitude of a ground remote sensing satellite, and constraining the three-axis attitude of the satellite according to the track angle at the time when the target passes overhead, so as to improve the pointing accuracy of the scanning observation and realize high-precision distortion-free scanning observation control of the ground target.

Description

Ground Tracking Method

Technical Field

The invention relates to the technical field of remote sensing satellites, and in particular to a ground track tracking method.

Background Art

With the development of high-tech and the promotion of demand, remote sensing micro-nano satellites have shown good development prospects in scientific research, national defense and commercial fields such as resource management, environmental monitoring, land planning, and geographic surveying and mapping with their advantages of light weight, small size, low power consumption, short development cycle, high functional density, high performance-price ratio, and the ability to form fleets and networks.

With the increasing mission demands and target accuracy requirements for high-resolution remote sensing, the relationship between the remote sensing satellite camera's ability to monitor its optical axis position and imaging quality during the mission has become increasingly close, which has directly affected the design level of the remote sensing satellite system.

Since the data processing and payload data processing of remote sensing micro-nano satellite platforms are mostly designed independently, there is actually a certain error between the satellite attitude data and the actual attitude of the optical payload, which has a great impact on the payload imaging quality.

In order to achieve the best imaging effect, the remote sensing satellite camera must ensure that the optical axis of the camera is consistent with the ground design after entering orbit, which requires a lot of experimental verification and flight state simulation. However, the optical axis disturbance caused by the vibration interference of the satellite platform during the orbit operation is difficult to measure and compensate. Therefore, it is particularly important to perform attitude control of the optical axis micro-vibration of the remote sensing satellite camera in real time on orbit to restore the image quality of the remote sensing camera.

The existing on-orbit control methods for micro-vibration of remote sensing satellite cameras in China cannot meet the high-precision measurement requirements of remote sensing satellite cameras during their on-orbit lifespan; the existing technology cannot directly and accurately control the key factor affecting the imaging quality of remote sensing cameras: the camera optical axis. In addition, the reliability of the mechanical sensitive components required by the control system for long-term on-orbit operation and the resulting system complexity also reduce the reliability and ease of use of the remote sensing satellite camera system.

Summary of the invention

The purpose of the present invention is to provide a ground track tracking method to solve the problem that the existing remote sensing satellite attitude control accuracy is low, which affects the scanning accuracy.

In order to solve the above technical problems, the present invention provides a ground track tracking method, which comprises:

Through the scanning attitude control of the earth remote sensing satellite, the satellite ground tracking control points at different times are obtained, and the three-axis attitude of the satellite is constrained and controlled according to the track angle when the target passes overhead, so as to improve the pointing accuracy of the scanning observation and realize high-precision distortion-free scanning observation control of ground targets.

Optionally, in the ground track tracking method, the method further includes:

Share the data processing parameters of the remote sensing micro-nano satellite platform and the payload data processing to eliminate the error between the satellite attitude data and the actual attitude of the optical payload, and ensure that the optical axis of the camera after entering orbit is consistent with the ground design;

Eliminate the optical axis disturbance caused by satellite platform vibration during orbit operation by measuring and compensating;

Perform attitude control on the optical axis micro-vibration of remote sensing satellite cameras in real time on orbit to improve the image restoration quality of remote sensing cameras;

The on-orbit measurement accuracy requirements of remote sensing satellite cameras are met through the on-orbit micro-vibration control method of remote sensing satellite cameras;

The camera optical axis is directly and accurately controlled to affect the imaging quality of the remote sensing camera.

Optionally, in the ground track tracking method, the time at which the earth remote sensing satellite passes over the ground observation target point is calculated;

Calculate the ground track angle of the scanning observation according to the overhead time;

Calculate ground track tracking points based on the time series and the ground track angle;

Calculate the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point;

The scanning attitude of the earth remote sensing satellite located at the current control point is determined according to the direction of the optical axis of the earth remote sensing satellite payload.

Optionally, in the ground track tracking method, calculating the time at which the earth remote sensing satellite passes over the ground observation target point comprises:

receiving a signal of a ground observation target point in real time, and calculating in real time a position of the ground observation target point in a VVLH coordinate system at a current moment, wherein the position of the ground observation target point in the VVLH coordinate system at a current moment includes a first X coordinate position value, a first Y coordinate position value, and a first Z coordinate position value;

According to the position of the ground observation target point in the VVLH coordinate system at the current moment, determining whether the distance between the earth remote sensing satellite and the ground observation target point is greater than a first threshold;

If the distance between the earth remote sensing satellite and the ground observation target point is greater than a first threshold, calculating the position of the ground observation target point in the VVLH coordinate system at the first moment;

The first moment is the sum of the current moment and a first threshold time, and the first threshold time is equal to the first threshold divided by the relative speed between the satellite and the target point;

If the distance between the earth remote sensing satellite and the ground observation target point is less than or equal to the first threshold, calculating the position of the ground observation target point in the VVLH coordinate system at the second moment;

The second moment is the sum of the current moment and the X-coordinate time, and the X-coordinate time is equal to the first X-coordinate position value divided by the relative speed between the satellite and the target point;

Repeat the above steps until the value of the first X-coordinate position value is less than the second threshold value, and the corresponding current moment is the passing moment of the ground observation target point.

