JP2007033258A - Method and device for observing object to be observed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an image to be interfered without using a yaw steering function of a synthetic opening antenna by controlling the bow azimuth of an aircraft. <P>SOLUTION: The synthetic opening antenna 4 mounted on a flying body is moved horizontally in the sky over an object to be observed, and electric wave is transmitted and received from the synthetic opening antenna. Reflected wave received by the synthetic opening antenna 4 is signal-processed to image data. A plurality of image data acquired by repeating the processing is interference-processed, and SAR image data is acquired. When the synthetic opening antenna is moved, the shift of drift angle by cross wind received by the flying body is controlled, thereby aligning the observation direction to the object to be observed of the synthetic opening antenna. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an observation method and apparatus for an observation target object that observes the observation target object using a synthetic aperture radar.

  According to the literature published on the website of the Geographical Survey Institute, radar radiates radio waves from an antenna toward an observation object, and receives and observes the radio waves reflected by the observation object. Using the radar, the approximate distance to the observation object can be measured by measuring the time it takes for the size and surface properties of the observation object to be known from the reflected radio wave and the return of the radio wave. It is.

  When performing radar observations, to improve the resolution of the observation object, narrow the directivity of the radar antenna and irradiate a thin beam toward the observation object. The dimensions need to be increased. For example, in the case of a satellite-borne radar, in order to obtain a resolution of 10 m or higher on the ground surface, the antenna size “aperture” exceeds 1 km, and there is a problem as a device mounted on the satellite.

  Therefore, as a technology to artificially “synthesize” the “aperture” so that an image equivalent to an antenna with a large aperture is obtained by transmitting and receiving radio waves while a flying object such as an artificial satellite or an airplane moves. Synthetic aperture radar has been developed.

  Techniques have been developed for observing crustal movements using this synthetic aperture radar. By using this synthetic aperture radar to obtain repeat path interference SAR (Synthetic Aperture Radar) images, it is possible to image crustal movements and landslides of several centimeters from aircraft and artificial satellites.

  As shown in FIG. 9, the repeat path interference SAR by the aircraft 1 acquires SAR images almost twice from the same flight course 2a, 2b at different times. The flight courses 2a and 2b need to be within the interference limits determined by the wavelength, distance, resolution, and incident angle as shown in the following formula, and the L band, 3m resolution, 40 degree incident angle, 15.7km observation distance Then, it is set in a pipe-like airspace F having a diameter D of about 520 m or less. Formula B = λrtanθ / 2 · Rs. Here, B: maximum interference possible distance, λ: wavelength, θ: incident angle, Rs: slant range resolution, r: distance to the target.

In the acquired SAR image, information on the reflectance of the surface of the observation object is recorded as a signal amplitude, and distance information to the observation object is also recorded as a phase. Therefore, if the flight courses are exactly the same, the difference in phase between the two SAR images at the same position is calculated, and the observation object that occurred during the period when these two SAR images were observed, such as changes in the crust, is imaged. Can be Actually, it is difficult to make the flight courses exactly the same, so the component due to the altitude of the target is also imaged. Therefore, by correcting the influence of the difference between the two flight courses, the altitude component is removed, and only the target fluctuation component can be obtained.
Geographical Survey Institute website (http://gsi.go.jp/sokuchi/sar/mechanism/)

  However, there are two problems in actually obtaining a repeat path interference SAR image. For one thing, it is very difficult for aircraft to fly in exactly the same orbit, and under the influence of crosswinds, the aircraft has a nose angle based on the differential GPS method using GPS satellites 3. (Heading angle) and altitude are corrected while flying in the vicinity of the daily trajectory of the pipe-shaped airspace F.

  This problem can be corrected if the actual flight trajectory is within a certain error indicated by the interference limit distance, and the error can be recorded with sufficiently high accuracy with respect to the wavelength. Actually, the kinematic GPS method is used to record the trajectory of the airplane in the space with an accuracy of about 1 cm, and the correction is made based on the recorded data.

