The concept of a Global Positioning System (GPS) receiver as a tracking facility and a gradiometer as a separate instrument on a low orbiting platform offers a unique tool to map the Earth's gravitational field with unprecedented accuracies. The former technique allows determination of the spacecraft's ephemeris at any epoch to within 3--10 cm; the latter permits the measurement of the tensor of second-order derivatives of the gravity field to within 0.01--0.0001 E¿tv¿s units depending on the type of gradiometer. An analytical technique is described and applied for any error analysis of gravity field parameters from gradiometer and GPS observation types. Results are discussed for the configuration proposed on Aristoteles, indicating that a ''GPS only'' solution may be computed up to degree and order 85, whereas a combined GPS/gradiometer experiment may result in an acceptable solution up to degree and order 240. ¿American Geophysical Union 1991