A multi-mode observation method and system based on hyperspectral UAV remote sensing

Abstract

The invention discloses a multi-mode observation method and system based on hyperspectral unmanned aerial vehicle remote sensing, including: a ground reflection end arranged on the ground, used to reflect the direct solar spectrum into the ground direct solar spectrum and then incident on the pupil platform; the pupil platform is carried on the unmanned aerial vehicle, used to carry out spectral observation including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and the sky direct solar spectrum of 0° to 90°, the limb scattering spectrum of 0°, the ground scattering spectrum of 0° to ‑30°, and the pitch angle of the ground direct solar spectrum of ‑30° to ‑90° reflected by the ground reflection end and the azimuth angle of 180° in front of the unmanned aerial vehicle. The invention can realize multi-mode large-angle observation of the pitch angle of ‑90° to 90° and the azimuth angle of 180° range based on the hyperspectral unmanned aerial vehicle remote sensing payload, and realize all-round observation by rotating the unmanned aerial vehicle, thereby improving the practicality of the hyperspectral unmanned aerial vehicle remote sensing payload and the reliability of data monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical remote sensing, and in particular relates to a multi-mode observation method and system based on hyperspectral unmanned aerial vehicle remote sensing. Background Art

[0002] As a cutting-edge atmospheric environment monitoring technology, hyperspectral UAV remote sensing has shown great potential in monitoring complex and high-concentration atmospheric pollutant emissions due to its unique advantages. This technology not only breaks through the limitations of traditional monitoring methods, but also provides a more efficient and accurate monitoring method. Compared with satellite remote sensing technology, the core advantage of hyperspectral UAV remote sensing is that it is completely unaffected by cloud cover. Hyperspectral UAV remote sensing also has a higher spatial and temporal resolution, which means that it can capture more detailed and accurate atmospheric pollution information, providing more powerful data support for environmental protection and governance.

[0003] In addition, the concealment and flexibility of hyperspectral UAV remote sensing are also its advantages that cannot be ignored. Due to the small size, light weight and easy operation of small UAVs, they can easily perform flight operations without attracting attention. This concealment enables hyperspectral UAV remote sensing to efficiently observe the interior of the factory without going deep into the factory area, thereby realizing effective monitoring and tracing of atmospheric pollutants emitted by industrial parks. This non-contact monitoring method not only improves monitoring efficiency, but also reduces monitoring costs, bringing more convenience to environmental protection work.

[0004] However, despite the many advantages of hyperspectral UAV remote sensing technology, it still faces some challenges and limitations in practical application. Among them, the problem of being unable to effectively observe large depression angles during ground measurement due to the limited flight altitude of UAVs is particularly prominent. Large depression angle observation refers to observations within the range of 30° to 90° (-30° to -90°) horizontally downward, which is crucial for a comprehensive and accurate understanding of atmospheric pollutant emissions. However, due to the limitation of the flight altitude of UAVs, hyperspectral UAV remote sensing often cannot cover a large depression angle range when conducting ground measurements, which greatly limits its observation range and observation effect. When the UAV flies at a low altitude, the hyperspectral remote sensing equipment it carries cannot capture the pollutant emissions within a large range below the ground, which may not only lead to the lack and inaccuracy of monitoring data, but also affect the accurate tracing and positioning of atmospheric pollutant emission sources. Therefore, how to overcome the limitation of the flight altitude of UAVs and improve the observation capability of hyperspectral UAV remote sensing for large depression angles is one of the current problems that need to be solved urgently.

[0005] On the other hand, the current ground-based sky observation instruments (0° to 90°) also have certain limitations. These instruments are usually installed at measurement sites or vehicle-mounted platforms to observe the concentration and distribution of pollutants in the atmosphere. However, due to the obstruction of trees and buildings, these instruments often have blind spots during the observation process, resulting in incomplete and inaccurate monitoring data. Especially in complex environments such as cities, where buildings are dense and trees are lush, ground-based sky observation instruments are more susceptible to obstruction and interference, which affects the accuracy and reliability of monitoring results.

