Articles | Volume 13, issue 2
https://doi.org/10.1007/s00585-995-0189-6
https://doi.org/10.1007/s00585-995-0189-6
28 Feb 1995
28 Feb 1995

Interference filter spectral imaging of twilight O+(2P-2D) emission

Y. Ma, R. N. Peterson, S. P. Zhang, I. C. McDade, R. H. Wiens, and G. G. Shepherd

Abstract. A spectral imager specifically designed to measure the O+(2P-2D) emission in the thermosphere during twilight has been constructed and tested in Toronto (43.8°N, 79.3°W), and found to show promise for long-term and campaign-mode operations. A modification of the mesopause oxygen rotational temperature imager (MORTI), it consists basically of a narrow-band interference filter (0.14 nm bandwidth) to separate wavelengths as a function of off-axis angle, a lens to focus the spectrum into a series of concentric rings, and a focal plane array (CCD) to record the spectral images in digital form. The instrument was built with two fields of view, one for the zenith and one for 20° above the horizon, movable to track the azimuth of the Sun, in order to provide appropriate data for inversion. Data gathered during June 1991 provided measurements of the column-integrated emission rate with a precision of about 3%. An atomic oxygen profile was deduced that showed good agreement with that predicted by the MSIS-90 model atmosphere. Geomagnetically induced variations of the O+ lines, calcium spectra resulting from meteor showers, and OH nightglow were also observed.