Computer-aided estimates of the rotational temperature of O2 in the mesosphere

Measurements have been made of the apparent rotational temperature of O2 (b(1)Sigma(g-)) atmospheric (0,1) band emissions. The data were taken at nighttime in the auroral zone at Poker Flat, Alaska, on March 1, 1975. The average apparent temperature was 210 k and the zenith radiance of the band was 500 R (uncorrected for atmospheric extinction). A comparison technique was developed to compare the band shape of the measured band with theoretical spectra synthesized at different, but specific, rotational temperatures. Three methods of comparison were used and it was concluded that a sum of squares weighting approach is near optimal for estimating rotational temperatures. The effect of noise was tested by adding real typical noise to the synthetic model. The same comparison technique was then applied to assess the benefits of noise. The uncertainty of the measurement is estimated to be 5 K. A 'wavelike' fluctuation of the apparent rotational temperature, with a period on the order of 1/2 to 1 hour, was observed. The fluctuation on this occasion appeared to covary with the intensity of the OH airglow emission.