Radar Facility Research Articles

Development of the Chinese Dual Auroral Radar Network and Preliminary Results

AbstractLed by the National Space Science Center of the Chinese Academy of Sciences, we have built a Chinese dual auroral radar network in northern China, which is called the CN‐DARN. The CN‐DARN consists of three pairs of high‐frequency coherent scattering radar facilities and is one of the key parts of the Chinese Meridian Project Phase II. It has been fully constructed and started trial operations at the end of 2023. The detection range of the radar network extends longitudinally over approximately 9 hr of local times and covers the middle to high latitudes of the entire Asia region above 40. In this paper, we present the basic design of the CN‐DARN and its preliminary observations of ionospheric irregularities, subauroral polarization streams (SAPSs) and traveling ionospheric disturbances (TIDs). We also investigate its contribution to the ionospheric convection pattern of the Northern Hemisphere derived from Super Dual Auroral Radar Network (SuperDARN) observations. The results indicate that the CN‐DARN provides excellent measurements and better specifications of flows in the Asian sector, improving our understanding of the global‐scale ionospheric convection pattern in the Northern Hemisphere. These encouraging results lead us to believe that the CN‐DARN will play an important role in studies on the evolution of ionospheric irregularities, the characteristics and evolution of SAPSs, the propagation of TIDs, and global‐scale ionospheric convection dynamics.

Dynamical and Microphysical Aspects of Two Distinct Precipitation Systems in the Himalayas With 206.5 MHz Radar and WRF Model

AbstractThe dynamical and microphysical aspects of two different precipitating systems have been investigated using the ARIES Stratosphere‐Troposphere Radar (ASTRad) facility and further substantiated by Weather Research Forecasting (WRF) model over Manora Peak. The first event (Case‐I) is associated with the southwest Indian summer monsoon that occurred on 4 August 2020, with a vertical extension of 10–12 km and leads to liquid phase precipitation. The second event (Case‐II) linked to the winter western disturbance occurred on 5 February 2021. This precipitating system was developed with a vertical extension of 6–7 km, resulting in both liquid and solid phase precipitation. Such distinct vertical extension of the systems is found to be associated with the thermodynamical conditions and prevailed large‐scale circulations. By analyzing the vertical structure of these systems using three Doppler moments estimated from the ASTRad (equivalent Reflectivity dBZe, Doppler velocity, and Spectral width), maximum dBZe (∼60 dB) is observed in Case‐II, while higher spectral width (>2 m s−1) is associated to Case‐I. The microphysical processes assessed by the WRF model pointed out that Case‐I involved snow accretion on supercooled droplets, leading to graupel and raindrop formation, while in Case–II, solid and liquid precipitation resulted from ice processes, including accretion or autoconversion. These findings highlight the significance of integrating radar and modeling data to understand the dynamical and microphysical evolution of precipitation under the influence of orography in the Himalayan region.

A model of the radar situation of the coastal vessel traffic control system

Since the elements of the ship traffic control system at sea (VTS) are geographically distributed, and the observed spaces have well-defined zones, the radar facilities (radars) that make up their technological basis are evaluated by the ability to detect, classify (recognize), and ensure tracking of ships at a certain range in the spatial zone. The solution of these problems is probabilistic in nature, and the indicators are represented by random functions. However, due to the complexity of accounting for random factors in such stochastic control systems, calculations of their efficiency indicators are usually carried out deterministically for the "average" values of random parameters. The development of a mathematical model for evaluating the effectiveness of VTS in its ability to detect marine targets is a scientific task, the solution of which is possible using elements of the theory of random functions and processes.

