Atmospheric Studies with the Tri-Band Beacon Instrument on the COSMIC Constellaion

Observing System for Meteorology, Ionosphere, and Climate (COSMIC) can be used to study the plasma in the upper atmosphere by (1) providing profiles and two dimensional images of the ionosphere and (2) monitoring phase and amplitude scintillations induced in radio waves propagating through the ionosphere. In addition, the received radio data can be applied to the neutral atmosphere by (a) detecting horizontal fluctuations in tropo spheric water vapor and (b) yielding accurate position data for satellite drag and neutral density determination. A three-frequency radio beacon called the Tri-Band Beacon (TBB) is being developed for the COSMIC pro gram to provide transmissions at VHF, UHF and L-band. Tomographic imaging of the ionosphere is a recently developed technique that uses inte grated measurements and computer reconstructions to determine electron densities. The integral of electron density along vertical or oblique paths is obtained by employing radio transmissions from low-earth-orbiting (LEO) COSMIC satellite transmitters to a chain of receivers on the earth's sur face. Analyzing the total electron content (TEC) data using computerized ionospheric tomography (CIT) produces two-dimensional maps of the iono spheric plasma.Difficulties associated with CIT arise from the non-unique ness of the reconstructions owing to limited angle measurements or non-. optimal receiver. Improvements in both reconstruction algorithms and CIT measurement systems are being implemented for the COSMIC mission by combining the GPS occultation data with the TBB measurements of TEC.