A high-resolution, agile optics and laser integrated satellite imaging method

Abstract

The application provides a high-resolution agile optical and laser integrated satellite imaging method, which comprises the following steps: step one, acquiring the central point longitude and latitude of a satellite imaging plan target, an imaging orbit height, an imaging time length and scene parameters; step two, combining a satellite maneuvering capability to perform a symmetrical M satellite pointing imaging action sequence deduction with the central point of the target as the center to obtain an attitude maneuvering angle of each time; step three, according to the scene parameters T and the attitude maneuvering angle, sequentially judging the availability of laser data under M satellite imaging tasks; step four, marking different virtual channel marks on different types of working mode marks, laser data and engineering measurement data; and step five, recording and transmitting the optical, laser and auxiliary data according to the set working mode and signal path.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical remote sensing satellites, and particularly relates to a high-resolution agile optical and laser integrated satellite imaging method. BACKGROUND

[0002] Traditional mapping satellites obtain different view image pairs through multiple cameras at different angles to achieve high-precision stereo mapping, and a small number of mapping satellites are equipped with laser altimeters (such as ZY-3 and GF-7) to improve the height accuracy under the condition of no control points. Foreign high-resolution stereo imaging satellites (such as Worldview and GeoEye series satellites) obtain different view image pairs through satellite agility to achieve high-precision stereo positioning.

[0003] With the increasing demand for high spatial resolution and height information accuracy in space remote sensing, the concept of high-resolution agile optical and laser integrated imaging satellites has been gradually developed in China. The optical and laser integrated camera configured by the high-resolution agile optical and laser integrated imaging satellite adds a high-precision laser altimeter and a laser high-precision transceiver matching function compared with a traditional camera, and is a multi-dimensional information comprehensive acquisition space optical remote sensing system that can simultaneously realize high-resolution optical images and high-precision laser ranging information.

[0004] Currently, the imaging process of an optical mapping satellite with a laser does not need to swing the satellite platform for pointing, but only needs to perform strip push-broom imaging on a predetermined imaging area, which limits the flexibility of photographing non-nadir targets. The existing high-resolution agile optical satellite does not yet carry a laser rangefinder, and multi-angle stereo imaging does not need to consider the availability of laser echo data under different side-swing-pitch conditions and the matching and correlation of laser data and optical images. For the recently proposed high-resolution agile optical and laser integrated satellite, there is no public report on the design of its working mode. Therefore, it is particularly important and urgent to develop a high-resolution agile optical and laser integrated satellite imaging method to promote the engineering application of such a system. SUMMARY

[0005] The application proposes a high-resolution agile optical and laser integrated satellite imaging method, which realizes the combination of high-resolution agile multi-angle imaging and laser ranging mode on the same platform of a remote sensing satellite, effectively introduces laser ranging data into multi-angle image pair data to realize the simultaneous acquisition of high-resolution optical images and three-dimensional stereo information, and meets the requirements of stereo positioning accuracy and target photographing efficiency.

[0006] The application is implemented through the following technical solutions.

[0007] A high-resolution agile optical and laser integrated satellite imaging method, comprising the following steps:

[0008] Step one, obtaining the satellite imaging plan task target center point longitude and latitude, imaging orbit height, imaging time length and scene parameters;

[0009] Step two, according to the task target center point longitude and latitude, imaging orbit height and imaging time length, combined with the satellite maneuvering ability, the M satellite pointing imaging action sequence centered on the target center point is deduced, and the attitude maneuvering angle of each time is obtained;

[0010] Step three, according to the scene parameters T and the attitude maneuvering angle, the availability of laser data under M times satellite imaging task is judged in turn, if available, the laser channel is started to record, if not available, the laser channel is not started; If the cumulative laser start number N=0, this working mode is not applicable, and the process is ended.

[0011] Step four, different virtual channel identifiers are marked on the working mode identifier, laser data and engineering measurement data according to different types, and the data transmission subsystem alternately processes, arranges and stores the working mode identifier, laser data and engineering measurement data of each channel input to the data transmission subsystem according to the different virtual channel identifiers.

[0012] Step five, according to the set working mode and signal path, the optical, laser and auxiliary data are recorded and transmitted.