Planning the Optimal Reference Flight Path of an Aircraft Using a Terrain Map

In connection with the development of aviation technology, the expansion of the functionality of modern aircraft and the complication of the tasks being solved, additional stringent requirements are imposed on the accuracy of air navigation. Along with high accuracy, navigation autonomy is also required. The autonomy of aircraft navigation implies the navigation of an aircraft without the use of active radar facilities. In this article, to calculate the optimal reference flight path of an aircraft in a horizontal plane, the Bellman dynamic programming method is proposed using a digital terrain map. A technique, algorithms have been developed, and a numerical experiment has been carried out using fragments of a digital terrain map. High accuracy and autonomy of navigation are necessary, among other things, to ensure stealth (invisibility) of aircraft by ground-based radar facilities of a potential enemy in low-altitude flight mode. The best stealth of an aircraft flight in a low-altitude flight mode is achieved not only by flying around, but also by avoiding obstacles, due to the shielding properties of the earth’s surface. Autonomy of navigation provides periodic correction of the reference flight path during long-term flight, and high accuracy prevents aircraft collisions with the earth’s surface in low-altitude flight mode. The purpose of this work is to select the optimal reference trajectory (route) of an aircraft flight in the low-altitude flight mode. This article discusses a method developed based on the principle of dynamic programming for calculating the reference flight path in the horizontal plane depending on the DEM and the implementation of the algorithm based on the proposed method with a specific numerical example. The method makes it possible to calculate the optimal flight route, which provides the greatest secrecy of the aircraft in the low-altitude flight mode using the screening properties of the earth’s surface irregularities.

Эволюция межпланетных миссий радиолокационных исследований планет Солнечной системы с учетом развития бортовых радиолокационных средств космических аппаратов

The paper gives a detailed retrospective review of radio studies of the Solar system planets. The history of missions and the evolution of the spacecraft designed for radar research are considered. It presents analysis of the options in constructing the existing spacecraft radar facilities for interplanetary research. On the basis of this analysis, the appearance of a new generation of radar equipment for interplanetary research missions is proposed. Principles of construction and technical solutions for creation of the onboard radar equipment for the promising research spacecraft were determined. Promising missions of the Venus radar survey were analyzed, and approaches to construction of the spacecraft radar equipment based on the advanced technical solutions were proposed.

Modulation of polar mesospheric summer echoes (PMSEs) with high-frequency heating during low solar illumination

Abstract. Polar mesospheric summer echo (PMSE) formation is linked to charged dust/ice particles in the mesosphere. We investigate the modulation of PMSEs with radio waves based on measurements with EISCAT VHF radar and EISCAT heating facility during low solar illumination. The measurements were made in August 2018 and 2020 around 20:02 UT. Heating was operated in cycles with intervals of 48 s on and 168 s off. More than half of the observed heating cycles show a PMSE modulation with a decrease in PMSE when the heater is on and an increase when it is switched off again. The PMSE often increases beyond its initial strength. Less than half of the observed modulations have such an overshoot. The overshoots are small or nonexistent at strong PMSE, and they are not observed when the ionosphere is influenced by particle precipitation. We observe instances of very large overshoots at weak PMSE. PMSE modulation varies strongly from one cycle to the next, being highly variable on spatial scales smaller than a kilometer and timescales shorter than the timescales assumed for the variation in dust parameters. Average curves over several heating cycles are similar to the overshoot curves predicted by theory and observed previously. Some of the individual curves show stronger overshoots than reported in previous studies, and they exceed the values predicted by theory. A possible explanation is that the dust-charging conditions are different either because of the reduced solar illumination around midnight or because of long-term changes in ice particles in the mesosphere. We conclude that it is not possible to reliably derive the dust-charging parameters from the observed PMSE modulations.

Long‐Term Trends in the Upper Atmosphere Using the Incoherent Scatter Radar Observations Over Arecibo

AbstractUpper atmospheric long‐term trends have been characterized through the analysis of the ionospheric ion temperature (Ti). Previous studies used Ti observations from various incoherent scatter radar (ISR) facilities located at different latitudes. In this paper, we analyze Arecibo Observatory's (AO) ISR (18°20’N, 66°45’W) data sets from 1985 to 2019 to detect Ti long‐term trends as a function of altitude from ∼140 to ∼677 km. We empirically modeled the responses of Ti to the known forcings of solar activity, geomagnetic activity, and the annual and semi‐annual oscillations. The Ti trend is determined through least squares fitting to the residuals of the Ti, which were estimated by removing the empirically modeled Ti from the observed Ti. Since the ions and neutrals are closely coupled, our results indicate that the upper atmosphere/ionosphere over Arecibo has been cooling over the 35 years studied. Above 350 km, a latitudinal dependency is seen by comparison of all ISR estimated Ti trends, which agrees with the earlier reported results. These observed cooling trends exceed the magnitude expected by the modeling studies from increased greenhouse gas (GHG) concentrations. These excess coolings are as high as −1.2 K/year below 320 km altitude, where an increase in GHG dominates. Nighttime cooling trends in the altitude of ∼320–400 km might be caused by the increasing GHG concentrations and magnetic field variations since the trends of AO‐ISR match with the Whole Atmosphere Community Climate Model eXtension simulations.