Optionally, in the ground track tracking method, the first threshold is 2000 km and the second threshold is 0.1 km.

Optionally, in the ground track tracking method, calculating the ground track angle of the scanning observation according to the overhead time includes:

Generate the geographical longitude and latitude of the target point and the velocity vector of the satellite in the ground fixed system at the time of passing the target point through the ground planning module or the onboard autonomous mission planning module;

After obtaining the passing time of the earth observation target point, calculate the angle between the velocity vector of the earth remote sensing satellite in the earth fixed system at that time and the true north direction of the earth observation target point in the north-east earth coordinate system, and use the angle as the ground track angle. When the ground track angle deviates from north to east, it is positive, and when the ground track angle deviates from north to west, it is negative;

The transformation matrix of the earth observation target point from the earth fixed system to the north-east earth coordinate system is:

Wherein, (J ₀ ) is the geographic longitude of the target point, (W ₀ ) is the geographic latitude of the target point, and the true north direction vector _Ne of the earth observation target point in the earth-fixed system is:

N _e =[-cos(J ₀ )sin(W ₀ ),-sin(J ₀ )sin(W ₀ ),cos(W ₀ )]

The angle between the velocity vector _Ve of the satellite in the earth-fixed system and the due north vector _Ne of the target point in the earth-fixed system at the moment of passing the earth observation target point is calculated as the ground track angle.

Optionally, in the ground track tracking method, calculating the ground track tracking point based on the time series and the ground track angle includes:

The ground planning module or the on-board autonomous task planning module generates the start time _{t_start} and the end time _{t_end} of the star-scanning observation according to the passing time of the earth observation target point and the total duration of the star-scanning observation.

t _{_start} =T _pass -△T/2, t _{_end} =T _pass +△T/2;

Among them, △T is the total duration of the scanning observation, and T _pass is the time when the target point of the ground observation passes over the top;

Generate a time series Tm=(Tm ₁ , Tm ₂ , ..., Tm _n ) from the start time of the scanning observation to the end time of the scanning observation according to the attitude control cycle 0.25 second step length;

Among them, Tm _i+1 =Tm _i +0.25s, i=1, 2,...,n;

The total length of the condensation sweep is N = v△T,

Wherein, the total length of the condensation scan includes the transition track and the actual imaging track, and v is the rotation speed of the earth;

The time difference between each moment in the time series and the passing moment of the ground observation target point is calculated as: △t _i =Tm _i -T _pass ;

The ground distance between the ground track tracking point and the ground observation target point at each moment in the time series is calculated as: Si = v△t _i ;

The mid-latitude method is used to calculate the longitude and latitude of the ground track tracking point, including:

The longitude difference Dλ and latitude difference between each ground track tracking point and the ground observation target point for;

Dλi＝Si*sinC*secW ₀ /R_e*(180/Π);

Wherein, C is the ground track angle, R_e is the reference ellipsoid radius of the ground observation target point, and the longitude and latitude of each ground track tracking point are:

According to the longitude and latitude and geographic altitude of each ground track tracking point, the position vector P _hj of each ground track tracking point in the ground fixed system is calculated respectively.

Optionally, in the ground track tracking method, calculating the distance from the earth center of the earth observation target point by using the reference ellipsoid radius of the earth observation target point includes:

The latitude and longitude of the target point of the above task is the geographic latitude W ₀ , and the normalization angle u is calculated as:

tan(u)＝0.9966471615*tan(W ₀ )

x＝acos(u)＝6378.137*cos(u)

y＝bsin(u)＝6356.752*sin(u)

R_e＝sqrt(x^2+y^2)

The distance between the earth observation target point and the earth's center is:

R_tg＝R_e+h ₀

Where _h0 is the geographic height of the earth observation target point.

Optionally, in the ground track tracking method, calculating the position vector P _hj of each ground track tracking point in the ground fixed system according to the latitude, longitude and geographic altitude of each ground track tracking point includes:

Assume the longitude range is -180° to +180°, with west longitude being negative and east longitude being positive;

Convert the geographic latitude of a ground track point to geocentric latitude:

Calculate the geocentric distance R_tg_ctrl of the current ground track tracking point according to the geocentric distance of the ground observation target point;

Calculate the coordinates of the ground track tracking point in the ground fixed system:

tg_ctrl_x_fixed=R_tg_ctrl*cosd(phi_dixin)*cosd(λ _i )

tg_ctrl_y_fixed=R_tg_ctrl*cosd(phi_dixin)*sind(λ _i )

tg_ctrl_z_fixed=R_tg_ctrl*sind(phi_dixin)

Among them, tg_ctrl_x_fixed, tg_ctrl_y_fixed, and tg_ctrl_z_fixed are the three-axis coordinates of the position vector of the ground track tracking point in the ground fixed system.

