RU2526850C2 - Method of obtaining radar image of portion of earth's surface and synthetic aperture radar station (versions) - Google Patents

Abstract

FIELD: physics, navigation.

SUBSTANCE: invention can be used to obtain radar images of the earth's surface using synthetic aperture radar (SAR) stations mounted on spacecraft. The method employs a non-periodic phase-code modulated radio pulse as a probing pulse in SAR, and the vertical dimension of the antenna aperture of the radar station is selected according to the required scanning band. The SAR is in form of coherent side-looking radar, the antenna area of which is defined by the product of the selected vertical dimension of the antenna the horizontal dimension, which is defined by design capabilities of the spacecraft. To expand the scanning band of the antenna, the SAR can be in form of a waveguide-slit grating which realises in the vertical plane a beam pattern with a special shape which compensates for the effect of the change in range and specific radar cross-section in the frame of a radar image on radar reflection signal power.

EFFECT: smaller radar antenna area and larger scanning bandwidth for radar images without complication of the antenna design, which simultaneously reduces power consumption, weight and size characteristics of on-board equipment of aircraft and high reliability thereof.

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Description

The invention relates to the field of radar and can be used in the formation of radar images (RLI) of the earth's surface using radars with synthesized aperture (SAR), placed on spacecraft (SC).

Information technology for obtaining a radar image of the Earth from space is implemented with time sharing and includes the following.

1. Conducting a radar survey, the result of which is a digital array of registered radar data (radio hologram) (implemented using on-board radar equipment located on the spacecraft).

2. The formation of radar images (carried out on ground software and hardware by means of coherent processing of radar data, taking into account the parameters of the spacecraft in the process of shooting).

The algorithm for generating a radar image of a terrain is implemented in the form of a coordinated filtering of the trajectory radar signal of a point target, carried out for each element of the earth's surface, included in the area of radar observation.

The radar image is characterized by spatial resolution and the geometric dimensions of the recorded area.

The spatial resolution of the radar image is ensured through the use of a broadband probe signal and the coherent processing of radar signals obtained on a portion of the path of the SAR carrier (synthesis interval - synthesized aperture) during radar imaging.

The geometrical dimensions of the radar image are determined by the length of the survey route (in the direction along the spacecraft trajectory) and the dimensions of the survey strip (capture strip) on the Earth's surface (in the transverse direction relative to the spacecraft trajectory).

An analogue of the present invention related to a method for producing radar images is a method for implementing an on-board radar complex of a burst mode of radiation, wherein the packet of probe pulses has phase-phase modulation from pulse to pulse, and the signals reflected from the Earth undergo coordinated processing in a ground-based complex [S. L. . Vnotchenko, V.V. Riemann, A.V. Telichev, V.S. Chernyshev, A.V. Shishanov. Systemic principles for the implementation of the Severyanin-M space radar. K 71 Space Radar [Electronic Resource]: All-Russian Radiophysical Scientific Readings and Conferences in Memory of N. A. Armanda. Sat reports of the scientific-practical conference (Murom, June 28 - July 1, 2010). - Murom: Publishing house-printing center MI VlSU, 2010, pp. 20-29]. In this case, the azimuthal resolution of the radar image is determined by the duration of the packet of probe pulses. The disadvantage of this method is the reduction of the signal-to-noise ratio in the radar element, the degree of which is proportional to the duty cycle of the probe pulse train.

Closest to the proposed invention relating to a method for producing radar images is a method that consists in emitting a modulated probe pulse, receiving and recording reflected signals using a radar station with a synthesized aperture of the antenna, and then conducting consistent filtering of the reflected signals for elements of the observed surface . [Problems of modern radio engineering and electronics. Repl. ed. V.A. Kotelnikov. M., "Science", 1987, pp. 59-62]. In this method, the probe pulse is phase-modulated by a code of a periodically repeated M-sequence (maximum length code [1]), and the antenna pattern (BOTTOM) parameters (the width of the main lobe and the position of the BOTTOM electric axis relative to the local vertical) are selected from the condition of effective interference suppression ambiguities in radar imagery.

