The satellite clocks used in the BeiDou-2 satellite navigation System (BDS) are Chinese self-developed Rb atomic clocks, and their performances and stabilities are worse than GPS and Galileo satellite clocks. Due to special periodic noises and nonlinear system errors existing in the BDS clock offset series, the GPS ultra-rapid clock model, which uses a simple quadratic polynomial plus one periodic is not suitable for BDS. Therefore, an improved prediction model for BDS satellite clocks is proposed in order to enhance the precision of ultra-rapid predicted clock offsets. First, a basic quadratic polynomial model which is fit for the rubidium (Rb) clock is constructed for BDS. Second, the main cyclic terms are detected and identified by the Fast Fourier Transform (FFT) method according to every satellite clock offset series. The detected results show that most BDS clocks have special cyclic terms which are different from the orbit periods. Therefore, two main cyclic terms are added to absorb the periodic effects. Third, after the quadratic polynomial plus two periodic fitting, some evident nonlinear system errors also exist in the model residual, and the Back Propagation (BP) neural network model is chosen to compensate for these nonlinear system errors. The simulation results show that the performance and precision using the improved model are better than that of China iGMAS ultra-rapid prediction (ISU-P) products and the Deutsches GeoForschungsZentrum GFZ BDS ultra-rapid prediction (GBU-P) products. Comparing to ISU-P products, the average improvements using the proposed model in 3 h, 6 h, 12 h and 24 h are 23.1%, 21.3%, 20.2%, and 19.8%, respectively. Meanwhile the accuracy improvements of the proposed model are 9.9%, 13.9%, 17.3%, and 21.2% compared to GBU-P products. In addition, the kinematic Precise Point Positioning (PPP) example using 8 Multi-GNSS Experiment MGEX stations shows that the precision based on the proposed clock model has improved about 16%, 14%, and 38% in the North (N), East (E) and Height (H) components.

An Improved Predicted Model for BDS Ultra-Rapid Satellite Clock Offsets

This study analyzes the quality of onboard data of tracking signals from GPS satellites on the far side of the earth and determines the orbit of the geostationary satellite using code and carrier phase observations with 30-h and 3-day orbit arc length. According to the analysis results, the onboard receiver can track 6–8 GPS satellites, and the minimum and maximum carrier to noise spectral densities were 24 and 45 dB-Hz, respectively. For a GPS receiver on a high-altitude platform above the navigation constellations, the blocking of the earth and a weak signal strength usually cause a piece-wise GPS signal tracking and an increase in the number of ambiguity parameters. Individual GPS satellites may be continuously tracked for as little as several minutes and as long as 3 h. Moreover, considering the negative sign of elevation angles reflects the fact that GPS satellites are tracked below the receiver in the study. GPS satellites appear mainly in the elevation angle range of − 53° to − 83°, and dilution of precision values could reach ten or one hundred and more. Also, it is observed that when a signal suffers from atmospheric refraction, other GPS signals tracked simultaneously by the receiver experience strong systematic errors in the code observations. Based on single-frequency code and carrier phase measurements, the mean 3D root mean square (RMS) value of the overlap comparisons between 30-h orbit determination arcs is 2.14 m. However, we found that there were also some biases in the carrier phase residuals, which contributed to poor orbit accuracy. To eliminate the effects of the biases, we established a correction sequence for each GPS satellite. After corrections, the mean 3D RMS was reduced to 0.99 m, representing a 53% improvement.

TJS-2 geostationary satellite orbit determination using onboard GPS measurements

Condition: New. Publisher/Verlag: Springer, Berlin | Measuring Technology and Mechatronics Automation in Electrical Engineering includes select presentations on measuring technology and mechatronics automation related to electrical engineering, originally presented during the International Conference on Measuring Technology and Mechanatronics Automation (ICMTMA2012). This Fourth ICMTMA, held at Sanya, China, offered a prestigious, international forum for scientists, engineers, and educators to present the state of the art of measuring technology and mechatronics automation research. | Adoption of Mobile Content Service in 3G Era: An Empirical Analysis in China.A Game Analysis on Multi-level Emergency Management for Construction Accident.Agentbased Modeling of Water Bloom Mechanism in Reservoirs.A Hardware-in-the-Loop System for Development of Automotive Battery Management System.A Master-Slave System for Intelligent Visual Surveillance.A Method of Detection and Tracking for Laser Spot.Analysis of Starting Process for Medium-sized Induction Motors with High-voltage.An Epipolar Rectification Algorithm for Uncalibrated Images.A New Approach for Multi-objective-optimization-based Fuzzy-PID Control.A New Naive Style Possibilistic Network Classifier.An Improved Ant Clustering Algorithm Based on Habitation-searching Method.An Optimal Model of Full Postponement Strategy in a TwoStage Supply Chain.Application of an Improved Watershed Algorithm in Craniocerebrum MRI Image.Application of Data Fusion in Ecological Environment Monitoring System.-...

Measuring Technology and Mechatronics Automation in Electrical Engineering

GNSSs such as GPS, GLONASS, Galileo, and Beidou have demonstrated to be a valid and efficient system for various space applications in LEO. Since the 1990s precise GNSS-based positioning of GEO, MEO, HEO, and even deep space exploration satellites has also been considered feasible. This paper analyzes the GNSS satellite visibility and PDOP performances for 6 space users, including two GEO, one MEO, and three HEO satellites. The simulation results show that a single GNSS receiver with the sensitivity of about −180 to −188 dBW is enough for space user below 50,000 km while the receiver of a Lunar explorer must be able to process the received signal low to −202 ~ −208 dBW. As for a multi-GNSS receiver, the sensitivity requirements decrease about 2–4 dBW compared with the single GNSS one. Viewed from the sensitivity standpoint, a GPS-only receiver and a BDS+GPS receiver are the best single GNSS and multi-GNSS choice for most of the six space users while a Beidou-only receiver performs the best for GEO1 satellite which is fixed above the Asia-Pacific area. It can be concluded that for the space users below 50,000 km, it is possible to attain an average PDOP of below 20 with a receiver sensitivity no higher than −184 dBW. An important conclusion drawn from the analysis is that the higher the space user flies, the more important role multi-GNSS application plays.

GNSS Performance Research for MEO, GEO, and HEO

Orbit determination of CE-4′s relay satellite in Earth-Moon L2 libration point orbit

The data processing and analysis for the CE-5T1 GNSS experiment

Multipath is one of the dominant causes of error in pseudorange observations for GNSS (Global Navigation Satellite Systems) reference station receivers whose multipath mitigation performances are related to four factors: the receiving scenario, the antenna height, the antenna gain pattern (up-to-down gain ratio) and the receiver-internal multipath mitigation technique. However, quantitative analysis of relations between the code tracking multipath error and the antenna parameters (including the height and up-to-down ration) is still absent. With two assumptions that the reflectors in the typical GNSS reference station receiving scenario are horizontal planes and the receiver-internal technique is Double-delta technique, the paper derives the functional relations between the code tracking multipath error and the antenna parameters. Based on these functions, this paper proposes theoretical formulae for the antenna up-to-down gain ratio design given the upper limit of the code tracking multipath error and antenna height. The quantitative and exercisable results presented in this paper are significant and instructive in the multipath-rejecting antenna design for GNSS reference station receivers.

Geshi Tang

Papers

The data processing and analysis for the CE-5T1 GNSS experiment

GNSS Performance Research for MEO, GEO, and HEO

The Antenna Up-To-Down Gain Ratio Design for Multipath Mitigation of GNSS Reference Station Receivers