Unraveling the dynamics of an intense pre-monsoon hailstorm and summer monsoon deep convective system over the central Himalayas using a VHF radar

Himalayan region being influenced by extratropical and monsoon weather systems coupled with orographically forced convection, are frequently impacted by severe thunderstorms. Negligible ground based observations over this region have restricted the analysis of these storms up to coarse statistical features utilising reanalysis data and space-borne radar missions. High spatiotemporal resolution of the Very High Frequency (VHF) radars makes them well suited for the study of large convective storms. In this context, a 206.5 MHz ARIES ST Radar (ASTRAD) facility at Nainital (29.4oN, 79.5°E, 1793 m amsl) has been used to probe mesoscale dynamics of severe deep convective systems in the pre-monsoon and monsoon season for the first time over the Himalayan region. Pre-monsoon event on May 5, 2020 was observed to have characteristic features of a supercell storm resulting in a nearly two hour long hailstorm (∼1430–1630 IST). Vigorous updrafts with maxima of 15.5 ms-1 were observed extending from the mid-troposphere to up to the lower stratosphere region and downdrafts up to 15.7 ms−1 were detected in the lower troposphere within the hailstorm. Hodographs during peak convective activity revealed strongly ‘veered’ winds up to upper troposphere with Storm Relative Helicity maxima of 484 m2s−2. The strength of convection was moderate (updrafts maxima of 4.5 ms−1) in summer monsoon case on September 2, 2020. In this case, trailing stratiform region is observed with double bright band structure in the radar reflectivity factor. Weakening of the stratified stable layer structures in the UTLS region have been observed for both the case in the regions of strong updraft gradients. Spectral and hodograph analysis of the quasi sinusoidal undulations in the wind components fluctuations revealed the presence of upward propagating short-period gravity waves in the Upper Troposphere and the Lower Stratosphere (UTLS) region for both the cases. The observed period of oscillation was 35.6 min and 27 min with vertical wavelengths of ∼8.4 km and ∼ 5.7 km for the May 5 and September 2 case respectively. Momentum flux enhancement of 30–40 times was observed during convection with extremely large values during the hailstorm indicating enhanced flux exchange between troposphere and stratosphere. The findings of this study will aid the forecasting of these storms and improve their simulation in the mesoscale models, particularly over this Himalayan region having complex topography.

Mimo technology in multi-radar systems for detecting stealthy air objects

The main trends in the development of air objects are analyzed (the means of air attack in the conduct of the Russian-Ukrainian war are taken as a basis). It has been established that the increase in the efficiency of radar surveillance of airspace is currently being carried out due to the quantitative increase in radar stations. In this paper, to improve the quality of detection of subtle air objects, the use of multi-position location (based on MIMO systems) is proposed. The principle of operation of a spatially coherent MIMO system is considered. The set of spaced positions of a spatially coherent multi-position system is considered as a single sparse antenna array. The possibility of increasing the resolution in planar coordinates in a MIMO system compared to the resolution of a single autonomous radar station is shown. The calculated ratio for increasing the resolution of such a system is given. Detection curves are given for the case of a spatially coherent MIMO radar system for the case when the radar stations of the system operate simultaneously in the transceiver mode. It has been established that the transition from an autonomous radar station to a MIMO system leads to a significant shift in detection characteristics to the left. It has been established that an increase in the number of radar stations in the system leads to a less significant shift in the detection characteristics to the left, which indicates a decrease in the effect. The radar systems proposed by MIMO can be built on the basis of existing radar stations of a predominantly new fleet. It is especially advantageous to use radar facilities based on phased antenna arrays for these purposes. It is advisable to use such systems in particularly dangerous areas to cover important military, government and critical infrastructure facilities