The radar, selected as a prototype of the inventive device for conducting radar imaging, contains an antenna of area S connected to the input / output of the circulator, the input and output of which are connected, respectively, to the first output and the input of the coherent transceiver path [Earth radar. Ed. G.S. Kondratenkova, M .: "Radio and communications", 1983, p.203-204].

The ambiguity effect due to the use of a periodic sounding signal leads to the fact that in the radar image, in addition to the useful signal generated by the observed element of the earth's surface, there are specific reflections - the so-called interferences of ambiguity. The formation of ambiguity interference involves elements of the earth’s surface, spaced apart from the sighted object in oblique range and azimuth over considerable distances, determined by the value of the repetition period of the probe pulses and the geometry parameters of radar observation. The suppression of ambiguity interference in the implementation of the technology for producing radar images is carried out by selecting the antenna pattern parameters that are consistent with the SAR carrier speed V and the observation range R. This leads to a known limitation on the aperture area of the radar antenna S [2, pp. 255-257]:

$$S=l\cdot h>k\cdot \frac{\mathrm{four}V\lambda R\cdot tg\left(\varphi \right)}{c}\left(\mathrm{one}\right)$$

where l is the horizontal size of the antenna; h is the vertical size of the antenna; k = 1-3 is a coefficient depending on the field distribution over the antenna aperture and a given level of suppression of ambiguity interference; λ is the working wavelength; R is the slant range to the observed portion of the earth's surface; φ is the angle of incidence of the electromagnetic wave; c is the speed of light.

From (1) it follows that the requirements for the magnitude of the aperture area of the radar antenna increase sharply with increasing working angle of incidence φ of the electromagnetic wave. At the same time, to realize the possibility of obtaining radar data in a wide field of view, it is necessary to use the working angular sector of radar sensing, expanded in the direction of large values of the angle of incidence. Moreover, the implementation of a wide band of shooting (capture) requires the introduction of electronic scanning with a narrow beam of the antenna along the elevation angle.

Thus, the disadvantage of the known method of obtaining radar images and implementing this method of radar is the need to provide a wide band of radar, placement on the spacecraft of the antenna with large aperture, providing electronic scanning of the antenna beam.

The proposed inventions solve the problem of reducing the area of the antenna of the synthetic-aperture radar located on the spacecraft.

Also, the proposed inventions achieve a technical result, which consists in increasing the width of the capture band (shooting strip of the radar image) without complicating the design of the antenna (introducing electronic scanning), which at the same time leads to a decrease in power consumption, overall mass characteristics of the onboard spacecraft equipment and to increase its reliability.

To obtain the named technical results in the proposed method for obtaining a radar image of a piece of the earth’s surface from the spacecraft, which consists in the fact that they emit a modulated probe pulse, receive and register the reflected signals using a radar with a synthesized aperture of the antenna and conduct matched filtering of the reflected signals for earth surface elements, the probe pulse is selected in the form of a radio pulse with a non-periodic phase modulation, and the vertical size h of the aperture of the antenna of the radar station is selected in accordance with the required size L of the capture band

$$h\cong \frac{\lambda \cdot R}{L\cdot \cos \left(\varphi \right)}\left(2\right)$$

where λ is the working wavelength; R is the slant range to the middle of the capture band; φ is the angle of incidence of the electromagnetic wave.

To achieve the aforementioned technical results, a radar station with a synthesized aperture of the antenna is proposed, comprising an antenna with an aperture area S connected to the input / output of the circulator, the input and output of which are connected, respectively, to the first output and the input of the coherent transceiver path. At the same time, the coherent transmitting and transmitting path is made providing the formation of a probing radio pulse with non-periodic phase-phase modulation at the first output. The antenna opening area S is selected from the condition

$$S=l\cdot \frac{\lambda \cdot R}{L\cdot \cos \left(\varphi \right)}\left(3\right)$$

where l is the horizontal size of the antenna.

