Optimization of a spaceborne sensor for the determination of cloud speed and height with a numerical simulation system

摘要

Abstract: A simulation system allows analyses of specific sensor configurations. Application areas for such an approach are: (1) design and optimization of optical sensors for specific (well known) applications, (2) sensitivity of different data products to position and calibration errors, (3) test of retrieval algorithms, and (4) mission support. The simulation system consists of mathematical and physical models to simulate the passage of electromagnetic radiation from the source of the emission to the sensor. The key part of this simulation system is a ray tracer interacting with a digital terrain model around an ellipsoid, it also includes sensor opto- electronics and spacecraft orbit calculation. Other parts are the simulation of the planetary atmosphere and the hardware of the sensor with additional retrieving algorithms. The usefulness of the simulation system for the optimization has been shown with a three-line CD sensor for the determination of cloud position and speed. For the simulation system clouds are assumed as a partly transparent, uniformly moving body, modeled by a digital terrain model over the surface. Furthermore a simple radiometric model was implemented: A cloud has a constant transmission, the ground surface and the clouds have constant albedos. The simulation shows that some conditions are mandatory for the determination of cloud speed and height, especially the movement of the sensor has to be an accelerated one. This will be reached though a highly elliptical orbit of the satellite. However, the determination will not be possible near pericentre. !13