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Sherbrooke, Canada

Lambert C.,Canadian Space Agency | Kumar B.S.,Com Dev Inc. | Hamel J.-F.,NGC Aerospace Ltd. | Ng A.,Canadian Space Agency
Acta Astronautica | Year: 2012

Formation flying using only differential drag forces is possible in low Earth orbit. The effectiveness of this technique is addressed for a practical satellite mission. Formation control algorithms typically rely on knowledge of the mean relative position between spacecrafts but this information is not readily available from sensor data and must be approximated using instantaneous sensor data for position and velocity. Several different approaches of obtaining the mean relative position are presented and compared. Two independent controllers are required to achieve precise formation control, one for secular formation maneuvers and another for periodic motion. The performance of each controller is examined using different methods for obtaining estimates of mean relative positions. © 2011 Elsevier Ltd. Source

Ulrich S.,Carleton University | Cote J.,NGC Aerospace Ltd.
61st International Astronautical Congress 2010, IAC 2010 | Year: 2010

The impact of unknown attitude perturbations on payload pointing performance of Earth-orbiting satellites is well known. The real-time three-axis estimation of those perturbations in order to improve the pointing accuracy is therefore critical, especially for high accuracy observation missions, such as Sun observation experiments. Current solutions to this problem consist in either increasing the bandwidth of the main attitude filter or to use an optimal estimation algorithm. Whereas the first solution reduces the stability margin of the overall guidance, navigation and control system, the second solution is computationally intense and is therefore not suitable for real-time space operations. In this paper, a novel solution to the in-flight estimation of perturbation torques problem is presented. The novel algorithm, NDO (nonlinear disturbance observer), is computationally efficient and is suitable for any Earth-orbiting spacecraft. The results presented in this paper show that the proposed strategy is a promising perturbation estimation technology even for small satellites equipped only with low-cost attitude sensors and without a gyroscope. Copyright ©2010 by the International Astronautical Federation. All rights reserved. Source

Simard Bilodeau V.,Universite de Sherbrooke | Clerc S.,Thales Alenia | Drai R.,European Space Agency | De Lafontaine J.,NGC Aerospace Ltd.
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

Major space agencies have an increasing interest in highly accurate (200 m) autonomous landing on the Moon. Inertial-only navigation is not compatible with this challenging requirement. The techniques currently investigated rely on vision-based navigation. A first approach consists in tracking features between sequences of images in order to measure the angular rate as well as the direction of the velocity vector of the spacecraft. A second approach aims at identifying image features using a georeferenced on-board database to determine the attitude and the position of the spacecraft. However, existing algorithms are computationally prohibitive and have a limited robustness to varying illumination conditions and surface characteristics. This paper presents the development of an innovative autonomous vision-based navigation system addressing these problems. Numerical simulations have shown that this system is capable of estimating the position and velocity of the vehicle with an accuracy better than 100 m and 0.1 m/s respectively. This work is the result of a successful collaboration between the Université de Sherbrooke, NGC Aerospace Ltd., Thales Alenia Space and the European Space Agency. The proposed system has been selected as the main navigation algorithm in three major research and development projects sponsored by European Space Agency and the Canadian Space Agency. © IFAC. Source

Bilodeau V.S.,NGC Aerospace Ltd. | Hamel J.-F.,NGC Aerospace Ltd. | Iles P.,Neptec Design Group
Proceedings of the International Astronautical Congress, IAC | Year: 2013

Accurate relative localisation is a critical aspect for future rover planetary exploration missions. In previous work, NGC Aerospace and Neptec Design Group have developed, implemented and tested a generic and robust vision-based pose estimation system for the lunar exploration rover prototype "Artemis". This activity took place in the context of a lunar rover design study sponsored by the Canadian Space Agency. This rover prototype, initially designed for Earth-bound demonstration, is now being considered as the vehicle to carry and operate the NASA RESOLVE payload for an In-Situ Resource Utilisation (ISRU) experiment mission at the South Pole of the Moon. This paper describes how the Artemis relative localisation system design can be adapted to the baseline RESOLVE mission, taking into account the constraints of a Moon South Pole exploration mission, and what level of performance is expected. © 2013 NGC Aerospace Ltd. All rights reserved. Source

Cote J.,NGC Aerospace Ltd. | Kron A.,NGC Aerospace Ltd. | De Lafontaine J.,NGC Aerospace Ltd. | Naudet J.,QinetiQ
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

The PRoject for On-Board Autonomy (PROBA) is an ESA technology- demonstration program aimed at the in-orbit validation of autonomy-enabling space technologies. Following the success of PROBA-1, the PROBA-2 spacecraft was launched on 2 November 2009 and continues the in-flight demonstration of on-board autonomy by performing a Sun observation mission as well as numerous flight experiments. This paper completes previously published articles by presenting the in-flight results of two innovative autonomous GNC functions: (1) Star Tracker Earth Exclusion Angle Prediction for Earth avoidance and (2) Large-Angle Rotation around Fixed Axis. Finally, flight results of the Attitude and Orbit Control System (AOCS) nominal operation using these innovative GNC functions will be presented. © 2011 IFAC. Source

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