To achieve the aforementioned technical results, a second version of a radar station with a synthesized aperture of the antenna is proposed, comprising an antenna connected to the input / output of the circulator, the input and output of which are connected, respectively, to the first output and input of the coherent transceiver path. In this case, the coherent transceiver path is made capable of generating a radio pulse with non-periodic phase-code modulation at the first output, and the antenna is made in the form of a waveguide-slot array providing the radiation pattern G (ε) in the vertical plane

$$G\left(\epsilon \right)\cong \frac{\mathrm{one}}{K}\cdot \sqrt{\frac{\sin \epsilon \cdot {\left[k_s\cdot \cos \epsilon -\sqrt{\mathrm{one}-{\mathrm{<figure-callout\; id="2"\; label="k\; s"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_s^{}\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000018.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\epsilon }\right]}^3}{{\cos }^2\left[\arcsin \left(k_s\cdot \sin \epsilon \right)\right]}}$$

where ε is the elevation angle, K = 0.1569, k _s = 1 + H / R _s , H is the flight altitude of the spacecraft, R _s is the radius of the Earth.

To ensure the efficient use of the radio channel for transmitting radar information to ground-based reception points, a buffer memory was introduced into the radar with a synthesized aperture of the antenna, the input of which is connected to the second output of the coherent transceiver path and the output to the output of the radar station.

As an example of execution, the coherent transceiver path includes a master oscillator, a digital-to-analog converter, an analog-to-digital converter, a digital signal conditioner, a transmitter and a receiver, the first and second outputs of the master oscillator being connected, respectively, to the first input of the digital-to-analog converter and to the first input of the analog -digital converter, the output of the digital signal driver is connected to the second input of the digital-to-analog converter, the output of which is connected to the input of the transmitter, the transmitter output is connected to the first output of the coherent transceiver path, the input of the receiver is connected to the input of the coherent transceiver path, the output of the receiver is connected to the second input of the analog-to-digital converter, the output of which is connected to the second output of the coherent transceiver path.

The proposed method and device is illustrated by the drawings shown in figures 1-6.

Figure 1 shows the geometry of the sighting of the earth's surface using a synthetic aperture radar.

Figure 2 shows a cross-section of the geometry of radar sighting in the elevation plane, taking into account the sphericity of the Earth.

Figure 3 presents the sounding radio pulse with several options for non-periodic phase-phase modulation.

Figure 4 shows the shape of the normalized antenna pattern of power in the elevation plane.

Figure 5 shows a structural diagram of a radar with a synthesized aperture of the antenna.

Figure 6 shows a structural diagram of a coherent transceiver path of a radar with a synthesized aperture of the antenna.

When conducting a radar survey of a portion of the earth's surface, the radar moves along a portion of the path of the carrier AB, which is a synthesized aperture (see figure 1). In figure 1, point C is an element of the earth's surface belonging to a capture band of width L, the orbit height of the spacecraft is denoted by H, and the elevation angle (measured from the local vertical) of the electric axis of the antenna pattern (BOTTOM) is indicated by ε ₀ .

Figure 2 shows the elevation section of the geometry of radar sighting taking into account the sphericity of the Earth. The effective beam width in the elevation plane (for double wave propagation) is Δε, φ is the angle of incidence of the electromagnetic wave, measured from the local vertical. The slant range R (ε) from the radar to an arbitrary point belonging to the capture band depends on the current elevation angle ε. The relationship between the angle of incidence φ and elevation angle ε is given by the formula sin (φ) = k _s sin (ε), where k _s = 1 + H / R _s ; H - the height of the orbit of the spacecraft; R _s is the radius of the Earth.

The task of reducing the area of the synthesized aperture radar antenna located on the spacecraft is solved by radiation and receiving a special type of signal.

The radar uses a pulsed radiation mode (see figure 3). The type of the probe signal is an extended modulated radio pulse with non-periodic phase-phase modulation. A radio pulse consists of N monochromatic subpulses having a duration of τ. When implementing phase-phase modulation, the controlled parameters of the subpulse can be:

1) the initial phase φ _n , taking one of two values 0 or π (see figa);

2) the initial phase, as well as the amplitude, which can take a zero value (see fig.3b and fig.3c).