  There is another issue in obtaining repeat path interference SAR images. In conventional repeat-path interferometric SAR observation using an aircraft, the aircraft travels at a relatively high altitude in order to obtain a wide observation range, and the observation is performed using the most efficient speed of the aircraft. Wind speed and direction change depending on the day. At high altitudes, the wind blows in a certain direction depending on the season. However, the wind speed can vary greatly from day to day. When the aircraft flew at high altitude, the stall speed and the maximum speed were close, making it difficult to change the speed significantly. Therefore, there is a problem that the drift angle changes every time observation is performed, and the observation data cannot be fully utilized.

  The problem is that in conventional repeat path interference SAR observation with an aircraft, the speed of the aircraft is almost constant at each observation, so when the two SAR images are interfered, the Doppler frequency bands of the images match. It is necessary to be.

  That is, as shown in FIG. 10, only the portion O where the signal Doppler band of the first observed image G1 and the signal Doppler band of the second observed image G2 overlap is an interference component. The spatial resolution of the interference image is determined by the frequency band of the overlapping portion O. For this reason, when there are few overlapping portions O, there is a problem that an image with reduced spatial resolution or an interference image cannot be obtained.

  One way to solve the problem is to give the synthetic aperture radar a yaw steering function. A synthetic aperture antenna having a yaw steering function can direct its beam center toward the Doppler frequency of 0 Hz regardless of the nose direction of the aircraft.

  However, in order to rotate the synthetic aperture antenna, the rotation mechanism becomes complicated, and there are problems of an increase in weight and a high price. Furthermore, since the heading of the aircraft constantly fluctuates during flight, it is necessary to continue control so that the beam center direction of the antenna is constantly directed in the direction of the Doppler frequency of 0 Hz.

  An object of the present invention is to provide a method and an apparatus for observing an object to be observed that can correct an aircraft heading and obtain an image to be interfered without using a yaw steering function.

In order to achieve the above object, an observation method of an object to be observed according to the present invention moves a synthetic aperture antenna mounted on a flying object in the horizontal direction over the object to be observed, and transmits radio waves from the synthetic aperture antenna. Sending and receiving; and
Signal processing the reflected wave received by the synthetic aperture antenna into image data;
A step of interference processing a plurality of image data obtained by repeatedly executing the step to obtain an interference image,
When the synthetic aperture antenna is moved, the observation direction of the synthetic aperture antenna with respect to the object to be observed is made to coincide with each other by controlling a deviation of a drift angle caused by a cross wind received by the flying object. It is. Here, the observation direction means an angle of the antenna beam center direction with respect to the velocity direction of a flying object such as an aircraft.

  According to the present invention, when the synthetic aperture antenna is moved, the drift angle caused by the cross wind received by the flying object is controlled. Even when a plurality of flights are performed, based on the control process, the observation direction of the synthetic aperture antenna with respect to the observation target is converged in substantially the same range. Moreover, the synthetic aperture antenna moves on substantially the same trajectory in a plurality of flights.

In matching the observation direction of the synthetic aperture antenna with respect to the object to be observed, the relative wind direction with respect to the flight course is θ degrees, the wind speed is Vw knots, and the drift angle of the nose direction with respect to the flight course of the flying object is φ degrees. ,
By setting the flying speed Va of the flying object to Va = (Vwsinθ) / sinφ, the drift angle of the flying object in the movement trajectory of the synthetic aperture antenna can be controlled to φ degrees.

  Also, avoid flying at high altitude where the stalling speed and maximum speed of the flying object approach each other and the allowable speed range is narrow, and the flying altitude of the flying object has a wide allowable speed range between the stalling speed and the maximum speed. It is desirable to drop the flying object at a high altitude. In this case, it is desirable to set the flying height of the flying object to an altitude in the range of 3,000 m to 6,200 m.

  Compared to the high altitude where the stalling speed and the maximum speed of the flying object are close to each other and the allowable speed range is narrow, the direction of the seasonal wind is constant at the altitude where the allowable speed range between the stalling speed and the maximum speed is wide. The wind speed is relatively small. Therefore, the drift angle of the flying object can be easily controlled, and the observation direction of the synthetic aperture antenna with respect to the observation target object can be matched in a plurality of flights.

