Small Satellite Space Mission Instruments for Far Ultraviolet Measurements of the Effects of Solar Activity on Earth's Upper Atmosphere

This presentation describes two proposed space missions for studies of Earth's upper atmosphere and the near-Earth space environment, as a function of solar activity, by means of far-ultraviolet measurements from low- or medium-altitude, high-inclination Earth orbits. The first of these would measure the temperature vs. altitude of the upper atmosphere (above 100 km altitude) by observing the upward expansion of the atmosphere with solar activity (increased scale height with temperature). It would use remote sensing of the far-ultraviolet spectra of hot stars, as these stars are occulted by the atmosphere above the altitude of the satellite, as the spacecraft orbits Earth. The instrument would utilize a very high-resolution spectrograph, observing in the far-UV spectral range. Two separate wavelength ranges, one shortward and one longward of the hydrogen Lyman-alpha geocoronal emission line, would be used to study molecular nitrogen, and atomic/molecular oxygen, absorption line intensities respectively. The second of these missions, using an even simpler instrument, would be a gravity-gradient-stabilized, zenith-viewing satellite which would measure the Lyman-alpha emission of Earth's hydrogen geocorona as a function of location along the orbit, solar activity, and time. This latter satellite could be a very simple device, not much larger than a CubeSat, and could be a basis for student involvement in a real space mission. Data obtained by either or both of the proposed missions would be compared with simultaneous measurements of solar activity by other solar physics, upper atmospheric, and space environment missions operating in parallel.