Limb view spectrum of the Earth's airglow

Abstract

Sometimes the Earth's airglow layer, when observed in the limb view, appears to be a double layer. During one of these occasions we were able to obtain absolute spectral intensity and altitude profiles for most well‐known airglow features from the space shuttle on the STS‐37 mission. The lower of the two airglow layers consisted of the OH Meinel bands, the ground state of the O2 atmospheric band at 762 nm and an intense nighttime sodium layer at 598 nm peaking near 92 km. The upper airglow layer consists of the atomic oxygen lines at 557.7, 630, and 636.4 nm, and a blue green continuum. Significant 557.7, 630, and 636.4 nm OI emissions were observed to extend above 110 km into the lower F region. The volume emission rate distribution as a function of altitude was modeled, and the model limb intensity distribution was compared to the data. From the spectral profile of the modeled volume emission distribution, the green continuum located at 103 km ± 2 km altitude was identified as recombination emission of NO2 produced by a dense NO layer. Another layer which was present at each of the modeled wavelength regions had a volume emission peak at 90 km. Our observations did not show the presence of continuum emission with increasing intensity toward the near infrared. The observed regions were quite near the equator.