The Global Ionospheric Monitoring and Forecasting System (GIMSYS) computer program generates global maps of the total electron content (TEC) (electron density integrated over all altitude) of the ionosphere, maps of ionospheric irregularities, and related data byproducts. The maps are generated primarily from signal-propagation measurements taken by more than 100 continuously operating two-frequency Global Positioning System (GPS) receivers in a world-wide network. GIMSYS interpolates the measurements temporally and spatially generating a global TEC map every 15 minutes. When updating the map with new measurements, GIMSYS uses a Kalman filter and stochastic estimation to obtain an optimal combination of the measurements with constraints derived from ionospheric physics and empirical ionospheric models. By applying time-series analysis to recent TEC maps, GIMSYS can also generate forecast TEC maps that are reasonably accurate for 2 to 4 hours. The numerous actual and potential users of the data products of GIMSYS include military, industrial, and academic organizations concerned with radio communication, navigation, mapping, scientific observations, and effects of ionospheric storms on power-distribution systems.
This program was written by Ulf J. Lindqwister; Charles D. Edwards, Jr.; Ron Muellerschoen; Xiaoqing Pi; Anthony J. Mannucci; Lawrence Sparks; Thomas Runge; Byron A. Iijima; Mark Reyes; and Brian Wilson of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Software category.
This software is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393-3425. Refer to NPO-20460.
This Brief includes a Technical Support Package (TSP).
Generating Maps of the Ionosphere From GPS Measurements
(reference NPO-20460) is currently available for download from the TSP library.
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Overview
The document outlines the Global Ionospheric Monitoring and Forecasting System (GIMSYS), a sophisticated program developed to monitor and forecast the ionosphere on a global scale. Utilizing a network of over 100 continuously operating dual-frequency Global Positioning System (GPS) receivers, GIMSYS generates global maps of ionospheric total electron content (TEC) and irregularities, which are crucial for understanding and predicting the effects of ionospheric variability on communication systems, power grids, and other technologies.
GIMSYS produces a global snapshot of vertical TEC every 15 minutes by performing spatial and temporal interpolation of GPS-based TEC measurements. The system employs a Kalman-type filter to optimally update the global ionospheric map as new data becomes available. Additionally, it can incorporate TEC measurements from other satellite missions, enhancing the accuracy of its outputs. The accuracy of the global TEC maps has been validated through comparisons with independent ionospheric measurements, demonstrating good agreement with predictions from coupled thermosphere-ionosphere models during storm events.
The document highlights several applications of GIMSYS, including global wide-area differential GPS (WADGPS) systems, calibration of satellite ocean altimetry missions, monitoring and prediction of space weather conditions, and regional ionospheric studies. The system is also capable of detecting and monitoring ionospheric storms by comparing current conditions to quiet-time averages, allowing for the analysis of TEC enhancements and depletions during storm phases.
Furthermore, GIMSYS employs time-series analysis to produce short-term forecasts of ionospheric conditions, which can be reasonably accurate for 2-4 hours. This capability is particularly valuable for various stakeholders, including NASA, the U.S. Navy, the U.S. Air Force, NOAA, and commercial users, who utilize the data for applications ranging from space weather monitoring to real-time ionospheric corrections for aviation.
In summary, GIMSYS represents a significant advancement in ionospheric research and monitoring, providing critical data that supports a wide range of scientific, commercial, and defense applications. Its ability to deliver timely and accurate ionospheric information is essential for mitigating the impacts of ionospheric variability on modern technology and infrastructure.
