The various systems developed by, or under the responsibility of Engins MATRA, and which are related to the dynamics of the satellite, i.e.: the de-spin system, the precession damper, and the spin-up system will be described as well as the Attitude Control of the ESRO II spacecraft.

Before discussing these particular subjects, the general characteristics of the ESRO II satellite will be recalled:

The orbit is nearly polar (approximately 98° inclined to the equator) and has perigee at 350 km and apogee at 1200 km; the orbital plane precessions, in the retrograde sense, by about 1° per day; the orbit is thus synchronous with the sun's apparent motion. The launch time was chosen at 6 pm so that the orbital plane be, and remain, perpendicular to the sun's direction, at least in a first approximation. This is assuming a polar orbit and neglecting the angle between the plane of the Ecliptic and the plane of the Equator.