[0006] Therefore, in order to make up for the defects of existing hyperspectral UAV remote sensing large-angle observation and make full use of the advantages of hyperspectral UAV remote sensing to solve the problem of blind spots in existing ground instrument measurements, a remote sensing technology that can be carried on a UAV and perform multi-mode observation is very necessary. Summary of the invention

[0007] In view of the above, the purpose of the present invention is to provide a multi-mode observation method and system based on hyperspectral UAV remote sensing, which inherits the flexibility and high temporal and spatial resolution of hyperspectral UAV remote sensing, and expands the observation angle through the coordinated setting of the ground reflection end and the entrance-pupil gimbal, so that the observation mode of hyperspectral UAV remote sensing is expanded to six modes, realizing multi-mode large-angle observation of -90° to 90° pitch angle and 180° azimuth angle, which helps to realize more comprehensive and accurate monitoring of atmospheric pollutant emissions.

[0008] In order to achieve the above-mentioned invention object, the technical solution provided by the present invention is as follows:

[0009] An embodiment of the present invention provides a multi-mode observation system based on hyperspectral UAV remote sensing, comprising: a ground reflection end and an entrance pupil gimbal;

[0010] The ground reflection end is arranged on the ground, and is used to reflect the direct solar spectrum into the ground direct solar spectrum and then incident on the entrance pupil platform, so that the entrance pupil platform can observe a large depression angle range of -30° to -90° to the ground;

[0011] The entrance-pupil gimbal replaces the original spectrum collection part of the hyperspectral UAV payload, is set up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload, and is used for full-angle multi-mode spectral observation including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and sky direct solar spectrum of 0° to 90°, the edge scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, and the pitch angle of the ground direct solar spectrum of -30° to -90° reflected by the ground reflection end and the azimuth angle of 180° in front of the UAV.

[0012] Preferably, the ground reflection end comprises: a reflector, a substrate, a fixing device, a small electric cylinder and a light flux detector;

[0013] The reflector is formed by arranging a plurality of regular hexagonal plane mirrors with metal materials as the substrate, and is attached to the front of the substrate, with the front facing the sky;

[0014] The substrate is a thin metal plate used to carry the reflector;

[0015] The fixing device is evenly fixed on the edge of the substrate, and the small electric cylinder is fixed on the center of the back of the substrate, with the back facing the ground. The fixing device is used to apply downward pressure to the substrate on all sides, and the small electric cylinder is used to apply upward thrust to the center of the substrate, so that the substrate drives the reflector to undergo a slight deformation with a convex middle and concave edges;

[0016] The light flux detector is fixed at the center of the front side of the substrate and is used to identify the UAV and monitor whether there is sunlight reflected back by the entrance pupil gimbal.

[0017] Preferably, the surface of the reflector is coated with a high-reflection film, and the high-reflection band of the high-reflection film is selected according to the strong absorption band of the target trace gas inverted by the hyperspectral UAV payload, and the required curvature radius of the reflector is 100m to 500m.

[0018] Preferably, the light flux detector is implemented as follows:

[0019] The light flux detector uses a wide-angle camera with a field of view of 120° or more. After distortion correction, the drone is identified through a recognition algorithm. When the ground reflection end successfully reflects the light to the drone, a light spot reflected by the entrance pupil gimbal will appear in the middle of the identified drone.

[0020] Alternatively, the luminous flux detector uses a small field of view camera with an undistorted field of view angle of less than or equal to 60°. Through the rotation of the motor, the small field of view camera is constantly tracking and aiming at the drone. When the ground reflector successfully reflects light to the drone, a light spot reflected by the corner reflector will appear in the middle of the identified drone.

[0021] Preferably, the entrance pupil platform comprises: a pitch angle right angle prism, an azimuth angle right angle prism, a lens, a spectrometer, and a corner reflector;

[0022] The pitch angle right angle prism is used to receive the multi-mode spectrum and refract it to the azimuth angle right angle prism, and then the azimuth angle right angle prism refracts it to the lens, and the light passing through the lens is focused into the optical fiber and then enters the spectrometer for detection;

[0023] The corner reflector is used to receive the direct solar spectrum from the ground and reflect it back to the ground reflection end.

[0024] Preferably, the lens adopts a 0.5-inch lens barrel and lens, the lens meets the numerical aperture NA of the optical fiber, the lens part adopts at least one plano-convex lens with the convex surface outward, and the lens also includes a detachable light attenuator to prevent direct sunlight from being too strong to damage the spectrometer.

[0025] Preferably, the size of the pitch angle right angle prism and the azimuth angle right angle prism is less than or equal to 15×15×15 mm, and the incident surface of the pitch angle right angle prism does not block the circular field of view of the lens, so that the incident surface does not become the aperture stop of the lens.