Optionally, in the ground track tracking method, calculating the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point includes:

Calculate the pointing vector of the load optical axis in the ground fixed system:

V _boresight =P _hj -P _sat ;

Wherein, _Phj is the position vector of each ground track tracking point in the ground fixed system; _Psat is the position vector of the satellite in the ground fixed system at the corresponding time of each ground track tracking point;

Convert the pointing vector of the load optical axis in the ground-fixed system into the pointing vector V _{b_vvlh} of the load optical axis in the orbital system;

Vb_vvlh＝R _oi ·R _ie ·V _boresight ;

Where: R _ie is the transformation matrix from the earth-fixed system to the J2000 coordinate system, and R _oi is the transformation matrix from the J2000 coordinate system to the orbital system.

Optionally, in the ground track tracking method, determining the scanning attitude of the earth remote sensing satellite located at the current control point according to the direction of the optical axis of the earth remote sensing satellite payload includes: taking the satellite center of mass as the origin and the distance from the satellite to the ground track tracking point as the Z axis, determining the X axis according to the Z axis, determining the Y axis according to the right-hand rule, establishing a scanning direction coordinate system, and calculating the conversion matrix from the orbit system to the scanning direction coordinate system according to the scanning direction coordinate system:

The four elements of the attitude in the orbital system are calculated according to the transformation matrix, and the attitude angular velocity is output.

Optionally, in the ground track tracking method, the load optical axis pointing vector is normalized in the orbital system to obtain the load optical axis pointing unit vector u_Vb_vvlh, then the unit vector of the Z axis in the orbital system is ZS;

ZS＝u_Vb_vvlh

The unit vector of the satellite velocity vector in the earth-fixed coordinate system at the moment of passing the earth observation target point is IX_0_fix, which is converted into the unit vector in the orbital system at the current moment:

IX_0_vvlh＝R _oi *R _ie *IX_0_fix

The geographic latitude and longitude of the earth observation target point are (W ₀ , J ₀ , h ₀ ), which are converted to geocentric latitude

W_p_x＝atand(0.99330559*tand(W ₀ ))

Then the position of the earth observation target point in the earth fixed system is:

P_tg_fix_z=R_tg.*sind(W_p_x);

P_tg_fix_x=R_tg.*cosd(W_p_x).*cosd(J ₀ );

P_tg_fix_y=R_tg.*cosd(W_p_x).*sind(J ₀ );

The unit position vector of the earth observation target point in the current VVLH coordinate system is u_P_tg_vvlh. u_P_tg_vvlh points from the center of the earth to the target point. The line field projection vector of the earth observation target point is calculated as follows:

cross1＝IX_0_vvlh×u_P_tg_vvlh

In the orbital system, cross1 is cross-multiplied by the unit vector pointing to the optical axis and normalized to obtain the unit vector XS of the X axis in the orbital system;

The unit vector of the Y axis of the scanning coordinate system in the orbital coordinate system is:

YS＝ZS×XS.

The present invention also provides a ground track tracking system, which includes a ground planning module or an on-board autonomous mission planning module, an on-board payload sensor module and a scanning algorithm module, wherein:

The on-board payload sensor module receives a signal from a ground observation target point and sends it to the ground planning module or the on-board autonomous mission planning module;

The ground planning module or the on-board autonomous mission planning module calculates the overpass time of the ground observation target point and the ground track angle according to the signal of the ground observation target point;

The ground planning module or the on-board autonomous task planning module calculates the start time and the end time of the scanning according to the passing time of the ground observation target point;

The ground planning module or the on-board autonomous task planning module sends the passing time of the ground observation target point, the ground track angle, the start time of the scanning observation and the end time of the scanning observation to the scanning algorithm module;

The scanning algorithm module calculates the ground track tracking point according to the time series and the ground track angle;

The scanning algorithm module calculates the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point;

The scanning algorithm module determines the scanning attitude of the earth remote sensing satellite located at the current control point according to the direction of the optical axis of the earth remote sensing satellite payload.

In the ground track tracking method provided by the present invention, the ground track tracking method is adopted to obtain the satellite ground tracking control points at different times, and the three-axis attitude of the satellite is constrained and controlled according to the track angle when the target passes overhead, thereby improving the pointing accuracy of the scanning observation and realizing high-precision distortion-free scanning observation control of ground targets.

