HY-2 (HaiYang means 'ocean' in Chinese) is a marine remote sensing satellite series planned by China (HY-2A to HY-2G).

HY-2 belongs to a serie of ocean-oriented satellites :

• HY-1A and HY-1B (respectively launched on May, 2002 and April, 2007) are designed to measure the ocean color and temperature with the visible and infrared sensor,
• HY-2 is focused on the marine dynamic environnement,
• HY-3 will combine visible/infrared and microwave sensors.

The objective of HY-2A and HY-2B is to monitor the dynamic ocean environnement with microwave sensors to detect sea surface wind field, sea surface height and sea surface temperature. It includes an altimeter dual-frequency in Ku and C-bands, a scatterometer and a microwave imager.

The orbit is sun-synchronous: in the first period (initially planned over the first 2 years) with a 14-day cycle (altitude 971 km), then in a second period (initially planned to last one year) with geodetic orbit (168-day cycle, 5-day  approx. subcycle,  altitude 973 km).