[0026] Preferably, the entrance pupil gimbal further comprises: an imaging auxiliary module, and a space and communication module;

[0027] The imaging auxiliary module is used to record the field of view area observed by the camera and provide real-time feedback to the operator, and to calculate the surface albedo in the field of view area based on the observation data of the camera and the lens to assist in later inversion and imaging, wherein the camera and the lens observe the same direction;

[0028] The space and communication module is used to measure the parameters of the entrance-pupil gimbal, including latitude and longitude, altitude, pitch angle, azimuth angle and roll angle, and return the parameter information to the hyperspectral UAV payload and operator.

[0029] Preferably, the entrance-pupil gimbal further comprises: a pitch angle servo motor, an azimuth angle servo motor and a roll angle servo motor;

[0030] The pitch angle servo motor is used to rotate the four parts of the pitch angle right angle prism, the corner reflector, the imaging auxiliary module, and the space and communication module fixed together to control the entrance pupil gimbal to observe different pitch angles;

[0031] The azimuth servo motor is used to rotate the azimuth right-angle prism, the pitch right-angle prism, the corner reflector, the imaging auxiliary module, and the space and communication module to control the entrance pupil gimbal to observe different azimuth angles;

[0032] The roll angle servo motor is used to control the movement of the entrance-pupil gimbal in the roll direction, and together with the pitch angle servo motor and the azimuth angle servo motor, controls the observation angle of the entrance-pupil gimbal to be an absolute angle relative to the ground, which does not change with the change of the drone's attitude.

[0033] To achieve the above-mentioned purpose of the invention, an embodiment of the present invention further provides a multi-mode observation method based on hyperspectral UAV remote sensing, which is implemented by using the above-mentioned multi-mode observation system based on hyperspectral UAV remote sensing, and includes the following steps:

[0034] The ground reflection end is arranged on the ground, and the direct solar spectrum is reflected by the ground reflection end as the ground direct solar spectrum and then incident on the entrance-pupil gimbal, so that the entrance-pupil gimbal can observe a large depression angle range of -30° to -90° to the ground;

[0035] The entrance-pupil gimbal replaces the original spectrum collection part of the hyperspectral UAV payload, is set up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload. The entrance-pupil gimbal is used to perform full-angle multi-mode spectral observations, including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and sky direct solar spectrum from 0° to 90°, the edge scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, the pitch angle of the ground direct solar spectrum from -30° to -90° reflected by the ground reflection end, and the azimuth angle of 180° in front of the UAV.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention expands the observation angle by coordinating the ground reflection end and the entrance-pupil gimbal, thereby making up for the defect that the hyperspectral UAV remote sensing cannot effectively observe the ground at a large pitch angle (-30° to -90°). While inheriting the flexibility and high spatiotemporal resolution of the hyperspectral UAV remote sensing, the observation modes of the hyperspectral UAV remote sensing are expanded to six, realizing multi-mode large-angle observation of the pitch angle in the range of -90° to 90° and the azimuth angle in the range of 180°, and being able to realize all-round observation of the azimuth angle in the range of 360° by rotating the UAV, thereby improving the accuracy and reliability of the monitoring data. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 Schematic diagram of the overall structure of a multi-mode observation system based on hyperspectral UAV remote sensing provided by an embodiment of the present invention;

[0040] Figure 2 is a schematic structural diagram of a ground reflection end provided by an embodiment of the present invention;

[0041] Figure 3 is a schematic diagram of the structure of an entrance-pupil gimbal provided in an embodiment of the present invention;

[0042] Figure 4 It is a flow chart of a multi-mode observation method based on hyperspectral UAV remote sensing provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0044] The inventive concept of the present invention is: in order to inherit the characteristics of high spatiotemporal resolution, high concealment and high flexibility of the hyperspectral UAV payload, and at the same time solve the defects of large pitch angle (such as -30° to -90°) observation of the existing hyperspectral UAV payload and the problem of blind spots in ground instrument measurements, hyperspectral UAV remote sensing needs to perform multi-mode atmospheric pollution source monitoring. The embodiment of the present invention is based on the hyperspectral UAV payload and provides a multi-mode observation method and system based on hyperspectral UAV remote sensing. Through the cooperation of the ground reflection end 1 and the entrance pupil gimbal 2, the hyperspectral UAV remote sensing payload can be helped to achieve -90° to 90° pitch angle and 180° azimuth observation, as well as solar scattered light observation and solar direct light observation.

