Orbital Control of a Tethered Satellite System Using Tether-Length Variations

Paper number

IAC-05-C1.6.09

Author

Dr. Shinji Hokamoto, Kyushu University, Japan

Coauthor

Mr. Kazuo Setoyama, Kyushu University, Japan

Year

2005

Abstract

This study deals with orbital transfer of a tethered satellite system into a specified orbit (defined in the equatorial plane as a set of semilatus rectum, eccentricity, and augment of pericenter,) by using tether-length variations. The fundamental mechanism of this control caused by that variations of its tether-length in gravity gradient field generate perturbation forces for its orbital motion. 

In the last year conference (the 55th IAC), the tethered satellite system was assumed as a ‘rigid’ dumbbell type satellite. The system has two types of independent control inputs: attitude control torques and tether-length variations. Control theory for nonholonomic system was applied for the system to control its orbit, and the following were indicated as the results.
1. The governing equations for orbital transfer of the ‘rigid’ tethered satellite system can be transformed into a chained form, which means the system is controllable. (Later, it was analytically shown that the ‘rigid’ tethered system is controllable except just two points on the elliptic orbit, its pericenter and its apocenter.)
2. An example of orbital control to a specified orbit was demonstrated numerically for the system using nonholonomic control technique. 

The tethered satellite system dealt in this year is not rigid, therefore attitude control torques for the system are not applicable. Instead of that, multiple control inputs caused by changing tether-length are applied at different positions on the orbit. Considering the perturbation forces at those different points as a set of independent control inputs, controllability of the treated system can be discussed in the same procedure as the ‘rigid’ satellite system. In the presentation, some examples for orbital control will be explained.

Abstract document

IAC-05-C1.6.09.pdf

Manuscript document

IAC-05-C1.6.09.pdf (🔒 authorized access only).

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