Independent Ground Monitor Coverage of GPS Satellites

The Federal Aviation Administration plans to independently monitor signals in space from the Global Positioning System (GPS) for the purpose of providing immediate awareness to civil aviation users of the operational status of GPS when it is used in the National Airspace System. The operational status will be disseminated to Air Traffic Control and will possibly be broadcast from ground monitoring stations to GPS aviation users via a dedicated integrity channel. An algorithm is described that measures the coverage of a configuration of ground monitoring station locations, and is applied to several different configurations of ground monitoring stations to compare the coverage provided. Also included are the resulting ground monitoring station configurations that give the best coverage of GPS signals for several specific geographical areas, the conterminous United States (CONUS), Canada, and Alaska.     

Beam Area Determination for Multiple-Beam Satellite Communication Applications

An exact analytical model and a simple numerical solution are presented for determining the surface area of the Earth illuminated by a conical beam, with an elliptical cross section, emanating from a satellite. The model is used to generate sets of parametric curves for determination of the beam area as a function of the different satellite locations, beam locations, and beamwidths. Numerical results show that for a circular beam with a 0.25° beamwidth, the beam illuminating the northern Continental United States (CONUS) can cover an area about five times larger than the area covered by the same size beam illuminating the southern CONUS. Comparisons are also made with the available approximate methods.     

LORAN-C in the 21st Century

LORAN, which stands for long range navigation, was first brought into service during World War II. Its earliest form, LORAN-A, served us well up to the time the last station was taken off the air in December 1980. It was succeeded by LORAN-C as part of the Department of Defense's program to develop a new generation of radionavigation aids. LORAN-C not only has a greater range than LORAN-A but also provides better accuracy. With the declining cost of integrated circuits, LORAN-C receivers are becoming more affordable. This, along with good repeatable accuracy and excellent coverage, is increasing the worldwide popularity of navigation with LORAN-C. Fishermen, recreational boaters and the general aviation community make up a good percentage of this dramatic increase (an additional 75,000 marine and 10,000 aviation users the past year alone).     

The Impact of Cross-Rate Interference on LORAN-C Receivers

Wong [1] recommends that 16 additional LORAN-C ground stations are needed to provide redundant coverage throughout the conterminous U.S. so that LORAN-C can provide the primary navigation service to civil aviation. The purpose of this paper is to estimate the effect of the interference from the additional stations on the acquisition (phase code identification and third cycle selection) and track modes of a LORAN-C receiver whose detection process is based on the sequential decision theory. This receiver model represents a modern design using microprocessor technology. The results are compared against the requirement that acquisition be completed 90 percent of the time within 7.5 minutes. The impact of cross-rate interference (CRI) on the track mode is estimated using a time-domain analysis.     

Improving GPS-Based Landing System Performance using an Empirical Barometric Altimeter Confidence Bound

This paper develops an empirical confidence bound for barometric altimeter altitude errors and shows how this bound may improve the performance of GPS-based approach and landing systems. This empirical bound is developed using historical meteorological data collected at a set of geographically diverse locations over a thirty year period. The confidence bound developed is shown to provide a Gaussian overbound on altimeter altitude errors in standard atmospheric conditions between a 10-5 and 10-6 confidence level. This confidence bound is integrated into the standard methodology for analyzing the performance of GPS-based landing systems and the results of a performance trade study using the confidence bound are presented. The results show that incorporating the empirical barometric altimeter confidence bound provides an increase in the coterminous United States (CONUS) service volume for lateral precision with vertical guidance (LPV) type approaches. While this increase is approximately 2% for an L1 single-frequency GPS user, it jumps to roughly 40% for an L5 single-frequency user.     

International HARM precision navigation upgrade - a GPS/INS missile upgrade that improves effectiveness and minimizes friendly-fire accidents

The high speed anti-radiation missile (HARM) is an air-to-surface tactical missile designed to seek and destroy enemy radar-equipped air defense systems. Unfortunately, the HARM is "no respecter of persons," and it has been known, most notably during the Gulf War, to attack "friendly" targets. The international HARM upgrade project is a tri-national missile technology project sponsored by the United States, Italian, and German governments. The HARM precision navigation upgrade (PNU) program has as its goal, the development and installation of a PNU into the HARM that will improve the weapon's effectiveness, while nearly eliminating the likelihood of fratricide. The precision navigation system consists of a modern selective availability anti-spoofing module (SAASM) based Global Positioning System (GPS) receiver, and an inertial measurement unit (IMU), consisting of state-of-the-art fiber optic gyros and a modern micro-machined accelerometer triad.     