The present invention realizes the design of sharing parameters of remote sensing micro-nano satellite platform data processing and payload data processing, overcomes the defect of error between satellite attitude data and actual attitude of optical payload, improves payload imaging quality, ensures that the optical axis of the camera after entering orbit is consistent with the ground design, and achieves the best imaging effect of the remote sensing satellite camera; the scanning algorithm of the present invention is simple and easy to implement, and does not need to be implemented through a large number of experimental verifications and flight state simulations; the optical axis disturbance caused by the vibration interference of the satellite platform during the orbit operation is eliminated by measuring and compensating; the present invention realizes the attitude control of the optical axis micro-vibration of the remote sensing satellite camera in real time on orbit, and indirectly improves the quality of image quality restoration of the remote sensing camera; the present invention overcomes the problem that the existing on-orbit control method of micro-vibration of remote sensing satellite cameras cannot meet the high-precision measurement requirements of remote sensing satellite cameras during their on-orbit service life; the present invention realizes direct and accurate control of the key factor affecting the imaging quality of the remote sensing camera: the optical axis of the camera; in addition, the present invention improves the reliability of the long-term operation of the mechanical sensitive elements required by the control system on orbit, the system complexity of the present invention is relatively small, and the reliability and usability of the remote sensing satellite camera system are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a ground track tracking method according to an embodiment of the present invention.

DETAILED DESCRIPTION

The ground track tracking method proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

In addition, the numbering of the steps of the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps can be executed in different orders.

The core idea of the present invention is to provide a ground track tracking method to solve the problem that the existing remote sensing satellite attitude control accuracy is low, which affects the scanning accuracy.

To realize the above idea, the present invention provides a ground track tracking method, which includes: obtaining satellite ground tracking control points at different times through the scanning attitude control of the earth remote sensing satellite, and constraining the three-axis attitude of the satellite according to the track angle when the target passes over the top, so as to improve the pointing accuracy of the scanning observation and realize high-precision distortion-free scanning observation control of ground targets.

<Example 1>

The present embodiment provides a ground track tracking method, which includes: step one, calculating the time when a ground remote sensing satellite passes overhead relative to a ground observation target point; step two, calculating a ground track angle of a sweeping observation according to the time when the satellite passes overhead; step three, calculating a ground track tracking point based on a time series and the ground track angle; step four, calculating the direction of an optical axis of a payload of the ground remote sensing satellite at a specific time according to the ground track tracking point; and step five, determining the sweeping attitude of the ground remote sensing satellite located at a current control point according to the direction of the optical axis of the payload of the ground remote sensing satellite.

Specifically, in the ground track tracking method, calculating the time when the earth remote sensing satellite passes over the ground observation target point includes: receiving a signal of the ground observation target point in real time, calculating the position of the ground observation target point in the VVLH coordinate system at the current time in real time, wherein the position of the ground observation target point in the VVLH coordinate system at the current time includes a first X coordinate position value, a first Y coordinate position value, and a first Z coordinate position value; judging whether the distance between the earth remote sensing satellite and the ground observation target point is greater than a first threshold value according to the position of the ground observation target point in the VVLH coordinate system at the current time; if the distance between the earth remote sensing satellite and the ground observation target point is greater than the first threshold value, calculating the ground observation target point The position of the mark in the VVLH coordinate system at the first moment; the first moment is the sum of the current moment and the first threshold time, the first threshold time is equal to the first threshold divided by the relative speed between the satellite and the target point; if the distance between the earth remote sensing satellite and the ground observation target point is less than or equal to the first threshold, calculate the position of the ground observation target point in the VVLH coordinate system at the second moment; the second moment is the sum of the current moment and the X coordinate time, the X coordinate time is equal to the first X coordinate position value divided by the relative speed between the satellite and the target point; repeat the above steps until the value of the first X coordinate position value is less than the second threshold, and the corresponding current moment is the overpass moment of the ground observation target point. Wherein, in the ground track tracking method, the first threshold is 2000km and the second threshold is 0.1km.

Further, in the ground track tracking method, calculating the ground track angle of the scanning observation according to the passing time includes: generating the geographical longitude of the target point, the geographical latitude of the target point, and the velocity vector of the satellite in the ground fixed system at the passing time of the ground observation target point through a ground planning module or an on-board autonomous task planning module; after obtaining the passing time of the ground observation target point, calculating the angle between the velocity vector of the ground remote sensing satellite in the ground fixed system at this time and the due north direction of the ground observation target point in the northeast earth coordinate system, and taking the angle as the ground track angle, the ground track angle is positive when it deviates from north to east, and negative when it deviates from north to west; the transformation matrix of the ground observation target point from the ground fixed system to the northeast earth coordinate system is:

Wherein, (J ₀ ) is the geographic longitude of the target point, (W ₀ ) is the geographic latitude of the target point, and the true north direction vector _Ne of the earth observation target point in the earth-fixed system is:

N _e =[-cos(J ₀ )sin(W ₀ ),-sin(J ₀ )sin(W ₀ ),cos(W ₀ )]

The angle between the velocity vector _Ve of the satellite in the earth-fixed system and the due north vector _Ne of the target point in the earth-fixed system at the moment of passing the earth observation target point is calculated as the ground track angle.