  In addition, when moving the synthetic aperture antenna mounted on the flying object in the horizontal direction above the object to be observed, the first observation is a course that forms an angle of 45 degrees with respect to the wind direction, and a 90-degree azimuth from that course. It is desirable to move the synthetic aperture antenna along a course that forms an angle of −45 degrees with the wind direction.

  This makes it possible to move the synthetic aperture antenna along the other moving course even when it is difficult to move the synthetic aperture antenna along one moving course due to the wind direction during the second observation. It becomes.

  An observation apparatus that implements the observation method of an observation target object according to the present invention described above includes a synthetic aperture radar transmission / reception system and a synthetic aperture antenna that transmit and receive radio waves while moving while mounted on a flying object over the observation target object. A signal processing unit that obtains an interference image by performing interference processing on a plurality of image data obtained by imaging reflected waves received by the synthetic aperture antenna, and a crosswind received by the flying object when the synthetic aperture antenna is moved. By constructing a flight management system having a function of unifying the observation direction of the synthetic aperture antenna with respect to the object to be observed by controlling the deviation of the drift angle.

  Further, the flight management system is configured such that when the relative wind direction with respect to the flight course is θ degrees, the wind speed is Vw knots, and the drift angle of the flying object with respect to the flight course is φ degrees, the flying object has a drift angle φ degree. It is desirable that the airflow velocity Va is set to Va = (Vwsinθ) / sinφ so that the drift angle of the flying object in the moving trajectory of the synthetic aperture antenna is unified to φ degrees.

  The flight management system avoids flying at a high altitude where the stalling speed and the maximum speed of the flying object are close to each other and the allowable speed range is narrow, and the flying height of the flying object is set between the stalling speed and the maximum speed. It is desirable to have a function of flying the flying object at a high altitude with a wide allowable speed range.

  The flight management system has a function of moving the synthetic aperture antenna to a moving course having a different direction when moving the synthetic aperture antenna mounted on the flying object in the horizontal direction over the object to be observed. It is desirable to have. In this case, it is desirable to fly the flying object on the moving course in directions different by 90 degrees.

  As described above, according to the present invention, when the synthetic aperture antenna is moved, in order to correct the deviation of the drift angle caused by the crosswind received by the flying object, the correction process is performed even when a plurality of flights are performed. Based on this, the observation direction of the synthetic aperture antenna with respect to the object to be observed can be converged in substantially the same range. Furthermore, the synthetic aperture antenna can be moved on substantially the same locus in a plurality of flights.

  Therefore, it is possible to obtain a SAR image that is caused to interfere without using the yaw steering function.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, an observation apparatus used in an observation method for an observation object according to an embodiment of the present invention includes a device for transmitting and receiving observation radio waves, a flight information detection unit, and an aircraft 1 as a flying object. It comprises a system control unit for controlling, a signal processing unit 9 and a data recording unit 10. These are mounted on the aircraft 1 as a flying object. On the ground, a data recording unit 10a, a kinematic GPS 9a that inputs data from the GPS network of the Geographical Survey Institute and calculates a highly accurate position, and a signal processing unit 9 are installed.

  The device for transmitting and receiving the observation radio wave includes a synthetic aperture (radar) antenna 4, a switching unit 5, a high-power amplifier 7, and a transmission / reception unit 8.

  The transmission / reception unit 8 outputs a transmission signal to the high-power amplifier 7. The high power amplifier 7 amplifies the transmission signal from the transmission / reception unit 8 and outputs the amplified signal to the switching unit 5. The switching unit 5 outputs the amplified transmission signal from the high power amplifier 7 to the synthetic aperture antenna 4. The switching unit 5 outputs a reception signal received by the synthetic aperture antenna 4 to the transmission / reception unit 8. The transmission / reception unit 8 processes the reception signal output from the switching unit 5 and outputs an I / Q video signal as a SAR radar raw data signal to the data recording unit 10.