[0045] Figure 1 Schematic diagram of the overall structure of the multi-mode observation system based on hyperspectral UAV remote sensing provided by the embodiment of the present invention. Figure 1 As shown, the embodiment provides a multi-mode observation system based on hyperspectral UAV remote sensing, including: a ground reflection end 1 and an entrance pupil gimbal 2. The ground reflection end 1 is arranged on the ground, and the direct solar spectrum is reflected as the ground direct solar spectrum by the ground reflection end 1 and then incident on the entrance pupil gimbal 2, so as to realize the large-angle ground observation of the hyperspectral UAV payload from -30° to -90°. The entrance pupil gimbal 2 replaces the original spectrum collection part of the hyperspectral UAV payload, is set up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload. With the help of the ground reflection end 1, the entrance pupil gimbal 2 with two observation dimensions can observe: the pitch angle includes the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and the sky direct solar spectrum of 0° to 90°, the limb scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, and the ground direct solar spectrum of -30° to -90° reflected by the ground reflection end 1; the azimuth angle includes the range of 180° in front of the UAV, and the UAV is rotated to cover the range of 360°. That is, the overall observation range is a hemisphere of 2π solid angles, and after the drone rotates as a whole, the observation range can reach a sphere of 4π solid angles.

[0046] The ground reflection end 1 is used to reflect the direct sunlight onto the entrance pupil platform 2. Figure 2 As shown, the ground reflection end 1 includes: a reflector 11, a substrate 12, a fixing device 13, a small electric cylinder 14 and a light flux detector 15.

[0047] The reflector 11 is composed of a plurality of regular hexagonal plane mirrors with metal materials as the substrate. The curvature radius of the plane should be between 100m and 500m. The use of the regular hexagonal reflector 11 is suitable for assembling multiple reflectors 11, and can be seamlessly laid on substrates 12 of different sizes and shapes according to different needs. Figure 2 The substrate 12 is circular. The reflector 11 is coated with a high reflectivity film. The high reflectivity band of the high reflectivity film is selected according to the strong absorption band of the target trace gas inverted by the hyperspectral UAV payload. For example, if the hyperspectral UAV payload is inverting ozone and ozone precursor NO x For gases with strong absorption bands such as UV-visible and VOCs, a UV-visible high-reflection film with a band of 280nm-450nm should be applied. In addition, in order to reduce the error of spectral inversion in the later stage, the average reflectivity of the high reflectivity band should be greater than 95%, and the reflectivity error in the high reflectivity band should be less than 5%.

[0048] The substrate 12 is a thin metal plate used to support the reflector 11. When the two are fixed, the reflector 11 should be completely attached to the substrate 12. The reflector 11 using a metal material as a base is also to be able to deform to a certain extent when the substrate 12 is deformed.

[0049] The fixing devices 13 are used to fix the substrate 12. The number of the fixing devices 13 should be as large as possible. The specific number and position depend on the size and shape of the substrate 12. Figure 2 Only the circular base plate 12 and four fixing devices 13 are shown.

[0050] The small electric cylinder 14 is fixed on the same plane as the fixture 13 and is placed at the exact center of the back of the substrate 12 to give an upward thrust to the center of the substrate 12, while the corresponding multiple fixtures 13 will give a downward pressure on the four sides of the substrate 12, and the thinner substrate 12 will undergo a slight deformation with a convex middle and concave sides. This is to solve the problem that when the drone is far away from the reflector, it is difficult to reflect direct sunlight to the entrance pupil gimbal 2 on the drone if a flat reflector is used. Although the existing convex reflector can convert direct sunlight into divergent reflected light, which can be easily reflected to the entrance pupil gimbal 2 on the drone, the smaller radius of curvature will cause the reflected light to have an excessively large divergence angle, which will result in the luminous flux of the reflected light received by the entrance pupil gimbal 2 being weak and unable to meet the inversion requirements of the hyperspectral drone payload. According to calculations, the curvature radius of the reflector 11 that satisfies both the divergence of reflected light and the strong light flux is between 100m and 500m, which places extremely high demands on the processing of the reflector 11. By using the embodiment of the present invention, the required curvature radius can be met by slightly deforming the substrate 12. By adjusting the length of the small electric cylinder 14, it can adapt to different distances from the drone to the ground reflector end 1.