In addition, in the ground track tracking method, calculating the ground track tracking point based on the time series and the ground track angle includes: the ground planning module or the on-board autonomous task planning module generates the scanning observation start time _{t_start} and the scanning observation end time _{t_end} according to the passing time of the ground observation target point and the total duration of the scanning observation,

t _{_start} =T _pass -△T/2, t _{_end} =T _pass +△T/2;

Wherein, △T is the total duration of the scanning observation, and T _pass is the passing moment of the ground observation target point; a time series Tm＝(Tm ₁ , Tm ₂ , …, Tm _n ) is generated from the start time of the scanning observation to the end time of the scanning observation according to the attitude control cycle step of 0.25 seconds; wherein, Tm _i+1 ＝Tm _i +0.25s, i＝1, 2, …, n; the total scanning length N＝v△T, wherein the total scanning length includes the transition track and the actual imaging track, and v is the rotation speed of the earth; the time difference between each moment in the time series and the passing moment of the ground observation target point is calculated as: △t _i ＝Tm _i -T _pass ; the ground distance between the ground track tracking point and the ground observation target point at each moment in the time series is calculated as: Si＝v△t _i ; the longitude and latitude of the ground track tracking point are calculated by the mid-latitude method, including: the longitude difference Dλ and latitude difference Dλ between each ground track tracking point and the ground observation target point for;

Dλi＝Si*sinC*secW ₀ /R_e*(180/Π);

Wherein, C is the ground track angle, R_e is the reference ellipsoid radius of the ground observation target point, and the longitude and latitude of each ground track tracking point are:

According to the longitude and latitude and geographic altitude of each ground track tracking point, the position vector P _hj of each ground track tracking point in the ground fixed system is calculated respectively.

Furthermore, in the ground track tracking method, the distance from the earth observation target point to the earth center is calculated by referring to the ellipsoid radius of the earth observation target point, including: the longitude and latitude of the target point of the mission are the geographic latitude W ₀ , and the normalized angle u is calculated as:

tan(u)＝0.9966471615*tan(W ₀ )

x＝acos(u)＝6378.137*cos(u)

y＝bsin(u)＝6356.752*sin(u)

R_e＝sqrt(x^2+y^2)

The distance between the earth observation target point and the earth's center is:

R_tg＝R_e+h ₀ ;

Where _h0 is the geographic height of the earth observation target point.

Specifically, in the ground track tracking method, according to the longitude and latitude and geographic altitude of each ground track tracking point, the position vector P _hj of each ground track tracking point in the ground fixed system is calculated respectively, including: assuming that the longitude range is -180° to +180°, the west longitude is negative, and the east longitude is positive; converting the geographic latitude of the ground track tracking point into the geocentric latitude:

Calculate the distance R_tg_ctrl from the center of the earth to the current ground track tracking point according to the distance from the center of the earth to the ground observation target point; calculate the coordinates of the ground track tracking point in the ground fixed system:

tg_ctrl_x_fixed=R_tg_ctrl*cosd(phi_dixin)*cosd(λ _i )

tg_ctrl_y_fixed=R_tg_ctrl*cosd(phi_dixin)*sind(λ _i )

tg_ctrl_z_fixed=R_tg_ctrl*sind(phi_dixin)

Among them, tg_ctrl_x_fixed, tg_ctrl_y_fixed, and tg_ctrl_z_fixed are the three-axis coordinates of the position vector of the ground track tracking point in the ground fixed system.

In addition, in the ground track tracking method, calculating the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point includes: calculating the pointing vector of the optical axis of the payload in the ground fixed system:

V _boresight =P _hj -P _sat ;

Wherein, _Phj is the position vector of each ground track tracking point in the ground-fixed system; _Psat is the position vector of the satellite in the ground-fixed system at the corresponding time of each ground track tracking point; the pointing vector of the load optical axis in the ground-fixed system is converted into the pointing vector _{Vb_vvlh} of the load optical axis in the orbit system;

Vb_vvlh＝R _oi ·R _ie ·V _boresight ;

Where: R _ie is the transformation matrix from the earth-fixed system to the J2000 coordinate system, and R _oi is the transformation matrix from the J2000 coordinate system to the orbital system.

Finally, in the ground track tracking method, according to the direction of the optical axis of the earth remote sensing satellite payload, determining the scanning attitude of the earth remote sensing satellite located at the current control point includes: taking the satellite center of mass as the origin, the satellite to the ground track tracking point as the Z axis, determining the X axis according to the Z axis, determining the Y axis according to the right-hand rule, establishing a scanning direction coordinate system, and calculating the conversion matrix from the orbit system to the scanning direction coordinate system according to the scanning direction coordinate system:

The four elements of the attitude in the orbital system are calculated according to the transformation matrix, and the attitude angular velocity is output.

