Surface reflectance measuring device and method for simulating satellite observation angle

Abstract

The invention discloses a surface reflectance measuring device and method for simulating a satellite observation angle, and the device comprises a support, a one-dimensional steering engine holder, a two-dimensional steering engine holder, a ground object spectrometer and a circuit control box, and the circuit control box is internally provided with a main control module, a GPS positioning module, an electronic compass and a satellite orbit calculation module. The GPS positioning module obtains the geographic position and time parameters of an observation landmark, the electronic compass obtains the azimuth angle information of the observation direction, the satellite orbit calculation module calculates the transit time and observation angle of a satellite, and the main control module controls the one-dimensional steering engine holder to rotate. The measuring lens rotates from an initial position to a reference plate facing a fixed position and to a surface position facing no shadow, and the main control module controls the two-dimensional steering engine holder to drive the measuring lens to rotate. According to the measuring device, the error influence caused by BRDF model measurement and correction can be reduced, and the accuracy and efficiency of earth surface direction reflectivity measurement are improved.

Description

Technical Field

[0001] The invention relates to the technical field of satellite payload radiation calibration and surface product verification, and in particular to a surface reflectivity measuring device simulating a satellite observation angle. Background Art

[0002] Satellite remote sensing is an important means of monitoring the characteristics of large-area objects. However, the on-orbit performance of remote sensors will decay due to the space environment and the degradation of their own parameters. In order to ensure the accuracy of the data, radiation correction is required. The site substitution calibration method is a commonly used radiation correction method. It selects a large area of ​​uniform and stable site on the surface, conducts synchronous ground and satellite observations when the satellite passes by, and uses the radiation transfer model to calculate the apparent reflectivity of satellite observations. The radiation correction can be achieved by comparing it with the actual observations on the satellite.

[0003] The surface reflectivity is a key parameter that needs to be observed during radiation correction. When using the ground stabilization field to perform radiation calibration on the on-orbit satellite payload, due to the non-Lambertian nature of the ground objects, the surface directional characteristics in the satellite observation direction are different at different angles. Therefore, it is necessary to obtain the surface directional reflectivity consistent with the satellite observation direction. In actual operation, it is not easy to measure the surface reflectivity at the satellite observation angle. It is necessary to calculate the satellite transit time and observation angle according to the satellite orbit, and adjust the observation angle of the ground object spectrometer in time to carry out synchronous measurement. To adjust the observation angle of the ground object spectrometer, a compass plus an angle measurement device (such as a protractor) can be used to determine the azimuth and zenith angle of the observation respectively, but the error of manual angle adjustment is large. In addition, the satellite angle needs to be recalculated and the angle of the spectrometer needs to be adjusted every time the satellite passes, which is inefficient.

[0004] Therefore, the commonly used method for measuring the directional reflectivity of the ground surface is: using a ground object spectrometer to vertically measure the radiation values ​​of the ground surface and the reference plate at the moment of satellite transit, and then using the ratio method to calculate the vertical reflectivity of the ground surface. In order to obtain the directional reflectivity of the ground surface consistent with the satellite observation direction angle, it is necessary to use the bidirectional reflectance distribution function BRDF (bidirectional reflectance distribution function) model to correct the observation direction of the satellite payload. Among them, the BRDF model is a semi-empirical model obtained by fitting after measuring and screening the ground surface at different zenith angles and different azimuth angles in different time periods within one or several days in clear weather, combined with the physical characteristics of the ground object type, to describe the quantitative relationship of the non-Lambertian nature of the ground surface. When using the BRDF model to calculate the directional reflectivity of the ground surface, it is necessary to input the solar zenith angle, solar azimuth angle, zenith angle and azimuth angle of the satellite observation direction at the moment of satellite transit into the model to calculate the correction factor, and then multiply it by the real-time measured vertical reflectivity of the ground surface to obtain the directional reflectivity of the ground surface in the observation direction at the moment of satellite transit.

