Federal Radionavigation Plan-pie in the sky for civil aviation?

The Federal Radionavigation Plan states that all present navigation and landing guidance facilities will be retired starting in 2005, and full dependence for these functions will be placed on augmented GPS. Once this is implemented, civil aviation will be totally vulnerable to terrorist jamming of the GPS signals over wide earth areas with widespread disruption of air traffic and potential disasters. It has become apparent that the use of GPS/GNSS is complex and expensive for the required civil aviation functions. It is clear that a different system form is needed for civil aviation, a redundant satellite/ground based system that will prevent it from being a jamming target while providing ATC surveillance, area navigation, collision warning/avoidance, high-speed data link and Category I landing guidance globally, plus precision Category III guidance in the terminal areas as needed. Such a system will be described     

卫星导航系统中的RAIM技术

】全球定位系统（ＧＰＳ）已经达到初始运行能力，其完好性还不能满足全部飞行阶段的要求。接收机自主完好性监控（ＲＡＩＭ）为ＧＰＳ的航空用户提供了完好性监控手段。文中集中讨论了实现ＲＡＩＭ的几种检测和判定方法，并对ＲＡＩＭ技术及其潜能进行评估     

GPS Aided Inertial Navigation

The Global Positioning System is an extremely accurate satellite-based navigation system which, after its completion in 1989, will provide users worldwide, 24 hour. all weather coverage. A joint research project among Boeing, Rockwell-Collins, and Northrop has been completed in which a GPS receiver was integrated with a low-cost strap-down inertial navigation system and a flight computer. A Kalman filter in the latter allows in-fight alignment and calibration of the INS. In addition, feedback from the INS to the GPS receiver improves the system's ability to reacquire satellite signals after outages. The resulting system combines the accuracy of GPS with the jamming immunity and autonomy of inertial navigation. System tests were conducted in which a Boeing owned T-33 jet aircraft was flown through known test pattern to align and calibrate the INS. Earlier tests, including tests against an airborne jammer, were conducted in a modified passenger bus.     

A visionary look at aviation surveillance systems

The FAA's future aviation surveillance systems fall into four categories: Automatic Dependent Surveillance (ADS) will be used in the oceanic environment; ADS-Broadcast (ADS-B) will be used in the domestic en route environment; ADS-B will be used with a secondary radar backup in the terminal area; and ADS-B will be used with primary radar backup within the Airport Surface Traffic Automation (ASTA) system on the airport's surface environment. Two other systems introduced in this paper are Cockpit Display of Traffic Information (CDTI) and Traffic Advisory and Collision Avoidance System (TCAS). All these systems will use navigational signals emitted by the Global Positioning System (GPS) constellation of satellites     

Evaluation of Geometric Performance of Global Positioning System

The global positioning system (GPS) is a satellite-based radio navigation system to provide extremely accurate three-dimensional position fixes and system time to users anywhere on the Earth at any time regardless of weather conditions. The most significant performance parameter of the GPS is the degree of navigation accuracy which is strongly coupled to the choice of orbit configuration. The 3 X 8 orbit configuration has been considered as an operational GPS which consists of 24 satellites deployed in circular 63° inclined, subsynchronous 12-h orbits. In this paper, the geometric performance of several orbit configuration, including a 3 X 8 orbit configuration, is analyzed numerically by altering orbit period and elevation mask, respectively. It will be shown that 1) there are a few orbit configurations which are comparable to or better than the baseline 3 X 8 orbit configuration, and 2) for higher elevation mask, the geometric performance can be improved effectively by increasing orbit period to some extent.     

Mid-Continent LORAN-C Expansion

The Coast Guard is extending the Continental United States (CONUS) LORAN-C coverage as part of the Federal Aviation Administration project to incorporate LORAN-C into the National Airspace System. The increased coverage will expand the number of airports approved for LORAN-C non-precision instrument approaches and enable direct Instrumental Flight Rules (IFR) routing by suitably equipped aircraft in and through the mid-continent region of the United States. The project will involve construction of a new LORAN-C chain which will be linked to the existing CONUS chains. In addition to the aviation benefits, the Mid-Continent LORAN-C Expansion will broaden the availability of LORAN-C positioning to a growing number of terrestrial users such as resource management, emergency response and fleet management.     

EGNOS: project status overview

The European Geostationary Navigation Overlay System (EGNOS) is being developed in Europe to provide GPS and GLONASS satellite-based augmentation services to aviation, maritime and land users. EGNOS is a major element of the European Satellite Navigation Programme which is jointly being implemented by the European Union, the European Space Agency (ESA) and EUROCONTROL.     

全球导航完好性通道（GNIC）方案讨论

国际民航组织(ICAO)将采纳 GPS GLONASS INMARSAT 联合组成的 GNSS 系统供全球导航使用。对系统的增强和完好性监控是至关重要的问题。本文介绍近年来提出的各种地面完好性监控通道(GIC)的方案,包括地面监测台网、地面数据传输的通信链路和卫星转发。重点阐述 INMARSAT 提出的静止卫星加发导航信号的重叠(IGO)概念和全球性完好性监测台网(IMN)。然后进行比较和讨论,并提出需进一步跟踪研究。     

遥测接收站火焰衰减计算模型及应用

火焰衰减是运载火箭遥测系统设计及地面测站布站须重点考虑的问题.以火焰衰减对遥测地面站接收信号的影响为出发点,推导了火焰夹角与测站位置及火箭俯仰角之间的数学关系式,在此基础上依据已有的火焰夹角与火焰衰减关系模型,设计了理论弹道全程中地面测站火焰衰减量的计算程序.以某型遥测设备的接收信道链路为依据,在实际任务中对火焰衰减模型进行验证,结果证实模型具有一定的准确性,并在此基础上分析火焰衰减对遥测地面站某型变频器参数设置的影响,确定了实际任务中更加合理的变频器参数.     

