The High Resolution Ionospheric and Thermospheric Spectrograph (HITS) on the Advanced Research and Global Observing Satellite (ARGOS):: Quick look results

The High-resolution Ionospheric and Thermospheric Spectrograph (HITS) is a very high resolution (>0.5 Angstrom resolution over the 500-1500 Angstrom passband) Rowland circle spectrograph that is currently flying on the USAF Advanced Research and Global Observing Satellite (ARGOS, launched 23 February 1999). The ARGOS is in a sun-synchronous, near-polar orbit at 833 km altitude with an ascending node crossing time of 2:30 PM. The instrument is designed to spectrally resolve the 834 Angstrom triplet to demonstrate a new technique for remotely sensing the electron density in the F-region ionosphere. In addition, the HITS can spectrally resolve the rotational structure of the N-2 Lyman-Birge-Hopfield (LBH) bands, which can be used to infer the thermospheric temperature. The HITS can resolve the radiative recombination continuum produced by recombining O+ ions and electrons, which can be used to infer the electron temperature. The HITS will also produce a high spectral resolution survey of the 500-1000 Angstrom passband to produce a more accurate identification of some of the previously unresolved features of the dayglow spectrum. The instrument operates as a limb imager with a limb scan occurring every 100 seconds throughout the expected three year mission life. Its field-of-view is 0.06 degrees x 4.6 degrees, which corresponds to 3 km (altitude) x 230 km (along the horizon) at the limb. The instrument's field-of-regard is 17 degrees x 4.6 degrees, which covers the 100-750 km altitude range. We will present an overview of the instrument and discuss its calibration and in-flight performance.