[0005] The method of measuring the surface reflectivity vertically and correcting it to the satellite observation direction using the BRDF model is difficult to measure synchronously when the satellite passes by because the BRDF model measurement process is complicated and requires covering more solar angles and observation angles to ensure the accuracy of the model fitting. Usually, it is measured once a year or several years. However, since the surface characteristics change over time, the same BRDF model will produce different degrees of errors in different seasons and years. In addition, the angle coverage of BRDF measurement is limited. Taking the BRDF test measured in the Dunhuang field as an example, the test usually starts from 10 o'clock to 16 o'clock, the solar zenith angle is between 20° and 50°, the observation zenith angle is 15° intervals, ranging from -75° to 75°, and the observation azimuth angle is 30° intervals, ranging from 0° to 360°. The BRDF model obtained in this way corrects the vertically observed surface reflectivity, which will have large errors at large solar zenith angles and large observation angles. Summary of the invention

[0006] In view of this, the present invention proposes a surface reflectivity measurement device that simulates the satellite observation angle, adopts a GPS positioning module and a satellite orbit calculation module to obtain the satellite's transit time and observation angle in real time, and controls the observation lens to complete the measurement of the reference plate and the surface directional radiation, and obtains the surface directional reflectivity consistent with the satellite observation angle, thereby reducing the error impact caused by the BRDF model measurement and correction, and improving the accuracy and efficiency of the surface directional reflectivity measurement.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A surface reflectivity measuring device simulating satellite observation angle, comprising:

[0009] A bracket, wherein a one-dimensional steering gear platform is installed on the top of the bracket, a horizontal crossbar is installed on the horizontal turntable of the one-dimensional steering gear platform, a two-dimensional steering gear platform is installed on one end of the crossbar, and a measuring lens is installed on the two-dimensional turntable of the two-dimensional steering gear platform;

[0010] A ground object spectrometer, wherein a host of the ground object spectrometer is electrically connected to a measuring lens;

[0011] and a circuit control box, wherein the circuit control box is installed on the cross bar, and a main control module, a GPS positioning module, an electronic compass and a satellite orbit calculation module are arranged in the circuit control box, and the main control module is electrically connected to the GPS positioning module, the electronic compass, the satellite orbit calculation module, a controller of a one-dimensional steering gear pan-tilt and a controller of a two-dimensional steering gear pan-tilt respectively, the GPS positioning module is used to obtain the geographical location information and time parameters of the observation target, the electronic compass is used to obtain the azimuth information of the observation direction, the satellite orbit calculation module is used to retrieve the data in the skyfield library and calculate the time and observation angle of the satellite transit, the main control module controls the rotation of the one-dimensional steering gear pan-tilt based on the data obtained by the GPS positioning module and the electronic compass, so that when the satellite transits, the measuring lens rotates from the initial position to the reference plate facing the fixed position and to the position facing the surface without shadow, and the main control module controls the two-dimensional steering gear pan-tilt to drive the measuring lens to rotate based on the data obtained by the satellite orbit calculation module.

[0012] In order to better implement the above technical solution, optionally, a counterweight is installed on the crossbar, and the counterweight and the two-dimensional servo gimbal are respectively arranged at two ends of the crossbar.

[0013] Optionally, the support is a tripod with adjustable height.

[0014] Optionally, it includes an L-shaped adapter plate and a lens mounting sleeve, the lens mounting sleeve is mounted on the optical fiber part of the measuring lens end, the lens mounting sleeve includes a locking sleeve part, an external thread connection part and a spiral protective sleeve part which are connected in sequence, one plate body of the L-shaped adapter plate is fixedly arranged on the two-dimensional turntable of the two-dimensional servo gimbal, and the external thread connection part is fixedly screwed through the other plate body of the L-shaped adapter plate.

[0015] Optionally, a top screw is threadedly provided radially on the locking sleeve, and the inner end of the top screw presses against the side wall of the optical soldering part at the measuring lens end, so that the optical soldering part at the measuring lens end is fixedly fitted to the inner wall of the locking sleeve.