[0051] The light flux detector 15 is arranged at the center of the front surface of the substrate 12. Figure 3 The corner reflectors 26 in the entrance pupil gimbal 2 are used in combination to identify the drone and monitor whether there is sunlight reflected back by the corner reflectors 26. The light flux detector 15 has two implementation modes:

[0052] The first method is to use a wide-angle camera with a field of view of greater than or equal to 120°. After distortion correction, the drone is identified through a recognition algorithm. When the ground reflection end 1 successfully reflects light to the drone, a light spot reflected by the corner reflector 26 will appear in the middle of the identified drone. The advantage of this method is that the wide-angle camera is stationary relative to the ground reflection end 1, and the algorithm is relatively simple. However, sunlight may have a certain impact on the recognition algorithm of the wide-angle camera, resulting in the inability to normally identify the drone. In addition, since the drone is far away, an ultra-clear camera is required to identify the outline of the drone.

[0053] The second method is to use a small field of view camera with a distortion-free field of view angle of less than or equal to 60°. By rotating the motor, the small field of view camera is constantly tracking and aiming at the drone. When the ground reflector 1 successfully reflects light to the drone, a light spot reflected back by the corner reflector 26 will appear in the middle of the identified drone. The advantage of this method is that as long as the drone is within the camera's field of view, the drone image in the camera image occupies more pixels, making it easier to identify the drone. As long as the drone avoids flying in the direction of the sun, it will basically not be affected by sunlight. However, this method needs to be combined with a motor and a tracking algorithm needs to be added.

[0054] In the embodiment, Figure 1 As shown, the pupil gimbal 2 is fixed at the front end of the drone. Figure 3 As shown, the entrance-pupil gimbal 2 includes: a pitch angle right-angle prism 21, an azimuth angle right-angle prism 22, a lens 23, a spectrometer 24, an imaging auxiliary module 25, a corner reflector 26, a space and communication module 27, a pitch angle servo motor 28, an azimuth angle servo motor 29 and a roll angle servo motor 210.

[0055] Among them, the pitch right-angle prism 21, the azimuth right-angle prism 22 and the lens 23 are the main optical path systems of the entrance pupil platform 2, which are used to receive scattered light and direct light signals, and transmit the light signals to the spectrometer for processing through optical fibers. The pitch right-angle prism 21 can be rotated at a pitch angle, and the azimuth right-angle prism 22 can be rotated at an azimuth angle to reflect the light signals of different detection areas into the lens 23. The lens 23 is used to focus the light path into the optical fiber and finally enter the spectrometer 24. In order to increase the light signal entering the spectrometer 24 as much as possible, the lens in the lens 23 needs to meet the numerical aperture NA of the optical fiber, that is, the image-side aperture angle of the parallel light passing through the lens needs to be slightly larger than the acceptance angle of the optical fiber. At the same time, in order to improve the final imaging quality, specifically, the ground area observed each time does not overlap with the adjacent ground area observed, and no scattered light signals from other areas enter the optical system, then the aberration of the optical system should be considered. In order to minimize the aberration, the lens part adopts at least one plano-convex lens with the convex surface outward. In the embodiment, the comprehensive effect of using two plano-convex lenses with the convex surface outward is the best. Since the entrance pupil platform 2 is mounted on the drone, it is necessary to focus on the weight of one component on the basis of realizing the function. Here, the size of the pitch angle right angle prism 21 and the azimuth angle right angle prism 22 needs to be no more than 15×15×15mm, and the lens 23 adopts a 0.5-inch lens barrel and lens. It should be noted that the size and distance of the two prisms must meet the observation field of view requirements of the lens 23, that is, the incident surface of the pitch angle right angle prism 21 will not block the circular field of view of the lens 23, and the surface will not become the aperture stop of the lens 23. Finally, in order to undertake the task of observing the zenith scattering spectrum, there must be no obstruction directly above the pitch angle right angle prism 21 (including the structure of the entrance pupil platform 2 itself, the drone fuselage and the drone rotor), to ensure that the observation field of view range of the zenith scattering spectrum is consistent with the field of view range of the ground scattering spectrum observed from the ground.

