METHODOLOGY OF SELECTING FLYWHEELS FOR STEREO IMAGING SURVEY

Abstract

The problem of dynamic parameters of earth observation satellite angular motion is described. The process of Earth surface objects stereo imaging per 1 orbital period and flywheels requirements for it is considered. Stereo imaging process can be performed in two cases. In the first one - during several orbital periods, but with the significantly reduced efficiency of the received information.  In the second case - the stereo imaging process can be carried out in one orbital period. In the second case, within one orbital period and small reasonable attitude angles,  there is no information about determination of the time of spacecraft reorientation depending on its orbit in the existing methodologies. Let suppose that when a spacecraft is approaching the target of imaging (earth surface object) it is oriented relative to the nadir at an angle β and the corresponding angular velocity. This angular velocity ensures spacecraft orbital movement with a given deviation angle from nadir, thus the spacecraft is preliminary oriented for the first survey. Usually, the angle β is chosen in the range of 10-15⁰. It could be increased due to changing distance to survey target but the difficulties of information processing and scaling appear. The methodology of selecting flywheels on project stages is developed. This methodology takes into account the spacecraft characteristics, orbit height and acceptable survey angles. It allows the  stereo imaging survey in one orbital period. The dependencies of flywheel control torque, spacecraft characteristics and stereo imaging survey attitude angles are established. The recommendations of selecting flywheels for stereo imaging survey in one orbital period are developed. Simulation of spacecraft attitude control process in stereo imaging survey was carried out. According to this simulation the changes in requirements to flywheels for different spacecrafts, orbits and acceptable survey angles were estimated.