ETS-II Experiments Part IV: Characteristics of Millimeter and Centimeter Wavelength Propagation

Preliminary results of the ETS-II millimeter and centimeter wavelength propagation experiments are presented based on data collected over one year. Rain attenuation is discussed primarily from the statistical point of view. At 34.5 GHz attenuation in excess of 5, 10, and 19.5 dB were observed 1, 0.3, and 0.1 percent of the test time (5500 hr), respectively. At 11.5 GHz attenuation in excess of 2.5, 4.3, 6.3, 10, and 15.5 dB were observed 0.1, 0.03, 0.01, 0.003, and 0.001 percent of the test time, respectively. Duration time of attenuation is also examined for the benefit of a link design. The longest duration of attenuation of the 34.5-GHz wave exceeding 5 dB was about 150 min. At 11.5 GHz, the longest duration of attenuation in excess of 3 dB, was 60 min and that in excess of 6 dB was 10 min. Rain attenuation is discussed also with relation to the radar and the rain gauge data. Depolarization data of 34.5-GHz and 11.5-GHz waves are orocessed statistically, and it is shown that cross-polarization discriminations in excess of 21.5 dB and 29 dB are observed 0.1 percent of the test time at 34.5 GHz and 11.5 GHz, respectively.     

ETS-II Experiments Part III: Weather Radar System

The weather radar system used in conjunction with Earth-satellite propagation experiments for quantifying rainfall rate in a unit volume, determined by the beamwidth and the pulselength, is described. Firstly, methods for deriving rainfall rate per unit volume are stated in detail with special emphasis on calibration to determine unknown parameters associated with propagation losses in waveguides and the atmosphere. The calibration method is somewhat different from a conventional one but is useful for routine observation. Secondly, in addition to a simple explanation of the hardware of this radar system, the data modes, developed for measuring rainfall rate along the propagation path and radar reflectivity factor in the horizontal and vertical cross sections around the station are described. These data modes are effectively combined by the operational scanning modes for routine observation of propagation experiments, while each data mode can also be operated independently. Examples obtained by each data mode are also given.     

The untold Pearl Harbor radar story

Ever wonder what happened to the radar set that detected the Japanese aircraft before the raid on Pearl Harbor? This article reveals the fate of that SCR-270 radar set; describes some of the radar development background; and includes typical results of a World War II command, control and communications system that used the SCR-270 as its backbone radar. The SCR-270 was a radio-echo detection and direction finding set for locating aircraft. It operated by transmitting a short-duration pulse of high frequency radio waves, which would be reflected or re-radiated by any metallic or conducting surface within the field of the directive transmitting antenna; therefore, one or more aircraft within the antenna field appeared as a source of reflected radio waves. Rotating the antenna which also served as the receiving antenna, provided a means for determining the azimuth or direction of aircraft. The system measured the time it took a blip or reflected return from the target to appear on a cathode ray tube indicator, to give the distance or range to the detected aircraft. The maximum range of the radar was about 250 miles up to 50,000 feet under all atmospheric conditions including rain, mist, smoke or fog, and during daylight or darkness. The azimuth and range data supplied by the set permitted the plotting of the location of detected aircraft on maps. Major performance characteristics of the radar are provided in the included table     

Nostradamus: An OTH Radar

ONERA, funded by the French Ministry of Defence has conducted the realization and experimentations of the Doppler Skywave OTH radar called NOSTRADAMUS. One of the main characteristics of Skywave OTH radar is the dependence to the ionosphere for successful operation. The use of the HF band allows Skywave OTH radar to bounce radio waves from the ionosphere, receiving tiny signals back from reflecting surfaces as the sea, islands, ships and aircraft. The knowledge of the behavior of the ionosphere in a real time configuration is of primary importance because it influences on the choice of frequencies. Radars systems require developing a real-time frequency management system (FMS) using prediction program or measurements supplied by vertical or oblique sounders. The French OTH radar concept has been developed and implemented so that the radar could be completely autonomous with respect to others "ionospheric information providers." This paper presents the NOSTRADAMUS system, the frequency management system, and shows some results obtained during the past years     

Buried small objects detected by UWB GPR

A ground penetrating radar (GPR) using short-pulse is developed to detect small and shallow metal objects buried underground. A bistatic mode in which the GPR system uses separate transmitting and receiving antennas is applied. A modified fat dipole antenna is developed for the transmitting and receiving antennas. The prototype of the system is tested in the real environment and 2D visualization of raw data is achieved. We show that the developed system has a good ability to detect underground metal objects, and even small targets of several centimeters.     

