Analysis of Signal to Noise Ratio for Atmospheric ultraviolet Remote Sensing on Geostationary orbit with variations of solar incident angles

摘要

Ultraviolet (UV) sensors on a geostationary orbit (GEO) have important potential value in atmospheric remote sensing, but the satellites orbit mode of it is quit different from sun-synchronous orbit satellites, which result in the significant diurnal and seasonal variations in radiation environment of earth observation and radiation signal of sensors, therefore, the effect to sensor radiometric performance, such as signal to noise ratio for atmospheric ultraviolet remote sensing caused by variations of solar angle is significant in the performance design of sensors. The synthetic ultraviolet sensor is set at the geostationary orbit, 36000 km away from the sea level of the Equator with 8.75 degree field of view, and the subsatellite track point of which is located at 90 degrees east longitude and Equator. The Satellite scanning angles (SA) from 0 to 8.648 degree that cover the earth surface are selected corresponding to the 10 degrees equal interval view zenith angle, and the SA from 8.648 to 8.785 degree cover the earth lamb 100 km far away from earth tangent point. Based on the MODTRAN4 model, on normal atmospheric conditions, the distributions of the UV upwelling radiance from surface or limb viewing path of the earth could be simulated with the change of sun's right ascension. Moreover, the average signal to noise ratio to the atmospheric sounding is obtained in different UV spectra using the Sensor signal to noise ratio model. The results show that the thresholds range, tendency and shape of signal to noise ratio have a variety of features affected by variation of Sun hour angles and declinations. These result and conclusions could contribute to performance design of UV sensors on the geostationary orbit.