The extreme and far ultraviolet environment at shuttle altitudes

The astronomical data obtained by the Far Ultraviolet Space Telescope (FAUST) and the Very Wide Field Camera (VWFC) on board the Spacelab I mission have triggered questions on the natural and induced Extreme and Far Ultraviolet (EUV and FUV) environment of the space shuttle. Moreover, the recent discovery of ∼1k Rayleighs N₂ Lyman Birge Hopfield (LBH) nightglow emissions by the U. S. Air Force's S3-4 satellite, and subsequent confirmation by the Imaging Spectrometric Observatory (ISO) experiment on the Spacelab I mission have serious implications for the astronomical observations from the shuttle. Since both ISO and S3-4 experiments were conducted from shuttle altitudes, the implied EUV and FUV environment for astronomical observations can be severe. In order to address the question of the suitability of the shuttle as an astronomical platform, we have examined data from FAUST and other experiments. We conclude that the FAUST background is most likely due to the observation of tropical UV arcs, a natural airglow phenomenon. Strategies for future shuttle experiments to overcome this and other natural emissions are discussed.