民机航向道信标接收功能定量评估方法研究

针对民用飞机仪表着陆系统（ILS）航向道信标（LOC）接收功能试飞中机载LOC接收功能定量评估存在困难的问题,通过对LOC基本工作原理和机场LOC地面台信号的分析,并结合机场LOC地面台的飞行校验方法和校验结果,将试飞使用跑道LOC地面台本身存在的误差以及飞行校验的设备误差纳入考量,结合民用飞机机载LOC系统试飞科目的试飞方法和试飞内容,以相应系统规范的精度要求为依据,分为“飞机沿航向道飞行”和“飞机与航向道成夹角飞行”两种情况,制定出了一套现实可行的机载LOC接收功能定量评估方法。此外,用实际的试飞数据验证了该套方法的正确性和科学性,可作为目前国内仅作定性评估的有力补充和支撑,并且可为类似的系统提供定量功能评估思路、方法及验证路径的参考。     

WARLOC: A High-Power Coherent 94 GHz Radar

This paper describes the development of a high-power, coherent radar system at W-band and discusses potential applications of radars with this new capability. Previous radars in this frequency band were limited by available power-amplifier technology to about 500 W of average power; WARLOC radar represents an increase in power, by 20 times, over previous coherent radars at 94 GHz. This performance improvement is possible due to the development of a gyroklystron amplifier specifically for this and future radars in this frequency band. The gyroklystron amplifier tubes deliver 100 kW peak power and 10 kW of average power at a center frequency of approximately 94 GHz. Other novel features of this radar include the use of highly overmoded waveguides and rotary joints for the transmission of power from the final power amplifier (FPA) to the antenna, and a high-power quasi-optical duplexer. The system uses a relatively large 1.8 m diameter (580-wavelength) Cassegrain antenna, which required the development of an antenna with an rms surface accuracy of 0.0025 in, to obtain long-range detection and identification of small objects. Test data show an antenna gain of 62.5 dB, confirming that the needed surface accuracy was achieved. Two mobile shelters house the radar system, permitting relocation to various test sites. WARLOC is presently operational at the Naval Research Laboratory's Chesapeake Bay Detachment facility, Maryland. It is being employed in radar imaging of airborne and surface objects, and in the scientific study of propagation effects and atmospheric physics phenomena.     

The Impact of Strong Scintillation on Space Based Radar Design I: Coherent Detection

Electromagnetic signals which propagate through strongly disturbed regions of the ionosphere can experience angular scattering, causing appreciable amplitude and phase scintillation and angle-of-arrival fluctuations. The performance of a space based radar (SBR) subject to degradation due to signal propagation through a highly disturbed ionospheric channel is considered here. Pertinent characteristics of the disturbed channel and the received radar signal are described. The effects of the propagation path are investigated and the differences between monostatic and bistatic operation are presented. Results are presented which show the effect of severe scintillation on the coherent target detection performance of an SBR. It is shown that coherent detection performance can be seriously degraded in a scintillation environment if scintillation effects are not considered in the radar design.     

Radar network system to observe & analyze Tokyo Bay vessel traffic

A complete grasp of the actual vessel traffic flow by accurate observation is essential to carry out vessel traffic management, design of vessel traffic route, plan of port construction, etc. Up to now, the observation of vessel traffic has needed many efforts such as the use of a special ship or car equipped with radar observation systems and the observation staff preparation for a considerably long period. In order to perform accurate observation of vessel traffic without such efforts, the authors have developed a completely automated radar network system covering the main traffic route of Tokyo Bay. In August 2003, as the second remote radar station attaching AIS equipment was set at East Ogishima (the first was installed at the National Defense Academy in 2002), the observing range could be enlarged and cover most traffic routes in Tokyo Bay. These two radars can observe the vessel traffic in Tokyo Bay simultaneously so as to know the traffic flow accurately on the basis of analyzing the integrated radar data. In addition to the development of a radar network system, the software to analyze observed vessel traffic flow has been developed. This software has various functions such as tracking of ship's position, automatic determination of ship's size, animation of ship's movements, superposition of successive radar images, display of ship's tracks, calculation of ship's speed distribution, extraction of dangerous ship encounters using subjective judgment value and bumper model, etc. Some analyzed results on vessel traffic flow observed by the remote radars in January and September 2003 are shown in this paper.     