In the first case (Fig. 3a), phase-code modulation is based on binary sequences [12], for which, for the code length N, the duration of the probe radio pulse is T _N = τ · N.

In the second case, phase-phase modulation is based on ternary sequences [13] with a small (FIG. 3b) or large (FIG. 3c) number of gaps (zero subpulses). In this case, the duration of the probe radio pulse, equal to T _N , is determined by the specific type of sequence.

To exclude the blind zone in range, the maximum duration T _{N of the} emitted sounding signal is limited by the propagation time of the signal to the near edge of the capture band and vice versa, i.e.

$$T_N\le 2R_{\min }/c\left(\mathrm{four}\right)$$

where R _min is the slant range to the near edge of the survey strip, c is the propagation velocity of electromagnetic waves.

For example, with a minimum spacecraft orbit altitude of 815 km, this duration is TN≤5.9 ms. The next sounding signal is emitted only after receiving the reflected signals from the entire shooting band.

The azimuthal resolution δx of the radar is ensured by coherent processing (aperture synthesis) over the length of one probe signal; in this case, the synthesis time (interval of coherent signal accumulation) T _sint = T _N. With this processing method, there is a fundamental limit to the linear resolution value δx _min in azimuth. When synthesizing an aperture from a burst of pulses of a fixed length, the best azimuthal resolution δx _{min is} achieved at the near edge of the survey strip at R (ε) = R _min :

$$\delta x_{\min }=\frac{\lambda R_{\min }}{2V{T}_{sint}},\left(5\right)$$

where λ is the wavelength; V is the orbital velocity of the spacecraft.

Substitution of condition (4) into (5) gives an estimate of the minimum size of the resolution element in azimuth

$$\delta x_{\min }\ge \lambda c/\left(\mathrm{four}V\right)\left(6\right)$$

which in the X-range (wavelength of about 3 cm) has a value of the order of 300 m. Thus, synthesizing the aperture in the interval of duration T _{N of} one packet allows one to increase the azimuth resolution several times as compared with incoherent radar systems having a resolution of 1.3- 2.5 km [9, 10].

The proposed method is carried out in the following sequence. Using a radar station with a synthesized aperture of the antenna, a modulated probe pulse is emitted, signals received from the surface are received and registered, which are transmitted to ground-based reception points. Then, on the ground computing means, a consistent filtering of the reflected signals for the elements of the earth’s surface is carried out,

The proposed radar with a synthesized aperture of the antenna contains (see figure 5) an antenna 1 connected to the input-output of the circulator 2, the input and output of which are connected, respectively, to the first output and input of the coherent transceiver path 3, the second output of which is connected to the buffer random access memory 4, the output of which signals are fed to the radio equipment.

The coherent transceiver path of the synthetic aperture antenna radar station contains (see FIG. 6) a master oscillator 5, a digital-to-analog converter 6, an analog-to-digital converter 7, a digital signal driver 8, a transmitter 9 and a receiver 10. The first and second outputs of the master oscillator 5 are connected, respectively, with the first input of the digital-to-analog converter 6 and with the first input of the analog-to-digital converter 7. The output of the digital signal driver 8 is connected to the second input of the digital-to-analog converter 6, the output of which is connected to the input of the transmitter 9. The output of the transmitter 9 is connected to the first output of the coherent transceiver path. The input of the receiver 10 is connected to the input of the coherent transceiver path, the output of the receiver 10 is connected to the second input of the analog-to-digital converter 7, the output of which is connected to the second output of the coherent transceiver path.

A synthesized aperture antenna radar operates as follows. The digital array of samples of the probe signal through the DAC and the master oscillator is converted into a radio signal fed to the input of the transmitter, which carries out its amplification and broadcast through the circulator, providing isolation of the receiving and transmitting paths, into the antenna. The antenna emits a sounding radio pulse with directivity characteristics determined by the shape of the antenna pattern. The radio signals reflected from the surface of the earth are received by the antenna in the pauses between the emitted radio pulses, and are transmitted through the circulator to the receiver; from the output of the receiver, the radio signal is converted to digital form by means of analog-to-digital and frequency conversions implemented using the ADC and the master oscillator. The resulting digital array is recorded in a buffer memory (BOSU), from which the digital samples of the signal are then transmitted to the equipment of the radio data transmission line at ground receiving points.