[0016] A method for measuring the surface reflectivity of a simulated satellite observation angle, using the surface reflectivity measuring device described above, and comprising the following steps:

[0017] S10, the GPS positioning module automatically obtains the geographical location information and time parameters of the observation target location, wherein the geographical location information of the observation target location includes the latitude and longitude parameters of the observation target location;

[0018] S20, the satellite orbit calculation module retrieves the data in the skyfield library and calculates the satellite transit time and observation angle;

[0019] S30, when the satellite passes by, the main control module controls the one-dimensional servo gimbal to make the horizontal turntable drive the crossbar to rotate horizontally to the reference plate at a fixed position, the measuring lens vertically measures the spectrum of the reference plate, and the electronic compass obtains the azimuth information of the observation direction;

[0020] S40, the satellite orbit calculation module calculates the solar azimuth based on the data in S30, and the main control module controls the rotation of the one-dimensional servo gimbal based on the solar azimuth data to rotate the measuring lens to a position facing the surface without shadows;

[0021] S50, the main control module controls the two-dimensional servo gimbal to rotate according to the observation angle of the transit and drives the measuring lens to rotate to a direction consistent with the zenith angle and azimuth angle of the satellite observation, and after the measuring lens is stable, the measuring lens measures the surface spectrum;

[0022] S60, dividing the surface spectral data measured by the ground object spectrometer by the spectral data of the reference plate to obtain the surface directional reflectivity.

[0023] Beneficial effects of the present invention:

[0024] The present invention discloses a surface reflectivity measuring device and a measuring method for simulating satellite observation angles. The device adopts a GPS positioning module and a satellite orbit calculation module to obtain the transit time and observation angle of the satellite in real time, and automatically controls the rotation of a one-dimensional steering gear platform and a two-dimensional steering gear platform, thereby driving the observation lens to rotate synchronously to complete the measurement of the reference plate and the surface directional radiation, thereby directly obtaining the surface directional reflectivity consistent with the satellite observation angle, reducing the interference of manual operation, improving the measurement efficiency and the accuracy of angle positioning, and eliminating the correction deviation caused by the surface vertical measurement combined with the BRDF direction correction, thereby greatly improving the accuracy and efficiency of the surface directional reflectivity measurement, and providing efficient and accurate technical and data support for the satellite transit radiation correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a three-dimensional schematic diagram of a device for measuring surface reflectivity simulating a satellite observation angle according to an embodiment of the present invention;

[0026] Figure 2 yes Figure 1 A three-dimensional schematic diagram of the connection between the one-dimensional servo gimbal and the crossbar;

[0027] Figure 3 yes Figure 1 The front view of the connection between the one-dimensional servo gimbal and the crossbar;

[0028] Figure 4 yes Figure 1 A three-dimensional schematic diagram of the installation position of the two-dimensional servo gimbal and the measuring lens at one angle;

[0029] Figure 5 yes Figure 1 A three-dimensional schematic diagram of the installation of the 2D servo gimbal and the measuring lens from another angle;

[0030] Reference numerals:

[0031] Bracket 10, one-dimensional servo platform 20, connecting seat 21, cross bar 30, two-dimensional servo platform 40, L-shaped adapter plate 401, lens mounting sleeve 402, locking sleeve part 4021, external thread connecting part 4022, spiral protective sleeve part 4023, top screw 4024, measuring lens 50, circuit control box 60, counterweight body 70. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments, wherein the same components are represented by the same reference numerals.

[0033] See also Figures 1 to 5 An embodiment of the present invention discloses a surface reflectivity measuring device that simulates satellite observation angles, which includes a bracket 10, a ground object spectrometer, and a circuit control box 60.

[0034] like Figure 1 As shown, a one-dimensional servo platform 20 is installed at the top of the bracket 10, a horizontal cross bar 30 is installed on the horizontal turntable of the one-dimensional servo platform 20, a two-dimensional servo platform 40 is installed at one end of the cross bar 30, a measuring lens 50 is installed on the two-dimensional turntable of the two-dimensional servo platform 40, and the main unit of the ground feature spectrometer is electrically connected to the measuring lens 50.

[0035] In an embodiment of the present invention, the bracket 10 is a height-adjustable tripod. Specifically, the tripod has three telescopic gears, which can respectively achieve measuring heights of 0.6m, 1.1m and 1.6m. The bracket 10 is a finished structure in the prior art. A tripod is used as the bracket 10, which is easy to adjust and has high stability. In other optional embodiments, the bracket 10 is also a rod-shaped telescopic bracket 10.

