Odile de La Beaujardiere

New Satellite Will Forecast Ionospheric Disturbances

Low-latitude ionospheric irregularities have a detrimental effect on the performance of communications, navigation, and surveillance systems. A satellite will be launched in an equatorial orbit to predict when and where these irregularities will occur. Sophisticated models will use data from the satellite and from numerous ground-based ionospheric measurements to produce a real-time forecast of the global ionosphere and the irregularities within.

C/NOFS: A Satellite Mission to Forecast Equatorial Ionospheric Scintillation

The forecasting of low -latitude i onospheric irregularities that have detrimental effect on communication, navigation and surveillance systems will be achieved by a n AF satellite mission called Communication / Navigation Outage Forecasting System (C/NOFS). The satellite, scheduled for lau nch in 2005 into a low inclination (13°), elliptical (~ 375 x 710 km) orbit, is the main component of the C/NOFS Mission. Complementary ground -based measurements are also part of the Mission. C/NOFS sensors will measure the following parameters: ambient and fluctuating electron densities; ion and elect ron temperatures; neutral winds; AC and DC electric and magnetic fields. C/NOFS will also be equipped with a GPS occultation receiver, and a radio beacon. Ionospheric irregularities often occur after sunse t. They can be fairly benign, causing a small amount of scintillation and perturbing only UHF/VHF communications, or they can be very severe, causing L -band scintillation that prevents GPS receivers to function. In these severe cases, the ionospheric irr egularities can extend beyond 1000 km altitude. They are associated with large equatorial plasma bubbles. Sophisticated physics -based simulation models have been developed to forecast the ambient ionosphere and the ionospheric turbulence.

C/NOFS: a demonstration system to forecast equatorial ionospheric scintillation that adversely affects navigation, communication, and surveillance systems

The purpose of the Communication/Navigation Outage Forecasting System (C/NOFS) is to detect and forecast ionospheric irregularities that adversely impact communication, navigation and surveillance systems. The C/NOFS consists of ground sites that monitor the radio link to geosynchronous and GPS spacecraft, a fully-instrumented monitoring satellite scheduled for launch in 2005 and a central data collection facility that creates scintillation warnings in near real-time. The C/NOFS spacecraft will be launched into a low inclination (13°), elliptical (~ 375 x 710 km) orbit. Sensors on the C/NOFS spacecraft measure the ambient ionosphere near the equator and detect density fluctuations which cause scintillation. Ionospheric irregularities often occur after sunset within ±20° of the magnetic equator. These irregularities can be fairly benign, causing a small amount of radio scintillation and perturbing only UHF/VHF communications, or they can be very severe, causing L-band scintillation that interfere with the functioning of GPS receivers. In these severe cases, the ionospheric irregularities can extend beyond 1000 km altitude. One of the challenges of this project is to go beyond detecting irregularities and to predict scintillation-producing irregularities up to 8 hours into the future and estimating changes in the climatology 24 hours or more into the future.