Specifically, in the ground track tracking method, the load optical axis pointing vector is normalized in the orbital system to obtain the load optical axis pointing unit vector u_Vb_vvlh, then the unit vector of the Z axis in the orbital system is ZS;

ZS＝u_Vb_vvlh

The unit vector of the satellite velocity vector in the earth-fixed coordinate system at the moment of passing the earth observation target point is IX_0_fix, which is converted into the unit vector in the orbital system at the current moment:

IX_0_vvlh＝R _oi *R _ie *IX_0_fix

The geographic latitude and longitude of the earth observation target point are (W ₀ , J ₀ , h ₀ ), which are converted to geocentric latitude

W_p_x＝atand(0.99330559*tand(W ₀ ))

Then the position of the earth observation target point in the earth fixed system is:

P_tg_fix_z=R_tg.*sind(W_p_x);

P_tg_fix_x=R_tg.*cosd(W_p_x).*cosd(J ₀ );

P_tg_fix_y=R_tg.*cosd(W_p_x).*sind(J ₀ );

The unit position vector of the earth observation target point in the current VVLH coordinate system is u_P_tg_vvlh. u_P_tg_vvlh points from the center of the earth to the target point. The line field projection vector of the earth observation target point is calculated as follows:

cross1＝IX_0_vvlh×u_P_tg_vvlh

In the orbital system, cross1 is cross-multiplied by the unit vector pointing to the optical axis and normalized to obtain the unit vector XS of the X axis in the orbital system; the unit vector of the Y axis of the scanning coordinate system in the orbital coordinate system is:

YS＝ZS×XS.

In summary, the above embodiments describe in detail different configurations of the ground track tracking method. Of course, the present invention includes but is not limited to the configurations listed in the above embodiments. Any content that is transformed based on the configurations provided in the above embodiments belongs to the scope of protection of the present invention. Those skilled in the art can draw inferences based on the contents of the above embodiments.

<Example 2>

The present embodiment provides a ground track tracking system, which includes a ground planning module or an on-board autonomous task planning module, an on-board payload sensor module and a scanning algorithm module, wherein: the on-board payload sensor module receives a signal of a ground observation target point and sends it to the ground planning module or the on-board autonomous task planning module; the ground planning module or the on-board autonomous task planning module calculates the passing time of the ground observation target point and the ground track angle according to the signal of the ground observation target point; the ground planning module or the on-board autonomous task planning module calculates the passing time of the ground observation target point according to the passing time of the ground observation target point The ground planning module or the onboard autonomous task planning module sends the passing moment of the earth observation target point, the ground track angle, the sweeping observation start time and the sweeping observation end time to the sweeping algorithm module; the sweeping algorithm module calculates the ground track tracking point according to the time series and the ground track angle; the sweeping algorithm module calculates the optical axis pointing of the earth remote sensing satellite payload at a specific time according to the ground track tracking point; the sweeping algorithm module determines the sweeping attitude of the earth remote sensing satellite located at the current control point according to the optical axis pointing of the earth remote sensing satellite payload.

In the ground track tracking method provided by the present invention, the ground track tracking method is adopted to obtain the satellite ground tracking control points at different times, and the three-axis attitude of the satellite is constrained and controlled according to the track angle when the target passes over the top, thereby improving the pointing accuracy of the scanning observation and realizing high-precision distortion-free scanning observation control of ground targets.

The present invention realizes the design of sharing parameters of remote sensing micro-nano satellite platform data processing and payload data processing, overcomes the defect of error between satellite attitude data and actual attitude of optical payload, improves payload imaging quality, ensures that the optical axis of the camera after entering orbit is consistent with the ground design, and achieves the best imaging effect of the remote sensing satellite camera; the scanning algorithm of the present invention is simple and easy to implement, and does not need to be implemented through a large number of experimental verifications and flight state simulations; the optical axis disturbance caused by the vibration interference of the satellite platform during the orbit operation is eliminated by measuring and compensating; the present invention realizes the attitude control of the optical axis micro-vibration of the remote sensing satellite camera in real time on orbit, and indirectly improves the quality of image quality restoration of the remote sensing camera; the present invention overcomes the problem that the existing on-orbit control method of micro-vibration of remote sensing satellite cameras cannot meet the high-precision measurement requirements of remote sensing satellite cameras during their on-orbit service life; the present invention realizes direct and accurate control of the key factor affecting the imaging quality of the remote sensing camera: the optical axis of the camera; in addition, the present invention improves the reliability of the long-term operation of the mechanical sensitive elements required by the control system on orbit, the system complexity of the present invention is relatively small, and the reliability and usability of the remote sensing satellite camera system are improved.