[0036] like Figure 2 and Figure 3 As shown, in an embodiment of the present invention, the horizontal turntable of the one-dimensional servo gimbal 20 is equipped with a cross bar 30 through a connecting seat 21, the bottom of the connecting seat 21 is a connecting plate body 211, and the top of the connecting seat 21 is a pipe sleeve 212 with a locking screw. The connecting plate body 211 is connected to the horizontal turntable by screws penetrated through its edge, and the inner sleeve of the cross bar 30 is penetrated through the pipe sleeve 212 and locked by the locking screw. The cross bar 30 is installed in this way, which is convenient for adjusting the matching position of the cross bar 30 with the pipe sleeve 212, so that the operator can quickly and accurately adjust the position of the cross bar 30 according to the actual measurement requirements, which greatly improves the operability of the equipment and reduces the preliminary preparation time.

[0037] In the embodiment of the present invention, the cross bar 30 is a telescopic bar, and the length of the cross bar 30 can be adjusted according to usage requirements.

[0038] In an embodiment of the present invention, the one-dimensional servo platform 20 is equipped with a servo with a load of 60 kg, and the one-dimensional servo platform 20 can control the crossbar 30 to rotate and position at intervals of 0.2° within the range of 0 to 270°. The two-dimensional servo platform 40 is equipped with two servos with a load of 20 kg, wherein the first servo is used to drive the horizontal platform to rotate 0° to 360°, and the second servo drives the vertical platform to rotate -90° to 90°, thereby realizing the observation lens to rotate -90° to 90°, that is, to rotate -90° to 90° in the zenith angle direction. The use of the above-mentioned one-dimensional servo platform 20 and two-dimensional servo platform 40 can ensure that the measuring lens 50 can stably and accurately reach any angle position required to be measured, avoid measurement errors caused by angle deviation or equipment shaking, and greatly improve the reliability of measurement data.

[0039] like Figure 2 As shown, in an embodiment of the present invention, a counterweight body 70 is installed on the cross bar 30, and the counterweight body 70 and the two-dimensional servo platform 40 are respectively arranged at both ends of the cross bar 30, wherein different sections of the cross bar 30 are connected to the pipe sleeve 212, and the weight of the corresponding counterweight body 70 is different. The counterweight body 70 is composed of a plurality of counterweight blocks of different specifications, and the counterweight blocks are sleeved on the ends of the cross bar 30 and locked by nuts. The counterweight body 70 can balance the upward force of the two-dimensional servo platform 40 on the cross bar 30, so as to increase the stability of the cross bar 30 during rotation and measurement, and further improve the stability and accuracy of the measurement results.

[0040] like Figure 4 and Figure 5As shown, in the embodiment of the present invention, an L-shaped adapter plate 401 and a lens mounting sleeve 402 are included. The lens mounting sleeve 402 is sleeved on the optical fiber part at the end of the measuring lens 50. The lens mounting sleeve 402 includes a locking sleeve part 4021, an external thread connection part 4022 and a spiral protective sleeve part 4023 which are connected in sequence. One plate body of the L-shaped adapter plate 401 is fixedly mounted on the two-dimensional turntable of the two-dimensional servo gimbal 40 by a plurality of screws. The external thread connection part 4022 is fixedly screwed through the other plate body of the L-shaped adapter plate 401. The spiral protective sleeve part 4023 is a spiral plastic protective sleeve. The spiral protective sleeve part 4023 can be provided. The optical fiber part at the end of the measuring lens 50 is protected so that it is not easy to bend. A top screw 4024 is threadedly arranged in the radial direction of the locking sleeve 4021. The inner end of the top screw 4024 presses against the side wall of the optical fiber part at the end of the measuring lens 50, so that the optical fiber part of the measuring lens 50 is fixedly fitted to the inner wall of the locking sleeve 4021. The locking sleeve 4021 can be provided to lock the optical fiber part at the end of the measuring lens 50, thereby increasing the stability of the measuring lens 50. The use of the above-mentioned lens mounting sleeve 402 reduces data anomalies caused by optical fiber damage or lens looseness, prolongs the service life of the equipment, and reduces maintenance costs.

