RU2625542C1 - Radar facility for detecting the asteroids - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: radar facility is the spaced apart transmitting and receiving stations, where the ground radars of different ranges are used as the transmitting stations, distributed approximately uniformly over the Earth surface, and the receiving stations are positioned on space vehicles, moving along the orbits around the Earth or parallel with the Earth in space area, each of which contains the reception multifrequency antenna, connected to the receiving device inputs, which includes the first and the second receive paths, which outputs are connected to the first and the second inputs of the signal recording system, to the third input of which the synchronometer is connected. The first signal recording system output is connected to the first correlator input and to the first information storage device input, and the second signal recording system output is connected to the second correlator input and to the second information storage device input, which output is connected to the transmitting path, including the information signal generating system and the transmitting antenna, directed to the Earth, to transmit the information to the processing center at the frequency different from the receiving paths frequencies to provide its simultaneous operation.

EFFECT: increase of the extraterrestrial objects detection range and reliability and improvement of the trajectories measuring accuracy their flight in the near-earth and far outer space due to the use of the luminal effect phenomenon.

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Description

The invention relates to multi-position radar with detection "in the light" and can be used to detect, determine the flight path and accompany flying objects (asteroids, comets, artificial objects) both in near space and in the distant vicinity of the Earth (several million kilometers).

In connection with the fall to Earth of Chelyabinsk and a number of smaller meteorites in the winter of 2013, the problem of creating an asteroid-comet hazard warning system became more acute. In addition, it is assumed that a large number of undetected small sized celestial bodies rotate around the Earth inside the lunar orbit, which pose a threat to spacecraft (SC) and can periodically fall to the Earth.

From the point of view of economic costs, optical systems that conduct a continuous global survey of the sky, including to identify objects that pose a threat to the Earth, are still the most effective, however, they have a number of drawbacks, namely: 1) the sky can be surveyed only at night; 2) optical systems are not all-weather; 3) objects approaching the Earth from the side of the Sun by optical means are difficult to detect. Those. To create a reliable tracking system for objects hazardous to the Earth, it is necessary to supplement the optical observation systems with radar tools, devoid of optical imperfections and exceeding them in the accuracy of determining the object's motion parameters.

The experience of using traditional (mono- or bistatic) radars in radio astronomy has shown that, at least within the lunar orbit, location systems with large-diameter antennas can be used to accurately measure the motion parameters of asteroids already detected by optical means (Benner L., 2013 , http://echo.ipl.nasa.gov/asteroids/2012DA14/2012DA14_planning.html (Goldstone, USA), http://kaira.sgo.fi/2013_02_01_archive.html (Vierinen J., 2013. Haystack, USA) ) The margin of time from the start of tracking to the closest approach of the object to the Earth will be from several hours to several days.

Carrying out the location of asteroids in the radio range encounters at least two main problems, leading to uncertainties in estimating the magnitude of the signal reflected from the object. Firstly, the reflection coefficient of the substance of the celestial body in different ranges of radio waves is unknown. If one compares with the data on the parameters of the lunar soil (for example, T. Hagfors. Remote Probing of the Moon by Infrared and Microwave Emissions and by Radar. // Radio Science. 1970. V. 5, Issue 2. PP. 189-227) , the reflection coefficient of the asteroid substance in the radio range will not exceed 7-10%. Secondly, the complex shape and strong roughness of the surface of asteroids can lead to significant losses of the “useful” reflected signal even for large bodies. In the conducted experiments on the location of the asteroid 2012DA14 in a bistatic mode, it was obtained (M.B. Nechaeva, N.A. Dugin et al. Izv. VUZov Radiofizika, 2014, v. 57, No. 10, p. 774-783), that the reflected signal had an extremely irregular quasiperiodic character with moments of almost complete attenuation. This effect may be due to the rotation of the object and the roughness of its reflective surface. Such a signal cannot be considered reliable in solving the problem of detecting small celestial bodies.

