Research On Space-based Global Atmospheric Waves Imager

Imaging observations of mesosphere and lower thermosphere waves of the near space with a space-based instrument are significant for the atmospheric waves'studies. Developing space-based techniques to capture images of O₂ A(0-0) nightglows is an effective way to monitor global atmospheric waves in this region, which based on the theory that the atmospheric waves have an effect of modulation on airglows'lightness. This kind of instruments could use the time delay and integration Charge-Coupled Device (TDICCD) as its sensor. The signal to noise ratio(SNR) formula of the nightglow's images is deduced based on the way that the TDICCD works. The parameters of O₂ A(0-0) nightglows'images including SNR and exposure time are calculated. Besides, the drift angle and image drift in two different orbits with different inclinations are both calculated. The latitude-dependant horizontal resolutions are analyzed with a modulation transfer function(MTF), and furthermore, TDICCD image restoration is simulated with the wiener filter and MTF. The TDICCD pulse driven clock is designed and simulated. The block diagram of the global atmospheric waves imager (GAWI) is given including its characteristic parameters. Results indicate that the space-based atmospheric waves imaging observation is feasible.The main conclusions are listed as follows:1. Due to the high brightness and low background light of O₂ A(0-0) nightglow, the SNR of the nightglow images acquired by the TDICCD is sufficient to meet the specification of atmospheric waves observation. The CCD30-11 acquisition SNR can reach 42.9 with the exposure time of 12 seconds for the average brightness of the nightglow. The two parameters indicate that the O₂ A(0-0) nightglow images are feasible to study the atmospheric gravity waves. 2. MTF analysis indicates that, the TDICCD nightglow image quality increase with increasing latitude, so does the horizontal resolution. The most inferior horizontal resolution is 5.7 km in the orbit of 73°inclination and 3.1 km with an inclination of 30°when the TDICCD sweeps along the satellite flight direction; while the TDICCD sweeps along a particular direction, the most inferior horizontal resolution is 2.9 km in the orbit of 73°inclination and 1.8 km with an inclination of 30°. The simulation demonstrates that the TDICCD image restoration with wiener filter has a perceptible improvement.3 . A global atmospheric waves imager is proposed in 73°inclination orbit, which is capable of observing atmospheric waves with vertical wavelengths of 10 km or longer and horizontal wavelengths of 5.8 km or longer.