Design of Attitude Stability System for Prolate Dual-spin Satellite in Its Inclined Elliptical Orbit

J. Muliadi* , S.D. Jenie† and A Budiyono‡

Abstract— In general, most of communication satellites were designed to be operated in geostationary orbit. And many of them were designed in prolate dual-spin configuration. As a prolate dual-spin vehicle, they have to be stabilized against their internal energy dissipation effect. Several countries that located in southern hemisphere, has shown interest to use communication satellite. Because of those countries’ southern latitude, an idea emerged to incline the communication satellite (due to its prolate dual- spin configuration) in elliptical orbit. This work is focused on designing Attitude Stability System for prolate dual-spin satellite in the effect of perturbed field of gravity due to the inclination of its elliptical orbit. DANDE (De-spin Active Nutation Damping Electronics) provides primary stabilization method for the satellite in its orbit. Classical Control Approach is used for the iteration of DANDE parameters. The control performance is evaluated based on time response analysis.

Keywords— dual spin, prolate configuration, classical control approach, attitude control, DANDE

Abstrak— Secara umum kebanyakan satelit komunikasi dirancang untuk beroperasi pada orbit geostasioner. Dan kebanyakan dari satelit tersebut dirancang pada konfigurasi dual-spin prolate. Sebagai wahana dual-spin prolate, satelit harus distabilkan dari pengaruh disipasi energi internal. Beberapa negara yang terletak pada belahan selatan bumi telah menunjukkan minatnya untuk menggunakan satelit komunikasi. Karena letak negara yang berada di latituda selatan, sebuah ide muncul untuk menginklinasi satelit pada orbit eliptik. Makalah ini secara khusus membahas perancangan sistem stabilitas sikap untuk satelit dual-spin prolate pada pengaruh medan gravitasi terganggu akibat inklinasi dari orbit elipsik wahana. DANDE (De-spin Active Nutation Damping Electronics) memberikan metoda penstabilan utama pada satelit pada orbitnya. Pendekatan kendali klasik digunakan pada iterasi parameter DANDE. Unjuk kerja kendali dievaluasi berdasarkan analisis respons waktu.

Keywords— dual spin, konfigurasi prolate, pendekatan kendali klasik, kendali sikap, DANDE

• Department of Aeronautics and Astronautics, ITB, mie_pn@yahoo.com † Department of Aeronautics and Astronautics, ITB, sdjenie@ae.itb.ac.id ‡ Department of Aeronautics and Astronautics, ITB, the author to whom all correspondence to be addressed, agus.budiyono@ae.itb.ac.id

1. INTRODUCTION For a stability criterion, most of early dual-spin vehicles were designed in an oblate configuration. However, Kaplan [8] states that launch vehicle shroud constraints limited rotor diameters. In addition, the major axis stability condition effectively limited spinning spacecraft sizes. Since U.S. Air Force successfully by-passed this limitation by operating TACSAT, many of prolate spinners were launch to orbit. The first communication dual-spin satellite in prolate configuration is INTELSAT IV. As a case of study, this work used Palapa B2R physical data to design feedback control parameters for the attitude stability system. Near the satellite’s End of Life (EOL) time, several governments of Africans and Polynesians countries have shown interest to buy and re-use Palapa B2R. Because of those countries’ location in the southern latitudes, an idea emerged to incline the satellite’s orbit. When Palapa B2R is operating in its orbit, DANDE (De-spin Active Nutation Damping Electronics (Ref. [2] pp. 62-68, [1] pp. 127-129, [4], [5])) provides primary stabilization method for the vehicle, while ANC (Active Nutation Control (Ref. [1])) supplies the back-up mode. With the use of DANDE as the stabilization mode, the current paper elaborates the tuning of the feedback control parameters using classical control approach.

2. REFERENCE COORDINATE SYSTEM The reference coordinate systems used in describing the satellite are the body, stability and inertial axes. Ref [9] provides the definition and illustration of those axes in detail. Body Axes with their origin at the satellite’s c.g. while Error! Reference source not found. showed the axes in the space, as explained in Ref [9].

Fig. 1 Stability Reference Coordinate System

In particular, the Stability Reference Coordinate System (Stability Axes) is defined as a set of local horizon axes for the satellite. It is a target axes for the satellite’s Body Axes to point its antennae to the Earth. The stability axes is presented in Fig. 1.

3. EULER ANGLES (ORIENTATION ANGLES) The orientation of satellite in space with respect to a certain reference coordinate system is described by the Euler angles. Fig. describes the attitude of the satellite with respect t

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