Ionospheric forecasts improve warfighter communication efficiency

  • Published
  • By Michael P. Kleiman
  • Air Force Research Laboratory Space Vehicles Directorate Public Affairs
KIRTLAND AIR FORCE BASE, N.M. (AFPN) --  During specific times of the year over the Earth's equatorial region, turbulence in the ionosphere, known as scintillation, causes extended degradation for Department of Defense navigation and communication satellites.  But a sensor package installed at each of 14 locations worldwide has helped reduce the impact of this naturally occurring disruption. 

Developed by the Air Force Research Laboratory's space vehicles directorate here, the Scintillation Network Decision Aid, or SCINDA, receives data on disturbances in the upper atmosphere from Global Positioning System satellites and geostationary radio beacons to predict when and where potential communication interruptions will occur.

"The SCINDA is a regional nowcasting tool to assist researchers and users of space-based communication and navigation systems," said Dr. Keith Groves, program manager in the directorate's Ionospheric Impacts on Radio Frequency Systems office. "It is also a scientific collaboration to characterize and forecast low-latitude scintillation."

Evolving from a research project started in 1994 on the formation of low-latitude ionospheric disturbances, the SCINDA provides real-time information, updated every 30 minutes, to the Air Force Weather Agency at Offutt Air Force Base, Neb., and the Communication/Navigation Outage Forecasting System Data Center at Hanscom AFB, Mass. The data is used to predict satellite transmission disruptions and seasonal behavior of the cosmic storms.

From September through March, low latitude regions in the American sector can experience the intense effects of scintillation, which normally transpire at night within 20 degrees of the Earth's magnetic equator. This area comprises more than one-third of the world's surface. Mid-latitude regions, such as the continental United States, also can be affected by scintillation during magnetic storm events. 

Although the SCINDA has become operational at numerous locations worldwide, coverage gaps have existed from Hawaii westward through Southeast Asia and extending almost to the Middle East. With the installation of a sensor site in September 2005 on Kiritimati Island, also referred to as Christmas Island, in the Republic of Kiribati, a significant obstacle to scintillation forecasting was removed.

Discovered by Capt. James Cook on Dec. 24, 1777, Christmas Island, located 1,160 miles south of Honolulu, Hawaii, serves as a strategic geophysical location because the equator crosses near the South Pacific landmass.

"Christmas Island is important geophysically and operationally," Dr. Groves said. "It is a unique location that allows us to characterize ionospheric turbulence. AFRL receives the scintillation data from the site via Iridium telephone link and then passes it on to AFWA and the C/NOFS Data Center."

Consisting of two ship containers, a stand-alone optical system and a generator, the Christmas Island SCINDA station, staffed by one contractor, occupies an old National Oceanic and Atmospheric Administration radar site. Planned SCINDA network expansion does not stop at Christmas Island. In the next two years, an additional 10 to 12 research posts will become operational.

By the end of 2006, approximately six facilities will open on the African continent, and another three SCINDA data locations will become operational in India. United Nations officials helped with the establishment of the stations in Africa through their Basic Space Science Initiative Program dedicated to the International Heliophysical Year in 2007. These sites will also be funded by the AFWA.

"The objective of the SCINDA network expansion is to characterize the global behavior of the equatorial ionosphere in time to support users during the next solar maximum (several years of increased space weather activity including scintillation, solar flares, and coronal mass ejections, which begins in 2009)," Dr. Groves said. "Our goal is getting the global SCINDA network completed in the next couple of years to characterize the solar maximum for the first time."

With the SCINDA network predicting scintillation occurrences in real time, the warfighter now has the capability for using ultra high frequency satellite communication quality products for reliable operations, which enhances survivability in the combat environment. Nonetheless, scintillation research serves as the primary driver for the future of SCINDA.

"Research input is our foremost focus," Dr. Groves said. "Our objectives are to understand and get information on the dynamics of large-scale ionospheric disturbances and their impacts on the DOD's command, control, and communications system."

(Courtesy of Air Force Materiel Command News Service)