A method for on-orbit calibration of spaceborne laser radar

Abstract

The present invention discloses an on-orbit calibration method for a satellite-borne laser radar, which comprises laying a target field in a selected calibration area, entering a calibration orbit through satellite orbit maneuvers, and acquiring laser spots multiple times and quickly without transporting the target field, thereby realizing on-orbit calibration of the satellite-borne laser radar. The on-orbit calibration method described in the present invention does not rely on a calibration field and can be applied to geometric positioning of a satellite-borne laser radar.

Description

Technical Field

[0001] The invention belongs to the technical field of on-orbit calibration of satellite-borne laser radar, and in particular relates to an on-orbit calibration method of satellite-borne laser radar. Background Art

[0002] The vibration of satellite during launch, satellite orbit, attitude, time scale and ranging and pointing errors of lidar ground calibration will reduce the accuracy of laser measurement results used as elevation control. Therefore, it is necessary to calibrate the lidar parameters that affect the accuracy on-orbit.

[0003] At present, the calibration methods used for satellite-borne laser radar at home and abroad mainly include ground detector-based method, airborne infrared imaging method, terrain-based calibration method, satellite attitude maneuvering method, etc. Each method has its own advantages and disadvantages. Since domestic large-scale surveying and mapping cameras generally use high-stability large platforms, they are not suitable for satellite attitude maneuvering calibration methods; airborne infrared imaging methods have a low success rate and are difficult to implement; the ground detector-based method has a high success rate and high precision, but requires high laying costs and a long calibration cycle. Summary of the invention

[0004] The technology of the present invention solves the problem: overcomes the shortcomings of the prior art and provides an on-orbit calibration method for a satellite-borne laser radar, which can realize the on-orbit calibration of the satellite-borne laser radar without relying on a calibration field, and can be applied to the geometric positioning of the satellite-borne laser radar.

[0005] In order to solve the above technical problems, the present invention discloses an on-orbit calibration method for a space-borne laser radar, comprising:

[0006] Step 1, select a calibration area and lay out a target field in the calibration area;

[0007] Step 2, controlling the satellite to maneuver from the conventional orbit to the calibration orbit;

[0008] Step 3, predicting the satellite attitude and orbit information of the descending orbit segment in advance;

[0009] Step 4: In the satellite orbit descending phase, the onboard laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the ground distribution of the laser light intensity in the satellite orbit descending phase are determined according to the satellite attitude orbit information of the satellite orbit descending phase predicted in advance and the position information of the target field;

[0010] Step 5, predicting the satellite attitude and orbit information of the orbit raising phase in advance;

[0011] Step 6: During the satellite orbit raising phase, the onboard laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the ground distribution of the laser light intensity during the satellite orbit raising phase are determined according to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field;

[0012] Step 7, repeating steps 3 to 6, revisiting the target field multiple times in the satellite orbit descending and orbit ascending stages, and obtaining data obtained by multiple revisit measurements and solutions;

[0013] Step 8: perform laser pointing and ranging calibration and light output energy calibration based on the data obtained from multiple revisit measurements and solutions;

[0014] Step 9: After the calibration is completed, control the satellite to maneuver from the calibration orbit to the conventional orbit.

[0015] The above-mentioned on-orbit calibration method of the satellite-borne laser radar also includes: determining the theoretical position of the laser footprint according to the installation matrix of the satellite-borne laser radar and the satellite attitude orbit information; and laying out the target field in the calibration area according to the theoretical position of the laser footprint.

[0016] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, in the satellite orbit descending segment, the satellite-borne laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the laser light intensity distribution on the ground of the satellite orbit descending segment are determined according to the satellite attitude orbit information of the orbit descending segment and the position information of the target field predicted in advance, including:

[0017] During the satellite orbit reduction phase, the satellite-borne laser radar is controlled to start working in the target area. According to the satellite attitude orbit information of the orbit reduction phase predicted in advance and the position information of the target area, the satellite-borne laser radar light emission time and small-angle satellite attitude maneuvers are adjusted so that the footprint of the satellite-borne laser radar falls on the target area when it is turned on. When the emitted light of the satellite-borne laser radar shines on the target area, the target is illuminated, and the laser ranging value of the satellite orbit reduction phase, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground are measured and solved. Among them, the small-angle satellite attitude maneuvers include: small-angle roll, pitch and yaw maneuvers.

