Attitude determination using combined gps and three-axis magnetometer data (original) (raw)

Integer ambiguity resolution in GPS for spinning spacecrafts

IEEE Transactions on Aerospace and Electronic Systems

A procedure to compute the integer ambiguity problem when a GPS receiver is used in a multiple antenna configuration attached to a rotating spacecraft is presented. The method is applied to a simulation of an experimental satellite which uses the GPS receiver for attitude determination.

Real time attitude independent GPS integer ambiguity resolution

2003

In this paper, a new motion-based approach for Global Positioning System (GPS) integer ambiguity resolution is derived. The approach first represents the GPS sightline vectors in the body frame or the baseline vectors in the reference frame. The solution to this problem is always available as long as at least three non-coplanar baseline or sightline vectors exist. The body-frame sightline or reference-frame baseline observations are the sum of two vectors, one depending on the phase measurements and the other on the unknown integers. The vector containing the integer phases is identical to the three-axis magnetometer bias model, which can be converted into an attitude independent observation using scalar checking. The bias estimation problem is typically solved by using a batch process. In this paper, simple real time algorithms are developed based on both the extended Kalman filter and Unscented filter. Simulation results indicate that both algorithms provide accurate integer resolution in real time, but the Unscented filter is more robust to large initial condition errors and slow vehicle motions than the extended Kalman filter.

Attitude determination of GPS satellite vehicles

2016

There is an increasing demand for navigation systems that has led to rapid development of Global Positioning System (GPS) across industries. Apart from position and speed, precise attitude measurements are needed for many GPS applications. This thesis presents techniques for attitude determination of satellite vehicles in both real-time and stand-alone positioning applications. The GPS system used is a differential GPS system that estimates the body frame baselines using at least four receivers. The attitude information is obtained using these baselines and projecting them onto a local level frame. Integer ambiguity is a major constraint in attitude determination. Least Squares Ambiguity Deco-relation method is implemented to fix the ambiguities prior to baseline estimation. Estimation techniques such as Least Squares and Kalman Filter are implemented for deriving baseline components. Finally, this system will compute body frame coordinates and attitude components in reference to th...

Fast integer ambiguity resolution for GPS attitude determination

Guidance, Navigation, and Control Conference and Exhibit, 1999

In this paper, a new algorithm for GPS integer ambiguity resolution is shown. The algorithm first incorporates an instantaneous (static) integer search to significantly reduce the search space using a geometric inequality. Then a batch-type loss function is used to check the remaining integers in order to determine the optimal integer. This batch function represents the GPS sightline vectors in the body frame as the sum of two vectors, one depending on the phase measurements and the other on the unknown integers. The new algorithm has several advantages: it does not require an a-priori estimate of the vehicle's attitude; it provides an inherent integrity check using a covariance-type expression; and it can resolve the integers even when coplanar baselines exist. The performance of the new algorithm is tested on a dynamic hardware simulator.

Global Positioning System Integer Ambiguity Resolution Without Attitude Knowledge

Journal of Guidance, Control, and Dynamics, 1999

In this paper, a new motion-based algorithm for GPS integer ambiguity resolution is derived. The algorithm represents the GPS sightline vectors in the body frame as the sum of two vectors, one depending on the phase measurements and the other on the unknown integers. The vector containing the integer phases is found using a procedure developed to solve for magnetometer biases. In addition to a batch solution, this paper also provides a sequential estimate, so that a suitable stopping condition can be found during the vehicle motion. The new algorithm has several advantages: it does not require an apriori estimate of the vehicle's attitude; it provides an inherent integrity check using a covariance-type expression; and it can sequentially estimate the ambiguities during the vehicle motion. Its only disadvantage is that it requires at least three non-coplanar baselines. The performance of the new algorithm is tested on a dynamic hardware simulator.

An integer ambiguity resolution algorithm for real-time GPS attitude determination

Applied Mathematics and Computation, 2002

The problem of integer ambiguity resolution must be solved to fully exploit the information contained in the GPS carrier phase measurements for real-time attitude determination. A new algorithm for integer ambiguity resolution that uses single-difference smoothed pseudorange measurements is proposed that has several advantages over the conventional algorithms such as the search methods and the motion-based algorithms. These advantages include minimal computational effort at each epoch and an analytically derived equation which calculates the expected time to ambiguity resolution. The validity and the performance of the new algorithm are investigated through simulations although processing real data will be necessary to verify the usability of the proposed algorithm in real situations. Ó (S. Yoon). 0096-3003/02/$ -see front matter Ó 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 9 6 -3 0 0 3 ( 0 1 ) 0 0 0 2 9 -7

Satellite orbit and attitude estimation using three-axis magnetometer

The determination of satellite orbital and attitude position and velocity from measurement of a single earth magnetic field (emf) vector without additional measurements, but using a state estimator, is a challenging problem. It is not obvious from first glace whether a solution exists at all – whether the problem is observable with the measurement of only a single emf vector, and an analysis is necessary. This paper performs this analysis for a simple linear system model. Almost circular low earth nearly polar orbits and a dipole emf model are considered. Although these are rather restrictive assumptions they nevertheless provide considerable insight. Both a purely algebraic situation as well as dynamic estimation are studied. It is shown that if the emf induction vector magnitude is used to estimate satellite orbit (position and velocity) and its three projections are used to estimate the attitude, that the situation is sufficiently observable for orbit and attitude determination using just magnetometer measurements. However, for nearly polar orbits, longitude and east velocity are difficult to estimate due to weak observability, and estimation convergence time can be lengthy with poor accuracy. Biographical notes: Y. Kim graduated from the Moscow Aviation Institute as an Electro-Mechanical Engineer specialising in aerospace GN&C and avionics. After graduation he worked in the aerospace industry of the former USSR and various universities as an Engineer, Research Scientist, Professor and Manager, and obtained his PhD and Doctor of Technical Science degrees in aerospace GN&C. After the collapse of the USSR, he worked for IAI in Israel and then for the Canadian Space Agency as an Aerospace and Avionics System Engineer and Scientist. His more recent work has been in satellite control, specifically new methods for attitude and orbit determination and safe hold mode, and lecturing avionics. Hi main areas of interest and contribution are state estimation methods and multisensory navigation systems.

Aircraft Attitude Determination using GPS and an Interval Integer Ambiguity Resolution Algorithm

2009

GPS carrier phase measurements can be used to determine the attitude of an aircraft fitted with multiple GPS antennae. For this to succeed, an optimization needs to be performed to find the integer ambiguities corresponding to the number of complete carrier wave cycles between the antennae. In this paper an interval based algorithm for solving these ambiguities is proposed. The theory of interval analysis is used to encapsulate the phase measurements with an interval noise band, such that the true phase is inside this band. This algorithm has been successful for static baselines with low noise, but the goal of this paper is to evaluate the performance of this algorithm for highly dynamic baselines with higher noise levels. For this purpose the algorithm is applied to GPS phase measurements recorded during a test flight with a Cessna Citation II jet. Results show that multiple epochs of data are required to fix the ambiguities. Once the ambiguities are resolved, the attitude of the aircraft can be determined with high accuracy. Nomenclature N Integer ambiguity b Baseline between two antennae e Vector from antenna to satellite c Speed of light L 1,2 GPS carrier frequency Conventions [x] Interval variable x i , j W.r.t. receiver i,j p , q W.r.t. satellite p,q Symbols λ Wavelength [m] β Angle between e p and e q δ Rotation of b around e ρ Distance from satellite to antenna [m] φ Carrier phase [-] Φ Carrier phase multiplied with λ [m] ǫ Measurement error α Angle between b and e