Predictive Centroiding for Star Trackers with the Effect of Image Smear

Samaan, Malak; Pollock, Thomas Clark; Junkins, John L.

doi:10.1007/bf03546333

Cited by 30 publications

(9 citation statements)

References 1 publication

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“…The spacecraft motion is the second kind of error source. Due to the large angular velocity of the spacecraft, the starspot is smeared during the exposure time and ultimately forms extended tails on the focal plane (Samaan et al 2002;Michaels & Speed 2004). This will affect star detection sensitivity and cause a measurement uncertainty on star position, scale, and intensity.…”

Section: Error Resulting From Motionmentioning

confidence: 99%

“…To obtain accurate x t c ( ), an attitude matrix C t ( ) should be derived. According to the literature (Samaan et al 2002), a Taylor expansion of C t ( ) can be given by…”

Section: Error Resulting From Motionmentioning

confidence: 99%

“…We note that focal length and angular rate drift all the time. From Samaanʼs derivation (Samaan et al 2002), the position and velocity of the moving starspot can then be modeled as…”

Section: Error Resulting From Motionmentioning

confidence: 99%

See 2 more Smart Citations

Theoretic Studies of Full Constraints on a Star Tracker's Influential Error Sources for In-orbit Calibration

Zhang¹,

Hao²,

Wang³

et al. 2016

PASP

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To collect star transits data qualified for in-orbit calibration, this study derives the full error constraints to limit star trackerʼs influential error sources and computes their error boundaries from a theoretical perspective. The full constraints, including not only the minimum variance estimation of position but also the error bound prediction of scale and intensity of Gaussian-shaped starspots, are studied based on the Cramér-Rao Lower Bound (CRLB) theorem. By imposing these constraints on motion, drift in focal length, and other factors, their boundaries could be determined before launch. Therefore, the in-orbit correction accuracy is expected to be close to CRLB through suitable implementation of these constraints. The correctness of the theoretical position error of motion is demonstrated by the data-fitting procedure against test results of star tracker on dynamic performance. The simulation result shows that the drift in focal length can generate an error with the same magnitude as detector noise and thus might be the dominant error source when star tracker is working under stationary circumstance. Using the accuracy performance of some typical star trackers, this study shows that the CRLB constraint may be very effective to estimate the overall position error of a starspot or one axis, valuable data that can be used for online calibration. The overall position uncertainty analysis shows that a weighted method can be employed for calibration, a process where star data can be given a weight in inverse proportion to the CRLB value.

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Section: Error Resulting From Motionmentioning

confidence: 99%

“…To obtain accurate x t c ( ), an attitude matrix C t ( ) should be derived. According to the literature (Samaan et al 2002), a Taylor expansion of C t ( ) can be given by…”

Section: Error Resulting From Motionmentioning

confidence: 99%

See 1 more Smart Citation

Theoretic Studies of Full Constraints on a Star Tracker's Influential Error Sources for In-orbit Calibration

Zhang¹,

Hao²,

Wang³

et al. 2016

PASP

View full text Add to dashboard Cite

show abstract

“…This method ignores the lens distortion estimation. Samaan et al [20] has proposed a star sensor calibration algorithm that combines the least squares algorithm with a recursive Kalman filter. However, it assumes that the star sensor has no lens distortion.…”

Section: Introductionmentioning

confidence: 99%

Error suppression method of SINS/CNS integrated navigation based on diametrical stargazing

Xu,

Zhou,

Pang

et al. 2023

Meas. Sci. Technol.

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The strap-down inertial navigation system (SINS)/celestial navigation system (CNS) integrated navigation system is widely used in the aerospace field owing to its unique advantages. The internal parameter errors of the star sensor are one of the main factors that affect the navigation accuracy. In this paper, an error suppression method based on diametrical stargazing has been designed to suppress the navigation errors caused by the internal parameter errors of the star sensor. First, a SINS/CNS integrated navigation model based on Kalman filter has been established. Then the influence of the principal point error, image-plane tilt error and distortions of the optical system on the measurement accuracy of the star sensor has been analyzed, and the process of introducing the errors into the measurement equation is obtained. Finally, for different errors, two stargazing methods are designed to suppress the impact of these errors on navigation accuracy and meanwhile, the constant errors of the inertial device can be modulated. The simulation results demonstrate that the proposed method can effectively improve the positioning accuracy of the system, and verify the effectiveness of the algorithm.

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“…Liu et al [6] have described a star spot estimation approach with the Kalman filter. Kim [7] and Samman et al [8] have adopted estimated attitude and angular velocity to predict the location of guide stars in an image plane. These works primarily focus on star spot position estimation using gyro data, without gyro drift being discussed and estimated.…”

Section: Introductionmentioning

confidence: 99%

Deep coupling of star tracker and MEMS-gyro data under highly dynamic and long exposure conditions

Sun¹,

Xing²,

You³

et al. 2014

Meas. Sci. Technol.

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Star trackers and gyroscopes are the two most widely used attitude measurement devices in spacecrafts. The star tracker is supposed to have the highest accuracy in stable conditions among different types of attitude measurement devices. In general, to detect faint stars and reduce the size of the star tracker, a method with long exposure time method is usually used. Thus, under dynamic conditions, smearing of the star image may appear and result in decreased accuracy or even failed extraction of the star spot. This may cause inaccuracies in attitude measurement. Gyros have relatively good dynamic performance and are usually used in combination with star trackers. However, current combination methods focus mainly on the data fusion of the output attitude data levels, which are inadequate for utilizing and processing internal blurred star image information. A method for tracking deep coupling stars and MEMS-gyro data is proposed in this work. The method achieves deep fusion at the star image level. First, dynamic star image processing is performed based on the angular velocity information of the MEMS-gyro. Signal-to-noise ratio (SNR) of the star spot could be improved, and extraction is achieved more effectively. Then, a prediction model for optimal estimation of the star spot position is obtained through the MEMS-gyro, and an extended Kalman filter is introduced. Meanwhile, the MEMS-gyro drift can be estimated and compensated though the proposed method. These enable the star tracker to achieve high star centroid determination accuracy under dynamic conditions. The MEMS-gyro drift can be corrected even when attitude data of the star tracker are unable to be solved and only one navigation star is captured in the field of view. Laboratory experiments were performed to verify the effectiveness of the proposed method and the whole system.

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Predictive Centroiding for Star Trackers with the Effect of Image Smear

Cited by 30 publications

References 1 publication

Theoretic Studies of Full Constraints on a Star Tracker's Influential Error Sources for In-orbit Calibration

Theoretic Studies of Full Constraints on a Star Tracker's Influential Error Sources for In-orbit Calibration

Error suppression method of SINS/CNS integrated navigation based on diametrical stargazing

Deep coupling of star tracker and MEMS-gyro data under highly dynamic and long exposure conditions

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