RU2493530C1 - Method of concealing ground mobile object from radar observation from space - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method of concealing a ground mobile object from radar observation from space includes evaluating the time schedule of flights and directions to a space radar station, estimating the maximum radial component of the speed of the ground mobile object relative the direction of radar observation, estimating the required reduction in detection and recognition of the ground mobile object, estimating the capacity to shift the radar image of the object to a strongly reflecting background. To enable concealment of the mobile object from radar observation, acceleration on a selected section of the road in the required azimuthal direction is carried out and speed of the ground mobile object at the moment of radar observation, which provides shifting of its radar image to a selected section of the area, is maintained.

EFFECT: reduced level of detecting and recognising a ground mobile object during radar observation with a space radar station with high spatial resolution.

10 dwg

Description

The invention relates to the field of disguise of ground-based mobile objects from space-based systems of radar observation by reducing their reflective properties against the background of the surrounding area.

, где ΔX,ΔY - габаритные размеры (длина, ширина) объекта. Скрытие объектов на фоне УПЗ (снижение вероятностей обнаружения и распознавания к минимуму) будет достигаться, если РЛ контраст К объекта и фона не превышает некоторого заданного значения:Known methods for hiding ground mobile objects in both the optical and radar (RL) ranges by reducing the reflective characteristics of an object to the level of reflective characteristics of the background of the surrounding area. In the optical range, special types of coloring (protective, deforming and imitating colors for typical backgrounds of the terrain of the areas of application of objects) and camouflage nets are used. In the RL range on mobile objects, special radio-absorbing and radio-scattering coatings and masks are used that reduce reflection from the metal parts of objects to the level of reflective characteristics of the surrounding background area. As an analogue, you can specify a device that implements a method of reducing the reflection characteristics due to depolarization and fluctuation of the amplitudes and phases of the reflected signal [1]. Masking material in the form of a mat is installed over the roof of a ground-based mobile object and is equipped with a set of dipole reflectors with flexible mounting and random orientation in the horizontal and vertical planes and the ability to adjust the length in order to adapt to the radar wavelength. In fact, a device is installed on the roof of a ground-based mobile object that simulates a site with a vegetative background and, accordingly, reproduces with some degree of similarity its reflective characteristics - specific effective scattering area (UEPR) σ _Ф0 , taking into account angular, frequency, polarization, seasonal and meteorological dependence. For radar observation (RLN) of the Earth’s surface sections (OPS) from outer space, radars with a synthesized antenna aperture (RRS) are used with coherent signal processing in the mapping mode having a radar image resolution (RIR) of Δ up to a meter. Therefore, the radar image of stationary objects having some effective scattering area (EPR) σ will consist of a combination of elements (pixels) $$N\approx \frac{\Delta X\mathrm{<figure-callout\; id="2"\; label="\Delta \; Y\; \Delta "\; filenames="00000041.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}Y}{{\Delta }^{}}$$

where ΔX, ΔY are the overall dimensions (length, width) of the object. Hiding objects against the background of the SCL (reducing the probability of detection and recognition to a minimum) will be achieved if the radar contrast K of the object and the background does not exceed a certain specified value:

$$K=\frac{K_O-K_F}{K_O}<{\mathrm{TO}}_{d\mathrm{about}P.},\left(\mathrm{one}\right)$$

$$K_O=\sigma /N,\left(2\right)$$

- the intensity of reflection of the elements of the object,

$${\mathrm{TO}}_F={\sigma }_{F0}{\Delta }^2\left(3\right)$$

- the intensity of reflection of the background elements of the surrounding area,

- To _add - the acceptable value of the radar contrast.

The EPR of terrestrial mobile objects with radar radar from the upper hemisphere lies in the range of σ = 8-10 m ² [2, p.145]. Unlike airborne RSA, in KRSA, the mode of observation (selection) of moving targets (SDS) is not implemented due to the weakly correlated background arising from the high speeds of the movement of KRSA relative to the Earth’s rotating surface. At this stage of development, in some KRSA of foreign countries (Radarsat-2, TerraSAR-X, TanDEM-X), a longitudinal interferometry mode is implemented to observe only large-area moving objects such as sea currents.

For the method of concealment, the analogue provides for the exit of ground mobile objects from the road and their placement on roadside sections with the corresponding reflective characteristics for the period of observation, which means a loss of time during their relocation. Dirt roads and roads with improved coverage (gravel, asphalt, concrete) in the optical range are lighter than the surrounding background of the terrain, and in the radar range they are less rough (smoother), from which the mirror image of the incident radar signal occurs. When the object’s inclined radar index on a smooth background of the road, there is an additional amplification of signal reflection and, accordingly, an increase in the brightness of the radar pixels due to the dihedral angle “horizontal surface - vertical object” [3, p.90]. T.O. The method specified in the analogue does not provide a sufficient decrease in the reflective characteristics of a land mobile object.

