Agile Earth Observation Satellite Research Articles

Time–dependent Simple Temporal Networks: Properties and Algorithms

Simple Temporal Networks (STN) allow conjunctions of minimum and maximum distance constraints between pairs of temporal positions to be represented. This paper introduces an extension of STN called Time–dependent STN (TSTN), which covers temporal constraints for which the minimum and maximum distances required between two temporal positions x and y are not necessarily constant but may depend on the assignments of x and y. Such constraints are useful to model problems in which the duration of an activity may depend on its starting time, or problems in which the transition time required between two activities may depend on the time at which the transition is triggered. Properties of the new framework are analyzed, and standard STN solving techniques are extended to TSTN. The contributions are applied to the management of temporal constraints for so-called agile Earth observation satellites.

Multi-objective Planning for a Constellation of Agile Earth-Observing Satellites

Multi-objective Planning for a Constellation of Agile Earth-Observing Satellites

Bounding the optimum for the problem of scheduling the photographs of an Agile Earth Observing Satellite

The problem of managing an Agile Earth Observing Satellite consists of selecting and scheduling a subset of photographs among a set of candidate ones that satisfy imperative constraints and maximiz...

3222 初期ジンバル角最適決定ステアリング則によるコントロール・モーメント・ジャイロの動作解析と衛星多点指向制御への適用(宇宙用アクチュエータの制御)

This research proposed a steering law of Control Moment Gyros(CMGs) to increase maneuverability and pointing accuracy for spacecraft attitude control. The steering law optimizes initial gimbal angles of CMGs in order to maintain higher manipulability and compensate inner torque disturbance due to the control error of gimbals. In addition, by doing calculation of optimizing initial gimbal angles before starting to maneuver actually, on-board computer resource will be used effectively. In order to verify the feasibility of the proposed steering law, 4CMGs, named skew type configuration, dynamics was modeled. The numerical simulations were carried out by giving rapid multitarget pointing mission of an agile earth-observing satellite. From the simulation results of gimbal motion among maneuvering, it is also shown that the proposed steering law can realize singularity avoidance and disturbance compensation.

Selecting and scheduling observations of agile satellites

This article concerns the problem of managing the new generation of Agile Earth Observing Satellites (AEOS). This kind of satellites is presently studied by the French Centre National d'Études Spatiales (PLEIADES project). The mission of an Earth Observing Satellite is to acquire images of specified areas on the Earth surface, in response to observation requests from customers. Whereas non-agile satellites such as SPOT5 have only one degree of freedom for acquiring images, the new generation satellites have three, giving opportunities for a more efficient use of the satellite imaging capabilities. Counterwise to this advantage, the selection and scheduling of observations becomes significantly more difficult, due to the larger search space for potential solutions. Hence, selecting and scheduling observations of agile satellites is a highly combinatorial problem. This article sets out the overall problem and analyses its difficulties. Then it presents different methods which have been investigated in order to solve a simplified version of the complete problem: a greedy algorithm, a dynamic programming algorithm, a constraint programming approach and a local search method.