摘要:

ABSTRACTThe International Omega Association (IOA) has recently published the Memoirs of John Alvin Pierce, the inventor of Omega, in a special edition of the IOA Newsletter. NAVIGATION is pleased to be able to publish the majority of the Memoirs, including a foreword by Eric Swanson. The installment in this issue contains the foreword and Mr. Pierce's account of the development of Loran. The Summer issue of NAVIGATION will contain Mr. Pierce's account of the invention of Ω it will also include a question and answer session with Mr. Pierce on the history of Omega, conducted by Robert Revel, the editor of the Memoirs

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00977.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThis paper defines the GPS 21 Primary Satellite Constellation, along with its maintenance strategy, to be implemented in the mid‐1990s. This constellation will consist of 24 satellite positions (including 3 on‐orbit spares) to reduce significantly its sensitivity to satellite failure. Prior to its implementation, the Optimal 21 Satellite Constellation will be maintained. This constellation consists of 21 satellite positions providing complete full coverage, but it is also more sensitive to satellite failure. For both constellations, a slight (0.2 percent) altitude change is being considered for the fall of 1989. This would remove the need for all on‐orbit station‐keeping maneuvers. This paper presents satellite locations for both constellations, as well as positions for the first four Block II l

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00978.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTRadio Technical Commission for Aeronautics Special Committee‐159 (RTCA SC‐159) recently established a working group to address the design of a wide‐area broadcast service for providing rapid and frequent indications of the health of the GPS satellites. The GPS Integrity Channel Working Group has met over the last year to recommend a system architecture that would provide 10 s warning of any deterioration of service causing the navigation guidance accuracy to be outside the limits for nonprecision approach. The architecture to be selected was also to permit international implementation of the service. These requirements can be satisfied by a sparse ground‐monitoring network sending integrity messages through a satellite communications link. The working group considered the tradeoffs between placing the decision burden on the ground subsystem and placing it on the avionics processor. Their recommendations call for the broadcast of a coarse range measurement for each satellite; this will enable the on‐board GPS receiver to determine positively whether the GPS navigation accuracy is within prescribed limits. This paper addresses the tradeoffs, message content, data throughput requirements, and data link considerations involved in this

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00979.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThis paper addresses the problem of guiding the Gravity Probe B (GP‐B) spacecraft from its location after initial insertion to a very precise low earth orbit. Specifically, the satellite orbit is required to be circular to within 0.001 eccentricity, polar to within 0.001 deg inclination, and aligned with the direction of the star Rigel to within 0.001 deg. Navigation data supplied by an on‐board GPS receiver is used as feedback to a control algorithm designed to minimize the time to achieve the desired orbit. Translational control is provided by the proportional helium thrusters, which are used for drag‐free and attitude control during the remainder of the science mission. Simulations of the guidance system are presented which give an indication of performance characteristics for several types of orbit injection errors.This research is the first reported effort to use GPS as a sensor for a closed loop space guidance s

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00980.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThis paper considers the effects of vibration of the antenna and oscillator in a GPS receiver. These combine to cause a vibration‐induced phase shift in the carrier phase tracking loop. While the vibration (motion) of the antenna is not under the designer's control, the g‐sensitivity of the oscillator is amenable to choice. The quantitative effects are analyzed with reference to the design of a GPS receiver for ground‐mobile use.It is shown that the loss of lock of GPS signals under severe vibration is avoidable. A well‐designed equipment will exhibit increased carrier cycle slip when vibrated. This may be related to an equivalent loss of signal‐to‐noise ratio in

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00981.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTMany fields, such as geodetic surveying, positioning of airborne sensors (photogrammetric cameras), laser bathymetry, airborne gravimetry, and hydrographic surveys, require accuracies in the decimeter or even centimeter range in differential positioning. Using the full potential of the GPS in a dynamic environment, the Institute of Astronomical and Physical Geodesy (IAPG) has carried out several kinematic tests with respect to land‐based, shipborne, and airborne applications.After reviewing the main concepts in differential GPS kinematic positioning, this paper presents experiences with and practical results of kinematic GPS tests. Results of a Kalman filter covariance analysis are shown for the integration of GPS phase and pseudorange data with ring laser strapdown inertial systems in order to recover cycle slips and short‐time loss of lock in GPS. In particular, the question is discussed of the extent to which inertial strapdown systems can be used to bridge these times and to maintain centimeter accur

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00982.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTGPS offers significantly improved capabilities in precise positioning. Applications include 10 cm altitude determination for the Topex/Poseidon oceanographic satellite, centimeter positioning anywhere on the Earth, and precise attitude determination for synthetic aperture radar. In the pursuit of the most precise GPS‐based measurements, NASA has sponsored the development of new software and hardware tools related to GPS. The dual‐frequency Rogue receiver can track up to eight GPS satellites simultaneously. A new antenna design for the Rogue has reduced the combined effects of data noise and multipath to less than 15 cm peak with 2 min smoothing on the pseudorange. The corresponding contribution from data noise is less than 2 cm. Data noise for the carrier is insignificant, and multipath errors are about 1 cm for 2 min smoothing. The GPS Inferred Positioning SYstem (GIPSY) is a software system that includes state‐of‐the‐art Earth models, automatic data editing, and numerically stable and flexible square root filtering techniques for parameter estimation, including process noise modeling. With these tools, we have demonstrated submeter GPS orbits and measurements of positions on the Earth to a precision and accuracy of better than 20 parts pe

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00983.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThis paper describes one method of implementing a GPS C/A code digital receiver. Digital designs promise exceptionally low‐power, low‐cost, and miniaturized receivers in the near future. This has been made possible through recent advances in digital signal processing and very large scale integration (VLSI) techniques. The receiver described here attempts to minimize analog circuitry, which is difficult to integrate, and maximize the use of digital signal processing hardware and techniques. The digital signal processing has been carried out with a combination of standard integrated circuits and a commercially available digital signal processor. The signal processor is used to control digital code‐ and carrier‐tracking loops via numerically controlled oscillators (NCOs). Hardware and software implementations of these and other receiver functions, including correlation, 50 baud data extraction, and pseudoranging, are described in detail. All receiver software and hardware was designed and developed using a desk‐top computer as the host developme

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00984.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTDespite the global coverage and high accuracy achievable through GPS and GLONASS, a number of organizations in Europe see a need for alternative satellite‐based navaids. NAVSAT, GRANAS, Rexstar, Locstar, and INMARSAT'S proposed enhancements of GPS/SPS all use existing geostationary communications satellites. NAVSAT adds satellites in highly inclined orbits to those in geostationary orbit to achieve global coverage. Institutional and straight commercial issues assume considerably more importance in civil than in military system

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00985.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1989.tb00986.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY