Conveners:
Anthea Coster (ajc@haystack.mit.edu), MIT Haystack Observatory
Patricia Doherty (Patricia.Doherty@bc.edu), Institute for Scientific
Research, Boston College
2004 Monday 28 June 0100-0300 PM
The goal of this workshop was to bring the community together to design a series of collaborative experiments using GPS data. Specifically with the Advanced Modular Incoherent Scatter Radar (AMISR) coming on line, we have an opportunity to collect background information in the dynamic polar region. There also exist opportunities to plan investigations combining GPS data with measurements from the Communication/ Navigation Outage Forecast System (C/NOFS) satellite instrumentation. In this workshop, we attempted to identify and discuss the scientific areas such as the irregularities and spatial gradients of the equatorial anomaly and sub-auroral trough region that may be investigated with the combination of various types of instruments.
The workshop began with introductions demonstrating the purpose and capabilities of AMISR and C/NOFS. These presentations were followed with a description of GPS capabilities for ionospheric characterization and how GPS has been combined with other instruments. These presentations generated much discussion on the upcoming instrumentation and on the overall usefulness of GPS in development and experimentation.
The first presentation on the Advanced Modular Incoherent Scatter Radar (AMISR) was given by Rick Doe of SRI. AMISR will be constructed in two stages over the next four years. The first face will be constructed in Poker Flat, Alaska. A subsection of AMISR, an eight-panel radar, will be deployed at the Jicamarca Radio Observatory (JRO) in 2004. The remaining two faces will be built in Resolute Bay, Nunavut, Canada. Subsequent locations will be determined by a scientific advisory panel.
The AMISR faces will initially be pointed to sense the polar cap and auroral regions with some possibility of pointing equatorward to cover sub-auroral areas. In its high latitude position, AMISR is capable of monitoring the global polar convection pattern, polar cap arc, electrodynamics and F region patch structure and evolution. As was pointed out by Phil Erickson, the merging of GPS observations of storm enhanced density (SED) and the tongue of ionization with AMISR observations will help explain and interpret some of the complex phenomena observed in the polar ionosphere.
The second formal presentation was made by Odile de la Beaujardiere on C/NOFS. Odile initiated the discussion with a summary of the C/NOFS mission to provide continuous global scintillation forecasts of communication and navigation outages. The mission will also enable an improved understanding of the equatorial ionosphere and the scintillation triggers and inhibitors. The C/NOFS satellite will be equipped with various instruments that include a GPS receiver. Odile discussed efforts to complement the C/NOFS efforts with campaign data and data from various instruments. These instruments will include ground based TEC and scintillation measurements made from various GPS receivers. In particular, a network of TEC and scintillation receivers located along the west coast of South America have already been used to validate the background models of C/NOFS and will be an integral part of validation of the impending measurements.
The last invited presentation was made by Tony Mannucci. This presentation focused on the capabilities of GPS in ionospheric characterization. Tony provided a brief review of what GPS measures - both on the ground and in space. In many ways GPS data are complementary to other instruments. Tony showed examples of how GPS TEC measurements in the equatorial region were complementary to observations from the Julia radar at Jicamarca, how GPS TEC measurements were complementary to optical measurements in Puerto Rico and Hawaii, and how GPS scintillation measurements tracked magnetometer readings at the Bear Lake Observatory. GPS mapping techniques have provided a new visualization tool to observe the complex dynamics of storm-time TEC. GPS TEC measurements and their proxies are being successfully incorporated into next generation data assimilation models for the ionosphere. GPS has the advantage that it is continuously available, it can provide global and regional coverage, and it is sensitive to both small and large-scale plasma structure. Integrating GPS measurements into multi-instrument campaigns will lead to increased understanding of the complex physical processes in the high, mid, and low latitude ionosphere.
Much interest was generated from the workshop participants during these presentations. There were numerous comments and questions that revealed a general interest in elevating GPS for scientific investigations and collaborations with other instruments.
The formal presentations were followed by short presentations. Gary Bust discussed an open source GPS tool kit that facilitates processing raw GPS data to obtain ionospheric electron content. Larissa Goncharenko illustrated the usefulness of combining GPS with ISR data. John Makela talked about the capability to measure the worldwide ionosphere by combining GPS with imagers. John Foster made recommendations for using GPS in the Global Plasma Structures Radar Experiment, a planned 2005 ISR Campaign day. Tim Fuller-Rowell addressed the modeling aspect by showing the benefits of using multi-instruments, including GPS, in regional ionospheric modeling. Brent Ledvina described a promising technique to estimate the ionospheric scattering altitude from GPS measurements made from three receivers. Finally, J.Y. Liu showed how GPS signatures have great potential to detect earthquake epicenters.
Nearly 100 people attended this workshop. Although we did not realize the goal of designing collaborative experiments using multi-instruments, we were successful in initiating communication between various groups and in generating interest in these possibilities among student participants. Handouts were provided that described the basic GPS equations, information on processing techniques and problems, directions to data sources and relevant references. Overall, the convenors of this workshop were encouraged by the level of participation and interest in this topic.