DE 2 Fabry-Perot Interferometer (FPI), Thermospheric Neutral Gas Density, Meridional Wind, and Temperature, 8-sec data
The Fabry-Perot Interferometer, FPI, was a High-Resolution Remote Sensing Instrument designed to measure the Thermospheric Temperature, Meridional Wind, and Density of the following Metastable Atoms: Atomic Oxygen, Singlet S and D, and the 2P State of Ionic Atomic Oxygen. The FPI performed a Wavelength Analysis on the Light detected from the Thermospheric Emission Features by spatially scanning the Interference Fringe Plane with a Multichannel Array Detector. The Wavelength Analysis characterized the Doppler Line Profile of the emitting Species. A Sequential Altitude Scan performed by a Commandable Horizon Scan Mirror provided a Cross-Sectional View of the Thermodynamic and Dynamic State of the Thermosphere below the DE 2 Orbit. The Information obtained from this Investigation was used to Study the Dynamic Response of the Thermosphere to the Energy Sources caused by Magnetospheric Electric Fields and the Absorption of Solar Ultraviolet Light in the Thermosphere. The Instrument was based on the Visible Airglow Experiment, VAE, used in the AE Program. The Addition of a Scanning Mirror, the Fabry-Perot Etalon, an Image Plane Detector, and a Calibration Lamp were the Principal Differences. Interference Filters isolated Lines at 5577, 6300, 7320, 5896, and 5200, in Angstroms. The FPI had a Field of View of 0.53°, Half-Cone Angle. More Details are found in P. B. Hays et al., Space Sci. Instrum., 5(4), 395, 1981. From February 16, 1982 to September 11, 1982 the DE Satellite was inverted and the FPI measured Galactic Emissions. NOTE: Animations of DE2-FPI Science Products have been created as Daily Summary Files. The Animations contain Binned Averages displayed as a Color Code against a Geographic Background. The Bin Sizes are 7.5° Latitude and 24.0° Longitude. The Longitude Bin corresponds to the approximate Separation of adjacent Orbits, assuming that DE2 completed 15 Orbits per Day. The Animations are divided by Day, 06-18 LST, and Night, 18-06 LST, where LST is Local Standard Time. All Summary File Information and Animations employ Spacecraft Orbital Attitude Data. Users should note 1, that the DE2-FPI Experiment acquired Airglow Spectra by imaging the Terrestrial Limb below and ahead of the Spacecraft at an approximate Tangent Altitude of 250 km, 2, All Airglow Spectra were acquired while the DE2 Spacecraft orbited in it's Normal Configuration, which corresponded to Calendar Months August to February in 1981 to 1982 and n 1982 to 1983; 3, The Orbital Inclination of DE2 was 90° implying that DE2-FPI always viewed Ahead along the Meridian; 4, And that DE2 flew in an Elliptical Orbit with Perigee of 305 km and Apogee of 1300 km at Launch ans the Attitude of DE2 for each FPI Measurement is included with each reduced Data Point permitting Users to determine the Tangent Latitude corresponding to the 250 km Terrestrial Airglow Limb. The three GIF Animations are: 1. FPI_brightness.gif, which documents the OI, 630.0 nm,, Column Brightness in Units of log10 Rayleighs. Note different Scales for Day and Night. 2. FPI_temperature.gif, which documents the Neutral Thermosphere Temperature in Units of °Kelvin. 3. FPI_wind.gif, which documents the Line of Sight Neutral Wind Component in Units of m/s. The Wind Direction is positive when the Wind blows away from the approaching Spacecraft.
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