A new approach is shown to determine the angular velocity vector directly from star tracker measurements. The main advantage of this approach is that it requires no information of the star reference vectors or the att...
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A new approach is shown to determine the angular velocity vector directly from star tracker measurements. The main advantage of this approach is that it requires no information of the star reference vectors or the attitude. algorithms based on various difference approximations were developed. The estimate error covariances for each approximation is also shown. Each approximation requires a time delay in the angular velocity estimate, which becomes less significant as the sampling interval decreases. Simulation results use a realistic star tracker configuration. Results indicate that very accurate angular velocity estimation is possible when combined with a simple filter. Also, the computational burden of the angular velocity estimator combined with a simple filter is far less than a Kalman filter, but a Kalman filter using a complete dynamics model might produce even more accurate results. (Author)
This work presents the design and performance analysis of attitude determination algorithms for CubeSats that fuse rate gyros with a single vector measurement using a sensor set consisting of an inertial measurement u...
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This work presents the design and performance analysis of attitude determination algorithms for CubeSats that fuse rate gyros with a single vector measurement using a sensor set consisting of an inertial measurement unit and a three-axis magnetometer. An extended Kalman filter is used to fuse sensor measurements to estimate the spacecraft's attitude statistics in three dimensions. The observability (deterministic and stochastic) of the algorithms is assessed for a variety of orbit geometries and CubeSat attitude dynamics. Further, a stochastic observability test is implemented to identify conditions under which the attitudedetermination filter will converge as the Earth's magnetic field varies during orbit. This paper demonstrates that the filter converges within two orbits using CubeSat representative altitudes and estimate spacecraft attitude with bias of 2 & DEG;and estimation errors of 3 & DEG;(3-sigma) using orbital simulations with a commercial-grade inertial measurement unit.
An angles-only method for deep space orbit and attitudedetermination is presented. Using planetary ephemeris data and measurements of known planets and the Sun in the spacecraft's body frame, a geometric construc...
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ISBN:
(数字)9781624107115
ISBN:
(纸本)9781624107115
An angles-only method for deep space orbit and attitudedetermination is presented. Using planetary ephemeris data and measurements of known planets and the Sun in the spacecraft's body frame, a geometric construction is used to derive an equation to find the distance between the spacecraft and the Sun. Once this value is computed through a line search the spacecraft's position can be triangulated in the inertial frame. Once the position of the spacecraft is known in the inertial frame, any attitudedetermination algorithm can be used to determine the attitude of the spacecraft given the planet and Sun measurements. The complete algorithm is very fast and requires no matrix inversions, with the most computationally intensive aspect being a line search. A numerical example for the orbit determination using measurements of the Sun, Mars, and Jupiter is presented.
Validation of attitudedetermination and control technologies is challenging for any spacecraft program, but can be particularly hard for small spacecraft, such as CubeSats or nanosatellites. These missions typically ...
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This research outlines the investigation of star tracker algorithms and Kalman Fil- ter implementation of star tracker aided INS. In the first chapter, the usage areas of the star tracker sensor was investigated. The ...
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This research outlines the investigation of star tracker algorithms and Kalman Fil- ter implementation of star tracker aided INS. In the first chapter, the usage areas of the star tracker sensor was investigated. The purposes to use this sensor were also included. Furthermore, the sensor architecture and algorithms were examined. In the second chapter, the three main steps of the star tracker algorithms were investi- gated. First of all, literature survey about centroiding algorithms was done and two of them were examined in detail. Then, the literature about star matching algorithms was searched. Liebe's triangle method and Astrometry. net's quad method were in- vestigated in detail. Finally, the research about the attitude determination algorithms was made. The studies made about three of them which are SVD, Triad and Quest methods were shown. In the last chapter, the results of an Extended Kalman Filter im- plementation of star tracker aided INS were demonstrated. For this implementation, a high altitude aircraft was chosen because star tracker sensor gives more accurate results in high altitudes. To simulate a high altitude aircraft, X-15 aircraft simulation was used in the Airlib library of Simulink. Assumptions were made about the accu- racies of the star tracker sensor and INS according to the sensors that can be used in the high altitude aircrafts. Moreover, the simulation architecture of the Kalman Filter implementation, which makes attitude correction, was investigated.
The decomposition of the quaternion attitude representation in terms of a basis formed using observation unit vectors and a number of direct application of this result is investigated. In particular, the implementatio...
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The decomposition of the quaternion attitude representation in terms of a basis formed using observation unit vectors and a number of direct application of this result is investigated. In particular, the implementation of a global attitude estimation scheme in both recursive and batch form is considered. The latter batch algorithm is shown to be identical to the quaternion estimation (QUEST) algorithms.
Abstract This paper discusses a new star identification algorithm for multiple star trackers with unequal qualities. This algorithm is inspired by the star identification algorithm for small-FOV (Field-of-View) star t...
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Abstract This paper discusses a new star identification algorithm for multiple star trackers with unequal qualities. This algorithm is inspired by the star identification algorithm for small-FOV (Field-of-View) star trackers, which allows the star identification across the images as well as that within the image. The feature of this algorithm is that it has the robustness to the quality difference of the star trackers when more than one is used. By simulation, this feature is demonstrated and the feasibility of the algorithm is shown.
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