[0056] The imaging auxiliary module 25 includes a high-definition camera, a small circuit board carrying an image recognition algorithm and a surface albedo algorithm based on a radiation transfer model. Its function is, on the one hand, to record the field of view area observed by the high-definition camera and provide real-time feedback to the operator; on the other hand, it is used to identify the field of view area based on the observation data of the camera and lens 23, calculate the surface albedo in the field of view area, and assist in later inversion and imaging. Since the observation direction of the lens 23 is determined by the pitch angle right angle prism 21 and the azimuth angle right angle prism 22, and the imaging auxiliary module 25 and the pitch angle right angle prism 21 are fixed together, the observation direction of the lens 23 is consistent with the observation direction of the imaging auxiliary module 25. The image of the area currently being measured is recorded by a high-definition camera, and the image is semantically recognized using a pre-trained model, and a specific semantic category is assigned to each pixel in the image to distinguish different surfaces in the image. Then, according to the surface albedo corresponding to different surface types, the comprehensive albedo of the area in the image that overlaps with the observation field of the lens 23 is calculated, and the calculation of the comprehensive albedo is weighted averaged according to the area of ​​different surfaces in the overlapping area. The imaging auxiliary module 25 is only used when measuring the scattering spectrum, and it needs to be turned off when measuring the direct sunlight spectrum to prevent damage to the camera in the module.

[0057] The function of the corner reflector 26 is to reflect light from different directions back in the direction opposite to the original incident direction. The corner reflector 26 only returns a small part of the sunlight reflected by the ground reflection end 1 to the original path when measuring the direct sunlight spectrum. When the light flux detector 15 in the ground reflection end 1 receives the light signal from the corner reflector 26, it means that the ground reflection end 1 has successfully reflected the direct sunlight onto the entrance pupil gimbal 2, and then the direct sunlight spectrum can be measured.

[0058] The space and communication module 27 includes a positioning module, a gyroscope module and a communication module. The positioning module can return the latitude, longitude and altitude information of the pupil gimbal 2 in real time. The gyroscope module can return the current pitch angle, azimuth angle and roll angle of the module in real time. The communication module is used to return the information on the pupil gimbal 2 to the hyperspectral UAV payload and the ground operator.

[0059] The entrance pupil platform 2 also includes three servo motors: a pitch angle servo motor 28, an azimuth angle servo motor 29, and a roll angle servo motor 210. The four parts of the entrance pupil platform 2, namely, the pitch angle right angle prism 21, the imaging auxiliary module 25, the corner reflector 26, and the space and communication module 27, are fixed together. Figure 3 The pitch angle servo motor 28 can control the pupil platform 2 to observe different pitch angles by rotating these four parts. The azimuth angle servo motor 29 can control the pupil platform 2 to observe different azimuth angles by rotating the azimuth angle right angle prism 22 and these four parts.

[0060] For the observation of the scattering spectrum of the sky and the ground, the pitch angle servo motor 28 and the azimuth angle servo motor 29 cooperate with the pitch angle and azimuth angle fed back in real time by the space and communication module 27 to perform observations at different angles, thereby realizing two-dimensional scanning of the ground and the sky. In addition, although the azimuth angle can be rotated by rotating the drone, for the observation of the direct spectrum, it is necessary to always face the direct end of the sun or the ground, and the drone cannot be directly rotated, and it is difficult to perform real-time feedback. Therefore, it is necessary to design a two-dimensional rotating structure to realize flexible adjustment of the azimuth angle and the pitch angle. For the observation of the direct spectrum of the ground sun, the pitch angle servo motor 28 and the azimuth angle servo motor 29 cooperate with the longitude and latitude and altitude fed back in real time by the space and communication module 27, as well as the longitude and latitude and altitude of the ground reflection end 1 received by the space and communication module 27, to calculate the relative direction of the ground reflection end 1 and the entrance pupil platform 2, so that the observation direction of the entrance pupil platform 2 is always toward the ground reflection end 1, and the reflected direct sunlight is measured. The same is true for the sky solar direct spectrum. The relative angle between the sun and the entrance pupil platform 2 is calculated based on the longitude, latitude and altitude fed back in real time by the space and communication module 27, as well as the time information. Then the pitch angle servo motor 28 and the azimuth angle servo motor 29 make the observation direction of the entrance pupil platform 2 always face the sun to measure the direct sunlight.

