Concept Of Navigation System Research Articles

Multiple Model Adaptive Rank Estimation for Integrated Navigation During Mars Entry

Accurate navigation systems are required for future pinpoint Mars landing missions. A radio ranging augmented Inertial Measurement Unit (IMU) integrated navigation system concept is considered for the Mars entry navigation. The uncertain system parameters associated with the Three Degree-Of-Freedom (3-DOF) dynamic model, and the measurement systematic errors are considered. In order to improve entry navigation accuracy, this paper presents the Multiple Model Adaptive Rank Estimation (MMARE) filter of radio beacons/IMU integrated navigation system. 3-DOF simulation results show that the performances of the proposed navigation filter method, 70·39 m estimated altitude error and 15·74 m/s estimated velocity error, fulfill the need of future pinpoint Mars landing missions.

Autonomous navigation during the final ascent of a spacecraft into the geostationary orbit. Autonomous integrated navigation system concept

This paper is the first in a series of works devoted to the problems of a spacecraft in the geostationary orbit autonomous operation. The paper presents the conceptual design of the spacecraft onboard autonomous navigation system applying to its final ascent to the geostationary orbit using the low-thrust electric propulsion system. This design is based on both stochastic and minimax uncontrollable factors interpretation. The composition of needed hardware and the architecture of the spacecraft onboard integrated navigation system, which should be configured in accordance with standard sections of the final ascent trajectory, are determined. It is proposed to involve so-called interval estimation algorithms in order to ensure the reliability of obtained estimations, taking into account unknown nature of possible navigation measurements information violations. An optional smoothing algorithm based on dynamic Bayesian measurements filtering, considering preliminarily obtained estimations of systematic errors. As an additional means of improving the accuracy of the navigation estimations it is proposed also to involve navigation measurements optimal scheduling methods and algorithms in order to generate optimal schedules of measurements directly on board the spacecraft.

Autonomous navigation method based on unbiased minimum-variance estimation during Mars entry

Accurate navigation systems are required for future pinpoint Mars landing missions. A radio ranging augmented inertial measurement unit (IMU) navigation system concept is considered for the guided atmospheric entry phase. The systematic errors associated to the radio ranging and inertial measurements, and the atmospheric mission uncertainties are considered to be unknown. This paper presents the extension of an unbiased minimum-variance (EUMV) filter of a radio beacon/IMU navigation system. In the presence of unknown dynamics inputs, the filter joins the system state and the unknown systematic error estimation of a stochastic nonlinear time-varying discrete system. 3-DOF simulation results show that the performances of the proposed navigation filter algorithm, 100m estimated altitude error and 8m/s estimated velocity error, fulfills the need of future pinpoint Mars landing missions.

Experimental validation of GPS-INS-STAR hybrid navigation system for space autonomy

The experimental validation of the GPS-INS-STAR hybrid navigation system concept is performed. The hybrid navigation system combines the best features of employed sensors to improve total navigation performances. The GPS-INS-STAR hybrid navigation system consists of the three different sensors, a GPS receiver, an inertial navigation system and a STAR image sensor. In this concept, the system integrates a high positioning performance of the GPS system, an accurate attitude determination capability of the STAR image sensor and the INS signal with a wide bandwidth. It results in a complete 6-DOF (degrees of freedom) autonomous navigation system. The present paper shows the validation of the concept by the experiments using GPS, INS and STAR hardware systems. The experiments are divided into three steps. Firstly, the INS-STAR hybrid navigation system is constructed on the 3-axis motion table to verify the performances of its attitude loop. Secondly, the GPS-INS hybrid navigation system installed on the car shows the performance improvement in its translational loop. Finally, the full configuration of the GPS-INS-STAR hybrid navigation system is evaluated at night. Each experiment result is checked by the theoretical analysis. In the theoretical analysis, the concept of observability well explains the performances of the system. Its feasibility for space application is also evaluated in the point of existing hardware technology. It is concluded that the experiments vaidate the concept of the hybrid navigation system and confirm its capability to realize space autonomy.

Navigation and orbit computation aspects of the ESA NAVSAT system concept

The European Space Agency (ESA) presently studies a NAVSAT satellite navigation system concept, which may be considered a civil variant of the U.S. NAVSTAR Global Positioning System (GPS). A user of the NAVSAT system will be able to determine his 3-dimensional position in realtime with an absolute accuracy of better than 10 m, and his velocity with an accuracy of about 10 cm/s. Since 1983 the National Aerospace Laboratory (NLR) and Delft University of Technology (DUT) in The Netherlands are involved in the NAVSAT studies. This paper presents some results of a Study of NAVSAT Control Segment Characteristics. It starts with an introduction of the general concept. Then, the satellite orbit and tracking aspects are discussed and the ranging error budgets and the achievable user positioning accuracy are estimated. Subsequently, a proposed tracking data compression technique is described. The orbit determination of the satellites from the compressed tracking data is discussed in some detail and results are presented of orbit determination and orbit prediction error analyses. The paper concludes with an analysis of a realtime Kalman filter process to improve the orbit information during a satellite pass over a ground station.

Low-Cost Autonomous Navigation Method for Moderate-g Missions

This paper describes a low-cost inertial navigation system concept for a broad class of flight missions characterized by moderate accelerations and limited attitude variations. A novel hybrid mechanization, partially gimballed and partially strap down, is presented. Implemented by an unbalanced two-axis gimbal system controlled by a two-degree-of-freedom gyro, the gimbal torquers provide locally level two-axis acceleration information. Pitch and roll measurements are provided by the gimbal pickoffs and heading information by a second gyro mounted in the inner gimbal. The dispensing of accelerometer s and the simplified mechanization and computation imply a substantial saving in cost and potential improvement of reliability.