Robustness and Efficiency Improvements for Star Tracker Attitude Estimation (original) (raw)
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Attitude Determination and Autonomous On-Orbit Calibration of Star Tracker For GIFTS Mission
2000
A novel split field of view star tracker is being developed for the EO-3 GIFTS mission (2004). The camera is designed to be autonomously selfcalibrating, and capable of a rapid/reliable solution of the lost-in-space problem as well as recursive attitude estimation. Two efficient Kalman filter algorithms for attitude, camera principal point offset, and focal length estimation are developed. These algorithms make use of three axis gyros for the rate data and star camera split field-of-view line-of-sight vector measurements. To model the optics of the camera the pinhole model is used, which is found to be sufficiently accurate for most of star cameras. The relative merits of the two algorithms are then studied for estimating the principal point offset, focal length and attitude of a simulated spacecraft motion. Simulation results indicate that both algorithms produce precise attitude estimates by determining the principal point offset, focal length and rate bias; however, reliability and robustness characteristics favor the second algorithm.
Spacecraft angular rate estimation algorithms for star tracker-based attitude determination
2003
In this paper, two different algorithms are presented for the estimation of spacecraft body angular rates in the absence of gyro rate data for a star tracker mission. In first approach, body angular rates are estimated with the spacecraft attitude using a dynamical model of the spacecraft. The second approach makes use of a rapid update rate of star camera to estimate the spacecraft body angular rates independent of spacecraft attitude. Essentially the image flow of the stars is used to establish a Kalman filter for estimating the angular velocity. The relative merits of both the algorithms are then studied for the spacecraft body angular rates measurements. The second approach has an
1996
This paper describes, for a spacecraft equipped with a wide Field-Of-View (FOV) startracker, a fa st and robust autonomous attitude determination system, consisting of a new star identification tec hnique, here developed, working with a mixed EULER-q/QUEST-2 attitude estimation algorithm, presented in . The stars identification is based on the stars angular separation. Stars are directly identified within an overall large stars catalog without using the magnitude information. A first p roposed star-pair-ID technique is based on a best fitting criterion while a second faster one uses th ree vectors of integers. A proposed "reference-star" criterion is then used for star-matching identif ication. The algorithm robustness is such that, after spikes being deleted, at least three true stars ar e still available. An overall software block diagram of the proposed system is depicted. Extensive tests have been performed and the results are shown by plots.
Star camera calibration combined with independent spacecraft attitude determination
2009 American Control Conference, 2009
A methodology for determining spacecraft attitude and autonomously calibrating star camera, both independent of each other, is presented in this paper. Unlike most of the attitude determination algorithms where attitude of the satellite depend on the camera calibrating parameters (like principal point offset, focal length etc.), the proposed method has the advantage of computing spacecraft attitude independently of camera calibrating parameters except lens distortion. In the proposed method both attitude estimation and star camera calibration is done together independent of each other by directly utilizing the star coordinate in image plane and corresponding star vector in inertial coordinate frame. Satellite attitude, camera principal point offset, focal length (in pixel), lens distortion coefficient are found by a simple two step method. In the first step, all parameters (except lens distortion) are estimated using a closed-form solution based on a distortion free camera model. In the second step lens distortion coefficient is estimated by linear least squares method using the solution of the first step to be used in the camera model that incorporates distortion. These steps are applied in an iterative manner to refine the estimated parameters. The whole procedure is faster enough for onboard implementation.
Least Square Estimation of Spacecraft Attitude along with Star Camera Parameters
IFAC Proceedings Volumes, 2014
A methodology for determining spacecraft attitude and autonomous calibration of star camera, both independent of each other, is presented. In this paper, both attitude estimation and star camera calibration is done together, independent of each other, by directly utilizing the star coordinate in image plane and corresponding star vector in inertial coordinate frame. Both radial and decentering distortion of lens accounted in the analysis. Satellite attitude, camera principal point, focal length (in pixel), lens distortion coefficients are found by a simple three step method. In the first step, camera intrinsic parameters are estimated using a closed-form solution assuming lens is distortion free. In the second step lens radial distortion coefficient is estimated by linear least squares method using the solution of the first step to be used in the camera model that incorporates only radial distortion. These steps are applied in an iterative manner until the radial distortion coefficient converges. In third step, lens decentering distortion coefficients are calculated using the estimated camera parameters and lens radial coefficient estimated in the previous steps. The whole procedure is fast enough for onboard implementation.
Attitude and interlock angle estimation using split-field-of-view star tracker
The Journal of the Astronautical Sciences, 2007
An efficient Kalman filter based algorithm has been proposed for the spacecraft attitude estimation problem using a novel split-field-of-view star camera and three-axis rate gyros. The conventional spacecraft attitude algorithm has been modified for on-orbit estimation of interlock angles between the two fields of view of star camera, gyro axis, and the spacecraft body frame. Real time estimation of the interlock angles makes the attitude estimates more robust to thermal and environmental effects than in-ground estimation, and makes the overall system more tolerant of off-nominal structural, mechanical, and optical assembly anomalies.
Attitude and Interlock Angle Estimation Using Split-Field-of-View Star Tracker1
An efficient Kalman filter based algorithm has been proposed for the spacecraft attitude estimation problem using a novel split-field-of-view star camera and three-axis rate gyros. The conventional spacecraft attitude algorithm has been modified for on-orbit estimation of interlock angles between the two fields of view of star camera, gyro axis, and the spacecraft body frame. Real time estimation of the interlock angles makes the attitude estimates more robust to thermal and environmental effects than in-ground estimation, and makes the overall system more tolerant of off-nominal structural, mechanical, and optical assembly anomalies.
Advances in Space Research, 2015
Recently, small satellites have been employed in various satellite missions such as astronomical observation and remote sensing. During these missions, the attitudes of small satellites should be stabilized to a higher accuracy to obtain accurate science data and images. To achieve precise attitude stabilization, these small satellites should estimate their attitude rate under the strict constraints of mass, space, and cost. This research presents a new method for small satellites to precisely estimate angular rate using star blurred images by employing a mission telescope to achieve precise attitude stabilization. In this method, the angular velocity is estimated by assessing the quality of a star image, based on how blurred it appears to be. Because the proposed method utilizes existing mission devices, a satellite does not require additional precise rate sensors, which makes it easier to achieve precise stabilization given the strict constraints possessed by small satellites. The research studied the relationship between estimation accuracy and parameters used to achieve an attitude rate estimation, which has a precision greater than 1 × 10 ି rad/s. The method can be applied to all attitude sensors, which use optics systems such as sun sensors and star trackers (STTs). Finally, the method is applied to the nano astrometry satellite Nano-JAMSINE, and we investigate the problems that are expected to arise with real small satellites by performing numerical simulations.
Initial Attitude Determination Using a Single Star Sensor
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, 2007
An initial quaternion estimation method for the attitude determination of a spacecraft using an onboard star sensor is presented. In this method, we use a sequence of the number of stars in the field of view (FOV) of the star sensor as the measurement instead of the direction vector pairs of stars. A new statistical observation model is derived and coupled with the kinematics model of attitude to develop a cost function of the estimated initial quaternion. The attitude acquisition method proposed herein exploits generalized simulated annealing to optimize the cost function and find the initial quaternion. In addition, a virtual sub-FOV and its shuffling procedure for a more accurate estimation are presented. The performance of the proposed method is quantified using an extensive simulation.