[0018] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, during the satellite orbit raising phase, the satellite-borne laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the laser light intensity distribution on the ground of the satellite orbit raising phase are determined according to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field, including:

[0019] During the satellite orbit raising phase, the onboard laser radar is controlled to start working in the target area. According to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target area, the onboard laser radar light emission time and small-angle satellite attitude maneuvers are adjusted so that the footprint of the onboard laser radar falls on the target area of ​​the target area when it is turned on. The target is lit when the emitted light of the onboard laser radar shines on the target area, and the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit raising phase are measured and solved. Among them, the small-angle satellite attitude maneuvers include: small-angle roll, pitch and yaw maneuvers.

[0020] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, the expression of the centroid position of the laser spot is as follows:

[0021]

[0022] in, represents the centroid position of the laser spot, represents the coordinates of the satellite's center of mass in the Earth-fixed coordinate system, Represents the transformation matrix from the International Celestial Reference Coordinate System to the Earth-Fixed Coordinate System,

[0023] Represents the transformation matrix from the satellite body coordinate system to the international celestial reference coordinate system,

[0024] represents the fixed offset between the laser emission reference point and the satellite mass center, ρ represents the laser ranging value, and α and β represent the laser pointing installation angle.

[0025] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, the expression of the laser light intensity distribution on the ground is as follows:

[0026]

[0027] Where I represents the energy density at position (x, y) in J·m -2 ; η represents the unidirectional attenuation coefficient of the laser in the atmosphere; ω0 represents the laser radius corresponding to 86.5% of the ground laser energy, in m; E0 represents the pulse energy, in J.

[0028] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, the error equations of laser pointing and ranging are expressed as follows:

[0029]

[0030] Among them, ρ0 represents the laser ranging value calculated using the laser pulse time difference;

[0031] The three coefficients a, b, and c are expressed as follows:

[0032]

[0033] The ranging error Δρ is expressed as follows:

[0034]

[0035] Among them, Δρ x , Δρ y and Δρ z are the three-axis components of Δρ respectively.

[0036] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, the resolution of adjusting the light emission time of the satellite-borne laser radar is in the microsecond level.

[0037] In the above-mentioned on-orbit calibration method of the satellite-borne laser radar, the distance of the satellite maneuvering from the conventional orbit to the calibration orbit does not exceed 20 km.

[0038] In the above-mentioned on-orbit calibration method of satellite-borne laser radar, the satellite attitude orbit information includes: satellite attitude information and satellite orbit information; wherein, the satellite attitude information is obtained through a star sensor and a star camera, and the satellite orbit information is obtained through a navigation receiver.

[0039] The present invention has the following advantages:

[0040] The present invention discloses an on-orbit calibration method for a satellite-borne laser radar, which comprises laying a target field in a selected calibration area, entering a calibration orbit through satellite orbit maneuvers, and acquiring laser spots multiple times and quickly without transporting the target field, thereby realizing on-orbit calibration of the satellite-borne laser radar. The on-orbit calibration method described in the present invention does not rely on a calibration field and can be applied to geometric positioning of a satellite-borne laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flowchart of the steps of an on-orbit calibration method of a satellite-borne laser radar in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] One of the core ideas of the present invention is to provide an on-orbit calibration method for a satellite-borne laser radar, that is, to lay a target field in a selected calibration area, to enter the calibration orbit through satellite orbit maneuvers, and to obtain laser spots multiple times and quickly without transporting the target field, thereby realizing on-orbit calibration of the satellite-borne laser radar through satellite maneuvers and laser emission time adjustment.

[0044] like Figure 1 In this embodiment, the on-orbit calibration method of the satellite-borne laser radar includes:

[0045] Step 1: Select a calibration area and lay out a target field in the calibration area.

