The phase quartic algorithm and attitude-lean-loping estimator with GPS recursive operations (ALLEGRO) have been proposed in a study. Both of these algorithms demonstrate a high rate of error convergence. The phase qu...
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The phase quartic algorithm and attitude-lean-loping estimator with GPS recursive operations (ALLEGRO) have been proposed in a study. Both of these algorithms demonstrate a high rate of error convergence. The phase quartic is an eigenvalue-based estimation algorithm, whereas ALLEGRO is derived based on the minimal model error estimation algorithm. The quaternion vector has been used as the primary attitude representation, except for direction computational matrix (DCM) and attitude matrix solution (AMES) methods. The DCM uses Euler angles, whereas AMES uses nine elements of the attitude matrix as the attitude representation. This study focuses mainly on the existing real-time GPS-based attitudedetermination methods that are feasible for space application.
This paper presents practical analytical models for spin-axis attitudedetermination using measurements generated by sun and Earth sensors. In particular, explicit expressions for the least-squares estimates and their...
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This paper presents practical analytical models for spin-axis attitudedetermination using measurements generated by sun and Earth sensors. In particular, explicit expressions for the least-squares estimates and their associated covariance matrices are established. The adoption of the local reference frame defined by the instantaneous sun and Earth vectors leads to compact analytical results. These results provide a more immediate understanding of the attitude error covariance matrix in terms of its dependence on the sun Earth geometry. The application of the covariance results is illustrated by using the actual geometrical in-orbit conditions of two satellites.
The equal-chord method offers a straightforward and low-cost technique for the determination of the spin-axis attitude using sun and Earth sensor data. The Earth aspect angle follows from the time at which the chord l...
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The equal-chord method offers a straightforward and low-cost technique for the determination of the spin-axis attitude using sun and Earth sensor data. The Earth aspect angle follows from the time at which the chord lengths measured by the Earth sensor's two pencil beams are equal. An estimation technique is not required, but linear or quadratic fitting of the sensor data should be performed to remove the random errors. The accuracy of the attitude solution obtained by the equal-chord method in the presence of the relevant biases is evaluated. The result is insensitive to uniform biases in-the measured chord angles, caused for instance by errors in the Earth's infrared horizon. Finally, the application of the method is demonstrated using actual flight data of the CONTOUR spacecraft.
Generally, one has little cause to estimate an attitude in spaces of dimension higher than three. This exercise, however, affords an insight into the workings of a well-known attitudedetermination algorithm in three ...
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Generally, one has little cause to estimate an attitude in spaces of dimension higher than three. This exercise, however, affords an insight into the workings of a well-known attitudedetermination algorithm in three dimensions. In addition, should the dimensionality of our world ever increase without notice, we will be all the better prepared.
The determination of attitude from differential GPS range measurements was posed as an orthogonal Procrustes problem so that a closed-form solution could be found. It was shown that the attitudedetermination problem ...
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The determination of attitude from differential GPS range measurements was posed as an orthogonal Procrustes problem so that a closed-form solution could be found. It was shown that the attitudedetermination problem could be solved in not one but two different methods. The first method allowed for coplanar baselines, whereas the second method allowed for planar satellite geometry. Subsequent sensitivity and covariance analysis showed that both solutions yielded unbiased estimates. For small attitude changes, a general expression was derived for the covariance of the attitude solution that showed how poor geometry could adversely affect solution quality. (CSA)
作者:
BarItzhack, IYNASA
GODDARD SPACE FLIGHT CTRFLIGHT MECH BRANCHGREENBELTMD 20771
QUEST is a well-known algorithm for least squares fitting of the attitude quaternion of a spacecraft to vector measurements. QUEST, however, is a single time point (single frame) batch algorithm;thus, measurements tha...
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QUEST is a well-known algorithm for least squares fitting of the attitude quaternion of a spacecraft to vector measurements. QUEST, however, is a single time point (single frame) batch algorithm;thus, measurements that were taken at previous time points are discarded, The algorithm presented provides a recursive routine, which considers all past measurements. The algorithm is based on the fact that the so-called K matrix, one of whose eigenvectors is the sought quaternion, is linearly related to the measured vector pairs and on the ability to propagate K, The extraction of the appropriate eigenvector is done according to the classical QUEST algorithm, This stage, however, can be eliminated, and the computation simplified, if a standard eigenvalue-eigenvector solver algorithm is used.
The paper presents a practical spin-axis attitudedetermination approach based on the Tanygin-Shuster algorithm. The technique is illustrated by means of sensor measurement data originating from two satellites with ve...
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The paper presents a practical spin-axis attitudedetermination approach based on the Tanygin-Shuster algorithm. The technique is illustrated by means of sensor measurement data originating from two satellites with very different orbit and attitude characteristics. The most appropriate data intervals are identified using criteria based on measurement sensitivities. A minimum-variance technique is formulated for establishing the Earth aspect angle from the measured chord angles. The chain of covariance transformations from the fundamental sensor measurement errors to the final attitude error is presented. The unit-vector normalization technique, which is an inherent part of the Tanygin-Shuster method, is found to be beneficial for the stability of the attitudedetermination results under unknown biases, especially in cases in which only a subset of the measurement angles are available.
Determining spacecraft attitude in real time using only magnetometer data presents a challenging filtering problem. A flexible and computationally efficient method for solving the spacecraft attitude using only an ine...
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Determining spacecraft attitude in real time using only magnetometer data presents a challenging filtering problem. A flexible and computationally efficient method for solving the spacecraft attitude using only an inexpensive and reliable magnetometer would be a useful option for satellite missions, particularly those with modest budgets. The primary challenge is that magnetometers only instantaneously resolve two axes of the spacecraft attitude. Typically, magnetometers are used in conjunction with other sensors to resolve all three axes. However, by using a filter over an adequately long orbit arc, the magnetometer data can yield full attitude, and in real time. The method presented solves the problem using a two-step extended Kalman filter. In the first step, the magnetic field data are filtered to obtain the magnetic field derivative vector, which is combined with the magnetic field vector in the second step to fully resolve the attitude. A baseline scenario is developed, and a parametric study is conducted using the parameters of interest.
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