  As shown in FIG. 2A, the synthetic aperture antenna 4 is fixedly attached to the outer lower surface of the fuselage 1 a of the aircraft 1, and the surface thereof is covered with a radome 11. A cable 12 connects the synthetic aperture antenna 4 and the switching unit 5. In this embodiment, a planar patch antenna is used as the synthetic aperture antenna 4, but the present invention is not limited to this. Instead of a planar patch antenna, a planar slot antenna or the like may be used. In short, an observation beam can be emitted toward an object to be observed and a reflected wave reflected by the object to be observed can be received. Any configuration is possible.

  As shown in FIG. 1, the flight information detection unit includes a differential GPS 13, an inertial attitude measurement unit (IMU) 14, and a controller 15.

  There are two methods for the differential GPS 13. One of them is a method of correcting GPS position data by using a correction multi-purpose satellite MUS, which is about to start operation, and using a correction signal transmitted from the satellite. Another method is to receive a DGPS beacon signal transmitted by the Japan Coast Guard and use it as a correction signal. The measurement data of the differential GPS 13 is discontinuous data with a sampling frequency for acquiring data of about several Hz.

  The inertial posture measuring device 14 is composed of three accelerometers and three gyroscopes installed in three orthogonal directions. The accelerometer detects accelerations in three directions of the aircraft 1, and the gyroscope detects angular velocities around three axes.

  The controller 15 controls the operations of the differential GPS 13 and the inertial attitude measurement device 14. The controller 15 also outputs flight information acquired by the kinematic GPS 13 and the inertial attitude measurement device 14 to the system control unit.

  As shown in FIG. 1, the system control unit includes an aircraft information input I / F unit 16 that receives movement distance information and attitude azimuth information from the controller 15 of the flight information detection unit, and a flight management system 17. ing.

  In the flight management system 17, the built-in computer performs calculation processing that optimizes fuel efficiency in accordance with the flight conditions of the aircraft 1, and the control data (autopilot system) and thrust adjustment device (auto throttle system) are used by the calculation data. In addition to the function to control, it has a function to automatically perform flight management over the entire flight area from takeoff to landing. The built-in computer of the flight management system 17 stores navigation data (information on airports, runways, spots, air routes, flight routes, etc.) as a navigation database. The computer provides information on lateral navigation (L-NAV) and altitude navigation (V-NAV) on the CRT screen.

  Further, the flight management system 17 determines the position of the aircraft 1 based on the signal output from the differential GPS 13. Further, the flight management system 17 integrates acceleration information output from the inertial attitude measurement device 14, particularly an accelerometer, calculates speed data, and integrates the speed data to calculate distance data. Further, the controller 15 integrates the angular velocity information output from the inertial attitude measurement device 14, particularly the gyroscope, to calculate the attitude azimuth of the aircraft 1.

  Furthermore, the flight management system 17 according to the embodiment of the present invention covers the synthetic aperture antenna 4 based on the aircraft information such as the travel distance information and the attitude azimuth information received by the aircraft information input I / F unit 16. When moving over the object to be observed, a function of matching the observation direction of the synthetic aperture antenna 4 with respect to the object to be observed is corrected by correcting the deviation of the drift angle caused by the crosswind received by the aircraft 1.

  A specific description will be given of the function of the flight management system 17 that matches the observation direction of the synthetic aperture antenna 4 with respect to the object to be observed. As shown in FIG. When the relative wind direction with respect to the course is θ degrees, the wind speed is Vw knots, and the drift angle of the flying object with respect to the flight course is φ degrees, the flying air velocity Va of the flying object having the drift angle φ degree is expressed as Va = (Vwsinθ) / By setting sin φ, the drift angle of the flying object in the moving trajectory of the synthetic aperture antenna is unified to φ degrees. Here, 1 knot (Kt) of international knots = 1.852 km.