[0046] In this embodiment, the calibration area is a relatively large area, such as Ningxia. The target field is a specific location, such as a piece of farmland, a piece of sloping land, etc. The theoretical position of the laser footprint can be determined according to the installation matrix of the satellite-borne laser radar and the satellite attitude orbit information; then, according to the theoretical position of the laser footprint, the target field is laid in the calibration area.

[0047] Step 2: Control the satellite to maneuver from the conventional orbit to the calibration orbit.

[0048] In this embodiment, the position of the ascending and descending intersection of the conventional orbit will drift, while the ascending and descending intersection of the calibration orbit is distributed in a specified area and is relatively stable, so that the target area can be quickly revisited. Therefore, when calibrating, the satellite needs to be controlled to maneuver from the conventional orbit to the calibration orbit. The distance from the conventional orbit to the calibration orbit does not exceed 20 km.

[0049] Step 3: Predict the satellite attitude and orbit information of the descending orbit segment in advance.

[0050] In this embodiment, the satellite attitude and orbit information may include: satellite attitude information and satellite orbit information; the satellite attitude information and satellite orbit information may be written into satellite auxiliary data and transmitted to the ground together with the satellite auxiliary data. Further, the satellite attitude information may be obtained through a star sensor and a star camera; the satellite orbit information may be obtained through a navigation receiver.

[0051] Step 4, during the satellite orbit descent segment, control the onboard laser radar to start working in the target area, and determine the laser ranging value, laser spot centroid position and laser intensity distribution on the ground of the satellite orbit descent segment based on the satellite attitude orbit information and target area position information predicted in advance.

[0052] In this embodiment, during the satellite orbit reduction stage, the satellite-borne laser radar is controlled to start working in the target field area; according to the satellite attitude orbit information of the orbit reduction stage and the position information of the target field predicted in advance, the satellite-borne laser radar light emission time and the small-angle satellite attitude maneuver are adjusted so that the footprint of the satellite-borne laser radar falls on the target field when it is turned on; when the satellite-borne laser radar emits light on the target field, the target is illuminated, and the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit reduction stage are measured and solved. Among them, the small-angle satellite attitude maneuver includes: small-angle side swing, pitch, and yaw maneuvers; the resolution of adjusting the light emission time of the satellite-borne laser radar can reach microseconds.

[0053] Furthermore, the laser rangefinder value can be obtained based on the echo information obtained from the satellite information. There are usually two ways to obtain the centroid position of the laser spot: one is to use the target position with the largest target response as the centroid position of the laser spot, and the other is to fit and weight all the lit targets and use the final result as the centroid position of the laser spot.

[0054] Step 5: Predict the satellite attitude and orbit information of the orbit raising phase in advance.

[0055] Step 6, during the satellite orbit raising phase, control the onboard laser radar to start working in the target field area, and determine the laser ranging value, laser spot centroid position and laser intensity distribution on the ground of the satellite orbit raising phase according to the satellite attitude orbit information and target field position information predicted in advance.

[0056] In this embodiment, during the satellite orbit raising stage, the satellite-borne laser radar is controlled to start working in the target field area; according to the satellite attitude orbit information of the orbit raising stage and the position information of the target field predicted in advance, the satellite-borne laser radar light emission time and the small-angle satellite attitude maneuver are adjusted so that the footprint of the satellite-borne laser radar falls on the target field when it is turned on; when the satellite-borne laser radar emits light on the target field, the target is illuminated, and the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit raising stage are measured and solved. Among them, the small-angle satellite attitude maneuver includes: small-angle side swing, pitch, and yaw maneuvers; the resolution of adjusting the light emission time of the satellite-borne laser radar can reach microseconds.

[0057] Step 7, repeat steps 3 to 6, revisit the target field multiple times in the satellite orbit descending and orbit ascending segments, and obtain data obtained by multiple revisit measurements and solutions.

[0058] Step 8: Based on the data obtained from multiple revisit measurements and solutions, perform laser pointing and ranging calibration, and light output energy calibration.

[0059] In this embodiment, the error equations for laser pointing and ranging are expressed as follows:

[0060]

[0061] Among them, ρ0 represents the laser ranging value calculated using the laser pulse time difference;

[0062] The three coefficients a, b, and c are expressed as follows:

[0063]

[0064] The ranging error Δρ is expressed as follows:

[0065]

[0066] Among them, Δρ x , Δρ y and Δρ z are the three-axis components of Δρ respectively.

