Tuesday, 16 January 2007: 11:45 AM
Autonomous space-based radio monitors of the ionosphere
210A (Henry B. Gonzalez Convention Center)
Radio systems that monitor the ionosphere require EM wave sources and receivers to measure (1) integrated electron density (total elecron content – TEC) and (2) radio scintillations as the waves propagate through the intervening ionosphere. A new constellation of radio beacons called the Coherent Electromagnetic Radio Tomography (CERTO) will be available for these measurements. These beacons transmit unmodulated, phase coherent waves at VHF, UHF and L-Band frequencies. A fixed radio of 3/8 is used between successive frequencies. Total electron content (TEC) is obtained from the phase difference between two frequencies. The range between beacon and receiver is eliminated from the phase measurements leaving a differential phase that is proportional to TEC. The three CERTO frequencies cover a wide range for determination of the radio scintillation effects caused by diffraction after propagation though ionospheric irregularities. All of the CERTO beacons are in low-earth-orbit with inclinations ranging from equatorial to polar. Each satellite that carries CERTO has other plasma instruments that complement the beacon data. In addition, a scintillation and tomography receiver in space (CITRIS) instrument will be placed in orbit to detect signals from the CERTO beacons and from the array of 56 DORIS VHF/S-Band radio beacons placed around the word by the French CNES. CITRIS will record ionospheric occultations and radio scintillations with a unique occultation and ground-to-space geometry. New algorithms have been developed for the multi-frequency CERTO and CITRIS data to provide improved acquisition and analysis of TEC and scintillation data in ionospheric studies. The data from the CERTO constellation of beacons and receivers may be used to update space weather models.