NTRS - NASA Technical Reports Server

Back to Results
Accurate Magnetometer/Gyroscope Attitudes Using a Filter with Correlated Sensor NoiseMagnetometers and gyroscopes have been shown to provide very accurate attitudes for a variety of spacecraft. These results have been obtained, however, using a batch-least-squares algorithm and long periods of data. For use in onboard applications, attitudes are best determined using sequential estimators such as the Kalman filter. When a filter is used to determine attitudes using magnetometer and gyroscope data for input, the resulting accuracy is limited by both the sensor accuracies and errors inherent in the Earth magnetic field model. The Kalman filter accounts for the random component by modeling the magnetometer and gyroscope errors as white noise processes. However, even when these tuning parameters are physically realistic, the rate biases (included in the state vector) have been found to show systematic oscillations. These are attributed to the field model errors. If the gyroscope noise is sufficiently small, the tuned filter 'memory' will be long compared to the orbital period. In this case, the variations in the rate bias induced by field model errors are substantially reduced. Mistuning the filter to have a short memory time leads to strongly oscillating rate biases and increased attitude errors. To reduce the effect of the magnetic field model errors, these errors are estimated within the filter and used to correct the reference model. An exponentially-correlated noise model is used to represent the filter estimate of the systematic error. Results from several test cases using in-flight data from the Compton Gamma Ray Observatory are presented. These tests emphasize magnetometer errors, but the method is generally applicable to any sensor subject to a combination of random and systematic noise.
Document ID
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Sedlak, J.
(Computer Sciences Corp. Lanham, MD United States)
Hashmall, J.
(Computer Sciences Corp. Lanham, MD United States)
Date Acquired
September 8, 2013
Publication Date
May 1, 1997
Publication Information
Publication: Flight Mechanics Symposium 1997
Subject Category
Accession Number
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available