[0067] Based on the laser ranging values, laser spot centroid position and other data obtained by multiple revisit measurements and solutions, combined with the above-mentioned error equations of laser pointing and ranging, the calibration of laser pointing and ranging can be achieved through the least squares method.

[0068] Furthermore, based on the data of laser light intensity distribution on the ground obtained through multiple revisit measurements and solutions, the calibration of the output light energy can be achieved:

[0069]

[0070] Where N represents the number of effective passes over the target field.

[0071] Step 9: After the calibration is completed, control the satellite to maneuver from the calibration orbit to the conventional orbit.

[0072] In this embodiment, the expression of the centroid position of the laser spot is as follows:

[0073]

[0074] Among them, [X spot Y spot Z spot ] T represents the centroid position of the laser spot, represents the coordinates of the satellite's center of mass in the Earth-fixed coordinate system, Represents the transformation matrix from the International Celestial Reference Coordinate System to the Earth-Fixed Coordinate System,

[0075] Represents the transformation matrix from the satellite body coordinate system to the international celestial reference coordinate system,

[0076] It represents the fixed offset between the laser emission reference point and the satellite mass center, ρ represents the laser ranging value, α and β represent the laser pointing installation angles, α specifically refers to the angle between the projection of the laser light-emitting axis on the XOY plane of the body coordinate system and the positive direction of the X-axis, and β specifically refers to the angle between the laser light-emitting axis and its projection on the XOY plane.

[0077] In this embodiment, the laser energy is Gaussian distributed on the ground, so the distribution of laser light intensity on the ground can be expressed as:

[0078]

[0079] Where I represents the energy density at position (x, y) in J·m -2 ; η represents the unidirectional attenuation coefficient of the laser in the atmosphere; ω0 represents the laser radius corresponding to 86.5% of the ground laser energy, in m; E0 represents the pulse energy, in J.

[0080] Based on the above embodiment, a specific example is given below for explanation.

[0081] S1, select a calibration area: In this embodiment, a certain area in northern Ningxia is selected as the calibration area.

[0082] S2, lay out the target field in the calibration area.

[0083] The target field is a specific location, such as a piece of farmland, a piece of sloping land, etc. The theoretical position of the laser footprint is obtained according to the installation matrix of the satellite-borne laser radar and the satellite attitude orbit information, and the target field is laid according to the theoretical position of the laser footprint. The center of the target field detector position is:

[0084]

[0085] S3, controls the satellite to maneuver from the conventional orbit to the calibration orbit.

[0086] The position of the ascending and descending nodes of the conventional orbit drifts. The revisit period of the satellite in this embodiment is 73 days, and the spacing between adjacent tracks on the equator is 36 km. After the satellite maneuvers to the calibration orbit, the satellite can quickly revisit the target area in a short time interval; the calibration orbit is designed as shown in Table 1 below. Taking into account the revisit period and the fuel required for orbit adjustment, orbit No. 4 is selected as the calibration orbit, that is, the satellite maneuvers 1.0297 km to achieve a revisit of the target field in the 4-day descending orbit segment. Since the laser radar can also work at night, calibration work is also arranged in the satellite ascending orbit segment to improve the calibration efficiency. Therefore, considering the mode of simultaneous calibration of ascending and descending orbits, the target field can be revisited twice in 4 days.

[0087] Serial number Track height adjustment, km (conventional track - calibration track) Revisit period (days) 1 75.1856 2 2 25.9721 3 3 123.5249 3 4 1.0297 4 5 -14.0451 5 6 45.7640 5 7 104.2925 5

[0088] Table 1, schematic diagram of calibration track design

[0089] S4, predict the satellite attitude and orbit information of the descending orbit segment in advance.

[0090] After the satellite maneuvers to the calibration orbit, the satellite attitude information is obtained through the star sensor and star camera, and the satellite orbit information is obtained through the navigation receiver. The satellite attitude information and satellite orbit information are written into the satellite auxiliary data and transmitted to the ground together with the satellite auxiliary data.

