Summary The High Resolution Airglow/Auroral Spectrograph (HIRAAS) sounding rocket experiment was successfully launched into a proton aurora over Poker Flat, Alaska on March 11, 1994 and acquired the first high resolution (< 0.1 nm) EUV and FUV spectra of a proton aurora. The experiment consisted of two 0.5-m Rowland circle spectrographs covering the passband 50-180 nm using an electrographic camera detector, a medium resolution 0.125-m spectrometer covering the 180-320 nm wavelength region, and a video camera for aspect information. The high resolution spectrographs utilize a unique multiple entrance slit design which significantly increased the throughput. The observation scheme was to overfly the aurora, traveling 300 km north and reaching an apogee of 300 km. The spectra are recorded on electron-sensitive film, and though the signal-to-noise of the data was low due to film fogging in the developing process, extensive data processing has yielded encouraging results. We observed Doppler-shifted H I Lyman-alpha emission from precipitating aurora protons that undergo charge-exchange collisions in the atmosphere, as well as atomic, ionic, and molecular emission features attributed to precipitating and secondary electrons. These UV emissions provide information about the precipitation rate, peak energy, and energy/pitch angle distribution of auroral protons, as well as the state of the auroral ionosphere. Presentation Outline Abstract (the preceding summary) Instrumentation Observation Scheme Data Reduction Results Summary (the following conclusions) Basic Conclusions HIRAAS observed a proton aurora at a resolution of 0.05-0.1 nm over the bandpass 50-160 nm to infer the proton energy/pitch angle distribution from H I 121.6 nm (Lyman-alpha) emission. Such an observation has never been performed in the UV before. We successfully measured Doppler-shifted Lyman-alpha emission from precipitating protons that undergo charge-exchange collisions in the upper atmosphere. A unique multiple entrance slit format was employed to increase sensitivity and performed up to our most optimistic expectations. Due to a fogging problem in the developed film on which the spectra are recorded, the dynamic range and signal-to-noise of the data are significantly lower than expected. However, quantitative results can be obtained through extensive image processing. The full FUV and EUV spectrum is yet to be reduced. Combined with the MUV spectrum from the MUSTANG instrument, we will be able to characterize both the auroral atmosphere and the precipitating particles.

Click on the images to view a larger version. This picture of the aurora borealis was taken near Poker Flat, Alaska in March 1994. The orange glow near the horizon is the light of Fairbanks to the south. Sounding rocket 36.114DE was launched from Poker Flat Research Range, Alaska on March 11, 1994. The rocket was a Terrier-Black Brant that achieved an altitude of 300 km (180 mi) and traveled 300 km downrange. The 36.114DE payload was recovered by helicopter 300 km north of Poker Flat two days after launch. Here two scientists are preparing to remove film from the scientific payload. The plastic protects the hygroscopic detector from atmospheric water vapor.

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