[0013] The beneficial effects of the present application are:

[0014] 1. The present application can realize integrated acquisition of multi-dimensional information such as optical image information and high-precision laser elevation information, ensure good matching accuracy between multi-dimensional information, and improve the application effect of multi-dimensional data;

[0015] 2. The present application adopts a method of deducing optical imaging with different attitude angles for multiple times in one orbit, simultaneously considers the applicability analysis of laser to different task scenes under multi-angle optical imaging working mode, allows optical and laser integrated imaging under certain satellite attitude angle and certain terrain slope, and improves the on-orbit practicability of the system;

[0016] 3. The present application proposes to mark 1 or multiple imaging data according to one working mode task, and provides a fast transmission path for different types of optical data, laser data, pointing correlation data and attitude and orbit data, ensures the synchronicity of different types of data obtained by the application system, and improves the data application efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the satellite optical and laser integrated working mode of the present application;

[0018] Figure 2 It is a flow chart of the high-resolution agile optical and laser integrated satellite imaging method of the present application.

[0019] Figure 3 The figure shows the relationship between the laser echo signal-to-noise ratio and the detection probability of an embodiment of the present application. DETAILED DESCRIPTION

[0020] Exemplary embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the embodiments shown and described herein are merely exemplary and are not intended to limit the scope of the present application, which is defined by the appended claims.

[0021] As shown in the figure, a high-resolution agile optical and laser integrated satellite imaging method of the present application specifically comprises the following steps: Figure 2 Step 1: Obtain the central point longitude and latitude (L, H) of a satellite imaging plan target, the imaging orbit height H, the imaging time length t, and the scene parameter T;

[0022] Step 2: According to the central point longitude and latitude (L, H) of the target, the imaging orbit height H, and the imaging time length t, and in combination with the satellite maneuvering capability, perform M satellite pointing imaging action sequence deduction (M is an odd number) centered on the target central point to obtain the attitude maneuvering angle of each time

[0023] Specifically:

[0024] 2.1 Let the maximum satellite attitude maneuvering angle be ±Φ, then the single-time satellite attitude change angle is According to the satellite maneuvering capability, set the attitude change The time required is

[0025] 2.2 If then the M-time satellite pointing imaging can be achieved for this task, and then the satellite attitude planning module uses the central point longitude and latitude (L, H) and the imaging number M to perform attitude planning to obtain the satellite attitude maneuvering combined angle of each time Otherwise, M = M-1, repeat step 2.1 until M = 3, if still not satisfied, go to step 2.3;

[0026] 2.3 When M = 1, then only 1-time satellite pointing imaging can be achieved for this task, and the satellite attitude maneuvering combined angle is

[0027] ​For example, consider a satellite with a maximum attitude maneuverability of ±60° and an orbital altitude of 500km. Its nadir movement speed is approximately 7km / s. For a 5-second imaging mission, to achieve 7 imaging operations per orbit, the attitude maneuverability needs to meet a requirement of 17° / 16s. If the imaging mission lasts 10 seconds, it must meet 17° / 11s; otherwise, the number of imaging operations must be reduced to 5, requiring an attitude maneuverability of 30° / 31s. If the satellite's attitude maneuverability is less than 60° / 113 seconds, it means that only one satellite pointing imaging operation can be achieved in this mission.

[0028] Step 3: Based on the scenario parameter T and attitude maneuver angle... The availability of laser data under M satellite imaging missions is determined sequentially. If the data is available, the laser channel is powered on and recorded. If the data is unavailable, the laser channel is not powered on. If the cumulative number of laser power-on attempts N = 0, this working mode is not applicable, and the process ends.

[0029] In this embodiment, the task scenario parameter T includes terrain slope θ and target reflectivity ρ.

[0030] In practice, the analysis methods differ depending on the laser detection system. The following description uses a simulated laser detection system as an example, and the specific steps are as follows:

[0031] 3.1 Based on the detection probability P d False alarm rate P f Determine the signal-to-noise ratio requirement for the satellite laser detection system ≥

[0032] SNR=f(P d =99%, P f =1%);

[0033] Wherein, the noise distribution follows a Gaussian probability density distribution, the relationship between the detection probability, false alarm rate, and signal-to-noise ratio of the laser detection system is given by the following formula:

[0034]

[0035] like Figure 3 As shown, based on the above formula, we obtain... Figure 3 The curves showing the relationship between detection probability and signal-to-noise ratio indicate that, under the conditions of false alarm rate <1% and detection probability 99%, the laser echo signal-to-noise ratio is required to be ≥5.36:1.

