Abstract
Attitude data, which is the important data strongly correlated with the geometric accuracy of optical remote sensing satellite images, are generally obtained using a real-time Extended Kalman Filter (EKF) with star-tracker and gyro data for current high-resolution satellites, such as Orb-view, IKONOS, Quickbird,Pleiades, and ZY-3.We propose a forward-backward Unscented Kalman Filter (UKF) for post-processing, and the proposed method employs UKF to suppress noise by using an unscented transformation (UT) rather than an EKF in a nonlinear attitude system. Moreover, this method makes full use of the collected data in the fixed-interval and computational resources on the ground, and it determines optimal attitude results by forward-backward filtering and weighted smoothing with the raw star-tracker and gyro data collected for a fixed period. In this study, the principle and implementation of the proposed method are described. The post-processed attitude was compared with the on-board attitude, and the absolute accuracy was evaluated by the two methods. One method compares the positioning accuracy of the object space coordinates with the post-processed and on-board attitude data without using ground control points (GCPs). The other method compares the tie-point residuals of the image coordinates after a free net adjustment. In addition, the internal and external parameters of the camera were accurately calibrated before use for an objective evaluation of the attitude accuracy. The experimental results reveal that the accuracy of the post-processed attitude is superior to the accuracy of the on-board processed attitude. This method has been applied to the ZiYuan-3 satellite system for processing the raw star-tracker and gyro data daily.
Highlights
Satellite attitude is used in real-time support control and other decision functions, and it plays an important role in locating objects in remote sensing satellite images [1,2]. the ground location error of the satellite image would be influenced by many factors such as the camera parameters and orbit position et al, the attitude error is one of the main error sources
To improve attitude accuracy and stability, most high-resolution remote sensing satellites are equipped with several star trackers and gyros
The external parameters calibrated by the Taiyuan site were used to correct any systematic geometric errors
Summary
Satellite attitude is used in real-time support control and other decision functions, and it plays an important role in locating objects in remote sensing satellite images [1,2]. the ground location error of the satellite image would be influenced by many factors such as the camera parameters and orbit position et al, the attitude error is one of the main error sources. The ground location error caused by 1 arc s attitude error will be approximately 2.5 m for optical satellites from a nominal altitude of 504 km. To improve attitude accuracy and stability, most high-resolution remote sensing satellites are equipped with several star trackers and gyros. Star tracker, which has the highest accuracy and no drift, is used to obtain absolute inertial attitude with low frequency. Gyros can measure the angular velocity with high frequency. The combined attitude determination with star tracker and gyro data often uses filtering technology to produce the optimal result, i.e., better results than when using a single attitude sensor
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