  The flight management system 17 avoids flying at a high altitude where the stall speed and the maximum speed of the aircraft 1 are close to each other and the allowable speed range is narrow, and the flight altitude of the aircraft 1 is set to the stall speed and the maximum speed. The speed tolerance range between the two is lowered to a high altitude, and the flying object is allowed to fly. The basis of this flight altitude will be described with reference to FIG.

  In FIG. 5, in the repeat path interferometric SAR observation by an aircraft, it is possible to fly at a relatively high altitude with a wide observation width and fuel efficiency, for example, an altitude of 13.7 km, and use the most efficient speed of the aircraft. It is carried out. Although the high altitude depends on the type of aircraft, the stall speed M1 and the maximum speed M2 are very close to each other and the allowable speed range R1 is narrow.

  However, at the high altitude described above, the wind speed and direction change depending on the day. Moreover, although seasonal winds are blowing depending on the season, the wind speed may vary greatly depending on the day. When the aircraft flew at high altitudes, the stall speed and the maximum speed were very close, making it difficult to change the speed. Therefore, there is a problem that the drift angle changes every time observation is performed, and the observation data cannot be fully utilized.

  Therefore, the flight management system 17 according to the embodiment of the present invention avoids flying at a high altitude where the stall speed and the maximum speed of the aircraft 1 are close to each other and the allowable speed range is narrow, and the flight altitude of the aircraft 1 is The allowable speed range R2 between the stall speed M1 and the maximum speed M2 drops to a wide altitude H, and the aircraft 1 is allowed to fly. In this case, the flight altitude H of the aircraft 1 is set to an altitude in the range of about 3,000 m to 6,200 m (about 10,000 to 20,000 feet). At this altitude H, the direction of the seasonal wind is constant, and the wind speed changes little with the day. Moreover, since the adjustable range of the speed of the aircraft 1 is wide, the drift angle φ of the aircraft 1 can be easily controlled as shown in FIG. It is possible to easily match the resolution and movement trajectory due to the synthetic aperture with respect to the observation object.

  Further, as shown in FIG. 8, the flight management system 17 moves the synthetic aperture antenna 4 mounted on the aircraft 1 over the object to be observed in the horizontal direction. It has a function of moving the synthetic aperture antenna 4 on a course F1 having an angle of 45 degrees and a course F2 having an angle of −45 degrees with the wind direction, which is rotated 90 degrees from the course. In this case, it is desirable that the aircraft 1 fly on the moving courses F1 and F2 in directions relatively different by 90 degrees.

  The I / Q video signal as SAR raw data output from the transmission / reception unit 8 is recorded in the data storage unit 10 together with altitude, speed, position, and other data necessary for GPS kinematic post-processing for each flight of the aircraft 1. And put. Then, on the ground, as shown in FIG. 6, the signal processing unit 9 reads out two sets of SAR raw data acquired on a flight course capable of interference from the data recording unit 10a and performs SAR image reproduction processing. At this time, using the kinematic post-processing data read from the data recording unit 10a and the GPS reference data of the Geographical Survey Institute available on the Internet, the flight course is identified with high accuracy, and the ideal flight course Correction is performed so as to be equivalent to the data obtained in the case of flying, and two interferable SAR images S1 and S2 are obtained. Then, interference processing is performed on the SAR images S1 and S2 to obtain an interference SAR image S3.

  The signal processing unit 9 further performs interference processing, that is, phase difference extraction, and acquires an interference image. Interferometric SAR images are represented by striped colors. The color of the striped pattern represents a phase difference that occurs in accordance with the difference in distance between the two SAR images at the same position. Thus, since the phase difference corresponds to the amount of change of the observation object, the stripe pattern corresponds to the change of the observation object at that location.

  If there is a slight difference in the flight course during the observation of the interfering SAR raw data (if they are not exactly the same flight course), the interference SAR image data S3 is interfered based on the height of a mountain or hill in the target area. Stripes are included. These interference fringes are corrected based on geometric numerical calculation, the interference component due to the elevation data is deleted, crustal movement detection image data S4 is obtained, and based on the crustal movement detection image data S4, Detect crustal deformation. Since this series of image processing is general-purpose and is not a feature of the present invention, the details thereof are omitted.

