Introduction The High Resolution Airglow / Aurora Spectroscopy Experiment (HIRAAS) is under development to fly aboard the Advanced Research and Global Observations Satellite (ARGOS). The HIRAAS experiment consists of three high spectral resolution ultraviolet spectrographs designed to measure the naturally occurring thermospheric and ionospheric airglow. The experiment performs a limb scan in the anti-velocity vector direction from -10 to -27 degrees relative to the spacecraft horizon corresponding to tangent altitudes from 750 km to 50 km. The limb scan is a slow downward scan of about 90 seconds before a 15 second flyback and initialization of the next scan.

The HIRAAS instrument.

The HIRAAS measurements test a new technique for ionospheric and thermospheric remote sensing from space. These measurements are used to determine the density profiles and temperatures of atoms, molecules, and ions in the upper atmosphere. HIRAAS ionospheric measurements aid a number of systems like HF communication that rely on propagation through the ionosphere. Neutral density measurements are important for satellite drag calculations and vehicle reentry problems. The HIRAAS mobile Ground Support Equipment (GSE) was designed to operate the HIRAAS experiment throughout its life on Earth. The GSE is completely mobile and can be ready to ship anywhere in a matter of minutes. The HIRAAS instrument complement includes: The High Resolution Ionospheric/Thermospheric Spectrograph (HITS) The Low Resolution Airglow/Aurora Spectrograph (LORAAS) The Ionospheric Spectroscopy & Atmospheric Chemistry (ISAAC) Spectrograph.

The HIRAAS Rocket Experiment This sounding rocket experiment was successfully launched into a proton aurora on March 11, 1994 over Poker Flat, Alaska and acquired the first high resolution (< 0.1 nm) EUV and FUV spectra of a proton aurora.

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