[0036] 3.2 Based on the signal-to-noise ratio of the aforementioned detection system, establish the parameters from {terrain slope θ, satellite attitude maneuvering angle}. From target reflectivity ρ to laser echo pulse width t r Then, the mapping model of the signal-to-noise ratio (SNR) of the detection system;

[0037] In this embodiment, the laser radar model in the form of signal-to-noise ratio of the laser detection system is as follows:

[0038]

[0039] wherein E tr is the single pulse energy of the emitted laser, t r is the half pulse width of the laser echo signal, NEP is the noise equivalent power, B is the noise bandwidth, D t is the transmitting aperture, D r is the receiving system aperture, η t is the optical efficiency of the transmitter, η r is the efficiency of the receiving system, and α is the atmospheric extinction coefficient, R is the atmospheric transmission path length, and L is the distance from the satellite to the target.

[0040] Because the laser echo pulse width model based on the terrain slope is as follows:

[0041]

[0042] wherein ω is the beam half width, Δt r is the laser echo pulse broadening, t r + Δt r is the broadened laser echo pulse width.

[0043] 3.3 Calculation of the signal-to-noise ratio of the detection system and determine whether the condition is met: If the condition is met, go to step four, otherwise, the optical and laser integrated satellite working mode is not applicable for this task, and the process is ended.

[0044] For example, according to the commercial hardware parameters, the optical and laser integrated satellite is designed, L is set to 500 km, B = 50 MHz, the optical efficiencies of the transmitter η t and the receiver η r are 0.6, the receiving aperture D r is 1.5 m, the transmitting aperture D t is 0.0762 m, the single pulse energy of the laser E tr is 20 mJ, the half pulse width of the laser echo signal t r is 6 ns, the reflectivity of the target is between 0.12 and 0.53 at the wavelength of 1.06 μm, the optical efficiencies of the transmitter η t and the receiver η r are both 0.6, the atmospheric extinction coefficient is between 4.092 × 10 -3 m -1 and 7.7 × 10 -5 m -1between, the extinction coefficient is selected as 5km, i.e. 5x10 -4 m -1 ; the beam half-width ω is 0.02mrad.

[0045] The laser echo width t under different terrain slope θ, satellite attitude maneuver synthetic angle and target reflectivity ρ is calculated. r(n) and the signal-to-noise ratio SNR of the laser detection system n , as shown in the following table.

[0046]

[0047]

[0048] According to the scene combinations in the above table that satisfy the laser echo signal-to-noise ratio ≥5.36, it can be known that:

[0049] Under flat and hilly conditions (<6°), when the target reflectivity is 0.3: the satellite side swing within 15° can be realized.

[0050] Under mountain conditions (6°-15°), when the target reflectivity is 0.3: the satellite side swing within 10° can be realized.

[0051] Under high mountain conditions (>15°), when the target reflectivity is 0.3: the satellite side swing within 5° can be realized.

[0052] According to the above experiment, it can be seen that the method greatly expands the applicability of optical laser integrated imaging in different scenes.

[0053] Step four, the working mode identifier, laser data and engineering measurement data (including laser pointing correlation measurement data, attitude and orbit data) are marked with different virtual channel identifiers according to different types, and the data transmission subsystem alternately processes, arranges and stores the working mode identifiers, laser data and engineering measurement data of each channel input to the data transmission subsystem according to the different virtual channel identifiers.

[0054] Step five, according to the set working mode and signal path, record and downlink process the optical, laser and auxiliary data.

[0055] In specific implementation, the specific steps are as follows:

[0056] 5.1 Send an "integrated working mode" instruction package through the integrated electronic subsystem, control the computer to analyze the instruction package and complete one or more attitude adjustments according to the set working mode; the integrated camera computer analyzes the instruction package and completes the recording of corresponding optical, laser and auxiliary data according to the set working mode, and transmits to the data transmission subsystem;

[0057] 5.2 The data transmission subsystem packs the data once or multiple times according to the working mode task and marks the data, and the data is transmitted to the ground processing system through the data transmission channel. After the data transmission channel transmits the data, the payload data is recovered and processed.

[0058] 5.3 The ground processing system demodulates and decodes the data, extracts the working mode and the spacecraft identifier from the data according to the AOS format, and separates and analyzes the different virtual channel baseband data according to the specified virtual channel identifier and VCDU counter.