  Next, an operation according to the embodiment of the present invention will be described.

  In the embodiment of the present invention, as shown in FIG. 9, the flight management system 17 is mounted on the aircraft 1 while guiding the aircraft 1 along the flight course 2 a set for the first flight. The synthetic aperture antenna 4 is moved over the observation object 18 along the flight course 2a.

  When the synthetic aperture antenna 4 moves along the flight course 2 a, the transmission / reception unit 8 outputs a transmission signal and sends this transmission signal to the synthetic aperture antenna 4. The synthetic aperture antenna 4 radiates the received transmission signal toward the object 18 to be observed. Further, the synthetic aperture antenna 2 receives the reflected wave reflected by the observed object 18 and outputs the received signal to the transmission / reception unit 8.

  When receiving the reception signal from the synthetic aperture antenna 4, the transmission / reception unit 8 converts the reception signal into an I / Q video signal that is SAR raw data, and outputs the video signal to the data recording unit 10.

  As described above, when the acquisition of the SAR image by the first aircraft 1 is completed, the second flight by the aircraft 1 is performed after a set period in which crustal deformation is expected by the next flight. .

  The time of the flight by the second aircraft 1 has elapsed with respect to the time when the flight by the first aircraft 1 was performed, and the conditions of the crosswind received by the aircraft 1 may be different.

  As shown in FIG. 3A, when the aircraft 1 is flying along the set flight course F3, that is, the synthetic aperture antenna 4 mounted on the aircraft 1 is in the normal flight direction (set flight). When moving along the course F3), the observation direction 4a of the synthetic aperture antenna 4 with respect to the observed object 18 is indicated by a solid line.

  However, if the aircraft 1 receives a crosswind and its flight course F4 is shifted by an angle θ1 with respect to the set flight course F3, the observation direction 4a1 of the synthetic aperture antenna 4 with respect to the observation target 18 is a two-dot chain line. As shown, it deviates from the normal resolution 4a indicated by the solid line.

  Thus, when the observation direction of the object 18 to be observed by the synthetic aperture antenna 4 deviates from the first observation, as shown in FIG. 10, the azimuth direction Doppler signal component G1 of the first observation image of SAR data and The overlapping portion of the azimuth direction Doppler signal component G2 in the second observation image is reduced. Therefore, it is necessary to increase the overlapping parts.

  When flying the second aperture 1 along the flight course 2a of the aircraft 1 that acquired the first interference SAR image and moving the synthetic aperture antenna 4 over the object 18 to be observed, The drift angle φ of the nose of the aircraft 1 is controlled.

  As shown in FIG. 7, first, in step S10, the flight management system 17 obtains flight information from the second aircraft 1 from the flight information detector shown in FIG. Based on the received flight information, the flight management system 17 matches the direction of the synthetic aperture antenna 4 at the time of the first SAR image acquisition with the direction of the synthetic aperture antenna 4 at the time of the second SAR image acquisition. If yes (YES in step S10), the process proceeds to step S11, and the monitoring of the coincidence / mismatch of the synthetic aperture antenna 4 is continuously performed.

  Based on the received flight information, the flight management system 17 does not match the direction of the synthetic aperture antenna 4 at the time of the first SAR image acquisition and the direction of the synthetic aperture antenna 4 at the time of the second SAR image acquisition. When it is determined that there is (NO in step S10), as shown in FIG. 4, when the relative wind direction angle between the aircraft 1 and the cross wind is θ with respect to the flight course, the aircraft 1 has a drift angle φ with respect to the flight course. By flying at a speed Va in the direction, the flight is substantially made along the flight course.

  Therefore, in step S12 of the arithmetic processing in FIG. 7, as shown in FIG. 4, the flight management system 17 sets the relative wind direction with respect to the flight course to θ degrees, the wind speed to Vw knots, and the drift angle of the flying object to the flight course to φ. When the flying air velocity Va of the flying body having a drifting angle φ degree is set to Va = (Vwsinθ) / sinφ, the drifting angle of the flying object in the movement trajectory of the synthetic aperture antenna a plurality of times. Is unified to φ degrees.

