Global Thermospheric Densities Derived from ARGOS Measurements

The High Resolution Airglow and Aurora Spectroscopy (HIRAAS) experiment was launched from Vandenberg AFB, CA aboard the Advanced Research and Global Observation Satellite (ARGOS) on 23 February 1999 at 2:29:55 AM Pacific Standard Time. The ARGOS is in a sun synchronous, circular orbit at an altitude of 843 Km. The HIRAAS experiment contains the Low Resolution Airglow and Aurora Spectrograph (LORAAS). The LORAAS gathers limb scans over the 750-100 Km altitude range, covering the 800-1700 {Å} passband at 17 {Å} resolution. LORAAS observes limb profiles of the N{₂} Lyman-Birge-Hopfield and O I 1356 {Å} emissions. We report our measurements of the daytime thermospheric composition derived by analysis of the altitude profiles of the N{₂} Lyman-Birge-Hopfield and O I 1356 {Å} emissions. Our inversion algorithm inverts the photoelectron impact excited emissions and includes the effects of radiative recombination on the O I 1356 {Å} profile. The inversion process produces thermospheric densities of O, N{₂}, and O{₂}, as well as the ionospheric electron density required to reproduce the radiative recombination component of the O I 1356 {Å} emission. We find generally good agreement between the retrieved densities and the NRLMSIS-2000 model, although our densities tend to be somewhat lower than the NRLMSIS-2000 predictions for the case presented. We also find good agreement with the derived electron densities and measurements of the peak electron density and peak height derived by ionosonde observations.