Optimized Observation of an At Launch Unknown Ground Target Within Sensor Field of View

Satellite monitoring of ground targets is important for many civilian and government missions. The slant range impacts image quality, with a decrease in the slant range correlating with an increase in the amount of detail present in the image. An image taken with a camera that is nadir-pointing does not experience any stretching of the collected image. Because of these two factors, the highest quality images are collected with the camera nadir-pointing.When a ground target is known before launch, the satellite's orbit can be selected so that nadir-pointing images can be taken. If the ground target is unknown at the time of launch (such as for a natural disaster or military activity in a hostile nation), then the satellite may not achieve the desired nadir-pointing image collection geometry. To achieve the desired geometry, fuel must be used to alter the satellite's orbit.While nadir-pointing image collection is optimal, near-nadirpointing images have an almost identical slant range and minor image stretching. Relaxing the constraint of flying directly over the ground target and, instead, requiring the satellite's ground track to be within a bounded area near the ground target allows for less required maneuvering. Requiring less fuel to be used with minimal impact on image quality will result in a longer mission lifetime without significant performance degradation.This manuscript investigates the potential savings in maneuvering costs for maneuvering a constellation to observe a ground target of interest that is unknown at the time of launch daily while requiring the satellites to pass within a given region surrounding the ground target of interest.A stochastic programming approach is used to determine the set of initial orbital elements that will minimize the expected costs of maneuvering to observe a ground target that is unknown at the time of launch. The results show that there is a non-trivial savings in the expected maneuvering cost with the relaxation of the direct overfly constraint.