罗兰-C导航系统地面台站信号模拟器设计

针对罗兰-C远程导航系统机载设备在机务内场利用ATE系统进行定检测试时无信号模拟器的状况,研制了一种罗兰-C系统地面台站信号模拟器。该模拟器具有较强的使用环境适应性,既可通过GPIB接口进行程控操作,又可通过控制面板进行手动操作。本文分析了该罗兰-C系统地面台站信号模拟器的设计思路、电路工作原理和操作使用特性。     

ISO's Contribution to the Study of Clusters of Galaxies

Starting with nearby galaxy clusters like Virgo and Coma, and continuing out to the furthest galaxy clusters for which ISO results have yet been published (z = 0.56), we discuss the development of knowledge of the infrared and associated physical properties of galaxy clusters from early IRAS observations, through the “ISO-era” to the present, in order to explore the status of ISO's contribution to this field. Relevant IRAS and ISO programmes are reviewed, addressing both the cluster galaxies and the still-very-limited evidence for an infrared-emitting intra-cluster medium. ISO made important advances in knowledge of both nearby and distant galaxy clusters, such as the discovery of a major cold dust component in Virgo and Coma cluster galaxies, the elaboration of the correlation between dust emission and Hubble-type, and the detection of numerous Luminous Infrared Galaxies (LIRGs) in several distant clusters. These and consequent achievements are underlined and described. We recall that, due to observing time constraints, ISO's coverage of higher-redshift galaxy clusters to the depths required to detect and study statistically significant samples of cluster galaxies over a range of morphological types could not be comprehensive and systematic, and such systematic coverage of distant clusters will be an important achievement of the Spitzer Observatory. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.     

Geostationary Satellite Navigation Systems

The concept of position determination using geostationary satellites as an alternative to the global positioning system (GPS) is studied. The advantage of a geostationary system is that only three, or at most four, satellites are required to cover the continental United States. A total of twelve satellites are sufficient for global coverage (excluding polar regions), or eight if only longitude and latitude, but not altitude, are measured. The system involves the determination of the range to either four geostationary satellites or, if the altitude is not measured, three geostationary satellites. The accuracy of the proposed systems are evaluated to obtain the rms error associated with position determination, and the concept for the implementation of measurements required by the systems is presented. The accuracy of the systems are adequate for civilian use in the continental United States; however, there is a degradation in accuracy as the location of the user approaches the equator.     

航空发动机研制全寿命管理研究及建议

分析20世纪40年代以来,以美国为代表的世界航空发动机研制先进国家的技术发展理念的演变情况,深入研究了其航空发动机的发展和管理道路,结合中国航空发动机研制实际状况,提出了中国新型航空发动机按时间、分阶段(预先研究、工程研制和使用发展3大阶段)的全寿命管理方法,以不断提高发动机研制管理水平,实现控制发动机研制风险,提高部队战备完好率,降低全寿命成本的目标。     

Design of a space-based radar signal processor

Space-based radar (SBR) is capable of providing flexible wide-area coverage of air, land, and sea targets. Numerous studies have been carried out in the United States and Canada in recent years to investigate different concepts for SBR. The design of a suitable radar signal processor (RSP) is challenging due to the effects caused by the moving platform on target integration and clutter spectral spread. A candidate RSP is described that uses a corporate fed array (CFA) antenna as its primary radar sensor. The algorithmic definitions of the signal processing functions are provided; the relationships between these functions and the reasons for their location in the signal processing chain are also discussed. In addition, techniques for reducing the computational requirements are also presented     

Navy Navigation Satellite System (Transit)

The Navy Navigation Satellite System (TRANSIT) has provided 100% system reliability since being declared operational October 11, 1968. TRANSIT continues to carry out its function of precise, reliable, all weather navigation for the United States Navy and nearly 80,000 worldwide commercial users. TRANSIT's utility has been expanded to provide precise positioning information to those in the fields of geodesy and doppler surveying. While TRANSIT's history is illustrious, its life is limited. The transition from TRANSIT as the Navy's satellite navigation system to NAVSTAR GPS is planned for the 1990' s, with the result that TRANSIT is now scheduled for phase out by the United States Navy in 1994. This paper (essentially an update of reference [1]) will show the current status and plans for TRANSIT, following a brief historical overview.     

