2007 Workshop:Remote sensing of the ionosphere
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Contents |
Introduction
Ionospheric studies using radio occultation electron density profiles
Thursday, June 28th from 13:00 - 15:00 in Anasazi North
The radio occultation method retrieves profiles of electron density from 200-400 km altitude (F-region) with high vertical resolution and global sampling. Electron density profiles can be used to study ionospheric phenomena over daily or seasonal time scales that are geographically localized or global-scale.
This tutorial-format workshop covers the fundamentals of how the radio occultation method remotely senses Earth's atmosphere using low-earth orbiting constellations such as COSMIC / FORMOSAT-3 to receive GPS signals. We present specifics of how the UCAR Cosmic Data Analysis Archive Center (CDAAC) retrieves electron density profiles from the radio occultation measurements, followed by a tutorial on how to set up a system to download, read, and analyze data from CDAAC with netcdf and MATLAB. Three exciting examples using electron density follow: (1) assimilating electron density profiles into the GAIM ionospheric model, (2) setting up a system for long-term statistical studies of scintillation using CDAAC data that corresponds to ground site data, (3) fusing radio occultation data with ground-based airglow imagery using Google Earth for visualization of scintillation-causing irregularities in three dimensions.
Agenda
- 13:00-13:15 - Exploring the solar system with radio occultation (K. Cahoy, Stanford). The planetary heritage, math, and physics behind the radio occultation method, and how it has been applied on earth using GPS and low-earth orbiting satellites.
- 13:15-13:45 - Retrieval of electron density profiles (S. Syndergaard, UCAR). How radio occultation measurements are used to derive electron density profiles at CDAAC.
- 13:45-14:00 - Download and analyze electron density profiles (K. Cahoy, Stanford). Introducing the CDAAC data tool and how to download and analyze electron density profiles using netcdf and MATLAB.
- 14:00-14:20 - Assimilating COSMIC occultation data into a global ionosphere model (JPL/USC GAIM) (B. Wilson, JPL). How the high vertical resolution and global coverage of COSMIC radio occultation measurements will enable ionospheric data assimilation models to specify the 3D ionosphere (electron density altitude profiles) much more accurately.
- 14:20-14:40 - Ionospheric scintillation applications to complement GPS ground site data (T. Beach, AFRL). This application takes into consideration the geometry of selecting useful occultation lines of sight near ground sites, and how you would automate data retrieval from CDAAC for long-term statistical studies.
- 14:40-15:00 - Visualization of ionospheric scintillation (E. Miller, UIUC). Fusing ground-based airglow imagery and estimated scintillation indices from radio occultation receivers to localize scintillation-causing irregularities in three dimensions, with special emphasis using MATLAB and Google Earth tools. Data from the COSMIC / FORMOSAT-3 mission and a field-aligned airglow imager at Cerro Tololo, Chile.
We welcome our colleagues to bring their own applications and topics for group discussion.
Chairs and Presenters
Conveners
Presenters
Time and Location
June 28, 2007 Thursday, 13:00 - 15:00 in Anasazi North
Final Report
CEDAR 2007 Workshop Report Ionospheric studies using radio occultation electron density profiles Convener: Kerri Cahoy, Stanford University, kcahoy@stanford.edu
The successful launch and operation of the GPS radio occultation receivers on the COSMIC/Formosat-3 constellation, in addition to the availability of data from long-term precursor missions such as CHAMP, have substantially augmented the number, geographic and temporal resolution of electron density profiles available to the community. This workshop focused first on a general introduction of the method and the profile retrieval, and followed with examples of how these data compliment and support both modeling efforts and analyses with other instruments, such as incoherent scatter radar and airglow imagery.
K. Cahoy (Stanford) introduced the session and presented the planetary exploration heritage of the radio occultation method, and how the “classic” geometry used for capturing profiles of planetary atmospheres from an orbiter or during a fly-by was updated for application to remote sensing of our own Earth’s atmosphere, using GPS signals.
S. Syndergaard (UCAR) followed up with a detailed discussion of how electron density profiles are retrieved from the radio occultation observables, starting from the Appleton-Hartree (Appleton-Lassen) equation and progressing through how TEC can be calculated using the combination of L1 and L2 phase paths. Different boundary (auxiliary) conditions were discussed for different experimental configurations (e.g. CHAMP versus COSMIC/Formosat-3). A brief description of COSMIC/Formosat-3 and the Cosmic Data Analysis and Archival Center (CDAAC) were also presented, as well as previews of some seasonal studies being done using this data by postdoctoral students at UCAR.
The workshop completed its general background and tutorial segment with an introduction of the different centers that currently have publicly available electron density profiles, such as CDAAC and the JPL Genesis system as well as often the home institutions of the spacecraft mission. The NetCDF file format was briefly discussed as well as simple ways that MATLAB and other computational analysis software suites could be used to simply query the data.
B. Wilson (JPL) discussed how to assimilate COSMIC occultation data into a global ionosphere model (JPL/USC GAIM), and how the high vertical resolution and global coverage of COSMIC radio occultation measurements will enable ionospheric data assimilation models to specify the 3D ionosphere (electron density altitude profiles) much more accurately.
T. Beach’s (AFRL) presentation (via proxy, due to the Texas flooding at the time) focused on how to determine which electron density profiles would be most useful for comparative studies (with specific examples using incoherent scatter radar). The geometry and the atmospheric volume sensed during each radio occultation experiment were discussed, improving understanding of the paths traveled by the signals from which the resulting electron density profiles were retrieved.
E. Miller (UIUC) closed the session with a particularly cool visualization of ionospheric scintillation, fusing ground-based airglow imagery and estimated scintillation indices from radio occultation receivers to localize scintillation-causing irregularities in three dimensions, with special emphasis using MATLAB and Google Earth tools. Data from the COSMIC / FORMOSAT-3 mission and a field-aligned airglow imager at Cerro Tololo, Chile were used.
The workshop brought together researchers from various communities (simulation, optical measurements, radar measurements, and others). The tutorial-style initial format successfully segued into more detailed applications, allowing researchers unfamiliar with the data to not only get a quick-look of how it was acquired and made available, but also how it could be applied in comparative studies with other models, campaigns and data archives. K. Cahoy would like to thank all presenters for their expertise, enthusiasm, and much-appreciated contributions.
Recent Publications of Interest
Other Upcoming Workshops
2007 October 22 - 24
Boulder, Colorado
Second Formosat-3/COSMIC Data Users Workshop
Presentation Materials
Images, power point, pdf
Media: 2007-06-28-CEDAR-Cahoy.pdf
K. Cahoy, Introduction and using CDAAC with EIA example
Media: ionprf_cedar07.pdf
S. Syndergaard, Retrieval of electron density profiles
Media: CEDAR2007_occ_scints_final.pdf
E. Miller and J. Makela, Visualization of Ionospheric Scintillation
Note: Google Earth toolbox for MATLAB is available from the MATLAB Central file exchange on the Mathworks web site.
Comments and Questions
- Welcome and contact information
Welcome to colleagues interested in the Radio Occultation Electron Density Workshop.
Please feel free to contact me with any questions or comments:
Kerri Cahoy
Stanford University
kerri.cahoy@gmail.com
(650) 814-8148
Presenters: a projector is expected to be available for the workshop.
All: If you would like to bring handouts or post content on the workshop Wiki page, please feel free to do so! Please also feel free to post with any relevant topics, findings, or questions.
