  We obtain dispersion relations of magnetic field fluctuations for two
crossings of the terrestrial foreshock by Cluster spacecraft. These crossings
cover plasma conditions which differ significantly in their plasma $\beta$ but
not in the properties of the encountered ion population, both showing
shell-like distribution function. Dispersion relations are reconstructed using
two-point instantaneous wave number estimations from pairs of Cluster
spacecraft. The accessible range of wave vectors, limited by the available
spacecraft separations, extends to $\approx \!2 \times 10^4$ km. Results show
multiple branches of dispersion relation, associated with different power of
magnetic field fluctuations. We find that Sunward propagating fast magnetosonic
waves and beam resonant modes are dominant for the high plasma $\beta$
interval, while the dispersions of magnetically dominated interval include
Alfv\'{e}n and fast magnetosonic modes propagating Sunward and unit-Sunward.
