Author
Penina Axelrad
Other affiliations: Stanford University, Ohio State University, Colorado Center for Astrodynamics Research ...read more
Bio: Penina Axelrad is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Global Positioning System & Multipath propagation. The author has an hindex of 31, co-authored 149 publications receiving 3853 citations. Previous affiliations of Penina Axelrad include Stanford University & Ohio State University.
Papers published on a yearly basis
Papers
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Book•
01 Jan 1996
TL;DR: Volume I: GPS Fundamentals Introduction and Heritage and History of NAVSTAR, the Global Positioning System Overview of the GPS Operation and Design GPS Signal Structure and Theoretical Performance GPS Navigation Data Satellite Constellation and Geometric Dilution.
Abstract: Volume I: GPS Fundamentals Introduction and Heritage and History of NAVSTAR, the Global Positioning System Overview of the GPS Operation and Design GPS Signal Structure and Theoretical Performance GPS Navigation Data Satellite Constellation and Geometric Dilution of Precision GPS Satellite and Payload Fundamentals of Signal Tracking Theory GPS Receivers GPS Navigation Algorithms GPS Operational Control Segment GPS Performance and Error Effects GPS Error Analysis Ionospheric Effects on GPS Tropospheric Effects on GPS Multipath Effects Foliage Attenuation for Land Mobile Users Ephermeris and Clock Navigation Message Accuracy Selective Availability Introduction to Relativistic Effects on the Global Position System Joint Program Office Test Results Interference Effects and Mitigation Techniques
407 citations
TL;DR: This paper describes a method for autonomous GPS satellite failure detection and isolation (D/I) and presents results of applying the algorithm to measurement sets containing a biased measurement.
Abstract: The use of GPS for navigation-critical applications such as aircraft nonprecision approach or harbor and river crossings requires the navigation data to be both extremely accurate and extremely reliable. This paper describes a method for autonomous GPS satellite failure detection and isolation (D/I). The test statistic for the D/I algorithm is the range residual parameter for six or more satellites in view. Based on experiments conducted at Stanford, nominal carrier-aided pseudorange measurement errors are modeled as Gaussian random variables with mean in the range from - 5 m to + 5 m and standard deviation of 0.4 m. The theoretical statistical distribution of the range residual is given. Monte Carlo simulations present results of applying the algorithm to measurement sets containing a biased measurement. With a 100 m biased measurement present, successful detection is achieved 99.9 percent of the time, and successful D/I is achieved 72.2 percent of the time. The user is always aware when isolation is not possible. User positioning errors resulting from application of the algorithm are always the same or better than with the all-in-view solution.
382 citations
TL;DR: In this article, the GPS orbital repeat period was investigated and it was determined that it varies for each satellite and differs significantly from the generally assumed sidereal period, and the calculated orbit repeat period significantly reduced low frequency (0.001-0.04 Hz) errors in 1-Hz GPS position estimates.
Abstract: [1] High-rate (1-Hz) Global Positioning System (GPS) data are beginning to be used for a variety of geophysical monitoring purposes, including seismology. Improving the precision of high-rate GPS position estimates will increase the value of these 1-Hz GPS monitoring systems. One technique that has been used to improve high-rate GPS positioning takes advantage of the ground track repeat period of the satellites. This study investigates the GPS orbital repeat period and determines that it varies for each satellite and differs significantly from the generally assumed sidereal period. Orbit repeat periods are calculated and used to filter 1-Hz GPS position estimates. Using the calculated orbit repeat period significantly reduces low frequency (0.001–0.04 Hz) errors in 1-Hz GPS position estimates.
246 citations
TL;DR: In this paper, a methodology is described that uses existing networks of continuously operating GPS receivers to measure soil moisture fluctuations, where incoming signals are reflected off and attenuated by the ground before reception by the GPS receiver.