Known methods for hiding mobile objects (aircraft) from the radar homing head (radar seeker) missiles "air-to-air" by introducing a Doppler frequency shift in the re-emitted signal [4], corresponding to several false targets that differ in the radial velocity of the relative movement of the rocket and the aircraft. As a rule, depending on the type of pulsed Doppler radar of the GOS missile (radiation modes, magnitude of the pulse repetition rate, type of space survey), a lot of false (leading) gates in range and radial speed are formed, contributing to the disruption of tracking by filling all or some of the Doppler filters of the processing system of the radar seeker. Distracting interference is generated in a short period of time (up to tens of seconds), but sufficient to mislead the GOS radar processing system and the corresponding miss miss. Additionally, amplitude modulation of the leading strobes is performed, simulating a reduction in the EPR of the simulated targets and a combination of such electronic countermeasures along the direct and reflected interference beam for low-flying aircraft. The described methods of hiding a real target (aircraft) against the background of other false targets, including the background of UPZ, require a specialized jamming station on board (fuselage) of the aircraft or an active radar trap towed behind it on a cable [5]. A similar design of spatially separated sources of interference allows you to further counteract the tracking radar seeker in the angular position. Due to the aerodynamic effects, the oscillation of the cable leads to the angular movement of the aircraft and the trap relative to the line of sight of the radar seeker, i.e. additional tangential velocity of the observed targets. T.O. The method indicated in the analogue provides a sufficient decrease in the reflective characteristics of a mobile object (aircraft), but by using a complex radio interference station.

Of the known solutions, the closest in technical essence to the claimed invention is a method of hiding mobile objects (aircraft) from the radar, selected as a prototype, based on the maneuvers of evading missiles with radar seekers, i.e. interference for disruption of tracking radar seeker is not created by the targeted re-emission of the modified signals, but by the natural reflection of the radar signals from the fuselage of the aircraft, making the necessary short-term spatial movement relative to the far-angular position of the direction of approach of the rocket [6, p. 47; 7]. Evasion maneuvers involve an intensive change in the angular position of the aircraft in space with the simultaneous use of significant angular velocities and significant curvature of the trajectory when changing this position. The so-called guaranteed flap of the aircraft trajectory at an angle of up to 90-120 ° in the vertical plane (short-term maneuver - up to 5-6 seconds - such as “Pugachev’s cobra”, “bell”, “Frolov’s chakra”, “dive”), in the horizontal plane ( short-term maneuver of the type “hook”, “horizontal cobra”) and in both planes (short-term maneuver of the type “turn / turn”, “corkscrew”) leads to a change (decrease) in both radial (long-range) and an increase in tangential and transverse (t .e angular) components of the relative expansion of the irradiated aircraft and the radar radar of the GOS missile due to aerodynamic braking of the aircraft fuselage and curvature of its trajectory [8]. Such maneuvers lead to the failure of guidance and tracking of radar seeker missiles. The spectrum of the reflected signals (packs of coherent pulses of the radar seeker radar) changes - due to the radial component of the object (airplane) speed, its Doppler shift occurs, and due to the tangential and transverse components, it is blurred (expanded), as a result, the signal from the target falls into the passband several Doppler filters of the processing system of the radar seeker. Given the decrease in the power spectral density of the reflected signal due to the expansion of the spectrum, this leads to a decrease in the X-ray contrast against the background of meteorological and / or Earth surfaces. With a short range to the target, when the reflected signal has a large power, blurring the spectrum of several filters can lead to a false decision about the presence of several targets. Thus, the prototype provides a decrease in the reflective characteristics of the mobile object by performing short-term spatial maneuvers, but the use of range gating in the processing system of the radar seeker can influence the background of the Earth and weather patterns.

The objective of the invention is to reduce the level of detection and recognition of a ground-based mobile object during radar observation by space radar with high spatial resolution by performing targeted maneuver - short-term movement of the object at a certain speed along the road with a certain azimuthal orientation at the time of the radar observation based on the reflection characteristics of the terrain background surrounding the road.

