The existing methods to estimate satellite attitude by using radar cross section (RCS) sequence suffer from problems such as low precision, computation complexity, etc. To overcome these problems, a novel model of satellite attitude estimation by the local maximum points of the RCS sequence is established and can reduce the computational time by downscaling the dimension of the feature vector. Moreover, a particle swarm optimization method is adopted to improve efficiency of computation. Numerical simulations show that the proposed method is robust and efficient.

In this letter, a novel on-orbit estimation and calibration method of GPS antenna geometry offsets for attitude determination of LEO satellites is proposed. Both baseline vectors in the NED coordinate system are achieved epoch-by-epoch firstly. Then multiple epochs' baseline vectors are united to compute all the offsets via an UKF for a certain long time. After on-orbit estimation and calibration, instantaneous and accurate attitude can be achieved. Numerical results show that the proposed method can obtain the offsets of each baseline in all directions with high accuracy estimation and small STDs, and effective attitudes can be achieved after antenna geometry calibration using the estimated offsets. The high accuracy give the proposed scheme a strong practical-oriented ability.

In these days, recognizing a user personality is an important issue in order to support various personalized services. Besides the conventional phone usage such as call logs, SMS logs and application usages, smart phones can gather the behavior of users by polling various embedded sensors such as GPS sensors. In this paper, we focus on how to predict user attitude based on GPS log data by applying location clustering techniques and extracting features from the location clusters. Through the evaluation with one month-long GPS log data, it is observed that the location-based features, such as number of clusters and coverage of clusters, are correlated with user attitude to some extent. Especially, when SVM is used as a classifier for predicting the dichotomy of user attitudes of MBTI, over 90% F-measure is achieved.

Using a single-site lightning location technique, a new portable lightning location system is developed. We incorporate an attitude detection technique using inertial sensors to detect an accurate electromagnetic field vector of sferics by palm-sized electromagnetic sensors which can have arbitrary attitude. The present paper describes the concept and the performance of the developed prototype of the portable system.

In view of the frequent and complex changes of GNSS visible satellite constellation in attitude determination system, an improved attitude signal simulation algorithm for high dynamic satellite signal simulator is proposed. Based on Software Radio architecture, elevation calculation in the antenna coordinate system and channel state control logic under the condition of carrier attitude changes are introduced into the algorithm to implement synchronous scheduling of visible satellite constellation and attitude signal simulation. This work guarantees the simulator to run constantly and stably for a long time with the advantages of high precision and low complexity. Compared with synchronous positioning results from the receiver, the simulation results show that not only can the output signals of the simulator accurately reflect the carrier's attitude characteristics, but also no step error is generated and the positioning precision is not influenced when visible satellite constellation changes.

Actuator-induced disturbances are among the most crucial factors in correct spacecraft attitude pointing and stability for fine attitude control problems. In order to develop a CMG as an actuator for fine controls, CMG-induced disturbances should be analyzed. Therefore, this paper aims to develop an analytic model that predicts the effect of disturbances to CMGs by assuming static and dynamic imbalances. The proposed analytical model with respect to the disturbances of a CMG is derived using the Lagrange energy method based on the small-signal assumption.

This primary objective of this study is to demonstrate simulation and ground-based experiment for the attitude control of flexible spacecraft. A typical spacecraft structure consists of the rigid body and flexible appendages which are large flexible solar panels, parabolic antennas built from light materials in order to reduce their weight. Therefore the attitude control has a big problem because these appendages induce structural vibration under the excitation of external forces. A single-axis rotational simulator with a flexible arm is constructed with on-off air thrusters and reaction wheel as actuation. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The experiment of flexible spacecraft attitude control is performed using only the reaction wheel. Using the reaction wheel the performance of the fuzzy-PID controller is illustrated by simulation and experimental results for a single-axis rotational simulator.

In this letter we provide a steering law for redundant single-gimbal control moment gyros. The proposed steering law is an extended version of the singular direction avoidance (SDA) steering law based on the singular value decomposition (SVD). All internal singularities are escapable for any non-zero constant torque command using the proposed steering law.

A fast capture algorithm of the initial attitude is proposed for the spacecraft using reaction wheels. This algorithm is composed of two steps. The first step deals with absorption of the initial angular momentum of the spacecraft into the reaction wheels and the second step a rest-to-reset large angle maneuver for sun tracking. A criterion of the initial attitude capture and a controller for the fast large angle maneuver method are presented under considering constraints of the reaction wheels. Simulation results show that the proposed algorithm has several advantages of the initial attitude capture and fast large angle maneuver. This algorithm can be applied to the near minimum time rotation control of the spacecraft.

An analytical error characteristics of GPS compass which determines heading and elevation of the vehicle using carrier phase measurements from 2 antennae is given. It is also shown that to obtain more precise heading, longer baseline along the vehicle is preferred and the accuracy of heading is always better than that of elevation since the vertical measurement uncertainty caused by geometry of satellites affects only on that of elevation. These results can be applied as basic directions for attitude determination: to what direction should the baseline be located to minimize the error, which satellites should be selected to minimize the error.

In this paper, we review recent developments in interferometric fiber-optic gyroscopes for industrial applications. These gyroscopes use only elliptical-jacket or elliptical-core polarization-maintaining-fibers to make their optical systems immune to environmental effects, and they use open-loop or closed-loop signal processing circuitry. We have begun mass production of a gyroscope for automotive navigation and location systems. The more accurate gyroscopes have been applied to a number of consumer applications such as attitude control systems of unmanned agricultural helicopter, pipe-mapping and north-finding systems. For further enhancement in terms of size, cost, and accuracy, we have developed an application specific integrated circuit and an integrated optical circuit.