Atomic Power Engineering under Falsified Safety Standards

In July 1970 the United States Department of Justice accused the American Society of Mechanical Engineers (ASME) of violating the Sherman Antitrust Act and of acting in restraint of trade by restricting the ASME Certificate of Authorization and the use of the Code Symbol Stamps to boilers and pressure vessels manufactured in the United States and Canada. During the succeeding two years attorneys for the parties in the case formulated a Consent Decree without a public confrontation in the Court. Furthermore, the membership of ASME was kept uninformed until October of 1972, after the Consent and Final Judgment had become effective and new procedures had been developed for allowing foreign manufacturers to apply the ASME Code Symbol Stamps to their products. As a consequence, a breakdown in engineered safety standards has been sanctioned and this is undermining the engineering profession's overriding responsibility to protect the public health and safety. This breakdown of professional responsibility is especially serious in the new technology of atomic power. American insurance companies, which have traditionally written 100% insurance coverage for property damage and third party liability against explosions of high pressure steam boilers bearing the ASME Code Stamp, have refused to write such insurance coverage on nuclear reactors. In the author's opinion there is evidence that the Consent was formulated under collusive proceedings and he calls on the members and the Council of ASME to appeal for dismissal of the Consent Decree.     

A Domestic Satellite Design

This paper deals with the design parameters of a communications satellite which would be capable of providing domestic telephony, data, and television distribution services. Certain important aspects of the design are discussed, including satellite antenna beam coverage, transponder bandwidth, and transponder radiated power for a given weight range. A baseline satellite design is then presented which has 24 transponders (with 4000 watts radiated power on-axis and 34-MHz radio-frequency bandwidth) fully accessible from the 48 contiguous United States. The design uses crossed linear polarization to reuse the satellite transmit and receive frequency spectrum.     

In this issue technically: 12th DASC report-our archaic airtransport control: What can be done?

Commercial airplanes in the Fiji archipelago fly straight from take-off to their destination, using global-positioning-satellite (GPS) receivers. So can general-aviation airplanes in the United States. Commercial airplanes on U.S. transcontinental routes fly dog-legs from city to city. An airplane flying across the Atlantic occupies an exclusive 10,000-cubic-mile moving box. These practices, plus waiting for take-off and landing opportunities, cost United Airlines $2 billion a year. The available USAF flight-management technology is reviewed to see what can be adapted for use in management of the commercial air-space. The problems and plans for implementing a seamless world-wide flight management system, are examined     

The Role of Modern Sensor Applications in the United Nations Resource Exploration and Evaluation Programs

In the first six months of 1971, the United Nations executed surveys using a number of the recently developed geophysical sensors on behalf of the United Nations Development Program in Ethiopia, Kenya, and Lesotho. The Ethiopia and Kenya surveys had the objective of direct exploration for and inventory of geothermal resources and involved coverage of some 39 000 km2 and 1550 km2, respectively, of thermal scanning in the 3 to 5 micron and 8 to 14 micron ranges. The Lesotho survey, experimental in nature, had the objective of exploration for diamondiferous kimberlite pipes and involved some 2600 km2 of aerial survey, utilizing true color, false color, and multispectral photography, scanning in the ultraviolet and 3 to 5 micron and 8 to 14 micron infrared spectra, infrared radiometry, and aeromagnetics. A preliminary evaluation of the results indicates a degree of success that will dictate expanded use of these methods by the United Nations in the future.     

Late Stages of Stellar Evolution

A large fraction of ISO observing time was used to study the late stages of stellar evolution. Many molecular and solid state features, including crystalline silicates and the rotational lines of water vapour, were detected for the first time in the spectra of (post-)Asymptotic Giant Branch (AGB) stars. Their analysis has greatly improved our knowledge of stellar atmospheres and circumstellar environments. A surprising number of objects, particularly young planetary nebulae with Wolf-Rayet (WR) central stars, were found to exhibit emission features in their ISO spectra that are characteristic of both oxygen-rich and carbon-rich dust species, while far-IR observations of the PDR around NGC 7027 led to the first detections of the rotational line spectra of CH and CH⁺. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA.     

基于民航校验飞机的星基增强服务性能评估CSCD

为了进一步拓展全球卫星导航系统(GNSS)在民用航空等高生命安全领域的应用,世界各国争相发展星基增强系统(SBAS),美欧等SBAS已正式向民用航空领域提供了决断高度200英尺(约60.96m)的垂直导航信标性能(LPV-200)服务。我国的BDSBAS也已经完成系统建设,将向中国及周边区域提供满足国际民航组织(ICAO)一类垂直引导进近(APV-I)指标要求的单频增强服务。重点针对单频增强服务性能评估开展研究工作,首先从定位精度、完好性、可用性和连续性四个方面对星基增强服务评估方法进行了论述;再通过多次航空飞行试验对BDSBAS单频增强服务性能进行了验证,结果表明,航空飞行试验期间可满足APV-I设计指标要求;最后对BDSBAS单频增强服务在全国301个中大型机场的可用性进行了分析,非精密进近(NPA)可用性、APV-I可用性、LPV-200可用性在全国机场的覆盖率分别达到了97%、89.7%和83.1%。