[4] The satellite mission was designed to further an understanding of the earth's gravitational field, size and shape of the terrestrial geoid, deep ocean tides, sea state, current structure, crustal structure, solid earth dynamics, and remote sensing technology.

[5] GEOS-1 and GEOS-2 had provided useful information about the structure of the earth's gravitational field, but new technology was deemed necessary to gain a further understanding.

[5] The project was cancelled due to budgetary concerns after an initial one-year study, but was re-instated in late 1971.

[6] The following is a list of instruments/systems that were on board or part of the GEOS-3 satellite, including a description of their general purpose:[5][7] The GEOS-3 mission provided data that furthered scientific understanding in various fields.

[5] Ocean height also provided information about quasi-stationary departures from the geoid (the sea surface topography), for events like currents, eddies, storm surges, etc.