No abstract

In this paper an advanced method for the navigation system correction of a spacecraft using an error prediction model of the system is proposed. Measuring complexes have been applied to determine the parameters of a spacecraft and the processing of signals from multiple measurement systems is carried out. Under the condition of interference in flight, when the signals of external system (such as GPS) disappear, the correction of navigation system in autonomous mode is considered to be performed using an error prediction model. A modified Volterra neural network based on the self-organization algorithm is proposed in order to build the prediction model, and the modification of algorithm indicates speeding up the neural network. Also, three approaches for accelerating the neural network have been developed; two examples of the sequential and parallel implementation speed of the system are presented by using the improved algorithm. In addition, simulation for a returning spacecraft to atmosphere is performed to verify the effectiveness of the proposed algorithm for correction of navigation system.

As the number of space objects (SO) increases, collision avoidance problem in the rendezvous tasks or reconstellation of satellites with SO has been paid more attention, and the dangerous area of a possible collision should be derived. In this paper, a maneuvering method is proposed for avoiding collision with a space debris object in the phasing orbit of the initial optimal solution. Accordingly, based on the plane of eccentricity vector components, relevant dangerous area which is bounded by two parallel lines is formulated. The axises of eccentricity vector system pass through the end of eccentricity vector of phasing orbit in the optimal solution, and orientation of axis depends on the latitude argument where a collision will occur. The dangerous area is represented especially with the graphical dialogue, and it allows to find a compromise between the SO avoiding and the fuel consumption reduction. The proposed method to solve the collision avoidance problem provides simplicity to calculate rendezvous maneuvers, and possibility to avoid collisions from several collisions or from "slow" collisions in a phasing orbit, when the protected spacecraft and the object fly dangerously close to each other for a long period.

The micro-thruster of micro-nano satellite cannot provide a large impulse for a single time to satisfy the requirements of the general phasing maneuver because of the constraints of thrust and the stability of attitude control system. A multi impulses phasing method is proposed based on the four impulses phasing maneuver, which satisfies the constraint of the working time of the micro thruster. In this method, a large impulse is divided into multiple small impulses, and the impulses can be re-optimized under the constraint of phasing time, which can realize the phasing maneuver of micro-nano satellites using microthrusters. The simulation results show that the error of phasing time is less than 30 s, and the phasing accuracy in two-body orbit dynamic is less than 0.2 km. Considering the perturbation and the error of the micro thruster, the phasing accuracy is less than 5 km, which meets the time limit and fuel consumption limit in phasing maneuver of the micro-nano satellite.