[0059] 5.4 The ground processing system judges the working mode. If it is M = 1 mode, the processing generates the geometric correction product of the high-resolution optical image system and the three-dimensional data product of the laser point, and the superimposed fusion product of the two. In this mode, the laser detection obtains the ground laser M ≥ 3 mode, and the ground generates the high-resolution optical stereo image pair through joint adjustment processing, and improves the elevation accuracy of the stereo image pair.

[0060] Those skilled in the art will realize that the embodiments described herein are for the purpose of helping the reader understand the principles of the present application, and should be understood as not being limited to such specific embodiments and examples. Those skilled in the art can make various other specific modifications and combinations according to the technical inspiration disclosed in the present application without departing from the spirit of the present application, and these modifications and combinations are still within the scope of protection of the present application.

Claims

1. A high-resolution agile optical and laser integrated satellite imaging method, characterized in that, Comprising the following steps: Step one, obtaining the central point of the satellite imaging plan target latitude and longitude, imaging orbit height, imaging time length and scene parameters; Step two, according to the central point of the task target latitude and longitude, imaging orbit height and imaging time length, combined with the satellite maneuvering ability, the M satellite pointing imaging action sequence centered on the target center point is deduced, and the attitude maneuvering angle of each time is obtained; The specific steps are as follows: 2.1 Let the maximum satellite attitude maneuver angle be ± , then the single satellite attitude change angle is ; Setting the attitude change according to the satellite maneuvering capability The time required is ; 2.2 If , then this task can achieve M times of satellite pointing imaging, and then the satellite attitude planning module uses the central point longitude and latitude (L, H) and the imaging times M to plan the attitude, and the satellite attitude maneuver synthetic angle of each time is , otherwise M = M-1, repeat step 2.1 until M = 3, if still not satisfied, go to step 2.3; 2.3 When M = 1, the satellite can only realize one satellite pointing imaging, and the satellite attitude maneuver synthesis angle is ; Step three, according to the scene parameters and attitude maneuver angle, the availability of laser data under M satellite imaging tasks is judged in turn, if available, the laser channel is turned on to record, if not available, the laser channel is not turned on; if the cumulative number of laser on N = 0, this mode is not applicable, end the process; the specific steps are as follows: 3.1 According to the detection probability , false alarm rate Determine the signal-to-noise ratio requirement of satellite laser detection system ≥ ; Wherein, the noise distribution is according to Gaussian probability density distribution, then the relationship between the detection probability, false alarm rate and the signal-to-noise ratio of laser detection system is given by the following formula: （1） 3.2 The mapping model from {terrain slope , satellite attitude maneuver synthetic angle , target reflectivity } to laser return pulse width , and then to the probe system signal-to-noise ratio is established according to the probe system signal-to-noise ratio. 3.3 Calculate the signal-to-noise ratio of the detection system And determine whether the condition is met: If it is met, go to step four, otherwise, the optical and laser integrated satellite working mode is not applicable for this task, and the process ends. Step four, different virtual channel identifiers are marked on the working mode identifier, laser data and engineering measurement data according to different types, and the data transmission subsystem alternately processes, arranges and stores the working mode identifier, laser data and engineering measurement data of each channel input to the data transmission subsystem according to the different virtual channel identifiers; Step five, according to the set working mode and signal path, the optical, laser and auxiliary data are recorded and downlink processed; The specific steps are as follows: 5.1 Send the "integrated working mode" instruction package through the integrated electronic subsystem, control the computer to analyze the instruction package, and complete one or more attitude adjustments according to the set working mode; The integrated camera computer analyzes the instruction package according to the set working mode, completes the recording of corresponding optical, laser and auxiliary data, and transmits to the data transmission subsystem; 5.2 The data transmission subsystem packs one or more data according to one working mode task and marks it with an identifier, and the data is downlinked to the ground processing system through the data transmission channel. After the data transmission channel downlink data, the payload data is recovered and processed; 5.3 The ground processing system demodulates and decodes the data, extracts the working mode and spacecraft identifier from the data according to the AOS format, and separates and analyzes the different virtual channel baseband data according to the specified virtual channel identifier and VCDU counter; 5.4 The ground processing system judges the working mode, if M=1 mode, generates high-resolution optical image system geometric correction product and laser point three-dimensional data product, and their superposition fusion product; In this mode, the laser detection obtains the ground laser M≥3 mode, and the ground generates high-resolution optical stereo image pair through joint adjustment processing, and improves the height accuracy of the stereo image pair.

2. The high-resolution agile integrated optical and laser satellite imaging method according to claim 1, wherein, The scene parameters include terrain slope and target reflectivity.

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