[0041] The circuit control box 60 is installed on the crossbar 30. The circuit control box 60 is provided with a main control module, a GPS positioning module, an electronic compass and a satellite orbit calculation module. The main control module is electrically connected to the GPS positioning module, the electronic compass, the satellite orbit calculation module, the controller of the one-dimensional steering gear pan-tilt 20 and the controller of the two-dimensional steering gear pan-tilt 40 respectively. The GPS positioning module is used to obtain the geographical location information and time parameters of the observation target. The electronic compass is used to obtain the azimuth information of the observation direction. The satellite orbit calculation module is used to retrieve the data in the skyfield library and calculate the time and observation angle of the satellite transit. The main control module controls the rotation of the one-dimensional steering gear pan-tilt 20 based on the data obtained by the GPS positioning module and the electronic compass, so that when the satellite transits, the measuring lens 50 rotates from the initial position to the reference plate facing the fixed position and to the position facing the surface without shadow. The main control module controls the two-dimensional steering gear pan-tilt 40 to drive the measuring lens 50 to rotate based on the data obtained by the satellite orbit calculation module.

[0042] In the present invention, it should be noted that Skyfield is a Python library for astronomical calculations and orbital mechanics, which is used for celestial position calculations, time processing, orbit calculation and analysis, astronomical observation simulation, and planetary ephemeris generation.

[0043] Based on the above-mentioned surface reflectivity measurement of a simulated satellite observation angle, the present invention also provides a surface reflectivity measurement method of a simulated satellite observation angle, comprising the following steps:

[0044] S10, the GPS positioning module automatically obtains the geographical location information and time parameters of the observation target location, and the geographical location information of the observation target location includes the latitude and longitude parameters of the observation target location;

[0045] S20, the satellite orbit calculation module retrieves the data in the skyfield library and calculates the satellite transit time and observation angle;

[0046] S30, when the satellite passes by, the main control module controls the one-dimensional steering gear pan / tilt 20 to make the horizontal turntable drive the crossbar 30 to rotate horizontally to the reference plate at a fixed position, the measuring lens 50 vertically measures the spectrum of the reference plate, and the electronic compass obtains the azimuth information of the observation direction;

[0047] S40, the satellite orbit calculation module calculates the solar azimuth based on the data in S30, and the main control module controls the one-dimensional steering gear platform 20 to rotate based on the solar azimuth data, so that the measuring lens 50 rotates to a position facing the surface without shadows;

[0048] S50, the main control module controls the two-dimensional rudder of the two-dimensional rudder 40 to rotate according to the observation angle of the transit and drives the measuring lens 50 to rotate to a direction consistent with the zenith angle and azimuth angle of the satellite observation. After the measuring lens 50 is stable, the measuring lens 50 measures the surface spectrum;

[0049] S60, dividing the surface spectral data measured by the ground object spectrometer by the spectral data of the reference plate to obtain the surface directional reflectivity.

[0050] In S30 - S40 , the main control module transmits control instructions to the controllers of the one-dimensional servo platform 20 and the two-dimensional servo platform 40 via the Bluetooth module.

[0051] The present invention discloses a surface reflectivity measuring device and a measuring method for simulating satellite observation angles. The device adopts a GPS positioning module and a satellite orbit calculation module to obtain the transit time and observation angle of the satellite in real time, and automatically controls the rotation of a one-dimensional steering gear platform 20 and a two-dimensional steering gear platform 40, thereby driving the observation lens to rotate synchronously to complete the measurement of the reference plate and the surface directional radiation, thereby directly obtaining the surface directional reflectivity consistent with the satellite observation angle, reducing the interference of manual operation, improving the measurement efficiency and the accuracy of angle positioning, and eliminating the correction deviation caused by the surface vertical measurement combined with the BRDF direction correction, thereby greatly improving the accuracy and efficiency of the surface directional reflectivity measurement, and providing efficient and accurate technical and data support for the satellite transit radiation correction.

[0052] The technical solution of the present invention is described in detail above in conjunction with specific embodiments, and the described specific embodiments are used to help understand the concept of the present invention. Derivations and modifications made by those skilled in the art based on the specific embodiments of the present invention also fall within the protection scope of the present invention.