To solve this problem in the proposed method of hiding a ground mobile object:

reduce the reflective characteristics of the ground-based mobile object to the level of reflective characteristics of the background areas of the surrounding area,

give the Doppler frequency shift to the reflected radar signal by making a short-term ground avoidance maneuver by the ground mobile object in the interval of radar observation,

based on the a priori known geographical location of the route of movement of a ground-based mobile object, orbital parameters and orientation parameters of the radiation pattern of a space radar antenna, the time moments of flight of the space radar of the points of minimum distance from it and the corresponding elevation angles and azimuth of the direction of radar observation are calculated;

determining a section of the road network along the relocation route of a ground-based mobile object having a sufficient length, coverage quality and azimuthal orientation close to the azimuth of the radar observation direction at the time of flight of the space radar;

based on the a priori known frequency range, polarization and resolution of the radar image generated by the space radar, the dimensional and reflective characteristics of the ground mobile object and areal terrain objects having angular, frequency, polarization, seasonal and meteorological dependence, determine the radar contrast of the elements of the radar image of the ground mobile the object and background of the surrounding area near the road section;

on the basis of the a priori known maximum developed speed of the ground mobile object, an area terrain object is selected near the road section that provides the minimum radar contrast of the ground mobile object against the terrain and is located at a distance along the flight path of the space radar that does not exceed the maximum possible azimuthal shift of the radar image of the ground mobile object relative to the road section;

accelerate on a selected section of the road in the required azimuthal direction and maintain the speed of the land mobile object at the time of radar observation, providing a shift of its radar image to the selected area.

Due to the laws of land survey (the radar direction is perpendicular to the track and is limited by a certain range of DND roll angles Δγ = γ _max- γ _min and, respectively, elevation angles ΔУМ = УМ _max- УУМ _min ) and the orbital movement of the ballistic missile system, a discrete radar system has been established both in angles and in time [9]:

$$\mathrm{At}{M}_{\max ,\min }=\arccos \left(\frac{\left(R_3+H\right)\cdot \sin {\gamma }_{\min ,\max }}{R_3}\right),\left(\mathrm{four}\right)$$

R _W = 6371 km the average radius of the Earth,

H is the height of the orbit of KRSA.

The azimuth of radar station AZ is determined through the central angle ψ _γ corresponding to the roll angle of the bottom

$${\Psi }_{\gamma \max ,\min }=\arcsin \left(\frac{\left(R_3+H\right)\cdot \sin {\gamma }_{\max ,\min }}{R_3}\right)-{\gamma }_{\max ,\min }\left(5\right)$$

round / review left side of the review right side of the review ascending

$$\cos A3=\frac{\sin B\cdot \sin {\Psi }_{\gamma }-\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

$$\cos \left(360°-A3\right)=\frac{\sin B\cdot \sin {\Psi }_{\gamma }+\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

downward $$\cos \left(360°-A3\right)=\frac{\sin B\cdot \sin {\Psi }_{\gamma }-\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

$$\cos A3=\frac{\sin B\cdot \sin {\Psi }_{\gamma }+\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

(6) In - the geographical latitude of the observed UPZ,
i is the inclination of the orbit of KRSA.

Depending on the geographical latitude of the observed UPZ location, the range of azimuth angles of the radar heading from space is limited: both because of the limitation of elevation angles (roll angles of the bottom of the beam), and because of the side of the radar from the track and the inclination of the orbit of the beam. The angle of heel of the DND to be realized during the flight of KRSA and, consequently, the elevation angle of the MIND direction of the radar uniquely determines its azimuth angle AЗ; as a result, the direction to KRSA - the direction of the radar - corresponds to the shortest (traverse) distance to it. Periodic corrections of the KRSA orbit to maintain the required altitude, based on the goals of implementing the radar-assisted radar modes, maintaining the ballistic structure of the KRSA system and loading the ground segment of the control complex, leads to isomarousness (repeatability) of the KRSA tracks. This means that of the entire continuous set of the range of elevation angles and azimuth of the radar direction, only discrete values are realized. In addition, the interval between the spans of one KRSA and the corresponding radar station on the traverse direction is a multiple of the orbit period, which for practical cases of KRSA orbits is ~ 1.5 hours. If several CRSA are included in the orbital group, then the interval between the radar radar will be determined by the parameters of the ballistic structure. The duration of the RLN moments (the actual interval of synthesis of the antenna aperture) is from fractions to 10-12 seconds. Spatial (discrete elevation and azimuth angles) and temporal (CRRS flight times and intervals between them) radar direction indicators are stable: with ballistic forecasting of CRRS flight up to 1-2 months, radar radar intervals vary within units of minutes, and radar angles are units degrees. Thus, each RLSA KRSA corresponds to a set of parameters:

