Studies on dynamic motion compensation and positioning accuracy on star tracker

Abstract

Error from motion is the dominant restriction on the improvement of dynamic performance on a star tracker. As a remarkable motion error, the degree of nonuniformity of the star image velocity field on the detector is studied, and thus a general model for the moving star spot is built. To minimize velocity nonuniformity, a novel general method is proposed to derive the proper motion compensation and location accuracy in cases of both uniform velocity and acceleration. Using this method, a theoretic analysis on the accuracy of time-delayed integration and similar techniques, which are thought of as state-of-the-art approaches to reduce error from motion, is conducted. The simulations and experimental results validate the proposed method. Our method shows a more steady performance than the dynamic binning algorithm. The positional error could be neglected when the smear length is far less than 3.464 times the scale of star spot, which suggests accuracy can be maintained by changing frame-integration time inverse proportional to the velocity on the focal plane. It also shows that the acceleration effect must be compensated to achieve accuracy close to the Cramér-Rao lower bound.

A Hamming Distance and Spearman Correlation Based Star Identification Algorithm

“…In [13], the authors added the positional deviation with a nominal standard deviation (σ) of 0.062 pixels and a maximum of 0.31 pixels. In our simulations, we assign a limit of 1.0 pixel as the maximum positional deviation for a star is usually around 1.0 pixel in the space environment according to a recent finding [31]. Geometric distance between the stars is the most affected feature due to the positional deviation of stars.…”

Accurate and Autonomous Star Acquisition Method for Star Sensor under Complex Conditions

“…Under dynamic imaging conditions, the star area is dragged and the centroiding error will be unacceptable without any restoration or compensation. Several algorithms have been proposed for star restoration or motion compensation [11,18,19]. However, angular velocity information provided by gyros is indispensable in these algorithms, which complicates the navigation system and blemishes the autonomy of star sensor.…”

GMM-Based Adaptive Extended Kalman Filter Design for Satellite Attitude Estimation under Thruster-Induced Disturbances

“…The authors of [5] employed a correlation filter to conduct denoising and improve the signal for deblurring star images, considering the angular velocity of the spacecraft to be a constant speed. In addition, the authors of [6] proposed a method to model the PSF of star images and compensate for it under a constant angular velocity and nonfixed angular velocity. Meanwhile, [7] developed a method to simulate multiple blurred star images with uniform and nonuniform blur.…”