Abstract
A novel method was presented for increasing the accuracy of subpixel centroid estimation for smearing star image. Model of the smearing trajectory of smearing star was built. It helped to study the analytical form of the errors, caused by image smearing, for centroid estimation. In the algorithm, the errors were estimated with accuracy and used to revise the centroid processed by CoM (centre of mass). Simulations have been run to study the effect of angular rates, integration time, and actual position of star on the accuracy of centroid estimation. Results were presented which suggested that the proposed algorithm had a precision better than 1/10 of a pixel when the angular rate was up to 3.0 deg/s.
Highlights
A star sensor is a device which outputs pose for its carrier by measuring the directions of stars in the FOV
Four things become apparent from the results: (1) the variation of te and f can affect the degree of the smear; (2) a detector with suitable pixel size should be chosen to increase the performance of the star sensor in dynamic condition; (3) position of a star in the FOV is a weighty element, usually ignored, and might affect its smearing degree; (4) angular rate of the spacecraft might vary all the time during the flight and contribute to the smearing of the star image as would be discussed later
Angular rates and te are changeable and star images with different smearing degree can be simulated which might help to validate the efficiency of the proposed method
Summary
A star sensor is a device which outputs pose for its carrier by measuring the directions of stars in the FOV (field of view). A gyrocontrol platform might be designed to eliminate the effect caused by angular movement of the spacecraft This scheme resulted in increased size, weight, and complexity of the star sensor. Adjusting the integration time to the variation of the angular rates can weaken the effect on processing centroid, while smear is inevitable and errors caused by the smearing still cannot be neglected. To overcome the difficulties arisen from smeared star image, a novel and effective method was presented in this paper, aiming at obtaining better centroid. After this introduction, the mechanism of operation of a typical star sensor and its imaging geometrical model are outlined.
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