Satellite attitude determination based on GPS carrier phase measurements

Özten, Evrim
With the developments in the GPS receiver technology, GPS receivers have been preferable equipments also for the space applications. In the early eighties, they have been used only for position, velocity and time determination. With the further improvements, it has been proven that they can provide not only the positioning information, but also attitude knowledge with the accuracy less than 1 degree. In this thesis, an estimation algorithm is developed in the MATLAB Simulink environment for the attitude determination using the GPS carrier phase measurements from four antennas. Because the attitude dynamics of a satellite is nonlinear, Extended Kalman Filter (EKF), a nonlinear estimator, is decided to use. The algorithm is implemented using three quaternion and three inertial angular velocity error states. For the attitude determination, four antennas in a square shape with 1 meter inter-antenna distance are assumed to be used. A simulation is conducted in order to evaluate the performance of the algorithm. The simulation includes a satellite in J2 perturbed orbit. The yaw stabilization of the satellite is maintained by using a momentum wheel with a spin axis perpendicular to the orbit plane. GPS pseudorange, pseudorange rate and differential carrier phase measurements are also modeled in the simulation environment. Because most of the measurement errors are quite small in the carrier phase measurement or they mostly cancel out after the single differencing process, only the multipath error and receiver noise is modeled in the simulation. An integrated GPS/Gyro case is also considered in this study. For the integrated GPS/Gyro case, the developed EKF is modified by adding gyro bias drift parameter to the state vector. In order to model the gyro measurements, a gyroscope error model is developed. The gyro measurements are generated by adding errors like bias, bias drift, scale factor and misalignment to the true angular rates. The algorithms developed for GPS only and GPS/Gyro integrated cases are tested with different GPS visibility conditions. After the simulation test, it is observed that the achieved attitude accuracy with the GPS only case is better than 0.4 degrees. Moreover, the integration with three axis gyro assembly improves the attitude performance especially for the cases with poor GPS satellite visibility.


Vector tracking loop design for GPS receivers
Üzel, Deniz; Baykal, Buyurman; Department of Electrical and Electronics Engineering (2016)
This study describes the design of a modern GPS receiver architecture based on vector tracking loops. Since the traditional tracking loops process the signals independently, there is no information exchange between channels. Due to that fact, aiding of weaker signals in the presence of relatively strong signals is impossible. On the other hand, vector tracking loops simultaneously process the signals from all visible channels. Therefore, they are able to perform better than the traditional tracking loops in...
Design of smart antenna array for interference suppression in GPS
Dabak, Ömer Can; Alatan, Lale; Koç, Seyit Sencer; Department of Electrical and Electronics Engineering (2016)
GPS jammers add excessive noise to received low power GPS signals and have capability to weaken or completely destroy the positioning performance of GPS receivers. The most popular technique to overcome GPS jamming problem is suppression of jammers by using array signal processing techniques. In this thesis, a GPS anti-jamming system is constructed by designing an active antenna array and implementing adaptive beamforming techniques. This thesis mainly include the design of four element active circularly po...
Improved positioning by distance-based differential GPS
Ghaziani, Matin; Konukseven, Erhan İlhan; Koku, Ahmet Buğra; Department of Mechanical Engineering (2013)
This study presents a new method of differential GPS which is based on distance between GPS receivers. To navigate a robot on unstructured area, different methods have been used. One of the important methods is using GPS. Using single GPS leads to inaccurate navigation of a robot. One way to overcome this problem is using Differential GPS which is based on using one or several based stations and rover receivers. These base stations depend on exact coordinate of its coordinates and without them; this method ...
Interference Suppression in a GPS Receiver with 4 Element Array Design and Implementation of Beamforming Algorithms
Dabak, Omer Can; Erdem, Fatih; Sonmez, Tolga; Alatan, Lale; Koç, Seyit Sencer (2016-04-14)
Global Positioning System (GPS) jammers add excessive noise to the received low power GPS signals and have capability to either weaken or completely destroy the positioning performance of GPS receivers for both civilian and military users. Researchers are actively working to develop GPS receiver systems resistant to interference sources. Our aim is to develop a system based on spatial filtering of jamming signals through the use of an active antenna array which is capable to control its radiation pattern by...
Implementation of software GPS receiver
Günaydın, Ezgi; Tuncer, Temel Engin; Department of Electrical and Electronics Engineering (2005)
A software GPS receiver is a functional GPS receiver in software. It has several advantages compared to its hardware counterparts. For instance, improvements in receiver architecture as well as GPS system structure can be easily adapted to it. Furthermore, interaction between nearby sensors can be coordinated easily. In this thesis, a SGR (software GPS receiver) is presented from a practical point of view. Major components of the SGR are implemented in Matlab environment. Furthermore, some alternative algor...
Citation Formats
E. Özten, “Satellite attitude determination based on GPS carrier phase measurements,” M.S. - Master of Science, Middle East Technical University, 2013.