Abstract: Measurements of soil moisture are important for studies of climate and weather forecasting, flood prediction, and aquifer recharge studies. Although soil moisture measurement networks exist, most are sparsely distributed and lack standardized instrumentation. Measurements of soil moisture from satellites have extremely large spatial footprints (40–60 km). A methodology is described here that uses existing networks of continuously-operating GPS receivers to measure soil moisture fluctuations. In this technique, incoming signals are reflected off and attenuated by the ground before reception by the GPS receiver. These multipath reflections directly affect signal-to-noise ratio (SNR) data routinely collected by GPS receivers, creating amplitude variations that are a function of ground reflectivity and therefore soil moisture content. After describing this technique, multipath reflection amplitudes at a GPS site in Tashkent, Uzbekistan are compared to estimates of soil moisture from the Noah land surface model. Although the GPS multipath amplitudes and the land surface model are uncalibrated, over the 70-day period studied, they both rise sharply following each rainfall event and slowly decrease over a period of ∼10 days.
235 citations
TL;DR: In this article, a prototype GPS bistatic radar participated in airborne measurements during the Soil Moisture Experiment 2002 (SMEX02) and was mounted on the NCAR C-130 aircraft to make co-located measurements with other instruments.
174 citations
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Journal Article•
TL;DR: Differential GPS and Integrity Monitoring differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Aut autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting
Abstract: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing Using GPS Precision Landing of Aircraft Using Integrity Beacons Spacecraft Attitude Control Using GPS Carrier Phase Special Applications GPS for Precise Time and Time Interval Measurement Surveying with the Global Position System Attitude Determination Geodesy Orbit Determination Test Range Instrumentation.
2,409 citations
Book•
01 Jan 1996
TL;DR: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomic Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing of Aircraft Using Integrity Beacons Spacecraft Attitude
Abstract: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing Using GPS Precision Landing of Aircraft Using Integrity Beacons Spacecraft Attitude Control Using GPS Carrier Phase Special Applications GPS for Precise Time and Time Interval Measurement Surveying with the Global Position System Attitude Determination Geodesy Orbit Determination Test Range Instrumentation.
2,275 citations
Book•
31 Dec 2007
TL;DR: In this paper, the authors present a single-source reference for navigation systems engineering, providing both an introduction to overall systems operation and an in-depth treatment of architecture, design, and component integration.
Abstract: Navigation systems engineering is a red-hot area. More and more technical professionals are entering the field and looking for practical, up-to-date engineering know-how. This single-source reference answers the call, providing both an introduction to overall systems operation and an in-depth treatment of architecture, design, and component integration. This book explains how satellite, on-board, and other navigation technologies operate, and it gives practitioners insight into performance issues such as processing chains and error sources. Providing solutions to systems designers and engineers, the book describes and compares different integration architectures, and explains how to diagnose errors. Moreover, this hands-on book includes appendices filled with terminology and equations for quick referencing.
1,351 citations
Patent•
16 Sep 1998
TL;DR: A location reporting paging communication system comprising space satellites, ground stations and a remote receiving unit adapted to resolve a global position from signals transmitted from a communication transmitter is described in this paper.
Abstract: A location reporting paging communication system comprising space satellites, ground stations and a remote receiving unit adapted to resolve a global position from signals transmitted from a communication transmitter. The subscriber in possession of the remote receiving unit updates the paging network with global positioning information. A caller paging a subscriber in possession of the remote receiving unit may request the global location of the remote receiving unit. The paging network could divulge or block such information from a caller depending on the requirements of the subscriber.
1,162 citations
01 Jan 2014
TL;DR: The history of attitude sensor development has emphasized increased resolution and accuracy as well as decreased size, weight, and power (often abbreviated as SWaP).
Abstract: This chapter will discuss several kinds of sensors and actuators used to determine and control spacecraft attitude [26, 44, 54, 66]. The history of attitude sensor development has emphasized increased resolution and accuracy as well as decreased size, weight, and power (often abbreviated as SWaP). Actuator technologies have also been scaled down to be appropriate for microsatellites and cubesats. We begin with a brief introduction to redundancy considerations, and then consider some specific sensors and actuators.
740 citations