50 & 25 Years Ago

Application of Digital Computers to Air Traffic Control in the United States; Howard J. Kirshner (p. 14): “Radar-oriented tracking and alphanumeric display systems using digital computers are just now emerging as the key data processing tool in air traffic control, although the Great Falls Center, using air defense computer and display facilities, has been in operation since 1963.” (p. 15) “Aircraft operations in the United States are conducted under two forms of ATC procedures. The first procedure is called Visual Flight Rules, or VFR, and the second, Instrument Flight Rules, or IFR. … Under Visual Flight Rules, it is the responsibility of the aircraft’s pilot to maintain adequate separation from other aircraft. … The ground-based ATC system is responsible for providing separation among aircraft flying under IFR, although in clear weather the pilot also has a responsibility to see and avoid other traffic, since not all aircraft in most segments of low-altitude airspace will be under control of the ground system.” (p. 16) “At 61 locations having radars and beacons, the computer-based Advanced Radar Terminal System (ARTS) is being deployed.” [Editor’s note: The article describes in detail the use of computers to analyze and display information that is captured by radar and beacon facilities. The impression is that none of these systems is yet (1972) ready for use but will become available soon.]

Determining the Origin of Tidal Oscillations in the Ionospheric Transition Region With EISCAT Radar and Global Simulation Data

AbstractAt high‐latitudes, diurnal and semidiurnal variations of temperature and neutral wind velocity can originate both in the lower atmosphere (UV or infrared absorption) and in the thermosphere‐ionosphere (ion convection, EUV absorption). Determining the relative impact of different forcing mechanisms gives insight to the vertical coupling in the ionosphere. We analyze measurements from the incoherent scatter radar (ISR) facility operated by the EISCAT Scientific Association. They are complemented by meteor radar data and compared to global circulation models. The amplitudes and phases of tidal oscillations are determined by an adaptive spectral filter (ASF). Measurements indicate the existence of strong semidiurnal oscillations in a two‐band structure at altitudes ≲110 and ≳130 km, respectively. Analysis of several model runs with different input settings suggest the upper band to be forced in situ while the lower band corresponds to upward‐propagating tides from the lower atmosphere. This indicates the existence of an unexpectedly strong, in situ forcing mechanism for semidiurnal oscillations in the high‐latitude thermosphere. It is shown that the actual transition of tides in the altitude region between 90 and 150 km is more complex than described so far.

History of the Tromsø ionosphere heating facility

Abstract. We present the historical background of the construction of a major ionospheric heating facility, “Heating”, near Tromsø, Norway, in the 1970s by the Max Planck Institute for Aeronomy; we also detail the facility's subsequent operational history to the present. Heating was built next to the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter (IS) radar facility and in a region with a multitude of diagnostic instruments used to study the auroral region. The facility was transferred to EISCAT in January 1993 and continues to provide new discoveries in plasma physics and ionospheric and atmospheric science to this day. It is expected that Heating will continue operating along with the new generation of IS radar, called EISCAT_3D, when it is commissioned in the near future.

Structural design of the radar station of “Besna Kobila” Serbia

Abstract The location of the new radar station facility is located at the top of the Besna Kobila mountain in Serbia at an altitude of approximately 1904 m. The construction of the building is reinforced concrete. The building consists of ground floor and first floor with technical and other areas. From the 2nd to the 6th floor there is a communication central reinforced concrete core. At the level of the 6th floor, a platform was formed for storing equipment and supporting the antenna dome with a diameter of R = 15. The total height of the building with a dome is H = 37.0 m. Horizontal floor structures are in the form of reinforced concrete slabs supported on reinforced concrete walls 20 (30) cm thick, columns of different dimensions, and a system of reinforced concrete beams of different cross section. The vertical construction consists of load-bearing reinforced concrete columns, external and internal concrete walls. In the central part of the building, there is a staircase in the form of reinforced concrete slabs with a thickness of d = 16 cm, as well as reinforced concrete elevator core with a square base of approximately 560.0 cm. The calculation of the structure is performed for loads from its own weight, constant loads from the materialization of the object, loads from the equipment and for payloads: from snow and wind and seismic loads of intensity IX. The basic load of the dome is the wind according to the average speed of 70.0 m / sec (according to the measured data). The foundation of the building is on a reinforced concrete slab and reinforcements-capitals under the columns.