  In step S13, the flight management system 17 continues to monitor the direction of the synthetic aperture antenna 4 so that the direction of the synthetic aperture antenna 4 after controlling the drift angle φ has become the corrected direction, that is, the aircraft 1 It is determined whether the drift angle φ is controlled after the drift angle is corrected.

  If the drift angle φ of the aircraft 1 is not corrected, the flight management system 17 controls the speed of the aircraft 1 (step S14), and continues to monitor the direction of the synthetic aperture antenna 4 again. It is determined whether the direction of the synthetic aperture antenna 4 after correcting φ is the corrected direction, that is, whether the drift angle of the aircraft 1 is corrected to the drift angle φ after correction (step S15).

  If the direction of the synthetic aperture antenna 4 is not corrected as a result of the speed control of the aircraft 1 in step S15, the speed control of the aircraft 1 is continued until the direction is corrected (NO in step S15). Step S14).

  Based on the received flight information, the flight management system 17 matches the direction of the synthetic aperture antenna 4 at the time of the first SAR image acquisition with the direction of the synthetic aperture antenna 4 at the time of the second SAR image acquisition. If yes (YES in step S15), the process proceeds to step S16, and the monitoring of the coincidence / mismatch of the direction of the synthetic aperture antenna 4 is continuously performed.

  In the above description, the case where the synthetic aperture antenna 4 is moved only in one direction has been described. However, the present invention is not limited to this.

  As shown in FIG. 8, when the synthetic aperture antenna 4 mounted on the aircraft 1 is moved in the horizontal direction over the object to be observed, in the first observation, the course F1 that forms an angle of 45 degrees with the wind direction In addition, the synthetic aperture antenna 4 has a function of moving the synthetic aperture antenna 4 in a course F2 which is rotated by 90 degrees from the course and forms an angle of −45 degrees with the wind direction. In this case, the aircraft 1 is caused to fly on the moving courses F1 and F2 in directions relatively different by 90 degrees.

  When the second synthetic aperture antenna 4 is moved after acquiring the first SAR image data, it may not be possible to move the synthetic aperture antenna 4 along the moving course F2 depending on the wind direction. .

  In this case, if the synthetic aperture antenna 4 is moved along the remaining movement course F1 out of the two movement courses F1 and F2, the SAR image data is acquired by the second synthetic aperture antenna 4. Can do.

  As described above, according to the present invention, when the synthetic aperture antenna is moved, in order to control the deviation of the drift angle caused by the crosswind received by the flying object, the correction process is performed even when a plurality of flights are performed. Based on this, it is possible to converge the observation direction of the synthetic aperture antenna with respect to the observation target within the substantially same range. Furthermore, the synthetic aperture antenna can be moved on substantially the same trajectory in a plurality of flights, and an SAR image that can be interfered can be obtained without using the yaw steering function.

It is a block diagram which shows the observation apparatus of the to-be-observed target which concerns on embodiment of this invention. 2A is a front view showing a state in which the synthetic aperture antenna is attached to the aircraft, FIG. 2B is a plan view showing the synthetic aperture antenna whose surface is covered with a radome, and FIG. It is the cross-sectional side view which cut the synthetic aperture antenna by which the surface was covered with the radome. FIG. 3A is a perspective view showing a state of flying on a set flight course, and FIG. 3B is a perspective view showing a state of flying in response to a crosswind. It is explanatory drawing for adjusting the drift angle of the aircraft in the case of flying by receiving a crosswind. It is explanatory drawing explaining the flight altitude in embodiment of this invention. It is explanatory drawing which shows the flow until it interferes with the acquired SAR raw data and acquires interference SAR image data. It is a float chart explaining the operation | movement in embodiment of this invention. It is explanatory drawing which shows the example of the flight course in embodiment of this invention. It is explanatory drawing explaining the flight state for acquiring a repeat path interference SAR image. It is explanatory drawing explaining the interference process for obtaining an interference SAR image.

