  Numerical simulations carried out over the past decade suggest that the
orbits of the Global Navigation Satellite Systems are unstable, resulting in an
apparent chaotic growth of the eccentricity. Here we show that the irregular
and haphazard character of these orbits reflects a similar irregularity in the
orbits of many celestial bodies in our Solar System. We find that secular
resonances, involving linear combinations of the frequencies of nodal and
apsidal precession and the rate of regression of lunar nodes, occur in
profusion so that the phase space is threaded by a devious stochastic web. As
in all cases in the Solar System, chaos ensues where resonances overlap. These
results may be significant for the analysis of disposal strategies for the four
constellations in this precarious region of space.
