An alternative method of orbit and gravity field improvement for Doppler-tracked satellites is presented here, in view of the prospect of future geodetic and altimetric missions ( Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS)/SPOT 2, the Ocean Topography Experiment ( TOPEX)/Poseidon, ERS 1). Owing to a refined analysis of the Doppler residuals generated by a classical orbit computation, it is successively possible (1) to improve the computed spacecraft orbit with interesting by-products such as improved tracking station coordinates and Doppler reference frequencies, (2) to recover the disturbing forces due to a mismodeling of the geopotential model (i. e., regional gravity anomalies above the stations, in line-of-sight direction, and at satellite altitude), and (3) to globally refine the mismodeled gravity field from a dense set of this regional information. The paper deals with the first two steps with emphasis on step 1. The more classical geodetic problem of step 3 will be the subject of a future paper. Simulation results for Seasat and DORIS are presented and discussed: With a simulated random noise of 0. 3 cm/s, orbit error is recovered with an accuracy of a few decimeters. With a noise level of 0.3 mm/s, orbit and force errors are recovered with an rms accuracy better than 0.2 m and 0.2 mGal at 800 km altitude. This is very encouraging for future Doppler positioning systems like DORIS. ¿American Geophysical Union 1987