- spatial - angles RLN UM and AZ,

- time - the moment of the radar station T and the time interval after the previous radar station ΔT,

- radio - wavelength (frequency) radar signal λ, the polarization P and the resolution of the radar data Δ (determined by the width Δf spectrum radar signal and the pulse repetition frequency f _PRF emitted CASD)

$$RL{N}_k=〈\mathrm{BUT}{3}_k,\mathrm{At}{M}_k,T_k,\Delta T_k,{\lambda }_k,{\Delta }_k,P_k〉\left(7\right)$$

With an a priori unknown operating mode (resolution of the radar image Δ and polarization P) realized by the RRS in this radar, one can assume the worst case for a hidden object, i.e. the formation in KRSA of the most detailed radar images of the UPZ in multipolarization mode.

The linear velocity of a portion of the Earth’s rotating surface at geographic latitude B is determined through the linear velocity at the equator, _UE = 465 m / s

$${\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="00000041.png"\; state="\{\{state\}\}">V</figure-callout>}}_3=V_{3E}\cos B.\left(8\right)$$

The magnitude of this speed determines the parameters of the Doppler processing of reflected signals in KRSA in the mapping mode UPZ (reference function in the synthesis of radar data). The components of the linear velocity of the Earth’s rotation lie in the XOY plane tangent to the spherical surface of the Earth at the point of radar (Fig. 1), i.e. the longitudinal (azimuthal) projection onto the OY axis will be the tangential component, and the transverse and radial components will form a transverse projection onto the OX axis. This is a typical representation of the velocity components during the synthesis of radar contact lenses in the coordinates of “oblique-longitudinal range”, while the oblique (traverse) range from KRSA to the object in the middle of the synthesis interval is defined as

$$R=\sqrt{{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3^2+{\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)}^2-2R_3\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\cos {\Psi }_{\gamma }}={\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3\frac{\sin {\Psi }_{\gamma }}{\sin \gamma }=\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\frac{\sin {\Psi }_{\gamma }}{\cos \mathrm{At}M}\left(9\right)$$

The tangential component of the relative speed of movement of KRSA V and UPZ V _Z

$$V_T=V\pm V_{3Y}\left(10\right)$$

determines the slope of the linear frequency modulation (Fig. 2, solid line) and, accordingly, the width of the Doppler spectrum Δf _D for a known beam pattern of a real antenna KRSA θ (bottom spot width R _C ≈Rtgθ on the heading for a known oblique range R).

$$V=\sqrt{\frac{\mathrm{<figure-callout\; id="3"\; label="G\; M\; R"\; filenames="00000041.png"\; state="\{\{state\}\}">G\; </figure-callout>}M}{R_{}}}\left(\mathrm{eleven}\right)$$

where GM-398600.448 km ³ / s ² is the Earth's gravitational constant.

Selection of pulse repetition frequency _PRF value f in CASD determined precisely this component relative moving speed, based on the theorem Kotel'nikova. The sign “-” in the tangential component of velocity (8) corresponds to direct inclined orbits (0 ° <i <90 °), and the sign “+” corresponds to reverse inclined orbits (90 ° <i <180 °). The value of the tangential component of the linear velocity of the Earth’s rotation is determined by the orientation of the KRSA orbital plane

$$V_{3Y}\approx V_{3E}\cos i\left(12\right)$$

(ie, it is absent for polar orbits) and is almost constant over the entire orbit of KRSA due to the “coordinated” change in the linear velocity of the Earth’s rotation with the latitude of the sub-satellite point and the azimuthal direction of the KRSA path [10].

The radial component of the linear velocity of the Earth

$$V_{3R}=V_{3X}\cos \mathrm{At}M\left(13\right)$$

calculated on the basis of the transverse velocity projection (Fig. 3)

$$V_{3X}={\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="00000041.png"\; state="\{\{state\}\}">V</figure-callout>}}_3\cos {\beta }_X\left(\mathrm{fourteen}\right)$$

$$\begin{array}{ccc}{\beta }_X=90°-\mathrm{<figure-callout\; id="3"\; label="A"\; filenames="00000041.png"\; state="\{\{state\}\}">A</figure-callout>}3,& 0°<A3<90°,& \left(\mathrm{fifteen}\right)\\ {\beta }_X=A3-90°,& 90°<A3<180°,& \\ {\beta }_X=270°-\mathrm{<figure-callout\; id="3"\; label="A"\; filenames="00000041.png"\; state="\{\{state\}\}">A</figure-callout>}3,& 180°<A3<270°,& \\ {\beta }_X=A3-270°,& 270°<A3<360°,& \end{array}$$

AZ - azimuth of the radar direction, determined by (6).