A specific implementation of the proposed method for obtaining a radar image of a plot of the earth's surface can be carried out when solving the problems of studying the Earth's natural resources and operational hydrometeorology, including monitoring the ice situation using a space-based radar. Until now, these tasks could be solved in two ways:

1) using the implementation of ScanSAR-type survey survey modes in space-based coherent SARs located on RADARSAT-1,2, TerraSAR-X and CosmoSkyMed spacecraft [3-8] and using electronic scanning of the antenna beam in the elevation plane;

2) incoherent side-scan radars (BO) of the Okean [9] and Sich-1M spacecraft [10], which have a low linear resolution (of the order of 1.3–2.5 km) in the 450–460 km range.

Consider an example that allows you to compare the effective aperture areas of the antennas for one value of the elevation angle of the far edge of the capture band or for one capture band in the case of applying the known SAR method and the proposed shooting method. Let the radars operate in the range of 3.1 cm, and the height H of the orbit is 500 km. The minimum viewing angle ε _{min is} taken to be 20 °, which is a typical value for the considered class of radars, and the maximum viewing angle ε _{max is} taken to be 50 °. Then the elevation angle of the center of the capture band will be equal to

ε ₀ = (ε _max + ε _min ) / 2 = 35 °.

The capture band at given parameters for the spherical model of the Earth is 450 km. The vertical size h of the antenna of the proposed device in accordance with formula (2) is 5.5 cm. With an allowable structural length of 10 ÷ 15 m, the area of this antenna will be 0.55 ÷ 0.83 m ² .

The S area of the SAR antenna for the same conditions (H = 500 km, V = 7600 m / s) in accordance with formula (1) is 9.6 m ² . From this example it follows that the proposed method allows to reduce the area of the antenna device in 11 ÷ 17 times.

In practice, antennas with a vertical aperture of the order of 2λ are ineffective due to the low gain (gain). To ensure an acceptable KU and a wide capture band, you can use the antenna in the form of a waveguide-slot array with a special (cosecant type) beam pattern (beam pattern). The requirements for the shape of the MD of such an antenna in the working sector of elevation angles ε are determined based on the constancy of the reflection power for a given class of extended surface. In this case, the following factors are taken into account, affecting the change in the power of radar reflections in the capture band:

, действующая как 1/R³(ε);1) variable slant range $$R\left(\epsilon \right)=R_s\left(k_s\cdot \cos \epsilon -\sqrt{\mathrm{one}-{\mathrm{<figure-callout\; id="2"\; label="k\; s"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_s^{}\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000018.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\epsilon }\right)$$

acting as 1 / R ³ (ε);

2) linear resolution in horizontal range, the value of which is proportional to 1 / sin ε;

3) the dependence of the specific effective reflecting surface (ESR) on the angle of incidence, described by Lambert’s law [11], i.e. proportional to cos ² φ.

The analytical expression for the working section of the elevated DN taking into account the sphericity of the earth's surface (Fig. 2) has the form

$$G\left(\epsilon \right)\cong \frac{\mathrm{one}}{K}\cdot \sqrt{\frac{\sin \epsilon \cdot {\left[k_s\cdot \cos \epsilon -\sqrt{\mathrm{one}-{\mathrm{<figure-callout\; id="2"\; label="k\; s"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_s^{}\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000018.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\epsilon }\right]}^3}{{\cos }^2\left[\arcsin \left(k_s\cdot \sin \epsilon \right)\right]}}\left(7\right)$$

where ε is the elevation angle; K = 0.1569 - normalization coefficient; k _s = 1 + H / R _s ;

H is the flight altitude of the spacecraft; R _s is the radius of the Earth.

The corresponding shape of the pattern is shown in figure 4.

The specific type of phase-code modulation used in the sounding radio pulse is determined from the requirements of minimizing the side lobes of the button function of uncertainty (FN). In this case, signals based on binary Barker codes, M-sequences, as well as ternary codes, etc. can be used [12, 13].