Thus, traditional radars in the task of detecting asteroids cannot compete strongly with optical devices because of the high energy costs and the low probability of detecting an object. But optical means are also not able to detect an object with a low reflection coefficient ("black body"), as well as for the above reasons.

With the development of radar, designed to deal with stealth aircraft (including those made using the STELS technology), new so-called "clearance" radars were proposed.

Known bistatic radar stations (radars) (see Chernyak BC Multilink radar. - M.: Radio and communications, 1993, - 416 p., Guide to radar. Translated from English under the editorship of M. Skolnik. V.4. - M .: Soviet radio, 1979), including multi-position, in which the transmitting and receiving complexes of equipment are separated in space. This construction has several advantages compared to a monostatic radar (see Ufimtsev P.Ya. // Radio Engineering and Electronics, 1989, v. 35, No. 12. - pp. 2519-2527, Glaser J. Bistatic RCS of Complex Objects Near Forward Scatter, IEEE Transactions on aerospace and electronic systems. Vol. AES-21, No. 1, January, 1985. - p. 70-78), consisting in the possibility of implementing the radar method based on the luminous effect, which consists in the fact that when irradiated of an object whose dimensions are several times greater than the wavelength emitted by the transmitter, the energy scattered backward is several orders of magnitude (on average three) less than the energy scattered forward along the irradiation line, as a result of which the effective scattering area (EPR) of the object when observed in a “by light” bistatic radar is thousands of times greater than the EPR of the object for a traditional monostatic radar.

Known radar complex (see RU 2324197), containing a bistatic "translucent" radar station (radar), which is a spaced apart transmitting position as part of a series-connected transmitter and transmitting antenna and a receiving position as part of a series-connected receiving antenna with a multi-beam radiation pattern, the receiving device and the operator’s workplace, while the transmitting and receiving antennas are raised to a height that provides direct radio visibility, and the meetings are directed well, at the same time, a monostatic radar was introduced at the receiving position, the detection zone of which overlaps the detection zone of the bistatic “radar” radar, and the input-output of the monostatic radar is connected to the output-input of the operator’s workstation, providing the command to turn on the monostatic radar as instructed by the bistatic “radar” Radar, display, identification of radar information and the issuance of target designation to an external consumer in the form of output information from the radar system, while the operating frequencies of the bistatic Swetnam "monostatic radar and radar are offset to ensure their simultaneous operation.

In the described complex, the “luminous” radar performs the auxiliary function of detecting an object, followed by the “transmission” of its monostatic radar for further target designation.

Known radar complex (see RU 2422849), containing a bistatic, including "luminaire" radar station, which is a spatially spaced transmitting and receiving station, where space-based natural or artificial noise sources are used as a transmitting station, and the receiving station is terrestrial and contains an antenna and a receiving device including a main receiving path for noise signals, a registration system for a quantized noise signal, a correlator, synchronously emp, the primary receive path includes a low noise amplifier (LNA) with a wide reception band and is connected to the LNA output with the inverter connected to the registration system to which is also connected synchronometer and which comprises two recording channels, the outputs of which are connected to the correlator.

This version of the complex with the placement of transmitters on spacecraft, and receiving systems on Earth is effective, since objects far from the Earth will be detected immediately after the transmitter enters the bottom of the transmitter, as the whole Earth will fall into a narrow zone of detection (translucent effect) from far distances. This circumstance can lead to minimization of the number of spacecraft in distant orbits, but significant power expenditures will be required on the devices, which can hardly be provided with solar batteries, and there will be difficulties in creating any compact low-frequency transmitting antennas.

The problem to which the invention is directed is the use of translucent radar methods using probing signals with a different emission spectrum to obtain a technical result: increasing the range and reliability of detection of extraterrestrial objects (asteroids, comets) and increasing the accuracy of measuring their flight paths in near-Earth and far outer space.

The achievement of the specified technical result is ensured by the fact that in the invention, one or several antennas located on spacecraft moving in orbits around the Earth in near-Earth space or in deep space receive two monochromatic or quasi-noise signals - reflected from the object and reference from the transmitting station located on the surface of the earth. The reflected signal and (or) the correlation response between the reflected and direct signals carry information about the presence of an object (detection), the delay between the signals (direction to the object), the Doppler frequency and the change in time delay (speed).

