Following in the footsteps of the remarkable Topex/Poseidon and Jason-1 spacecrafts, the Ocean Surface Topography Mission has the responsibility of continuing one of the most important on-going chronicles of Earth's changing climate - the detailed measurements of global sea level. The spacecraft will use a JPL-built advanced microwave radiometer with state-of-the-art integrated circuit technologies along with a new, larger antenna design. These improvements have reduced its mass and power requirements and yet will provide better resolution, improved performance and reliability.