The radar signals received by the antenna of the coherent radar station during the receiving gate located between the probing radio pulses are sampled in time and quantized in amplitude and converted into digital complex signals using a high-speed analog-to-digital converter (ADC) and stored in a buffer memory ( see figure 5, 6).

From space-based radars, the received digital information is transmitted to ground-based receiving stations via a radio data line.

The ground processor algorithm implements a coordinated filtering of reflected signals for elements of the observed portion of the earth's surface, which ensures the synthesis of the antenna aperture over a time interval equal to the duration of the probing signal T _N , as well as signal compression in range.

Here is an estimate of the effectiveness of the method for the Earth observation radar complex, which has the following numerical values of the parameters of the radar and the geometry of sight:

- operating frequency f = 9650 MHz;

- orbit height H = 832 km;

- carrier velocity V = 7440 m / s;

- maximum angle of sight (from the local vertical) ε _max = 50 °;

- minimum angle of sight (from the local vertical) ε _min = 23 °;

- shooting strip L = 750 km.

These parameters are provided by the proposed radar with a synthesized aperture of the antenna with the following dimensions of the aperture of the antenna:

- horizontally D _x = 13.4 m;

- vertically D _y , = 0.1 m (with uniform amplitude field distribution);

- vertically D _y = 0.25 m (when using cosecant pattern); those. the antenna area S for the proposed method is 1.4 m ² (for the first radar option) or 3.3 m ² (for the second radar option).

At the same time, in accordance with formula (1), the area of the SAR _PCA antenna for the above conditions is 19.4 m ² , i.e. about 6-13 times more.

It should be noted that the obtained values of the antenna area S are noticeably smaller than that of the antennas of modern space radars. For example, the SAR placed on the CosmoSkyMed spacecraft [8] has an antenna area S _CSM = 8 m ² at a significantly lower orbit height H = 620 km and, therefore, shorter operating ranges.

Thus, from the description of the method and devices it follows that the radiation of a modulated probe signal selected in the form of radio pulses with non-periodic phase-code modulation, reception and registration of reflected signals using a radar station with a synthesized aperture of the antenna, and conducting consistent filtering of reflected signals for elements of the earth's surface allows reduce the effective area of the radar antenna located on the spacecraft.

Information sources

1. D.E. Wackman, R.M. Sedletsky. Issues of synthesis of radar signals. M .: Sov. Radio, 1971.

2. R. Lacomme, J.-P. Hardange, J.-C. Marchais, E. Normant. Air and Spacebome Radar Systems: An Introduction. William Andrew, N.-Y., 2001.

3. V.S. Willow, L.B. Nero, I.G. Osipov, V.E. Turuk. Space Based Radar Surveillance Systems. - M .: Radio engineering, 2010.

4. K. Rokosh. RADARSAT. Reprinted courtesy of Canadian Space Agency Compiled By - IEEE. Http://www.ieee.ca/millennium/radarsat/radarsat.pdf.

5. L.C. Morena, K.V. James, and J. Beck, "An introduction to the RADARSAT-2 mission," Can. J. Remote Sens., Vol. 30, no.3, pp. 211-234, Jun. 2004.

6. Wolfgang Pitz. The TerraSAR-X Satellite. / EUSAR 2006 - 6th European Conference on Synthetic Aperture Radar, Dresden, Germany, 2006.

7. TerraSAR-X Satellite and Mission / http://www.infoterra.de/terrasar-x-satellite.

8. Italian Space Agency. COSMO-SkyMed Mission. COSMO-SkyMed System Description & User Guide. Http://www.e-geos.it/products/pdf/csk-user_guide.pdf.

