High Precision Range Measurement Research Articles

Laser Stereo Vision-Based Position and Attitude Detection of Non-Cooperative Target for Space Application

Vision measurement for non-cooperative targets in space is an essential technique in space counterwork, fragment disposal, satellite on-orbit service, spacecraft rendezvous, because the position and attitude of the target aircraft or the object should be detected first of all in the process. The 2D passive camera loses the depth information and can not measure the position and attitude of non-cooperative target. Several kinds of range imaging methods are alternatives. The traditional triangulation method can provide very high precision range measurement at close range but the nature of the triangulation geometry means that the uncertainty grows when the range increases. Laser radar (LIDAR) based on TOF (time of flight) or phase difference principle is suitable for middle and long range, but it can not fit for short range. A novel structure system is put forward, in which a so-called synchronous scanning triangulation method is adopted combining a LIDAR system. The synchronous scanning triangulation system plays a role at the range from 0.5m to 10m for object’s attitude, and the LIDAR system plays a role at the range from 10m to 200m for object’s position (direction and range).They are merged into one path, and do not influence each other because of using two different wavelengths respectively. This mechanism makes the system more compact and less weight. The system performances, such as the measurement range and precision, are analyzed according to the system parameters. The principle prototype is designed and established, and the experimental results confirm that its performance is promising and can satisfy the requirement for space application.

An Unambiguous Tracking Method Based on Pseudo Correlation Function for AltBOC(15,10) Signal

The Galileo E5 or COMPASS B2 signal is the most precision civil and most challenging navigation signal which will be available in the near future for regular navigation. The excellent performance of this signal was reached by Alternative Binary Offset Carrier (AltBOC) modulation, which is specially designed for high precision range measurement and which is featured by extremely wide bandwidth. However, this modulation presents some drawbacks. The most severe one is the ambiguity problem in AltBOC signal acquisition and tracking, which introduces a large bias in the pseudo-range measurement. In order to solve this problem, an unambiguous tracking method based on a pseudo correlation function for AltBOC(15,10) modulation signal is proposed in this paper. It employs two local signals and a novel combination function, which completely removes side peaks from the correlation function while keeping the sharp main peak. Impacts of multipath on the proposed method are also investigated. Simulation results demonstrate that the proposed method is totally unambiguous while exhibiting an average multipath performance with respect to the existing unambiguous tracking methods.