HR: 08:15h
AN: G51D-02 INVITED    [Abstracts]
TI: Ionospheric Challenges for GNSS Based Augmentation Systems
AU: * Doherty, P
EM: dohertpd@bc.edu
AF: Boston College, Institute for Scientific Res. 400A St. Clement's Hall 140 Commonwealth Avenue, Chestnut Hill, MA 02467-3862, United States
AU: Valladares, C E
EM: valladar@bc.edu
AF: Boston College, Institute for Scientific Res. 400A St. Clement's Hall 140 Commonwealth Avenue, Chestnut Hill, MA 02467-3862, United States
AB: The ionosphere is a highly dynamic physical phenomenon that presents a variable source of error for Global Navigation Satellite System (GNSS) signals and GNSS based operational systems. The Federal Aviation Administration's (FAA) Wide-Area Augmentation System (WAAS) was designed to enhance the GNSS standard positioning service by providing additional accuracy, availability and integrity that is sufficient for use in commercial aviation. It is the first of a number of planned regional Satellite Based Augmentation Systems (SBAS). Other systems in development include the European EGNOS system, the MSAS system in Japan and the GAGAN system in India. In addition, the South American countries are investigating the feasibility of operating an SBAS system in this region. Much of the WAAS ionospheric research and development focused on defining and mitigating ionospheric challenges characteristic of the mid-latitude regions, where the ionosphere is well studied and relatively quiescent. The EGNOS and MSAS systems will primarily operate under a similarly quiescent mid-latitude ionosphere. SBAS system development in South America, India and other low-latitude regions, however, will have to contend with much more extreme conditions. These conditions include strong spatial and temporal gradients, plasma depletions and scintillation. All of these conditions have a potential to limit SBAS performance in the low latitude regions. This presentation will review the effects that the ionosphere has on the mid-latitude WAAS system. It will present the techniques that are used to mitigate ionospheric disturbances induced on the system during severe geomagnetic activity and it will quantify the effect that this activity has on system performance. The presentation will then present data from the South American Low-latitude Ionospheric Sensor Network (LISN) that can be used to infer the ionospheric effects on SBAS performance in the most challenging low-latitude ionospheric environment. LISN is a network of GNSS receivers and other ionospheric sensors that are in the process of deployment and installation across the western half of South America. Its purpose is to address key questions about the physics of the equatorial ionosphere and to develop forecasting/predictions capabilities concerning the onset of equatorial Spread F. The International Civil Aviation Organization has committed to transition to satellite navigation. This presentation will summarize the effects and the limitations that the ionosphere places on satellite based navigation systems.
DE: 2415 Equatorial ionosphere
DE: 2443 Midlatitude ionosphere
DE: 2494 Instruments and techniques
SC: Geodesy [G]
MN: 2007 Fall Meeting