The radial component of the linear velocity of the Earth’s rotation varies from the maximum value at the equator (B = 0 °) to zero at the vertex points of the orbit (B≈0 °) and determines the average frequency of the Doppler spectrum

$$f_D=\pm \frac{2V_{3R}}{\lambda }=\pm \frac{2V_{3X}\cos \mathrm{At}M}{\lambda }\left(17\right)$$

In addition, it is minimal at the near boundary of the Raman scan band (i.e., at γ _min and CM _max ) and maximum at the far border (at γ _max and CM _min ). The “+” sign of the average Doppler frequency corresponds to the left SRSA scan (to the left of the KRSA track) in the upward turn and the rightward view in the downward turn (UPZ “runs” onto the KRSA), and the “-” sign corresponds to the right view in the upward turn and the left view on downward turn (UPZ "runs away" from KRSA). To simplify the synthesis of radar images, the average Doppler frequency can be eliminated either by hardware (by orientation of the beam pattern towards the so-called “zero Doppler” direction ≈ ± 3 ° from the perpendicular direction), or programmatically during quadrature processing of reflected coherent pulses (Fig. 2, dashed line). The latter method is used as a standard mode in all cattle, as facilitates the constant maintenance of the spacecraft in a given angular orientation.

The movement and, accordingly, the components of the speed V _{C of the} ground-based mobile object (Fig. 1, 4) are determined by the azimuthal orientation of the road, the direction of movement (along the radial direction V _CX - to or from the KRSA track; along the tangential direction V _CY - towards or in the direction of the KRSA flight parallel to its route) and the magnitude of speed (driving properties of a land mobile object and the quality of the road surface). The transverse component of the speed of a land mobile object, formed due to the longitudinal slope of the road (the steepness of the ascent or descent), has negligible values for the effects under consideration due to building codes for road equipment [11].

Taking into account the frequency ranges of KRSA λ = 3 ÷ 23 cm (f ₀ = 10 ÷ 1.3 GHz), a limited range of elevation angles for KRSA UM = 20 ÷ 70 ° and the speed of ground mobile objects V _C = 0 ÷ 60 km / h (0 ÷ 16.7 m / s) the maximum achievable radial component of the velocity is 5.7 ÷ 15.7 m / s (respectively, the near and far border of the viewing band) and the maximum achievable average Doppler frequency ± 380 ÷ ± 1047 Hz for λ = 3 cm and ± 50 ÷ ± 137 Hz for λ = 23 cm. These values of the average Doppler frequency are additional to the Doppler shift from the radial component of the linear rotational speed Ze if, as one of the processing parameters, they lead to the displacement of the object's radar image in azimuth (longitudinal coordinate, along the KRSA path) of the frame of the synthesized radar image sensor relative to its true position on the road [3, p.178; 12, p. 305-308]. The phenomenon of azimuthal displacement of the object's radar image relative to its true position in the frame is observed for all land mobile objects - sea ships (Fig. 5), trains (Fig. 6), cars (Fig. 7a). The direction of the displacement is determined by the sign of the average Doppler frequency, and the displacement Δy is determined by the ratio of the radial component of the object’s speed V _CR to the speed of KRSA V and the magnitude of the slant range R

$$\Delta \mathrm{at}=\frac{R}{V}{V}_{\mathrm{Ts}R}=\frac{R}{V}{V}_{\mathrm{<figure-callout\; id="3"\; label="Ts\; cos\; A"\; filenames="00000041.png"\; state="\{\{state\}\}">Ts\; </figure-callout>}}\cos A{3}_{\mathrm{Ts}}\cos \mathrm{At}M,\left(\mathrm{eighteen}\right)$$

