Haiyang (satellite)

Haiyang (HY, ) is a series of marine remote sensing satellites developed and operated by the People's Republic of China since 2002. , eight satellites have been launched with ten more planned. Built by the state-owned aerospace contractor China Academy of Space Technology (CAST), Haiyang satellites carry a variety of ocean-imaging sensor payloads and are operated by the National Satellite Ocean Application Service (NSOAS), a subordinate agency of the State Oceanic Administration (SOA). Haiyang satellites are launched from Taiyuan Satellite Launch Center (TSLC) into Sun-synchronous orbit (SSO) aboard Long March-series rockets.

China's National Satellite Ocean Application Service owns three series of Haiyang-series satellites, Haiyang-1 (HY-1) are designed to measure ocean color, Haiyang-2 (HY-2) to study maritime environment dynamics, and Haiyang-3 (HY-3) to conduct ocean surveillance.

Satellite bus
The first three of a total four Haiyang 1-series satellites are based on the CAST968 minisatellite bus, the same used three years prior for the Shijian 5 and carry multiple payloads. First launched aboard a Long March 4B rocket with Fengyun-1D in May 2002 into sun-synchronous orbit, the 367 kg HY-1A measures 1.2m × 1.1m × 0.94m reaching a total length of 7.5 meters with its solar panels extended. These satellites uses three magnetorquers and liquid hydrazine monopropellant for attitude control and to conduct on-orbit station-keeping. The spacecraft maintain attitude to approximately a half-degree using a Sun sensor and infrared Earth sensor. The spacecraft's imaging, transmission, and thermal heating systems are powered by two extended solar arrays providing 405 Watts (320 by end of life) and two packs of nickel-cadmium batteries that produce 23 ampere hours of DC power when the satellites' solar panels are not exposed to the sun. Launched in June 2020, Haiyang 1D was the only satellite of the HY-1 series to be based on the CAST2000 bus instead of the CAST968 bus.

For telemetry, tracking, and command (TT&C) communication, the HY-1A uses the S-band with an uplink data-rate of 2 kilobits per second (kbps) and a downlink rate of 4 kbit/s. HY-1A stores up to 80 megabits of gathered payload data from the onboard COCTS and CZI instruments until it establishes communications with the Beijing, Hangzhou, and Sanya ground station to downlink the payload data over X-band with quadrature phase shift keying (QPSK) at a rate of 5.32 megabits per second.

Sensor payloads
All four Haiyang 1 satellites (HY-1A through HY-1D) bear two maritime imaging sensors, the Chinese Ocean Color and Temperature Scanner (COCTS) and the Coastal Zone Imagery (CZI). Developed by the Shanghai Institute of Technical Physics (SITP), a subcomponent of the China Academy of Sciences (CAS), COCTS comprises a focal plane array (FPA), scanner, an electronics box, and a series of optics. The 50 kg sensor system collects 1.1 km spatial resolution maritime imagery within ten bands (eight in visible near infrared, VNIR, and two in thermal infrared, TIR) through a 200 mm aperture. COCTS rotates its imager ±35.2º, approximately 1400 km per swath.


 * 0.42 – 0.50 μm to observe pollutants, vegetation growth, ocean color, and sea ice
 * 0.52 – 0.60 μm to observe suspended sediments, pollutants, vegetation, sea ice, and wetlands
 * 0.61 – 0.69 μm to observe suspended sediments, soil, and water vapor
 * 0.76 – 0.89 μm to observe soil and water vapor with atmospheric correction

Due to power issues, the CZI sensor aboard Haiyang-1A lost functionality seventeen months after launch on 1 December 2003.

Haiyang 1C and Haiyang 1D both carried an ultraviolet imager, abbreviated UVI, providing twice-daily global coverage. Used in conjunction with COCTS and CZI, HY-1C and HY-1D have been used to identify harmful algae blooms such as cyanobacteria in Lake Tai, detect marine oil spills near Indonesia, and measure nearshore turbidity with atmospheric correction. HY-1C and HY-1D's UVI images in two ultraviolet bands, 0.345 – 0.365 μm and 0.375 – 0.395 μm, both in the UV-A range.

Both HY-1C and HY-1D are equipped with a satellite calibration spectrometer (SCS) which provides on-orbit radiometric calibration for COCTS and UVI sensor systems.

Haiyang 1C and Haiyang 1D also maintain an automatic identification system (AIS) payload, used to track and identify ship locations, to collect, store, and relay AIS messages globally. HY-1C and HY-1D's AIS system simultaneously operates on four bands: 161.975 MHz, 162.025 MHz, 156.775 MHz, and 156.825 MHz with a swath width of over 950 kilometers.