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|5292 - AAF - Ann Arbor MI Fabry-Perot Interf Sp|
Instrument Type: Instrument > OpticalInstrument > Interferometer > FabryPerot
Observation Site: AAF - Ann Arbor MI Fabry-Perot Interf Sp
Instrument Page: AAFDescription:
The dispersing element of the spectrometer is an air-spaced, 14 cm diameter effective clear-aperture Fabry-Perot interferometer, which is self-aligning and self-stabilizing (Hernandez and Mills, 1973). The instrument was operated at the optimum point for kinetic temperature determinations (Hernandez, 1979; 1988). The spectrometer operated with narrow (<0.3 nm wide) interference filters -a necessity, in particular, for the 630.0 nm emission, in order to avoid contamination from the nearby OH emission lines (Hernandez, 1974). The inherent stability of the spectrometer is about 0.5 m/s (632.8 nm) for periods of months, because of its self-stabilizing properties. The instrumental internal stability calibration is updated every 9 s throughout the day, year round. The spectrometer observed wavelength with the Fritz Peak (FPO or fpf) and Ann Arbor (AAM or aaf) instrument has been the so-called red line (630.0 nm, kindat=17001, 1973-1985 at FPO and 1986-1987 at AAM) of atomic oxygen (OI) with typical emission height peak in the range 210 to 300 km. The spectrometer observed the night-sky at the 4 cardinal directions at 20-degree elevation above the horizon, as well as zenith. Since the instrument is light-limited, the time spent in observing this 5-direction cycle can be as short as 5 minutes during auroral activity. The instrument is internally time-limited to spend no less that one-minute and no more than 15 minutes in any given direction. Other observing protocols, such as two orthogonal directions and zenith, have also been used. The observations were made every evening and only those with clear weather -as reported by an observer on site- are reported here. Because of the narrow filters used, operation of the instrument is not affected by moonlight. Typically, about 30% of the nights observed were clear.