A detailed spin analysis of the San Marco 5 mission

The attitude of the San Marco 5 satellite flown in 1988 has been monitored by several sensors. Thus the history of the spin period is known with a high degree of accuracy. Because of the simple geometry (spherical body with several extremely long antennas) and the good mass balance (used for the accelerometer aboard) of the satellite it was possible to separate different effects of variations of the spin period. The influence of the drag on the spin period has been modeled. The results are used to derive total gas densities along the trajectory and compare them with model densities, in situ measurements from the drag balance instrument and densities derived by orbital drag methods.