Validation of Wind Measurements From a 53 MHz ST Radar Pilot Array Located at University of Calcutta With Collocated Radiosonde Launches

AbstractA Stratosphere‐Troposphere (ST) Radar operating at 53 MHz is being installed at Ionosphere Field Station (22.94°N, 88.51°E, and 34°N geomagnetic latitude) of University of Calcutta in the eastern part of India adjoining northern Bay of Bengal. This radar is unique, being the only one operational at this frequency in the entire eastern and northeastern part of the country and also in the south‐east Asian longitude sector. Two components of horizontal winds (zonal and meridional) measured by the Pilot version of this radar have been validated with 90 collocated simultaneous balloon‐borne radiosonde observations during July and August 2019. A good correlation of the order of 90%–99% and 75%–95% up to 8 km has been observed between the radar and radiosonde measured zonal winds and meridional winds respectively. This correlation is much stronger between 2 and 6 km altitudes. The correspondence is better for the zonal winds than meridional. However, there have been some data outliers, which may primarily be attributed to different measurement techniques, large beam width of the Pilot array and less antenna aperture. The differences between radar and radiosonde measurements are marginally higher for precipitation events compared to non‐precipitation cases. The zonal and meridional wind patterns exhibit different variations in July and August 2019 while the standard errors in zonal and meridional winds mostly lie within 1 m/s. These results are the first validation of the Pilot version of this radar facility.

The influence of a metal rod inside a spherical Luneberg lens on its characteristics

The paper discusses the option of installing a load-bearing element inside a spherical Luneberg lens (LL). The presence of a metal element inside the LL will increase the structural rigidity of the spherical antenna and thereby expand the scope of use of the LL at various mobile communications and radar facilities with severe operating conditions. The influence of a metal rod inside the main spherical structure on the radiation pattern in two main planes in the linear polarization mode and on the diffraction pattern of the radiation field is estimated. The results of the analysis of the directional characteristics and the diffraction pattern of the LL radiation field were obtained using modeling in the Ansys Electronics Desktop (HFSS Design) working environment, as well as mathematical modeling using the Green tensor function method. At the same time, the obtained mathematical relations can be used in the future to solve the problem of finding the optimal size and position of a metal element in the sphere of LL.

The Improved Capabilities of the Goldstone Solar System Radar Observatory

The Goldstone Solar System Radar (GSSR) facility is the largest fully steerable ground-based radar in the world for nonclassified high-resolution ranging and imaging of planetary and small-body targets. Over the years, the use of the GSSR to detect and characterize near-Earth objects (NEOs) has become critical to keep track of potential Earth-impacting hazardous NEO. This article relates the specific modifications made to the GSSR hardware and procedures in the last few years, as well as the new capabilities derived from those upgrades: reduced complexity in remote operations, increased experimental design versatility, and increased performance on bistatic radar experiments from GSSR to other complexes. In addition, we dedicate a section to provide an update on the current GSSR power capabilities as the new klystrons are installed. The work detailed in this article is intended to reach the broader science community in order to communicate how those modifications and the derived new capabilities can make science experiments more successful.

Requirements for radar navigation aids for operational safety of autonomous navigation of facilities of the Arctic oil and gas complex

An analysis of the requirements for radar systems for autonomous sea vessels operating in the Arctic regions shows that to ensure the safety of transport and oil and gas facilities, it is necessary to evolution to radar systems with characteristics that significantly exceed the existing classification requirements. The application of ultra-wideband and ultra-short-pulse radars, including those based on the principles of microwave photonics, which will provide a radio-imaging mode and decimetre levels of accuracy when measuring coordinates, as well as observation of small objects, ice conditions and detection of oil spills, is proposed. The use of such radar facilities to ensure high-precision navigation will make it possible to start solving the problem of creating autonomous vessels, provided that the safety of logistics operations in the oil and gas complex is ensured.