三级数据的遥测交互软件架构设计及实现

针对遥测交互分系统实时处理数据量大、数据种类多样、数据收发模式灵活、技术状态变换频繁、软件维护要求高的问题,提出了一种数据池—数据表—数据通道的三级数据交互软件架构,该架构对交互分系统中所有数据进行高度抽象,采用通用化的处理过程,可以很好地适应各种需求。目前,基于该架构的遥测数据交互软件已在国产麒麟系统下实现,通过快捷、可视化的配置及灵活的人机交互,可以快速实现任务状态转换,能够满足各种航天测量任务的需求。这表明,该架构是一种理想、高效的数据交互软件通用解决方案,可推广到雷达、光学等其他测量设备。     

基于遗传算法的多部测速雷达布站优化研究

通过部署于不同地点的多部无源多普勒测速雷达,可以对有辐射信号源的机动飞行目标进行跟踪测量,并且可以对目标位置和速度信息进行最佳估计。本文探讨了遗传算法在测速雷达布站优化中的使用方法,分析了误差传播矩阵,建立了简易目标函数,利用遗传算法对信标体制下的多普勒测速单站的布站几何进行了优化。     

A Microwave Hologram Radar System

An airborne microwave hologram radar system has been developed which is a two-dimensional analog to optical holography. The field of view of the radar is directly below and to either side of the aircraft. Resolution is realized in the along-track direction by utilizing the synthetic aperture technique, and in the cross-track direction by means of a phased receiving array. The theory of operation is summarized, the demonstration system is described, and results for both the normal and contouring modes of operation are presented.     

Application of a Highly Parallel Processor to Radar Data Processing

The application of a highly parallel computer known as PEPE (Parallel Element Processing Ensemble) to radar data processing is described. The PEPE computer consists of a large number of identical processing elements which operate in parallel and are controlled by a common control unit. Each of the processing elements is assigned to a particular radar target such that many targets can be tracked in parallel. PEPE is designed to augment a conventional computer rather than to stand alone. The total data processing load associated with a radar tracking system is distributed between PEPE and the sequential machine in a manner than maximizes the overall system efficiency and desensitizes the system performance to fluctuations in traffic levels. The use of PEPE provides very high data processing throughput potential to a radar data processing system.     

Radar Handbook, 3rd Edition (M.I. Skolnik, Ed; 2008) [Book Review]

Thirty eight radar experts contribute to this edition, which includes six completely new chapters on the following topics: ground penetrating radar; remote sensing with radar on satellites; multifunctional radar systems for fighter aircraft (MFAR); digital signal processing for radar; civil marine radar; and propagation. Each chapter contains references, ranging from 10 to 197, with a median of 71. The index runs 18 pages printed in double columns, but is not necessarily complete. Some topics, such as MIMO radar and long range radars to track satellites and ballistic missiles, will have to wait for a 4th edition. This text is the most authoritative, broadest, and deepest single volume on radar. The emphasis is on real world performance and real hardware that has been tested and works successfully in the real world, and the physics relevant to radar systems, as well as radar system engineering cost tradeoffs.     

脉冲雷达凝视模式下低轨碎片相对运动特征分析

脉冲雷达凝视模式是一种探测低轨小碎片的重要方式,其中低轨碎片与雷达的径向运动关系是碎片统计分析的基础.为推算碎片相对雷达的运动特征,基于坐标系的相互转换,先利用雷达测站信息,得到可见碎片在地惯坐标系下的轨道信息;再逆向将目标不同时刻的位置转换至测站坐标系下,得到目标的径向运动特征.在不同要素（雷达波束指向、雷达仰角、测站纬度、目标距离）下,仿真及对比分析了各个参数对速度模糊度、雷达可见性等的影响,得出在凝视模式下目标相对雷达近似做径向匀加速运动,这为后续试验工作提供有力的依据.     