Global Positioning System-the newest utility

The Global Positioning System (GPS) has become the high tech utility of the 20th century. It was developed by the US Department of Defense as a precise navigation reference for the military services. Although the signal available to civilian users had been purposely degraded in what is called selective availability (SA), it is one of a few technological success stories that had positive unintended consequences. Recent announcements indicate that this SA impediment has been removed. GPS currently has a huge civilian market in commercial and private aviation, ship navigation, mapping and surveying, telecommunications position determination, and recreational boating and hiking. By 2003 sales of GPS based products are expected to be $16 billion     

Impact of one satellite outage on ARAIM depleted constellation configurations

Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.     

Ground monitoring schemes for GPS integrity channel

Issues involved in the design and implementation of the ground monitor segment Global Positioning System (GPS) are analyzed. In particular, two alternative ground monitoring schemes are presented and compared, one using classified GPS information, and the other not. For each scheme, processing functions that must be performed by the ground monitoring segment are identified, considering both the impact of selective availability on monitoring and the integrity decision concept recommended by the Global Integrity Channel (GIC) Working Group of the Radio Technical Commission for Aeronautics Special Committee-159     

快速响应侦察的测控通信与地面站布设研究

快速响应侦察是空间快速响应技术的一个重要应用,而合理布设地面站以保障侦察卫星的发射测控和快速数据回收是侦察任务顺利完成的基础。通过分析近地快速覆盖轨道和近地重复覆盖轨道的对地覆盖特性,针对发射测控和快速数据回收提出了地面站的布设原则,结合我国领土特点给出了这2类轨道的地面站布设方案,并求解了该方案所能提供的发射测控弧段长度和侦察数据返回时间。分析表明,在我国境内布设地面站以保障快速响应侦察卫星的发射测控和快速数据回收是可行的,其数据返回时间小于1个轨道周期。     

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.     

Potential interference sources to GPS and solutions appropriate forapplications to civil aviation

When the GPS (Global Positioning System) is subjected to interference, the system performance gradually deteriorates as the interfering levels increase. Two modes of interference are discussed in detail, namely, that from transmissions at frequencies close to the GPS frequencies and that from transmissions with a harmonic in the GPS band. It is argued that the former requires RF filtering in the receiver with a quality better than that generally specified. The latter cannot be dealt with in such a way. Measurements carried out on the harmonic levels transmitted by one UK TV transmitter and several hundred aircraft VHF transmitters are reported. The measurements show there is a measurable level of harmonics in the GPS band. The UK TV transmitter does not, however, represent a threat to aviation unless the aircraft is so close as to represent a physical danger. The probability that one aircraft's VHF transmitter will interfere with the GPS receiver on another aircraft is tolerably small, but there is a significant probability that a GPS receiver can suffer when there is a VHF transmission from the same aircraft. Several recommendations are made, including an international effort to ensure that spurious emissions are both quantified and kept at a level significantly lower than that achieved today     

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.     

差分GPS的原理和实现方法

GPS卫星无线电导航系统预计在1995年投入正式运行。GPS信号中的P码仅供美军和特别用户使用,C/A码则向全世界民用开放。C/A码受选择可用性(SA)影响,导航静度下降到一个适当水平。为提高GPS定位精度,各国都争相研究差分GPS(DGPS)。本文从GPS误差入手,主要就DGPS原理和实现方法进行讨论。     

航模直升机微型组合导航与控制系统研究

以JR-260型航模直升机为研究对象,基于嵌入式Linux操作系统,开发一套微型组合导航与控制系统。系统硬件采用了组合导航系统MNAV100CA和嵌入式飞行控制计算机Stargate,集成了固态的加速度计、角速率传感器、磁航向计、大气机和GPS接收机,以及R/C接收机脉位调制（PPM）航模舵机接口。软件设计采用扩展的卡尔曼滤波和状态监视方法实现了导航系统设计,基于实时Linux线程机制编制了航模舵机的驱动程序,以802.11b无线网络实现空中飞参信号的实时下传,并在便携式地面站上实现了实时监控功能。     

On precision of GPS C/A code

The accuracy of clear acquisition (C/A) code for civilian users of the Global Positioning System, in comparison with precise (P) code, is discussed. Different design techniques for GPS receivers are presented. The 1-ms range ambiguity of C/A code is discussed, and a solution is given. Intentional degradation of GPS signals and denial of accuracy is discussed, and some predictions are presented. The issue of government support and protection of domestic GPS industry against possible unfair international competition is briefly discussed     

Forward error correction for radiobeacon broadcast of differentialGPS data

Marine radiobeacon networks are being used to broadcast differential Global Positioning System (DGPS) corrections to marine users. The correction data digitally modulate signals from some of the existing marine radiobeacons, which operate in the 285 to 325 kHz band, creating DGPS/radiobeacons. The corrections improve the accuracy of the GPS fix from 100 m to 5-10 m, and provide position fixing service for many marine applications which are too demanding for the normal GPS service. Forward error correction can be used to improve the reliability or range of the DGPS/radiobeacon signal. The improvements made possible by channel coding are analyzed, and a code for DGPS/radiobeacons is recommended