To achieve the indicated technical result, a radar complex for detecting asteroids is proposed, using the “translucent” effect phenomenon and representing a transmitting and receiving station spaced in space, where each of the receiving stations includes a receiving antenna, a receiving device, a signal registration system, a synchronometer, and a correlator. The radar complex contains several transmitting and receiving stations, where ground-based radars of various ranges distributed approximately uniformly on the Earth’s surface are used as transmitting stations, and the receiving stations are located on spacecraft (SC) moving in orbits around the Earth or in parallel with the Earth in outer space . Each of the receiving stations further comprises a transmitting path including an informative signal generating system and a transmitting antenna directed to the Earth. At the same time, in the receiving station, the multi-frequency antenna is connected to the inputs contained in the receiving device of the first and second receiving paths, the outputs of which are connected to the first and second inputs of the signal registration system. A synchronometer is connected to the third input of the signal registration system to issue time stamps. In this case, the first output of the signal registration system is connected to the input of the first correlator and the first input of the information storage device, and the second output of the signal registration system is connected to the input of the second correlator and the second input of the information storage device, the outputs of the correlators are connected to the third and fourth inputs, and the output of the information storage device connected to a transmitting path, including an informative signal generation system and a transmitting antenna directed to the Earth to transmit information to the processing center at frequencies Differing from the frequency of reception paths to ensure their simultaneous operation.

In FIG. Figure 1 shows a radar complex, which is a space-borne transmitting 1 and receiving 2 stations, where ground-based radars of various ranges distributed approximately uniformly on the Earth’s surface are used as transmitting 1 stations, and receiving stations 2 are located on spacecraft moving in orbits around the Earth or parallel to the Earth in outer space, and contain (Fig. 2) a receiving multi-frequency antenna 3 connected to the inputs of a receiving device 4, which includes receiving paths 5 and 6, a register system ation signals 7 synchronometer 8 correlators 9.1 and 9.2, and drive information (recording system) 10. The first low-frequency receiver chain 5 includes (Fig. 3a) connected in series a low noise amplifier (LNA) 11.1, 12.1 and filter system signal quantization 13.1. The second high-frequency receiving path 6 (Fig. 3b) contains the LNA 11.2, a frequency converter connected to it, which consists of a mixer 14, a local oscillator 15, a filter 12.2, an amplifier 16, and a signal quantization system 13.2. The output of the LNA 11.2 is connected to the first input of the mixer 14, to the second input of which the local oscillator 15 is connected, and the output of the mixer 14 is connected through a filter 12.2 to the input of the amplifier 16, the output of which is connected through the signal quantization system 13.2 to the signal registration system 7, to which it is connected synchronometer 8 for recording time stamps.

The correlators 9.1 and 9.2 are identical and equipped with software for processing monochromatic and noise signals.

The output of the information storage device 10 is connected to a transmitting path including an information signal generating system 17 and a transmitting antenna 18 directed to the Earth to transmit information at a frequency different from the frequencies of the receiving paths to ensure their simultaneous operation.

The operation of the device is as follows.

1. The emission mode of a continuous narrowband signal.

Used to increase the detection range of the object due to the greater radiation power. In correlators 9.1 and 9.2, autocorrelation processing of incoming signals of a certain duration is performed, which allows you to select a direct signal from a ground-based locator and a signal scattered from an object with a Doppler frequency offset. The magnitude and sign of the Doppler frequency determines the speed and direction of movement of the object.

2. The radiation mode of the quasi-noise signal.

It is used to accurately determine changes in the spatial delay of two received signals and the interference frequency, which determine the trajectory of the object.

