Status of standard pipeline pointing products: ground-based improvements (SPG 13.0 and beyond)

Scope of applicability

This page refers to the improved pointing information provided in products created in SPG 13.0 and later, derived from gyro-reconstructed attitude data. For data products created with SPG versions before 13.0, please refer to the page on improved pointing information from "simple" ground-based processing.

Background information

Despite the success achieved during the mission in improving the accuracy of the attitude measurements made by the star tracker [6, 21, 22], and later the success in further improving these measurements on-ground [7], it has been shown that the on-board attitude filter is still rather poor at following the high-frequency changes in the spacecraft attitude (i.e. the spacecraft jitter) [2, 3].1 A new method, the "gyro-based attitude reconstruction" method, was therefore proposed for combining the star tracker attitude measurements with the output from the Inertial Reference Unit (GYR) [8]. As the name implies, this method places much greater weight on the measurements made by the gyros, using attitude measurements constructed from star tracker data to provide an absolute reference and to account for gyro drifts. Although it has been demonstrated that this method is able to successfully reduce the high-frequency components of the Absolute Measurement Error (AME) it neverthess suffers from a couple of drawbacks (when compared with a conventional attitude estimator). When ‘calibrating’ the gyro measurements, firstly, only those attitude measurements close to the reference attitude may be used and, secondly, a deterministic model of the variation of the gyro drift rates must be assumed.2 Software based on the gyro-based attitude reconstruction method was first prototyped by H. Feuchtgruber and later implemented, in HIPE 12.0, by B. Vandenbussche.

-- MiguelSanchez - 08 Apr 2015

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Topic revision: r2 - 2015-04-08 - MiguelSanchez
 
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