#### Event Title

#### Start Date

4-1968 8:00 AM

#### Description

A satellite has permanent magnetism associated with it resulting from the magnetization of ferrous items distributed about its volume. The magnetism will interact with the earth ! s magnetic field producing a torque about the center of gravity of the satellite. If this torque is large, it can misalign the satellite and cause it to oscillate in its orbit. Prior to launch the magnetic field from the permanent magnetism can be measured and analyzed to determine how much torque will be produced by an external magnetic field. Ideally there exists some dipole moment called the "effective or resultant dipole moment of the satellite," which produces an equivalent interaction with respect to torque in the earth f s magnetic field.

This paper contains a general discussion of the process for defining the effective dipole moment of a satellite. Illustrations are included to clarify the discussion. A description is given of the coil facility in which the magnetic testing is accomplished and of the method for measuring the magnetic field of the satellite. Parameters that affect the measurements are described, e.g., the effect of instrument sensitivity and distance of measurement on the smallest measurable dipole moment. Basic analysis procedures are discussed, and possible methods for improving and extending the procedures are given. Computer generated curves are included as examples of typical measurement data. No attempt is made in this paper to provide thorough mathematical details although mention is made of harmonic analysis techniques and methods of least squares approximation. The purpose herein is to survey the general procedures for measuring and analyzing the magnetism of satellites.

Determining the Magnetism of Small Spacecraft

A satellite has permanent magnetism associated with it resulting from the magnetization of ferrous items distributed about its volume. The magnetism will interact with the earth ! s magnetic field producing a torque about the center of gravity of the satellite. If this torque is large, it can misalign the satellite and cause it to oscillate in its orbit. Prior to launch the magnetic field from the permanent magnetism can be measured and analyzed to determine how much torque will be produced by an external magnetic field. Ideally there exists some dipole moment called the "effective or resultant dipole moment of the satellite," which produces an equivalent interaction with respect to torque in the earth f s magnetic field.

This paper contains a general discussion of the process for defining the effective dipole moment of a satellite. Illustrations are included to clarify the discussion. A description is given of the coil facility in which the magnetic testing is accomplished and of the method for measuring the magnetic field of the satellite. Parameters that affect the measurements are described, e.g., the effect of instrument sensitivity and distance of measurement on the smallest measurable dipole moment. Basic analysis procedures are discussed, and possible methods for improving and extending the procedures are given. Computer generated curves are included as examples of typical measurement data. No attempt is made in this paper to provide thorough mathematical details although mention is made of harmonic analysis techniques and methods of least squares approximation. The purpose herein is to survey the general procedures for measuring and analyzing the magnetism of satellites.

## Comments

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