Designed to measure the height of the ocean - a key component to understanding how Earth's climate is changing - Sentinel-6/Michael Freilich consists of two identical satellites that will be launched five years apart. The staggered launches will help to ensure the continuation of a decades-long record of sea level observations out to 2030.

A secondary objective of the mission will be to measure temperature and humidity in the troposphere, the atmospheric layer in which we live. The satellites will also look at the stratosphere, the layer right above the troposphere. An instrument on board the satellites uses the Global Navigation Satellite System Radio-Occultation sounding technique, which analyses changes in signals from international global navigation system satellites to determine atmospheric temperature and humidity.

NASA is developing the mission with the European Space Agency, the European Organisation for the Exploitation of Meteorological Satellites, and the National Oceanic and Atmospheric Administration. The European Commission is providing funding support. France's space agency, the Centre National d'Etudes Spatiales, is also supporting the mission.