Measurements of low-energy ions made by the retarding ion mass spectrometer (RIMS) onboard the Dynamics Explorer 1 (DE 1) satellite are used to study some aspects of ''body-plasma interactions'' in the terrestrial plasmasphere. Preliminary experimental results are presented in an empirical, parametric manner, yelding the degree of ion (current) depletion in the wake of the DE 1 satellite in terms of (1) specific and average ion Mach numbers (S), (2) average ion mass (3) body size normalized to ionic Debye length (RDi) and (4) body potential normalized to ion thermal energy (ϕN). Some results from the RIMS measurements are compared with relevant results from the Explorer 31 and the Atmosphere Explorer C ionospheric satellites. These provide semiquantitative comparisons of certain aspects of ''body-plasma'' interactions in two different flow regimes, subsonic/transonic (0.4 ≤ S ≤ 2.3) and supersonic (S> 3.3). From the DE 1 measurements, it is found that the ion species act independently in expanding into the wake of the satellite, a result which is in accord with theoretical predictions. Comparisons of measurements from the magnetospheric and ionospheric satellites indicate that for a ''small'' body (RDi≲12), the wake depletion varies approximately linearly with RDi, while for a ''large'' body (RDi>50), the variation is exponential. The DE 1/RIMS measurements were also used to examine the utility of a simple ''neutral approximation'' for the maximum rarefaction region (wake) of a satellite orbiting in the terrestrial plasmasphere. The results indicate that the use of such a simple approximation is much more applicable for the subsonic/transonic flow regime (e.g., the plasmasphere) than it is for a supersonic/hypersonic flow regime (e.g., the ionosphere).