where AZ _C is the azimuthal orientation of the road. For the maximum radar displacement of the object to the right (along the longitudinal coordinate towards KRSA) relative to its true position in the frame of the radar control radar, the movement should be towards the KRSA AZ _C = AZ, for the shift to the left (along the longitudinal coordinate in the direction of flight) - from KRSA AZ _Ts = AZ ± 180 °. For orbit heights H = 400 ÷ 800 km and elevation angles UM = 20 ÷ 70 °, in accordance with (9), the inclined range lies in the range R = 427-977 ÷ 847-1720 km. Accordingly, the displacement range for the radial component of the object’s speed V _CR = ± 5.7 ÷ ± 15.7 m / s and KRSA velocity V = 7673 ÷ 7456 m / s is Δу = ± 317-1998 ÷ ± 648-3622 m, i.e. the radar object displacement value is commensurate with the bottom width RNA R _C for the width of the real BIRD bottom θ = 0.5-1 °. This means that the intensity of the pixels of the radar image of the object can be reduced to a level of 0.7 from the maximum due to a decrease in the reflection gain at the edges of the real BSSA bottom [13, p. 108]. The presence of speckle noise (granularities of radar images - variations in the intensity of reflection of pixels up to 10-15%) is characteristic of such highly detailed radar images of a uniform UPZ background; this additionally helps to hide the object radar image on the radar image intensifier. The combination of the speckle noise of the radar image and the decrease in the intensity of the radar image of the object when it is shifted to a uniform background with strong reflective properties allows you to achieve the required minimum radar contrast K <K _add and reduce the likelihood of its detection (in Fig. 7b a car with a speed of 37 km / h on the background radar the area around the airfield is not observed).

The most strongly reflecting backgrounds in the centimeter and decimeter ranges of radar observations for UM = 20 ÷ 70 ° include the following areal objects of the surrounding area [2, p. 12, p. 75]:

- industrial areas - σ _Ф0 = 5 ÷ 15 dB = 3.2 ÷ 30,

- settlements - σ _Ф0 = 0 ÷ -10 dB = 1 ÷ 0.1,

- forests (coniferous - in all seasons of the year), shrubs - σ _Ф0 = -10 ÷ -15 dB = 0.1 ÷ 0.03,

- grass cover (for cm-range) - σ _Ф0 = -12 ÷ -15 dB = 0.06 ÷ 0.03,

- slopes of the relief towards the radar site, increasing the local UM radar.

For example, for Radarsat-2 CRSA in the detailed radar mode with a resolution of Δ = 3 m, the vehicle’s radar (ΔX≈7 m, ΔY≈3.8 m) will occupy 6 pixels, therefore, at its maximum displacement along the longitudinal coordinate, the reflection intensity according to (2) will be K _O = 0.7σ / N≈0.93. The intensity of the background reflection of the forest type according to (3) K _Ф = σ _Ф0 Δ ² ≈0.9, i.e. the intensity of the pixels of the background and the shifted object become comparable, and speckle noise additionally masks their difference.

The tangential component of the velocity of the ground mobile object V _ЦY leads to a change in the steepness of the linear frequency modulation (Fig. 2, dash-dotted line), therefore, the quadratic phase incursion at the edges of the synthesized aperture, as well as the Doppler shift from the radial component of the velocity, leads to a mismatch of the support function and, therefore, the reduction and expansion of the response of the RRSA (uncertainty function) at the output of the processing system - the so-called defocusing the radar image of an object (Fig. 7c).

The movement of a ground-based mobile object (Fig. 4) - towards or in the direction of the flight of the CRSA AZ _C = AZ ± 90 ° - leads to the same effect of defocusing the radar object (expanding the uncertainty function while reducing the maximum) in accordance with the reference processing function

$$\phi \left(t\right)=\frac{\mathrm{four}\pi }{\lambda }\left(R+\frac{{\left(V\pm V_{\mathrm{Ts}R}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000041.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}{2R}\right).\left(19\right)$$

Due to the small contribution of the tangential velocity of the ground-based mobile object to the mismatch of the support function (V _C <16.7 m / s at V = 7673 ÷ 7456 m / s), defocusing of the object's radar image can be considered only as an additional effect of reducing the radar contrast. The sources of defocusing the radar image of a ground-based mobile object also include vibrations and angular vibrations of elements when it moves along the road.

The aforementioned areal areas of the terrain and road sections with the required azimuthal orientation and quality of coverage in accordance with the classifier of cartographic information can be a priori determined on the basis of a digital topographic map of the terrain for the area of movement of the land mobile object [14]. Acceleration sections of a ground-based mobile object can be selected along the route of movement in accordance with the time schedule of the radar relay control station. The planning of the relocation of a ground-based mobile object is carried out in such a way that by the time of the radar station it has the required azimuthal orientation, sufficient length of the section and the quality of the road surface to disperse the land-based mobile object to realize the maximum concealment effect - with large values of the UM radar, there is an increase in the SES of the background and greater defocusing, when small UM RLN greater azimuthal displacement is realized.

