Simultaneous inversion of total electron content and UV radiance data to produce F region electron densities

The High Resolution Airglow and Aurora Spectroscopy (HIRAAS) experiment was launched aboard ARGOS on 23 February 1999. The HIRAAS experiment operated from mid-May 1999 through March 2002. One of the HIRAAS instruments, the Low Resolution Airglow and Aurora Spectrograph (LORAAS), gathered limb scans over the 750–100 km altitude range of the 911-Å emission during the daytime and the O I 1356 Å emission at night; these emissions are useful for characterizing the ion density distribution in the F region. The Coherent Electromagnetic Radio Tomography (CERTO) experiment, a coherently emitting radio beacon operating at 150 and 400 MHz, also flew on the ARGOS. The slant total electron content (TEC) between ARGOS and the ground was measured, using the CERTO beacon emissions, by a receiver located at the Naval Research Laboratory during early 2001. During the mission life of ARGOS, the ARGOS and TOPEX/Poseidon satellites occasionally crossed paths, permitting additional validation of the ARGOS measurements against TOPEX vertical total electron content measurements. We present a comparison of the UV-derived TEC and the radio beacon–derived TEC over the Naval Research Laboratory during January–April of 2001, based on LORAAS and CERTO measurements; we also present the electron densities derived by simultaneously inverting both the UV radiances and the CERTO-derived TEC. These results are validated against ionosondes. The TOPEX and UV measurements are also inverted tomographically and are used to demonstrate enhanced spatial resolution of the ionospheric reconstructions.