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

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 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, Doris, a scatterometer an 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).

On March 23rd 2016, 4.5 years after the beginning of the mission, Hy-2A satellite moved from its nominal orbit to the geodetic orbit. The new orbit is now about 2 km higher, has a 168 day-cycle with 2315 orbits in the full cycle.