[0061] In order to make the optical observation of the entrance-pupil gimbal 2 more stable and eliminate the influence of the vibration of the drone body and the deflection of the body during flight on the optical path to a certain extent, a certain feedback module is necessary. The pitch angle servo motor 28 is adjusted according to the real-time pitch angle feedback from the gyroscope module in the space and communication module 27, the azimuth angle servo motor 29 is adjusted according to the real-time azimuth angle feedback from the gyroscope module in the space and communication module 27, and the roll angle servo motor 210 is adjusted according to the real-time roll angle feedback from the gyroscope module in the space and communication module 27. Through the cooperation of the three servo motors, the angle observed by the entrance-pupil gimbal 2 is an absolute angle relative to the ground, that is, the observation angle does not change with the change of the drone's attitude.

[0062] Based on the same inventive concept, Figure 4 As shown, the embodiment of the present invention also provides a multi-mode observation method based on hyperspectral UAV remote sensing, comprising the following steps:

[0063] S1, the ground reflection end is arranged on the ground, and the direct solar spectrum is reflected by the ground reflection end as the ground direct solar spectrum and then incident on the entrance pupil gimbal, so that the entrance pupil gimbal can observe a large depression angle range of -30° to -90° to the ground;

[0064] S2, replaces the original spectrum collection part of the hyperspectral UAV payload with an entrance-pupil gimbal, sets up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload. The entrance-pupil gimbal is used to perform full-angle multi-mode spectral observations, including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and sky direct solar spectrum of 0° to 90°, the limb scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, and the ground direct solar spectrum of -30° to -90° reflected by the ground reflection end, and the pitch angle of 180° in the azimuth range in front of the UAV.

[0065] It should be noted that the multi-mode observation system based on hyperspectral UAV remote sensing provided in the above embodiment belongs to the same inventive concept as the multi-mode observation method based on hyperspectral UAV remote sensing. The specific implementation process is detailed in the embodiment of the multi-mode observation method based on hyperspectral UAV remote sensing, which will not be repeated here.

[0066] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-mode observation system based on hyperspectral UAV remote sensing, characterized in that: include: Ground reflection end and entrance pupil gimbal; The ground reflection end is arranged on the ground, and is used to reflect the direct solar spectrum into the ground direct solar spectrum and then incident on the entrance pupil platform, so that the entrance pupil platform can observe a large depression angle range of -30° to -90° to the ground; Specifically, the ground reflection end includes: a reflector, a substrate, a fixing device, a small electric cylinder and a light flux detector; the reflector is formed by an array of multiple regular hexagonal plane mirrors with metal materials as the substrate, and is attached to the front of the substrate, with the front facing the sky; the substrate is a thin metal plate used to carry the reflector; the fixing device is evenly fixed on the edge of the substrate, the small electric cylinder is fixed at the center of the back of the substrate, with the back facing the ground, the fixing device is used to apply downward pressure on the four sides of the substrate, and the small electric cylinder is used to apply upward thrust to the center of the substrate, so that the substrate drives the reflector to undergo a slight deformation with a convex middle and concave edges; the light flux detector is fixed at the center of the front of the substrate, and is used to identify the drone and monitor whether there is sunlight reflected back by the entrance pupil gimbal; The entrance-pupil gimbal replaces the original spectrum collection part of the hyperspectral UAV payload, is set up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload, and is used for full-angle multi-mode spectral observation including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and sky direct solar spectrum of 0° to 90°, the limb scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, and the pitch angle of the ground direct solar spectrum of -30° to -90° reflected by the ground reflection end, and the azimuth angle of 180° in front of the UAV; Specifically, the entrance pupil gimbal includes: a pitch angle right-angle prism, an azimuth angle right-angle prism, a lens, a spectrometer, and a corner reflector; the pitch angle right-angle prism is used to receive a multi-mode spectrum and refract it to the azimuth angle right-angle prism, and then refracted to the lens by the azimuth angle right-angle prism, and the light passing through the lens is focused into the optical fiber and then enters the spectrometer for detection; the corner reflector is used to receive the ground solar direct spectrum and reflect it back to the ground reflection end.

2. The multi-mode observation system based on hyperspectral UAV remote sensing according to claim 1 is characterized in that: The surface of the reflector is coated with a high-reflection film, and the high-reflection band of the high-reflection film is selected according to the strong absorption band of the target trace gas inverted by the hyperspectral UAV payload, and the required curvature radius of the reflector is 100m~500m.

