Tandem Satellite Monitoring of All Equatorial Irregularities Around the Earth

Two simple satellites in a tandem equatorial orbit can provide the continuously undated state of all equatorial irregularities around the earth. A radio beacon transmitter and companion radio beacon receiver flying in low earth orbit can provide both radio scintillation and total electron content for the path passing through the ionosphere with a tangent height below the ionosphere. The 100 minute orbit of these two low inclination satellites provides all the information needed for global tracking of equatorial bubbles that impact radio navigation, communications, and radar systems. The CERTO beacon transmitter on the C/NFOS satellite in low earth orbit transmitting to an array of ground receivers has been used to produce high resolution images of equatorial bubbles using computerized ionospheric tomography. The CITRIS receiver on STPSat-1 in a 35 degree orbit has provided both radio scintillation indices and satellite to satellite total electron content with better than 0.01 TECU absolute accuracy. Placing the CERTO and CITRIS instruments on a pair of tandem orbit satellites separated by about 5000 km yields the optimum geometry for irregularity monitoring at every point around the equator.

This concept is being tested with a radio beacon CubeSat developed jointly with the Naval Post Graduate School and the Naval Research Laboratory. The receiver component of this system is being developed by the University of Saskatchewan in Canada. This two CubeSats will be launched on the same rocket in an equatorial orbit. Once the separation of the receiver and transmitter beacon satellites becomes large enough for the inter-satellite propagation path to penetrate through and below the ionosphere, all equatorial irregularities will be intersected by the radio signals. After each orbit, the location, velocity and intensity of the electron density irregularities will be determined and downlinked to an equatorial ground station. This instrument can be used to replace existing networks of ground beacon receivers used for regional monitorial of equatorial bubbles. Properly designed signals at UHF and L-Band frequencies will be resistant to scintillation and refraction effects in the equatorial ionosphere. Data from this tandem instrument configuration can be directly assimilated into operational space weather models.