The transmitting ground station 1 emits a phase-manipulated (quasi-noise) signal in the direction of one of the spacecraft 2 located in the far outer space (when it enters the antenna radiation pattern). Two signals arrive at the receiving antenna 3 of SC 2: the reference signal from a transmitting ground station, for example, a radar station (radar) 1 and scattered from a flying celestial body with a delay determined by the relative position of the object and receiving antenna 3. The general signal is input to the receive path 5 or 6. Two receiving paths are necessary for operation in two frequency ranges (low and high frequencies). Low frequencies (4-30 MHz) are needed to detect objects of large sizes (more than 100 m), high (30 MHz and more) - for objects of smaller sizes.

Quantization systems are typically used for signals in the video band (0-30 MHz). Therefore, in path 5, you only need to amplify the signal using the amplifier LNA 11.1, filter out the high frequencies using the filter 12.1 and apply for quantization using the signal quantization system 13.1. For higher frequencies (30 MHz or more) it is necessary to convert the signal - transfer it to a video strip using heterodyning, which is performed using a mixer 14, a local oscillator 15, a filter 12.2, then amplified by an amplifier 16 and converted to digital form (quantized) with using signal quantization systems 13.2. Then it is transmitted to the signal recording system 7. In the signal recording system 7, the data of one receiving path 5 or 6 are recorded simultaneously on two magnetic media for the formation of two information streams together with time stamps from the synchronometer 8, so that in the correlator 9.1 or 9.2 they are multiplied information flows with the required (estimated) time delay, which is introduced into one of the information flows.

Primary processing — obtaining a response by correlating two streams of information with the introduction of a variable delay (to compensate for the difference in the path of the received signals) is carried out directly in the process of observing in quasi-real time mode. The correlator 9.1 or 9.2 performs signal multiplication (software) with the introduction of a variable delay in one of the information flows. The exact delay between the signals is determined from the maximum of the cross-correlation signal, and the interference frequency determined by the movement of the source relative to the receiving antenna 3 is determined from the maximum of its spectrum. Depending on the relative position of the receiving antenna 3, the radar and the intended location of the object, the range of delay variation is calculated and, accordingly , accelerates the process of searching for the reflected signal. When the amplitude of the resulting signal exceeds a certain threshold level (the alleged detection of the object), the information recorded during this period from the information storage device 10 is transmitted to the informative signal shaper 17 and transmitted to the Earth through the transmitting antenna 18.

When the object is irradiated, the probe signal is scattered in almost all directions, but the scattered signal along the line of radiation (forward) is orders of magnitude greater than when scattered back and to the side. The ESR of the object σ in the forward direction is determined by the ratio

,

,

where S is the aperture area of an object with a linear size L, λ is the wavelength. The scattering angle θ is defined as an aperture radiation pattern with linear dimensions L at a given wavelength (at half power level)

.

.

Those. the area of the luminal effect is significantly expanded for bodies with dimensions comparable to the wavelength, for example, at L ~ (0.5-2) λ, the scattering angle will be in the range (120 ° ... 30 °). However, in this case, the effective scattering area (EPR) is significantly smaller, since it is inversely proportional to the square of the wavelength (1). Since the dimensions of cosmic bodies can vary within wide limits (from units to hundreds of meters), the question arises of optimizing the working wavelength and expanding the range to several wavelengths.

As an example of the existence and effectiveness of the "translucent" effect, we can present some of the results carried out at NIRSU NNGU im. N.I. Lobach experiments on the study of solar flare radiation at a frequency of 327 MHz on the antennas of the radio astronomy observatories NIRFI NNGU im. N.I. Lobachsky "Zimenka" and "Art. Desert. " Over the area where these antennas are located, there is a civilian flight path. For a long time, receiving antennas conduct continuous tracking of the radiation source with recording the signal to various registration systems, including control recorders for visual observation of the signal presence. During the observations, signals similar to recording the antenna radiation pattern from the radiation of artificial Earth satellites (AES) were repeatedly recorded. However, in orbits around the Earth there are no vehicles operating in this frequency range. An analysis of these phenomena showed that the phenomenon of "translucent" effect is observed when the plane flies in the region near the Sun in the radiation pattern of the receiving antenna. In FIG. Figure 4 shows the recording of the signal from the Sun on the recorder’s tape at Zimenka’s receiving station with the passage of an object (airplane) through the antenna pattern for about two minutes. It can be seen that the amplitude of the "translucent" signal is 25-30% of the total signal from the Sun, i.e. a very large value by radio astronomy standards.