3. The multi-mode observation system based on hyperspectral UAV remote sensing according to claim 1 is characterized in that: The implementation of the light flux detector includes: The light flux detector uses a wide-angle camera with a field of view of 120° or more. After distortion correction, the drone is identified through a recognition algorithm. When the ground reflection end successfully reflects the light to the drone, a light spot reflected by the entrance pupil gimbal will appear in the middle of the identified drone. Alternatively, the luminous flux detector uses a small field of view camera with an undistorted field of view angle of less than or equal to 60°. Through the rotation of the motor, the small field of view camera is constantly tracking and aiming at the drone. When the ground reflector successfully reflects light to the drone, a light spot reflected by the corner reflector will appear in the middle of the identified drone.

4. The multi-mode observation system based on hyperspectral UAV remote sensing according to claim 1 is characterized in that: The lens uses a 0.5-inch lens barrel and lens. The lens meets the numerical aperture NA of the optical fiber. The lens part uses at least one plano-convex lens with the convex surface outward. The lens also includes a detachable light attenuator to prevent direct sunlight from being too strong to damage the spectrometer.

5. The multi-mode observation system based on hyperspectral UAV remote sensing according to claim 1 is characterized in that: The size of the elevation right angle prism and the azimuth right angle prism is less than or equal to 15×15×15 mm, and the incident surface of the elevation right angle prism does not block the circular field of view of the lens, so that the incident surface does not become an aperture stop of the lens.

6. The multi-mode observation system based on hyperspectral UAV remote sensing according to any one of claims 1, 4 or 5, characterized in that: The entrance pupil platform further includes: an imaging auxiliary module, and a space and communication module; The imaging auxiliary module is used to record the field of view area observed by the camera and provide real-time feedback to the operator, and to calculate the surface albedo in the field of view area based on the observation data of the camera and the lens to assist in later inversion and imaging, wherein the camera and the lens observe the same direction; The space and communication module is used to measure the parameters of the entrance-pupil gimbal, including latitude and longitude, altitude, pitch angle, azimuth angle and roll angle, and return the parameter information to the hyperspectral UAV payload and operator.

7. The multi-mode observation system based on hyperspectral UAV remote sensing according to claim 6 is characterized in that: The entrance-pupil gimbal further comprises: a pitch angle servo motor, an azimuth angle servo motor and a roll angle servo motor; The pitch angle servo motor is used to rotate the four parts of the pitch angle right angle prism, the corner reflector, the imaging auxiliary module, and the space and communication module fixed together to control the entrance pupil gimbal to observe different pitch angles; The azimuth servo motor is used to rotate the azimuth right-angle prism, the pitch right-angle prism, the corner reflector, the imaging auxiliary module, and the space and communication module to control the entrance pupil gimbal to observe different azimuth angles; The roll angle servo motor is used to control the movement of the entrance-pupil gimbal in the roll direction, and together with the pitch angle servo motor and the azimuth angle servo motor, controls the observation angle of the entrance-pupil gimbal to be an absolute angle relative to the ground, which does not change with the change of the drone's attitude.

8. A multi-mode observation method based on hyperspectral UAV remote sensing, implemented by using the multi-mode observation system based on hyperspectral UAV remote sensing according to any one of claims 1 to 7, characterized in that: The following steps are involved: The ground reflection end is arranged on the ground, and the direct solar spectrum is reflected by the ground reflection end as the ground direct solar spectrum and then incident on the entrance-pupil gimbal, so that the entrance-pupil gimbal can observe a large depression angle range of -30° to -90° to the ground; The entrance-pupil gimbal replaces the original spectrum collection part of the hyperspectral UAV payload, is set up at the front end of the hyperspectral UAV payload, and is carried on the UAV together with the hyperspectral UAV payload. The entrance-pupil gimbal is used to perform full-angle multi-mode spectral observations, including the zenith scattering spectrum of 90° vertically upward, the sky scattering spectrum and sky direct solar spectrum from 0° to 90°, the edge scattering spectrum of 0°, the ground scattering spectrum of 0° to -30°, the pitch angle of the ground direct solar spectrum from -30° to -90° reflected by the ground reflection end, and the azimuth angle of 180° in front of the UAV.

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