Explanation of symbols

1 Aircraft (aircraft)
4 Synthetic aperture (radar) antenna 9 Signal processing unit 10 Data recording unit (mounting side)
10a Data recording / playback unit (ground side)
13 Differential GPS
14 Inertial attitude measurement device 17 Flight management system

Claims (11)

Moving the synthetic aperture antenna mounted on the flying object over the object to be observed in the horizontal direction and transmitting and receiving radio waves from the synthetic aperture antenna;
Signal processing the reflected wave received by the synthetic aperture antenna into image data;
A plurality of image data obtained by repetitively executing the above steps to perform interference processing to obtain SAR image data;
When the synthetic aperture antenna is moved, the observation direction of the synthetic aperture antenna with respect to the object to be observed is unified by controlling a deviation of a drift angle caused by a cross wind received by the flying object. Observation method of the object. When the relative wind direction with respect to the flight course is θ degrees, the wind speed is Vw knots, and the drift angle of the flying object with respect to the flight course is φ degrees,
The flying airspeed Va of the flying object having a drift angle φ of
By setting Va = (Vwsinθ) / sinφ,
The observation method of an observation target object according to claim 1, wherein the drift angle of the flying object in the movement trajectory of the synthetic aperture antenna a plurality of times is unified to φ degrees.   Avoid flying at high altitude where the stalling speed and maximum speed of the flying object are close to each other and the allowable speed range is narrow, and the flying altitude of the flying object is increased to an altitude with a wide speed allowable range between the stalling speed and the maximum speed. The method for observing an object to be observed according to claim 1, wherein the flying object is caused to drop and fly.   The method for observing an object to be observed according to claim 3, wherein the flying height of the flying object is set to an altitude in a range of about 3,000 m to 6,200 m.   When moving the synthetic aperture antenna mounted on the flying object in the horizontal direction over the object to be observed, the synthetic aperture antenna is moved to a moving course having a different direction to acquire image data. Item 2. An observation method of an object to be observed according to Item 1.   6. The observation method of the observation target object according to claim 5, wherein the moving course is set in a direction that is relatively different by 90 degrees. A synthetic aperture antenna that transmits and receives radio waves while moving on a flying object over the object to be observed;
A signal processing unit that obtains a SAR interference image by performing interference processing on a plurality of image data obtained by imaging the reflected wave received by the synthetic aperture antenna;
Flight management having a function of matching the observation direction of the synthetic aperture antenna with respect to the object to be observed by controlling the deviation of the drift angle caused by the cross wind received by the flying object when moving the synthetic aperture antenna An observation apparatus for an object to be observed characterized by having a system. The flight management system
When the relative wind direction with respect to the flight course is θ degrees, the wind speed is Vw knots, and the drift angle of the flying object with respect to the flight course is φ degrees,
The flying airspeed Va of the flying object having a drift angle φ of
By setting Va = (Vwsinθ) / sinφ,
The observation apparatus for an object to be observed according to claim 7, further comprising a function of unifying the drift angle of the flying object in the movement trajectory of the synthetic aperture antenna a plurality of times to φ degrees. The flight management system
Avoid flying at high altitude where the stalling speed and maximum speed of the flying object are close to each other and the allowable speed range is narrow, and the flying altitude of the flying object is increased to an altitude with a wide speed allowable range between the stalling speed and the maximum speed. The observation apparatus for an object to be observed according to claim 7, wherein the observation apparatus has a function of dropping and flying the flying object. The flight management system
8. A function of moving the synthetic aperture antenna to a moving course having a different direction when the synthetic aperture antenna mounted on the flying object is moved in the horizontal direction over the object to be observed. An observation device for an object to be observed described in 1. The flight management system
The observation apparatus for an object to be observed according to claim 10, comprising a function of causing the flying object to fly on the moving course in a direction that is relatively different by 90 degrees.

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