Space Advanced Research Team

Allenstown Elementary School, United States

Space Advanced Research Team

Allenstown Elementary School, United States
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De Florio S.,University of Glasgow | De Florio S.,Space Advanced Research Team | D'Amico S.,German Aerospace Center | Radice G.,University of Glasgow | Radice G.,Space Advanced Research Team
Journal of Spacecraft and Rockets | Year: 2013

The autonomous orbit keeping experiment on the PRISMA mission was executed successfully from 18 July to 16 August 2011 and has demonstrated the capability of autonomous precise absolute orbit control. Using GPS-based absolute navigation data, the onboard controller commanded thruster activations in the orbital frame to autonomously control the satellite's longitude of the ascending node within a predefined window. The main performance requirement of the experiment was a control accuracy of 10 m (1σ) with a maneuver velocity increment and decrement available budget of 0.5 m/s. After a four day commissioning phase, the reference orbit was acquired. A 3.5 day controller tuning was then followed by the fine orbit control phase, which commenced on 30 July 2011 and continued until the end of the experiment. The control accuracy requirement was fulfilled. The mean value of the longitude of the ascending node's deviation was -3.6 m with a standard deviation of 9.5 m during the fine control phase. The total Δv spent during the entire experiment was 0.1347 m/s, corresponding to 27% of the maneuvers budget allocated. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.


De Florio S.,University of Glasgow | De Florio S.,Space Advanced Research Team | D'Amico S.,German Aerospace Center | Radice G.,University of Glasgow | Radice G.,Space Advanced Research Team
Journal of Guidance, Control, and Dynamics | Year: 2014

This paper analyzes the problem of precise autonomous orbit control of a spacecraft in a low Earth orbit. Autonomous onboard orbit control means that the spacecraft maintains its ground track close to a reference trajectory, without operator intervention. The problem is formulated as a specific case of two spacecraft in formation in which one, the reference, is virtual and affected only by the Earth's gravitational field. A new parametrization, the relative Earth-fixed elements, is introduced to describe the relative motion of the two spacecraft's subsatellite points on the Earth surface. These relative elements enable the translation of absolute-into-relative orbit-control requirements and the straightforward useofmodern control-Theory techniques for orbit control.Asa demonstration, linear and quadratic optimum regulators are designed and compared, by means of numerical simulations, with an analytical autonomous orbit-control algorithm that has been validated in flight. The differences of the numerical and analytical control methods are identified and discussed. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


MacDonald M.,University of Strathclyde | MacDonald M.,Advanced Space Concepts Laboratory | McKay R.,University of Strathclyde | McKay R.,Advanced Space Concepts Laboratory | And 4 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2010

A study was conducted to demonstrate the development of an extension of the sun-synchronous orbit, which as per definition is a finite resource similar to a geostationary orbit, The extension to the sun-synchronous orbit was considered using an undefined, non-orientation-constrained, and low-thrust propulsion system. The low-thrust propulsion system was considered initially for the free selection of orbit inclination and altitude while maintaining the sun-synchronous condition. The maintenance of a given sun-synchronous repeat ground track was considered, using the low-thrust propulsion system to enable the free selection of orbit altitude. An analytical expression was developed to describe these extensions before validating the analytical expressions within a numerical simulation of a spacecraft orbit. The analytical analysis was also examined within a numerical simulation for validity.

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