Significant differences of the proposed method include:

1. Calculation of the moments of time of flight of a space radar of points of minimum distance from it and the corresponding elevation angles and azimuth of the direction of radar observation based on a priori known geographical location of the route of movement of a ground-based mobile object, orbit parameters and orientation parameters of the radiation pattern of the antenna of a space radar - to evaluate time schedule of flights and directions to the space radar.

- азимут направления радиолокационного наблюдения для восходящего витка орбиты и левой стороны обзора космического радиолокатора, град, $$A3=\arccos \frac{\sin B\cdot \sin {\Psi }_{\gamma }-\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

- azimuth of the direction of radar observation for the ascending orbit and the left side of the space radar, deg,

- азимут направления радиолокационного наблюдения для восходящего витка орбиты и правой стороны обзора космического радиолокатора, град $$A3=360°-\arccos \frac{\sin B\cdot \sin {\Psi }_{\gamma }+\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

- azimuth of the direction of radar observation for the upward turn of the orbit and the right side of the view of the space radar, deg

- азимут направления радиолокационного наблюдения для нисходящего витка орбиты и левой стороны обзора космического радиолокатора, град $$A3=360°-\arccos \frac{\sin B\cdot \sin {\Psi }_{\gamma }-\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

- azimuth of the direction of radar observation for the downward orbit of the orbit and the left side of the view of the space radar, deg

- азимут направления радиолокационного наблюдения для нисходящего витка орбиты и правой стороны обзора космического радиолокатора, град $$A3=\arccos \frac{\sin B\cdot \sin {\Psi }_{\gamma }+\cos i}{\cos {\Psi }_{\gamma }\cdot \cos B}$$

- azimuth of the direction of radar observation for the downward orbit of the orbit and the right side of the view of the space radar, deg

B - geographical latitude of the observation area, city,

i - the inclination of the circular orbit of the space radar, deg,

- центральный угол, соответствующий углу крена диаграммы направленности антенны космического радиолокатора, град, $${\Psi }_{\gamma }=\arcsin \left(\frac{\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\cdot \sin \gamma }{R_3}\right)-\gamma$$

- the Central angle corresponding to the angle of heel of the radiation pattern of the antenna of the space radar, deg,

- наклонная дальность от наземного мобильного объекта до космического радиолокатора, находящегося на траверсе орбиты, км, $$R=\sqrt{{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3^2+{\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)}^2-2R_3\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\cos {\Psi }_{\gamma }}={\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3\frac{\sin {\Psi }_{\gamma }}{\sin \gamma }=\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\frac{\sin {\Psi }_{\gamma }}{\cos \mathrm{At}M}$$

- the oblique range from the ground-based mobile object to the space radar located on the traverse of the orbit, km,

- угол места направления радиолокационного наблюдения космическим радиолокатором, град, $$\mathrm{At}M=\arccos \left(\frac{\left({\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="00000041.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+H\right)\cdot \sin \gamma }{R_3}\right)$$

- the elevation angle of the direction of radar observation by space radar, deg,

γ∈ [γ _min , γ _max ] - roll angle of the radiation pattern of the space radar, deg,

H - the height of the circular orbit of the space radar, km,

R _З = 6371 km is the average radius of the Earth.

2. Determination of the road network section along the relocation route of a ground-based mobile object with sufficient length, coverage quality and azimuthal orientation close to the azimuth of the direction of radar observation at the time of flight of the space radar — to estimate the maximum radial component of the speed of the ground-based mobile object relative to the direction of radar observation.

AZ _Ts ≈AZ ± 180 ° - azimuthal orientation of the road section of the ground mobile object to realize the azimuthal displacement of its radar image Δу in the direction of flight of the space radar, deg.

AZ _C ≈AZ - azimuthal orientation of the road section of the ground mobile object to realize the azimuthal displacement of its radar image Δy against the direction of flight of the space radar, deg,

3. Determination of the radar contrast of the elements of the radar image of the ground-based mobile object and the background of the surrounding area near the road section on the basis of the a priori known frequency range, polarization and resolution of the radar image generated by the space radar, the dimensional and reflective characteristics of the ground-based mobile object and areal terrain objects having angular , frequency, polarization, seasonal and meteorological dependence - for assessment we require Wow reduce the detection and recognition of ground-based mobile object.