Claims

1. A device for measuring surface reflectivity simulating satellite observation angle, characterized in that: include: A bracket (10), wherein a one-dimensional steering gear platform (20) is mounted on the top of the bracket (10), a horizontal crossbar (30) is mounted on the horizontal turntable of the one-dimensional steering gear platform (20), a two-dimensional steering gear platform (40) is mounted on one end of the crossbar (30), and a measuring lens (50) is mounted on the two-dimensional turntable of the two-dimensional steering gear platform (40); A ground object spectrometer, wherein a main unit of the ground object spectrometer is electrically connected to a measuring lens (50); and a circuit control box (60), the circuit control box (60) being mounted on the crossbar (30), the circuit control box (60) being provided with a main control module, a GPS positioning module, an electronic compass and a satellite orbit calculation module, the main control module being electrically connected to the GPS positioning module, the electronic compass, the satellite orbit calculation module, a controller of a one-dimensional steering gear pan-tilt platform (20) and a controller of a two-dimensional steering gear pan-tilt platform (40), respectively, the GPS positioning module being used to obtain geographical location information and time parameters of an observation target, the electronic compass being used to obtain information on the observation direction, and the satellite orbit calculation module being used to obtain information on the observation direction. Azimuth information, the satellite orbit calculation module is used to retrieve data in the skyfield library and calculate the satellite transit time and observation angle, the main control module controls the one-dimensional steering gear pan-tilt (20) to rotate based on the data obtained by the GPS positioning module and the electronic compass, so that when the satellite passes, the measuring lens (50) rotates from an initial position to a reference plate facing a fixed position and to a position facing a surface without a shadow, and the main control module controls the two-dimensional steering gear pan-tilt (40) to drive the measuring lens (50) to rotate based on the data obtained by the satellite orbit calculation module.

2. The device for measuring the surface reflectivity of a simulated satellite observation angle according to claim 1, characterized in that: A counterweight body (70) is installed on the crossbar (30), and the counterweight body (70) and the two-dimensional steering gear platform (40) are respectively arranged at two ends of the crossbar (30).

3. The device for measuring the surface reflectivity of a simulated satellite observation angle according to claim 1, characterized in that: The support (10) is a tripod with adjustable height.

4. The device for measuring surface reflectivity simulating satellite observation angle according to claim 1, characterized in that: The invention comprises an L-shaped adapter plate (401) and a lens mounting sleeve (402), wherein the lens mounting sleeve (402) is sleeved on the optical fiber part of the end of the measuring lens (50), and the lens mounting sleeve (402) comprises a locking sleeve part (4021), an external thread connection part (4022) and a spiral protective sleeve part (4023) which are connected in sequence, and one plate body of the L-shaped adapter plate (401) is fixedly arranged on the two-dimensional turntable of the two-dimensional steering gear platform (40), and the external thread connection part (4022) is fixedly screwed through the other plate body of the L-shaped adapter plate (401).

5. The device for measuring the surface reflectivity of a simulated satellite observation angle according to claim 4, characterized in that: A top screw (4024) is threadedly provided in the radial direction of the locking sleeve (4021), and the inner end of the top screw (4024) presses against the side wall of the optical soldering part at the end of the measuring lens (50), so that the optical soldering part at the end of the measuring lens (50) is fixedly fitted to the inner wall of the locking sleeve (4021).

6. A method for measuring surface reflectivity by simulating satellite observation angles, characterized in that: The surface reflectivity measuring device according to any one of claims 1 to 5 comprises the following steps: S10, the GPS positioning module automatically obtains the geographical location information and time parameters of the observation target location, wherein the geographical location information of the observation target location includes the latitude and longitude parameters of the observation target location; S20, the satellite orbit calculation module retrieves the data in the skyfield library and calculates the satellite transit time and observation angle; S30, when the satellite passes by, the main control module controls the one-dimensional steering gear platform (20) to make the horizontal turntable drive the crossbar (30) to rotate horizontally to the reference plate at a fixed position, the measuring lens (50) vertically measures the spectrum of the reference plate, and the electronic compass obtains the azimuth information of the observation direction; S40, the satellite orbit calculation module calculates the solar azimuth based on the data in S30, and the main control module controls the rotation of the one-dimensional steering gear platform (20) based on the solar azimuth data, so that the measuring lens (50) rotates to a position facing the ground surface without shadows; S50, the main control module controls the two-dimensional rudder of the two-dimensional rudder (40) to rotate according to the observation angle of the transit, and drives the measuring lens (50) to rotate to a direction consistent with the zenith angle and azimuth angle of the satellite observation, and after the measuring lens (50) is stabilized, the measuring lens (50) measures the surface spectrum; S60, dividing the surface spectral data measured by the ground object spectrometer by the spectral data of the reference plate to obtain the surface directional reflectivity.

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