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Mazal L.,Technion - Israel Institute of Technology | Gurfil P.,Distributed Space Systems Laboratory
53rd Israel Annual Conference on Aerospace Sciences 2013 | Year: 2013

Space Autonomous Mission for Swarming and Geolocation with Nano-satellites (SAMSON) is a new satellite mission, led by the Distributed Space Systems Lab at the Technion - Israel Institute of Technology. SAMSON will include three nanosatellites, built based on the CubeSat standard. The mission is planned for at least one year, and has two main goals: (i) Demonstrate long-term autonomous cluster flight of multiple satellites, and (ii) Determine the position of a radiating electromagnetic terrestrial source based on time difference of arrival and/or frequency difference of arrival. In this paper, the cluster flight control strategy for SAMSON is discussed. This strategy performs cooperative maneuvers upon necessity, when any inter-satellite distance reaches either the upper or lower bound. The maneuvers are conceived to avoid that the secular component of the inter-satellite distances exceed the prescribed distance bounds. To compute the maneuvers, a logic scheme is first applied, which establishes constraints on the differential mean semimajor axes to provide desired post-maneuver behavior. Then, a Lyapunov based control law steers the mean semimajor axis, eccentricity and inclination, to hold the aforementioned constraints. The considered actuators are constant-thrust-magnitude thrusters. Simulations for 1 year are shown, validating the potential implementability of the proposed algorithm on-board the SAMSON satellites.


Zimmerman F.G.,Technion - Israel Institute of Technology | Gurfil P.,Technion - Israel Institute of Technology | Gurfil P.,Distributed Space Systems Laboratory
Journal of Guidance, Control, and Dynamics | Year: 2015

One of the methods for maintaining a cluster of satellites in long-term bounded relative distances is keeping the satellites on near-circular orbits having the same mean semimajor axes and mean inclinations. This approach allows some freedom in determining the reference mean semimajor axis and reference mean inclination for the cluster. In this paper, this freedom is used to find the optimal target values of the mean semimajor axis and mean inclination, with the optimization criteria being either the total propellant consumption of the cluster or the fuel consumption differences among satellites. The optimization problems are solved analytically, assuming that a fixed-magnitude thruster is used for closed-loop orbit control, and new results are presented, providing simple closed-form expressions for the optimal target states. Simulations are used for validating the results, showing that much propellant can be saved by properly setting the cluster reference orbit. Copyright © 2014 by the authors.


Zhang H.,Technion - Israel Institute of Technology | Zhang H.,Distributed Space Systems Laboratory | Gurfil P.,Technion - Israel Institute of Technology | Gurfil P.,Distributed Space Systems Laboratory
Journal of Guidance, Control, and Dynamics | Year: 2014

One of the emerging topics in the realm of distributed space systems is cluster flight of nanosatellites. As opposed to formation flight, cluster flight does not dictate strict limits on the geometry of the cluster, and is hence more suitable for implementation in nanosatellites, which usually do not carry highly accurate sensors and actuators. The actuators are usually simple fixed-magnitude thrusters, which are prone to many sources of errors, such as attitude determination and control errors. In this context, the purpose of this paper is to develop a cluster-keeping control law that is capable of long-term operation under thrust uncertainties, assuming fixed-magnitude thrust provided by a simple cold-gas thruster. To that end, mean orbital elements are used for designing an inverse-dynamics controller. It is shown that, in the differential mean elements space, this controller is time-optimal. An adaptive enhancement is developed to mitigate the thrust pointing errors and restore the original optimal performance, thus saving much fuel. Several simulations and comparative studies are performed to validate the analytical results. Copyright © 2014 by the authors.


Ben-Yaacov O.,Technion - Israel Institute of Technology | Ben-Yaacov O.,Distributed Space Systems Laboratory | Gurfil P.,Technion - Israel Institute of Technology | Gurfil P.,Distributed Space Systems Laboratory
53rd Israel Annual Conference on Aerospace Sciences 2013 | Year: 2013

The idea to use differential drag (DD) for satellite formationkeeping emerged in the mid-Eighties, when the feasibility of DD-based control was proven assuming linearized relative dynamics for two satellites. Although almost three decades have passed, the most prevalent approach for investigating DD-based formationkeeping still utilizes linear models written for only a pair of satellites. However, such models are not adequate for long-term cluster flight of multiple satellites or multiple modules forming, e.g., a disaggregated satellite, with typical mission lifetimes exceeding a year. In the current work, an alternative, nonlinear method for DD-based cluster-keeping is developed. The method relies on orbital elements instead of Cartesian coordinates. The results are verified using simulations based on the forthcoming Space Autonomous Mission for Swarming and Geolocation with Nanosatellites.


Ben-Yaacov O.,Technion - Israel Institute of Technology | Ben-Yaacov O.,Distributed Space Systems Laboratory | Gurfil P.,Technion - Israel Institute of Technology | Gurfil P.,Distributed Space Systems Laboratory
54th Israel Annual Conference on Aerospace Sciences 2014 | Year: 2014

Differential drag (DD) as a means for passive satellite cluster keeping is an old idea, but so far using DD-based cluster keeping while relying on mean orbital elements feedback has not been proposed. This paper develops a DD-based maximum distance keeping method that uses Brouwer-Lyddane differential mean elements feedback for long-term control of the secular drift among satellites. The stability of the maximum distance keeping controller is proven using finite-time stability theory, and high-precision simulation results confirm that the new controller is able to arrest satellite relative drift for mission lifetimes exceeding a year. The maximum distance controller is automatically activated, and does not require a pre-determined activation time.

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