Normative and methodological support of control of electromagnetic fields at the ships

The seafarers carried out the professional activity in a complex electromagnetic environment (EME), with technical means, structural materials, depending on the purpose of the watercraft, architectural features, and vessel classification. There are static electric fields, permanent magnetic and low-frequency electric and magnetic fields on ships. Marine radio-electronic means (REM) creates Electromagnetic fields (EMF) of the radio frequency range that provide communication, the safety of navigation and operation, and solving navigation problems. According to the documents of the sanitary legislation, specialists carry out control of the maximum permissible EMF levels for watercraft and marine structures at the design stage of the vessel by calculating the intensity of electromagnetic fields during commissioning, instrumental control of EMF levels. There are new technical means in modern automated vessels of various types and purposes that create electromagnetic fields in the crew's stay zones, which makes it urgent to improve regulatory and methodological documents in the area of ensuring the electromagnetic safety of the team and passengers. The study aims to develop proposals for regulatory, methodological, and hardware control over compliance with the maximum permissible levels of electromagnetic fields on ships to ensure the electromagnetic safety of the crew. Generalization of materials of own research of EME on ships, systematization of sources of electromagnetic fields. Analysis of regulations in occupational safety and health for the protection of the crew from the effects of EME, methodological documents on the calculation forecasting, and instrumental determination of the levels of electromagnetic fields. Experts have revealed that there are electromagnetic fields of a wide frequency range in the premises of ships and on open decks. The study showed that electromagnetic fields of a wide frequency range are created in the premises of ships and on open decks. Indoors, the most significant is the impact on the crew of electric and magnetic fields with a frequency of 50 Hz created by the ship's electric power systems. In addition, on open decks (at workplaces and in crew recreation areas), the protection of the crew from EMF antennas of the radio frequency range is relevant. Therefore, it is necessary to develop methods for calculating the prediction of EMF levels and improve the means of measuring electromagnetic fields on ships. The most common sources of EMF in the crew's stay areas are radio communication and radar facilities, ship's electric power systems. The task of developing a methodological document on the calculated prediction of EMF levels in rooms and on open decks at the design stage of ships is urgent. In addition, it is necessary to develop devices-meters of electromagnetic fields for instrumental monitoring of EMF levels in actual operating conditions of the vessel.

Planetary radar science case for EISCAT 3D

Abstract. Ground-based inverse synthetic aperture radar is a tool that can provide insights into the early history and formative processes of planetary bodies in the inner solar system. This information is gathered by measuring the scattering matrix of the target body, providing composite information about the physical structure and chemical makeup of its surface and subsurface down to the penetration depth of the radio wave. This work describes the technical capabilities of the upcoming 233 MHz European Incoherent Scatter Scientific Association (EISCAT) 3D radar facility for measuring planetary surfaces. Estimates of the achievable signal-to-noise ratios for terrestrial target bodies are provided. While Venus and Mars can possibly be detected, only the Moon is found to have sufficient signal-to-noise ratio to allow high-resolution mapping to be performed. The performance of the EISCAT 3D antenna layout is evaluated for interferometric range–Doppler disambiguation, and it is found to be well suited for this task, providing up to 20 dB of separation between Doppler northern and southern hemispheres in our case study. The low frequency used by EISCAT 3D is more affected by the ionosphere than higher-frequency radars. The magnitude of the Doppler broadening due to ionospheric propagation effects associated with traveling ionospheric disturbances has been estimated. The effect is found to be significant but not severe enough to prevent high-resolution imaging. A survey of lunar observing opportunities between 2022 and 2040 is evaluated by investigating the path of the sub-radar point when the Moon is above the local radar horizon. During this time, a good variety of look directions and Doppler equator directions are found, with observations opportunities available for approximately 10 d every lunar month. EISCAT 3D will be able to provide new, high-quality polarimetric scattering maps of the nearside of the Moon with the previously unused wavelength of 1.3 m, which provides a good compromise between radio wave penetration depth and Doppler resolution.

Design and Implementation of the Weather Radar Mobile Monitoring System Based on WeChat Enterprise

In order to solve the problems of China’s new generation Doppler weather radar observation network, such as the lack of mobile monitoring platform, the untimely malfunction alarm and the slow interaction, a mobile operation monitoring system based on WeChat Enterprise has been designed, which is mainly composed of collection, processing, dispersal and feedback of radar’s operational status information, and interactive communication between different radar facilities and support personnel. This system can realize weather radar operating status monitoring based on cell phone, hierarchical automatic warning of operating status information, automatic video push of maintenance support activities and interactive feedback and exchange of information among maintenance support personnel, etc. Based on this system, the operational monitoring and technical support capabilities of China’s new generation Doppler weather radar are greatly improved, and it plays an important role in promoting the operational efficiency of the weather radar.