The changing geopotential and LAGEOS

The possibility is investigated of making a precise measurement of the (2,2 tesseral harmonic of the earth's gravitational field (and possibly its variations) by analyzing the tracking data form the LAGEOS satellite. The size and typical periodicity of the relevant perturbation are derived. At present, a relative accuracy of the order of 10 to the -4 seems difficult to reach because of the distribution of the measurements and the degrading of the orbit predictability due to drag-like forces. At higher precision, the effect of ocean tides must also be taken into account.