Based on the fact that asteroids smaller than 50 m in size are detected by optical means only at distances close to the Earth, and existing radars can fix them, mainly within the lunar orbit, at significant power consumption, the parameters of the proposed radar complex are calculated.

It is desirable to have the first largest operating wavelength in the range of 50 m (frequency 6 MHz). However, the ionosphere is constantly transparent for long waves shorter than 15 m (frequency> 20 MHz). In the range of 4-20 MHz (low-frequency path 4 of Fig. 3a), occasional nighttime operation is possible.

Examples of transmitting ground stations include MCT radars (operating range 40-50 MHz, power up to 1 MW), incoherent scattering radars (150-1000 MHz, power up to 3 MW) and ionospheric heating stands: SURA (Russia, Nizhny Novgorod region), HAARP (USA, Alaska) and Tromso (Norway), operating mainly in the range of 5-10 MHz. At frequencies (1–20) MHz critical for the ionosphere, episodic (depending on the location of the receiving stations and the transparency of the ionosphere) possible use of the available ionosphere stands SURA, HAARP and Tromso in the proposed transmitter complex without constructing new tools.

At the booth SURA NIRFI NNSU them. N.I. Lobachevsky conducted experiments on the location of the moon and the corona of the sun at frequencies of 5-9-26 MHz in both monostatic and bistatic modes, including with the reception of a signal onboard the spacecraft in deep space (A.N. Karashtin, G.P. Komrakov and other IzvVUzov “Radiophysics”, 1999, v. 42, No. 8, p. 765-779). The transmitting station at these frequencies has large dimensions (antenna fields of tens and hundreds of meters). The power of three transmitters of 250 kW each with a beam width of 20 °.

When receiving a spacecraft at a dipole antenna, it is necessary to use radiometers with an extremely low noise temperature for uncooled LNAs in order to provide the maximum possible space survey for spacecraft in distant orbits. The size of the minimum detectable object at low frequencies is estimated to be about 10 m, which will determine the next working wavelength - 5-10 m (frequency 30-60 MHz).

A transmitting station with a range of 30-60 MHz and higher (high-frequency path 5 of Fig. 3b) can be made on the basis of a radar with an aperture size of 30-40 m, the half-width of the beam (scattering angle) is about 5-20 °.

The need to use the following higher range will be determined by the tasks of the complex: asteroids less than 10 m in size do not pose a threat of serious damage to the Earth, at higher frequencies it is possible to monitor the state of “space debris” in near-Earth space.

The calculation of the orbits, the optimal number of receiving spacecraft and operating frequencies will depend on the requirements for the characteristics and tasks of the complex.

Claims (1)

A radar complex for detecting asteroids using the phenomenon of “translucent” effect and representing a transmitting and receiving station spaced in space, where each of the receiving stations includes a receiving antenna, a receiving device, a signal recording system, a synchronometer, a correlator, characterized in that the complex contains several transmitting and receiving stations, where ground-based radars of various ranges are used as transmitting stations, distributed approximately evenly over the Earth’s surface, and p Receiving stations are located on spacecraft moving in orbits around the Earth or in parallel with the Earth in outer space, and each of the receiving stations additionally contains a transmitting path, which includes an informative signal generation system and a transmitting antenna directed to the Earth, while the receiving station has a multi-frequency antenna connected to the inputs of the first and second receiving paths contained in the receiver, the outputs of which are connected to the first and second inputs of the signal registration system, to the third input of which a synchronometer is connected, the first output of the signal recording system is connected to the input of the first correlator and the first input of the information storage device, and the second output of the signal recording system is connected to the input of the second correlator and the second input of the information storage device, the output of which is connected to the transmitting path, wherein the transmitting antenna is designed to transmit information to the processing center on Earth at a frequency different from the frequencies of the receiving paths to ensure their simultaneous operation.

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