Conjugate excitation of atomic oxygen emissions in the far ultraviolet

Abstract

Rocket observations of far ultraviolet terrestial airglow emissions in the 1230–1450 Å band at night have been carried out from White Sands Missile Range. Three rockets carried 15.4 cm diameter far ultraviolet telescopes to≃220 km altitude at various times during the night from post sunset to predawn. Post sunset and predawn observations were made when the solar zenith angle at the conjugate ionosphere was≅95° and in both cases positive identification of strong Oi, 1304 Å emissions was made. Evidence that in these cases the 1356/1304 intensity ratio was less than 0.2 is presented. Observations made well into the night yielded only an upper limit to the combined Oi, 1304 and 1356 Å emissions of 20 Rayleighs, consistent with previous observations and theretical calculations. These results show that meaningful rocket observations of the cosmic far ultraviolet background can be made only when the solar zenith angle at the conjugate ionosphere of the launch site is larger than 105° or if atomic oxygen emission lines are excluded from the detectors' bandpass.