The Sentinel-3 satellite carries the following payload instruments:

• A dual-frequency SAR altimeter, derived from ENVISAT RA-2, CRYOSAT SIRAL and JASON-2/POSEIDON-3 heritage called the SAR Radar Altimeter (SRAL) instrument.
• A Microwave Radiometer (MWR) instrument, which supports the SRAL to achieve overall altimeter mission performance by providing wet atmosphere correction derived from ENVISAT MWR heritage.
• A Precise Orbit Determination (POD) package including a Global Navigation Satellite Systems (GNSS) instrument, a Doppler Orbit determination and Radio-positioning Integrated on Satellite (DORIS) instrument (SENTINEL-3A only) and a Laser Retro-Reflector (LRR).