[0091] S5, in the satellite orbit descending segment, control the satellite-borne laser radar to start working in the target area, adjust the satellite-borne laser radar light emission time and small-angle satellite attitude maneuvers according to the satellite attitude orbit information of the orbit descending segment predicted in advance and the position information of the target area, so that the footprint of the satellite-borne laser radar falls on the target area when it is turned on; when the emitted light of the satellite-borne laser radar shines on the target area, the target is lit, and the laser ranging value, laser spot centroid position and laser light intensity distribution on the ground of the satellite orbit descending segment are measured and solved.

[0092] The laser ranging value can be obtained based on the echo information obtained from the on-board information: the distance value from the satellite to the target field is determined based on the laser round-trip time information obtained by the satellite, and the ranging value is corrected using atmospheric hydrology, solid tide and other information to obtain an accurate distance value.

[0093] There are usually two ways to obtain the centroid position of the laser spot: Method 1: The target position with the largest target response is used as the centroid position of the laser spot; Method 2: All lit targets are fitted and weighted, and the final result is used as the centroid position of the laser spot.

[0094] For method 2, the calculation formula involved is as follows:

[0095]

[0096] Among them, A i represents the response intensity of the ith target, (xi,yi) represents the position of the ith target, and n represents the number of targets.

[0097] The laser energy is Gaussian distributed on the ground, so the laser intensity distribution on the ground can be expressed as:

[0098]

[0099] Among them, I can be based on It is obtained that A represents the target response intensity, d represents the distance between adjacent targets; η provides a specific value in combination with local meteorological information during calibration; ω0=25m; and the pulse energy E0 can be calculated.

[0100] S6, predicting the satellite attitude and orbit information of the orbit raising phase in advance. This is similar to step S4 and will not be described in detail.

[0101] S7, in the satellite orbit raising phase, control the satellite-borne laser radar to start working in the target field area; according to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field, adjust the satellite-borne laser radar light emission time and small-angle satellite attitude maneuvers, so that the footprint of the satellite-borne laser radar falls on the target field when it is turned on; when the satellite-borne laser radar emits light on the target field, the target is lit, and the laser ranging value, laser spot centroid position and laser light intensity distribution on the ground of the satellite orbit raising phase are measured and solved.

[0102] Due to orbital drift, when the satellite passes over the target field again, the laser spot may not fall exactly into the target field. There are two ways to make adjustments, namely, fine-tuning the light emission time of the onboard laser radar and small-angle satellite attitude maneuvers.

[0103] The measurement and calculation of the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground during the satellite orbit raising segment are similar to step S5 and will not be repeated here.

[0104] S8, repeating steps S4 to S7, revisiting the target field multiple times in the satellite orbit descending and ascending segments, and acquiring data obtained by multiple revisit measurements and solutions.

[0105] S9, based on the data obtained from multiple revisit measurements and solutions, laser pointing and ranging calibration, and light output energy calibration are performed.

[0106] S10, after the calibration is completed, the satellite is controlled to maneuver from the calibration orbit to the conventional orbit.