A multipath data association tracker for over-the-horizon radar

A new algorithm, multipath probabilistic data association (MPDA), for initiation and tracking in over-the-horizon radar (OTHR) is described. MPDA is capable of exploiting multipath target signatures arising from discrete propagation modes that are resolvable by the radar. Nonlinear measurement models exhibiting multipath target signatures in azimuth, slant range, and Doppler are used. Tracking is performed in ground coordinates and therefore depends on the provision of estimates of virtual ionospheric heights to achieve coordinate registration. Although the propagation mode characteristics are assumed to be known, their correspondence with the detections is not required to be known. A target existence model is included for automatic track maintenance. Numerical simulations for four resolvable propagation modes are presented that demonstrate the ability of the technique to initiate and maintain track at probabilities of detection of 0.4 per mode in clutter densities for which conventional probabilistic data association (PDA) has a high probability of track loss, and suffers from track bias. A nearest neighbor version of MPDA is also presented     

The Impact of Strong Scintillation on Space Based Radar Design II: Noncoherent Detection

Electromagnetic signals that propagate through strongly disturbed regions of the ionosphere can experience scattering which can cause significant amplitude, phase, and angle-of-arrival fluctuations. This paper considers the performance of a space based radar (SBR) that must operate through a highly disturbed propagation environment such as might occur during a barium release or after a high altitude nuclear detonation. A brief summary of the propagation channel characteristics is given in terms of quantities that are important to SBR design issues. Results are then given showing the effect of noncoherent integration on target detection performance. Both coherent and noncoherent detection performance can be seriously degraded by scintillation if scintillation is not adequately considered in the radar design.     

Mapping lightning channels in a thunderstorm by radar

The state of Georgia has experienced a number of tornados that occur without warning, and, in several cases have caused fatalities. Researchers at the Severe Storms Research Center (SSRC) of the Georgia Tech Research Institute (GTRI), Georgia Institute of Technology are attempting to detect tornado formation within severe thunderstorms occurring in the vicinity of Atlanta, Georgia, using non-radar sensors that may provide early tornado warning and provide cueing to existing National Weather Service (NWS) radars. The goal of these studies is to increase the warning time of tornado formation within the parent thunderstorm. GTRI researchers use real-time S-band Doppler weather radar data from three National Weather Service WSR-88D NEXRAD radars to complement the development of the non-radar tornado sensors. Three NWS Doppler radars provide severe weather surveillance coverage of the north Georgia area to determine if a thunderstorm contains the Doppler signature that indicates tornado formation. The radar data, displayed on a work station developed and optimized for tornado detection by the National Severe Storms Laboratory (NSSL), serves as ground truth data for the non-radar sensor development. GTRI can display cloud to ground (CG) lightning strikes, a capability provided by overlaying data from a national monitoring network onto the radar reflectivity map. GTRI also uses a local lightning direction finder (DF) system that supplies azimuth and range to the lightning strike. This paper discusses the early lightning channel research and the passive parasitic radar system being operated by the SSRC.     

Harmonic Radar Systems for Near-Ground In-Foliage Nonlinear Scatterers

The radar transmission equation for a harmonic radar operating over a planar, finite dielectric Earth through foliage is derived for an interesting class of nonlinear scatterers. The received power can typically depend on range to the (-14) power for small objects near the ground. The maximum detection range of a ground-based system is related to all major system parameters: it is most sensitive to polarization, transmit antenna height, and transmit wavelength; moderately sensitive to transmit power and transmit antenna area; and least sensitive to receive antenna area, harmonic scattering cross section, and mode of data processing. For example, there is seen to be a best apportionment of total available aperture area into disjoint transmit and receive apertures which can be well approximated by the equal gain condition. Also, there is seen to be a critical path distance through foliage; at distances less than this, small wavelengths are desirable and, conversely, the upper transmit frequency limit may be set by nonlinear scatterer response. Airborne synthetic aperture radar systems are discussed and quantification of harmonic noise and effects of scatterer fluctuation are made. A useful phenomenological model of a nonlinear scatterer is given that is consistent with some observations and predicts a frequency dependence. Nonlinear scatterer effects on range resolution are discussed.