Comparison of TEC Derived Ultraviolet Limb Scans to TOPEX TEC Data

In February of 1999, the Air Force Space Test Program launched the Advanced Research and Global Observations Satellite (ARGOS) into an 830 km altitude, near-polar sun-synchronous orbit with a 14:30 ascending node local time. On board the ARGOS satellite is a suite of remote-sensing instruments that measure density, composition, and temperature of both the thermosphere and ionosphere. The Low Resolution Airglow and Auroral Spectrograph (LORAAS) aboard ARGOS monitors upper atmospheric airglow in the far-ultraviolet and extreme-ultraviolet passband. LORAAS is identical to the Special Sensor UV Limb Imager (SSULI) instrument whose mission will be starting with the launch of the next Defense Meteorological Satellite Program (DMSP) satellite and continuing on the next four DMSP satellites. Limb scans, atmospheric radiance profiles, in the satellite's orbital plane are collected every ninety seconds. At night, the altitude distribution of the OI 1356 \x8F emission can be used to determine variations in the vertical electron density distribution. It is necessary for a validation effort to be performed to estimate the quality of the two-dimensional nightside ionosphere algorithm based using the LORAAS data set. The validation presented here will be a comparison of total electron content (TEC) derived from LORAAS UV limb sensing techniques to total electron content derived from TOPEX data of the nightside ionosphere. This comparison of TEC will be used to assess the accuracy of the UV inversion.