[0107] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0108] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for on-orbit calibration of a space-borne laser radar, characterized in that: include: Step 1, select a calibration area and lay out a target field in the calibration area; Step 2, controlling the satellite to maneuver from the conventional orbit to the calibration orbit; Step 3, predicting the satellite attitude and orbit information of the descending orbit segment in advance; Step 4: In the satellite orbit descending phase, the onboard laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the ground distribution of the laser light intensity in the satellite orbit descending phase are determined according to the satellite attitude orbit information of the satellite orbit descending phase predicted in advance and the position information of the target field; Step 5, predicting the satellite attitude and orbit information of the orbit raising phase in advance; Step 6: During the satellite orbit raising phase, the onboard laser radar is controlled to start working in the target field area, and the laser ranging value, the laser spot centroid position and the ground distribution of the laser light intensity during the satellite orbit raising phase are determined according to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field; Step 7, repeating steps 3 to 6, revisiting the target field multiple times in the satellite orbit descending and orbit ascending stages, and obtaining data obtained by multiple revisit measurements and solutions; Step 8: perform laser pointing and ranging calibration and light output energy calibration based on the data obtained from multiple revisit measurements and solutions; Step 9: After the calibration is completed, the satellite is controlled to maneuver from the calibration orbit to the conventional orbit; During the satellite orbit descent phase, the onboard laser radar is controlled to start working in the target field area. According to the satellite attitude orbit information of the orbit descent phase predicted in advance and the position information of the target field, the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit descent phase are determined, including: In the satellite orbit descending phase, the satellite-borne laser radar is controlled to start working in the target field area; according to the satellite attitude orbit information of the orbit descending phase predicted in advance and the position information of the target field, the satellite-borne laser radar light emission time and the small-angle satellite attitude maneuver are adjusted so that the footprint of the satellite-borne laser radar falls on the target field when it is turned on; when the satellite-borne laser radar emits light on the target field, the target is illuminated, and the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit descending phase are measured and solved; among them, the small-angle satellite attitude maneuver includes: small-angle roll, pitch and yaw maneuvers; During the satellite orbit raising phase, the onboard laser radar is controlled to start working in the target field area. According to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field, the laser ranging value, the center of mass position of the laser spot and the distribution of the laser light intensity on the ground of the satellite orbit raising phase are determined, including: In the satellite orbit raising phase, the satellite-borne laser radar is controlled to start working in the target field area; according to the satellite attitude orbit information of the orbit raising phase predicted in advance and the position information of the target field, the satellite-borne laser radar light emission time and small-angle satellite attitude maneuvers are adjusted so that the footprint of the satellite-borne laser radar falls on the target field when it is turned on; when the satellite-borne laser radar emits light on the target field, the target is illuminated, and the laser ranging value, laser spot centroid position and laser light intensity distribution on the ground of the satellite orbit raising phase are measured and solved; among them, the small-angle satellite attitude maneuvers include: small-angle roll, pitch and yaw maneuvers; The expression of the laser spot centroid position is as follows: Among them, [X spot Y spot Z spot ] T represents the centroid position of the laser spot, represents the coordinates of the satellite's center of mass in the Earth-fixed coordinate system, Represents the transformation matrix from the International Celestial Reference Coordinate System to the Earth-Fixed Coordinate System, Represents the transformation matrix from the satellite body coordinate system to the international celestial reference coordinate system, represents the fixed offset between the laser emission reference point and the satellite mass center, ρ represents the laser ranging value, and α and β represent the laser pointing installation angle; The expression of laser intensity distribution on the ground is as follows: Where I represents the energy density at position (x, y) in J·m -2 ; η represents the unidirectional attenuation coefficient of the laser in the atmosphere; ω0 represents the laser radius corresponding to 86.5% of the ground laser energy, in m; E0 represents the pulse energy, in J.

2. The on-orbit calibration method of a space-borne laser radar according to claim 1, characterized in that: Also includes: The theoretical position of the laser footprint is determined based on the installation matrix of the satellite-borne laser radar and the satellite attitude and orbit information; based on the theoretical position of the laser footprint, the target field is laid out in the calibration area.

3. The on-orbit calibration method of a space-borne laser radar according to claim 1, characterized in that: The error equations for laser pointing and ranging are expressed as follows: Among them, ρ0 represents the laser ranging value calculated using the laser pulse time difference; The three coefficients a, b, and c are expressed as follows: The ranging error Δρ is expressed as follows: Among them, Δρ x , Δρ y and Δρ z are the three-axis components of Δρ respectively.

4. The on-orbit calibration method of a space-borne laser radar according to claim 1, characterized in that: The resolution of adjusting the light emission timing of the satellite-borne laser radar is in microseconds.

5. The on-orbit calibration method of a space-borne laser radar according to claim 1, characterized in that: The distance that the satellite maneuvers from the conventional orbit to the calibration orbit does not exceed 20km.

6. The on-orbit calibration method of a space-borne laser radar according to claim 1, characterized in that: Satellite attitude orbit information, including: satellite attitude information and satellite orbit information; wherein, satellite attitude information is obtained through star sensors and star cameras, and satellite orbit information is obtained through navigation receivers.

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