9. Radar surface of the Earth from space. / Ed. L.M. Mitnik and S.V. Viktorova. - L .: Gidrometeoizdat, 1990.

10. Reception of the first radar image from the Sich-1M satellite. Http://www.ntsomz.ru/news/news_center/sich_29_03_05.

11. Reference radar. Ed. M. Skolnik. Volume 1. M .: Sov. radio, 1976.

12. L.E. Varakin. Communication systems with noise-like signals. - M .: Radio and communications, 1985.

13. J.V. Seventline, D. Elizabath Rani, K. Raja Rajeswari. Ternary Chaotic Pulse Compression Sequences. / Radioengineering, vol. 19, No. 3, p. 415-420, September 2010.

Claims (7)

1. A method of obtaining a radar image of a portion of the earth’s surface from the spacecraft, which comprises emitting a modulated probe pulse, receiving and recording signals reflected from the surface using a radar with a synthesized aperture of the antenna, and then carry out consistent filtering of the reflected signals for the elements of the plot earth surface, characterized in that the probe pulse is formed in the form of a radio pulse with a non-periodic phase-code module tion, and a vertical dimension h of the aperture radar antenna configured in accordance with the desired size of L swath

,
where λ is the working wavelength; R is the slant range to the middle of the capture band; φ is the angle of incidence of the electromagnetic wave. 2. A radar with a synthesized aperture of the antenna, comprising an antenna with an aperture area S connected to the input-output of the circulator, the input and output of which are connected, respectively, to the first output and input of the coherent transceiver path, characterized in that the coherent transceiver the path is made providing for the formation at the first output of the probe radio pulse with non-periodic phase-phase modulation, while the antenna opening area S is calculated as follows

,
where l is the horizontal size of the aperture of the antenna; λ is the working wavelength; R is the slant range to the middle of the capture band; L is the required size of the capture band; φ is the angle of incidence of the electromagnetic wave. 3. A radar station with a synthesized antenna aperture according to claim 2, characterized in that the coherent transceiver path includes a master oscillator, a digital-to-analog converter, an analog-to-digital converter, a digital signal conditioner, a transmitter and a receiver, the first and second outputs of the master the generator are connected, respectively, with the first input of the digital-to-analog converter and with the first input of the analog-to-digital converter, the output of the digital signal former is connected to the second input of the digital-to-analog A burn converter, the output of which is connected to the input of the transmitter, the output of the transmitter is connected to the first output of the coherent transceiver path, the input of the receiver is connected to the input of the coherent transceiver path, the output of the receiver is connected to the second input of the analog-to-digital converter, the output of which is connected to the second output coherent transceiver path. 4. A radar station with a synthesized antenna aperture according to claim 3, characterized in that a buffer random access memory is introduced into the device, the input of which is connected to the second output of the coherent transceiver path, and the output is connected to the input of the radio data line to ground receiving points. 5. A radar station with a synthesized aperture of the antenna, comprising an antenna connected to the input-output of the circulator, the input and output of which are connected, respectively, to the first output and input of the coherent transceiver path, characterized in that the coherent transceiver path is configured to form on the first the output of the probe radio pulse with non-periodic phase-phase modulation, while the antenna is made in the form of a waveguide-slot array, providing a directivity pattern in the vertical th plane G (ε)

where ε is the elevation angle, K = 0.1569, k _s = 1 + H / R _s , H is the flight altitude of the spacecraft, R _s is the radius of the Earth. 6. A radar station with a synthesized antenna aperture according to claim 5, characterized in that the coherent transceiver path includes a master oscillator, a digital-to-analog converter, an analog-to-digital converter, a digital signal conditioner, a transmitter and a receiver, the first and second outputs of the master oscillator being connected , respectively, with the first input of the digital-to-analog converter and with the first input of the analog-to-digital converter, the output of the shaper of the digital signal is connected to the second input of the digital-analog transducer, the output of which is connected to the input of the transmitter, the output of the transmitter is connected to the first output of the coherent transceiver path, the input of the receiver is connected to the input of the coherent transceiver path, the output of the receiver is connected to the second input of the analog-to-digital converter, the output of which is connected to the second output coherent transceiver path. 7. A radar station with a synthesized antenna aperture according to claim 6, characterized in that a buffer random access memory is introduced into the device, the input of which is connected to the second output of the coherent transceiver path, and the output is connected to the input of the radio data line to ground receiving points.

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