In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims (7)

1. A ground track tracking method, characterized in that it includes: Through the scanning attitude control of the earth remote sensing satellite, the satellite ground tracking control points at different times are obtained, and the three-axis attitude of the satellite is constrained and controlled according to the track angle when the target passes the top, so as to improve the pointing accuracy of the scanning observation and realize the high-precision distortion-free scanning observation control of the ground target; The method further comprises: Share the data processing parameters of the remote sensing micro-nano satellite platform and the payload data processing to eliminate the error between the satellite attitude data and the actual attitude of the optical payload, and ensure that the optical axis of the camera after entering orbit is consistent with the ground design; Eliminate the optical axis disturbance caused by satellite platform vibration during orbit operation by measuring and compensating; Perform attitude control on the optical axis micro-vibration of remote sensing satellite cameras in real time on orbit to improve the image restoration quality of remote sensing cameras; The on-orbit measurement accuracy requirements of remote sensing satellite cameras are met through the on-orbit micro-vibration control method of remote sensing satellite cameras; Direct and accurate control of the camera optical axis to affect the imaging quality of the remote sensing camera; The method further comprises: Calculate the time when the earth remote sensing satellite passes over the ground observation target point; Calculate the ground track angle of the scanning observation according to the overhead time; Calculate ground track tracking points based on the time series and the ground track angle; Calculate the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point; Determining the scanning attitude of the earth remote sensing satellite located at the current control point according to the direction of the optical axis of the earth remote sensing satellite payload; Calculating the ground track tracking point based on the time series and the ground track angle includes: The ground planning module or the on-board autonomous task planning module generates the start time _{t_start} and the end time _{t_end} of the star-scanning observation according to the passing time of the earth observation target point and the total duration of the star-scanning observation. t _{_start} =T _pass -△T/2, t _{_end} =T _pass +△T/2; Among them, △T is the total duration of the scanning observation, and T _pass is the time when the target point of the ground observation passes over the top; Generate a time series Tm=(Tm ₁ , Tm ₂ , ..., Tm _n ) from the start time of the scanning observation to the end time of the scanning observation according to the attitude control cycle 0.25 second step length; Among them, Tm _i+1 =Tm _i +0.25s, i=1, 2,...,n; The total length of the condensation sweep is N = v△T, Wherein, the total length of the condensation scan includes the transition track and the actual imaging track, and v is the rotation speed of the earth; The time difference between each moment in the time series and the passing moment of the ground observation target point is calculated as: △t _i =Tm _i -T _pass ; The ground distance between the ground track tracking point and the ground observation target point at each moment in the time series is calculated as: Si = v△t _i ; The mid-latitude method is used to calculate the longitude and latitude of the ground track tracking point, including: The longitude difference Dλ and latitude difference between each ground track tracking point and the ground observation target point for; Dλi＝Si*sinC*secW ₀ /R_e*(180/Π); Wherein, C is the ground track angle, R_e is the reference ellipsoid radius of the ground observation target point, and the longitude and latitude of each ground track tracking point are: According to the longitude and latitude and geographic altitude of each ground track tracking point, the position vector P _hj of each ground track tracking point in the ground fixed system is calculated respectively. 2. The ground track tracking method according to claim 1, wherein calculating the time at which the earth remote sensing satellite passes over the ground observation target point comprises: receiving a signal of a ground observation target point in real time, and calculating in real time a position of the ground observation target point in a VVLH coordinate system at a current moment, wherein the position of the ground observation target point in the VVLH coordinate system at a current moment includes a first X coordinate position value, a first Y coordinate position value, and a first Z coordinate position value; According to the position of the ground observation target point in the VVLH coordinate system at the current moment, determining whether the distance between the earth remote sensing satellite and the ground observation target point is greater than a first threshold; If the distance between the earth remote sensing satellite and the ground observation target point is greater than a first threshold, calculating the position of the ground observation target point in the VVLH coordinate system at the first moment; The first moment is the sum of the current moment and a first threshold time, and the first threshold time is equal to the first threshold divided by the relative speed between the satellite and the target point; If the distance between the earth remote sensing satellite and the ground observation target point is less than or equal to the first threshold, calculating the position of the ground observation target point in the VVLH coordinate system at the second moment; The second moment is the sum of the current moment and the X-coordinate time, and the X-coordinate time is equal to the first X-coordinate position value divided by the relative speed between the satellite and the target point; Repeat the above steps until the value of the first X-coordinate position value is less than the second threshold value, and the corresponding current moment is the passing moment of the ground observation target point. 