Passive magnetic attitude stabilization of the UNISAT-4 microsatellite
- Paper number
IAC-06-C1.1.05
- Author
Prof. Fabio Santoni, University of Rome "La Sapienza", Italy
- Coauthor
Dr. Mauro Zelli, Scuola di Ingegneria Aerospaziale, Italy
- Year
2006
- Abstract
The research and education program UNISAT has been established at Scuola di Ingegneria Aerospaziale of University of Rome “La Sapienza” with the aim to design, build, launch and operate small scientific and educational satellites, in the weight range of about 10kg. Three satellites have been successfully launched every other year since 2000 [1]. The microsatellites UNISAT-3, operational since almost two years in orbit, and UNISAT-4, scheduled for launch in June 2006, have a passive magnetic stabilization system, based on a permanent magnet and magnetic hysteresis rods. Passive magnetic stabilization have been extensively used in small satellites since the beginning of the space activity. Examples are Transit(1960), ESRO(1968), the four Microsat-NA satellites (1990), and, more recently, the Swedish satellite Munin and many Cubesats. The main features of passive magnetic stabilization are simplicity and reliability. However, sizing the system parameters, predicting the in orbit performance and obtainable accuracy of passive magnetic stabilization systems is a very difficult task. A detailed design procedure can be found in [2], in which an approximate solution of the attitude dynamics equations is obtained introducing simplifying assumptions and using the averaging technique. The main problem in the system design is accurate modelling of the hysterysis rods magnetization and the evaluation of the rods magnetic parameters, such as apparent permeability and shape factor, which are considerably affected by the rods manufacturing technological process and may change due to temperature effects in orbit. In this paper we study the possibility to include the magnetic hysteresis rods behaviour in the numerical simulation of the satellite dynamics by a “hardware in the loop” system. The complete satellite attitude equation of motion are numerically integrated, evaluating the orientation of the Earth magnetic field with respect to the satellite. The Earth magnetic field component along the hysteresis rod is evaluated at each integration step and imposed on a real hysteresis rod. The consequent rod magnetic dipole is measured and introduced in the attitude dynamic equations. In this way the approximations and uncertainties of building a mathematical model of the rods magnetization process are avoided. The main limitations to the accuracy obtainable by the proposed system are the noise introduced by the rods magnetic dipole measurement process and the non exact reproduction of the magnetic field in orbit. The results obtained will be applied to the UNISAT-4 passive magnetic stabilization system design and compared with traditional numerical simulations. The hardware in the loop simulation will be also validated analyzing the actual behaviour in orbit of the passive magnetic stabilization system installed on the UNISAT-3 microsatellite [3]. References: [1] F. Graziani, F. Santoni, F. Piergentili, F. Bulgarelli, M. Sgubini, S. Bernardini, Manufacturing and launching student-made microsatellites: “hands-on” education at the University of Roma, paper IAC-04-P.5.A.02, International Astronautical Congress, Vancouver, Canada, [2] M.Yu. Ovchinnikov, V.I. Penkov, Passive Magnetic Attitude Control System for the Munin Nanosatellite, Cosmic Research, Vol. 40, No.2,2002. [3] F.Santoni, F.Piergentili, UNISAT-3 attitude determination using solar panel and magnetometer data, paper IAC-05-C1.2.06, 56th International Astronautical Congress (IAC), Fukuoka, Japan, 17-21 October 2005.
- Abstract document
- Manuscript document
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