- радиолокационный контраст наземного мобильного объекта и фона участка окружающей местности, $$K=\frac{K_O-K_F}{K_O}<{\mathrm{TO}}_{d\mathrm{about}P}$$

- radar contrast of the ground mobile object and the background of the surrounding area,

K _O = σ / N, is the reflection intensity of the elements of the radar image of a land mobile object,

To _f = σ _{f 0} Δ ² - the intensity of the reflection of the background elements of the plot of the surrounding area,

To _add - the permissible value of the radar contrast, providing a given reduction in the detection and recognition of a ground-based mobile object,

- количество элементов радиолокационного изображения наземного мобильного объекта, $$N\approx \frac{\Delta X\Delta Y}{{\Delta }^2}$$

- the number of elements of the radar image of a ground-based mobile object,

ΔX, ΔY - overall dimensions (length, width) of a land mobile object, m,

σ is the effective scattering area of a land mobile object,

σ _Ф0 is the specific effective dispersion area of areal objects of the area, taking into account the angular, frequency, polarization, seasonal and meteorological dependence.

Δ is the resolution of the radar image formed by the space radar, m

4. The choice of an area terrain object near the road section that provides the minimum radar contrast of the ground mobile object against the terrain and is located at a distance along the flight path of the space radar that does not exceed the maximum possible azimuthal displacement of the radar image of the ground mobile object relative to the road section based on the a priori known maximum the developed speed of the ground mobile object - to assess the possibility of displacement p diolokatsionnogo image of the object on the highly reflective background terrain.

- величина азимутального смещения радиолокационного изображения наземного мобильного объекта относительно своего истинного положения на участке дороги, $$\Delta \mathrm{at}=\frac{R}{V}{V}_{\mathrm{<figure-callout\; id="3"\; label="Ts\; cos\; A"\; filenames="00000041.png"\; state="\{\{state\}\}">Ts\; </figure-callout>}}\cos A{3}_{\mathrm{Ts}}\cos \mathrm{At}M$$

- the magnitude of the azimuthal displacement of the radar image of the ground-based mobile object relative to its true position on the road section,

- скорость космического радиолокатора, $$V=\sqrt{\frac{\mathrm{<figure-callout\; id="3"\; label="G\; M\; R"\; filenames="00000041.png"\; state="\{\{state\}\}">G\; </figure-callout>}M}{R_{}}}$$

- space radar speed,

GM = 398600.448 km ³ / s ² - Earth's gravitational constant.

5. Acceleration at a selected section of the road in the required azimuthal direction and holding the speed of the ground-based mobile object at the time of radar observation, ensuring the displacement of its radar image to the selected area — to ensure that the ground-based mobile object is hidden from radar observation.

- - скорость движения наземного мобильного объекта в момент радиолокационного наблюдения космическим радиолокатором $$V_{\mathrm{Ts}}=\frac{\Delta \mathrm{at}\cdot V}{R\cdot \cos A{3}_{\mathrm{Ts}}\cos \mathrm{At}M}$$

- - the speed of the ground-based mobile object at the time of radar observation by space radar

Thus, this set of sequential actions of the proposed method for hiding a ground-based mobile object from radar observation from space eliminates the disadvantages of the above analogues and prototype and provides a reduction in the level of detection and recognition due to a significant decrease in the radar contrast of the image of the ground-based mobile object against the background of the radar image of the area surrounding the road .

LITERATURE

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Claims (1)

A method of hiding a ground-based mobile object from radar observation from space, including reducing the reflective characteristics of a ground-based mobile object to the level of reflective characteristics of the background areas of the surrounding area, imparting a Doppler frequency shift to the reflected radar signal by performing a short-term ground avoidance maneuver by the ground-based mobile object in the interval of radar observation, characterized in what time moments of flight of a space radar t check the minimum distance to it from the object and the corresponding elevation angles and azimuth direction based radar priori known geographic location route traffic on the mobile object, orbital parameters and orientation parameters of the radiation pattern of the antenna space radar; determining a section of the road network along the relocation route of a ground-based mobile object having a sufficient length, coverage quality and azimuthal orientation close to the azimuth of the radar observation direction at the time of flight of the space radar; determine the radar contrast of the elements of the radar image of the ground mobile object and the background of the surrounding area near the road section on the basis of the a priori known frequency range, polarization and resolution of the radar image formed by the space radar, the dimensional and reflective characteristics of the ground mobile object and areal terrain objects having angular, frequency polarization, seasonal and meteorological dependence; select an area terrain object near the road section that provides the minimum radar contrast of the ground mobile object against the terrain and is located at a distance along the flight path of the space radar that does not exceed the maximum possible azimuthal displacement of the radar image of the ground mobile object relative to the road section based on the a priori known maximum developed speed movement of a land mobile object; accelerate on a selected section of the road in the required azimuthal direction and maintain the speed of the land mobile object at the time of radar observation, providing a shift of its radar image to the selected area.

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