3. The ground track tracking method according to claim 2, wherein calculating the ground track angle of the scanning observation according to the overhead time comprises: Generate the geographical longitude and latitude of the target point and the velocity vector of the satellite in the ground fixed system at the time of passing the target point through the ground planning module or the onboard autonomous mission planning module; After obtaining the passing time of the earth observation target point, calculate the angle between the velocity vector of the earth remote sensing satellite in the earth fixed system at that time and the true north direction of the earth observation target point in the north-east earth coordinate system, and use the angle as the ground track angle. When the ground track angle deviates from north to east, it is positive, and when the ground track angle deviates from north to west, it is negative; The transformation matrix of the earth observation target point from the earth fixed system to the north-east earth coordinate system is: Wherein, (J ₀ ) is the geographic longitude of the target point, (W ₀ ) is the geographic latitude of the target point, and the true north direction vector _Ne of the earth observation target point in the earth-fixed system is: N _e =[-cos(J ₀ )sin(W ₀ ),-sin(J ₀ )sin(W ₀ ),cos(W ₀ )] The angle between the velocity vector _Ve of the satellite in the earth-fixed system and the due north vector _Ne of the target point in the earth-fixed system at the moment of passing the earth observation target point is calculated as the ground track angle. 4. The ground track tracking method according to claim 1, characterized in that the distance from the earth center of the earth observation target point is calculated by using the reference ellipsoid radius of the earth observation target point, comprising: The latitude and longitude of the target point of the above task is the geographic latitude W ₀ , and the normalization angle u is calculated as: tan(u)＝0.9966471615*tan(W ₀ ) x＝acos(u)＝6378.137*cos(u) y＝bsin(u)＝6356.752*sin(u) R_e＝sqrt(x^2+y^2) The distance between the earth observation target point and the earth's center is: R_tg＝R_e+h ₀ Where, h ₀ is the geographical height of the earth observation target point; According to the latitude and longitude and geographic altitude of each ground track tracking point, the position vector P _hj of each ground track tracking point in the ground fixed system is calculated respectively, including: Assume the longitude range is -180° to +180°, with west longitude being negative and east longitude being positive; Convert the geographic latitude of a ground track point to geocentric latitude: Calculate the geocentric distance R_tg_ctrl of the current ground track tracking point according to the geocentric distance of the ground observation target point; Calculate the coordinates of the ground track tracking point in the ground fixed system: tg_ctrl_x_fixed=R_tg_ctrl*cosd(phi_dixin)*cosd(λ _i ) tg_ctrl_y_fixed=R_tg_ctrl*cosd(phi_dixin)*sind(λ _i ) tg_ctrl_z_fixed=R_tg_ctrl*sind(phi_dixin) Among them, tg_ctrl_x_fixed, tg_ctrl_y_fixed, and tg_ctrl_z_fixed are the three-axis coordinates of the position vector of the ground track tracking point in the ground fixed system. 5. The ground track tracking method according to claim 4, wherein calculating the optical axis direction of the earth remote sensing satellite payload at a specific time according to the ground track tracking point comprises: Calculate the pointing vector of the load optical axis in the ground fixed system: V _boresight =P _hj -P _sat ; Wherein, _Phj is the position vector of each ground track tracking point in the ground fixed system; _Psat is the position vector of the satellite in the ground fixed system at the corresponding time of each ground track tracking point; Convert the pointing vector of the load optical axis in the ground-fixed system into the pointing vector V _{b_vvlh} of the load optical axis in the orbital system; Vb_vvlh＝R _oi ·R _ie ·V _boresight ; Where: R _ie is the transformation matrix from the earth-fixed system to the J2000 coordinate system, and R _oi is the transformation matrix from the J2000 coordinate system to the orbital system. 6. The ground track tracking method according to claim 5 is characterized in that, according to the direction of the optical axis of the earth remote sensing satellite payload, determining the scanning attitude of the earth remote sensing satellite located at the current control point comprises: taking the satellite center of mass as the origin and the distance from the satellite to the ground track tracking point as the Z axis, determining the X axis according to the Z axis, determining the Y axis according to the right-hand rule, establishing a scanning direction coordinate system, and calculating the conversion matrix from the orbit system to the scanning direction coordinate system according to the scanning direction coordinate system: The four elements of the attitude in the orbital system are calculated according to the transformation matrix, and the attitude angular velocity is output. 7. The ground track tracking method according to claim 6, characterized in that, in the orbital system, the load optical axis pointing vector is normalized to obtain the load optical axis pointing unit vector u_Vb_vvlh, then the unit vector of the Z axis in the orbital system is ZS; ZS＝u_Vb_vvlh The unit vector of the satellite velocity vector in the earth-fixed coordinate system at the moment of passing the earth observation target point is IX_0_fix, which is converted into the unit vector in the orbital system at the current moment: IX_0_vvlh＝R _oi *R _ie *IX_0_fix The geographic latitude and longitude of the earth observation target point are (W ₀ , J ₀ , h ₀ ), which are converted to geocentric latitude W_p_x＝atand(0.99330559*tand(W ₀ )) Then the position of the earth observation target point in the earth fixed system is: P_tg_fix_z=R_tg.*sind(W_p_x); P_tg_fix_x=R_tg.*cosd(W_p_x).*cosd(J ₀ ); P_tg_fix_y=R_tg.*cosd(W_p_x).*sind(J ₀ ); The unit position vector of the earth observation target point in the current VVLH coordinate system is u_P_tg_vvlh. u_P_tg_vvlh points from the center of the earth to the target point. The line field projection vector of the earth observation target point is calculated as follows: cross1＝IX_0_vvlh×u_P_tg_vvlh In the orbital system, cross1 is cross-multiplied by the unit vector pointing to the optical axis and normalized to obtain the unit vector XS of the X axis in the orbital system; The unit vector of the Y axis of the scanning coordinate system in the orbital coordinate system is: YS＝ZS×XS.