EARTH RADIANCE MODELING

摘要

Goodrich Corporation, a long 'time producer of high quality Earth sensors, has developed new analytical tools to more accurately predict the attitude determination error associated with Earth radiance variation, Infrared Earth sensors provide spacecraft attitude knowledge by sensing the radiant energy from the Earth's horizon in contrast to space. Radial and tangential radiance gradients within the field of view of the Earth sensors create error signals that limit the accuracy of attitude determination. Traditional Earth radiance models, such as LOWTRAN, MODTRAN, and CORPS, are seasonal in nature. They provide typical latitudinal radiance variation for different times of the year, but lack longitudinal variations and changes that can occur from one day to the next. Goodrich's new Earth radiance models use empirical Earth radiance databases created from remote IR sensing instruments such as HIRS/2 and VAS, which are onboard the NOAA and GOES satellites respectively. Earth radiance error analyses using actual radiance maps provide more accurate calculation of the errors to be expected during flight. This paper provides examples of the various radiance models that have been used and of the predicted attitude errors using Goodrich's latest generation Earth sensor, the Multi-Mission-Sensor (MMS).