China launched its latest Fengyun-3 polar orbiting meteorological satellite on Tuesday via a Long March 4C rocket. Launch – which included the HEAD-1 satellite as a co-passenger – took place at around 18:35 UTC from the LC9 Launch Complex of the Taiyuan Satellite Launch Center, Shanxi Province.
Operated by the CMA (China Meteorological Administration) and NSMC (National Satellite Meteorological Center), the FY-3 series represents the second generation of Chinese polar-orbiting meteorological satellites and are a cooperative program between CMA and CNSA (China National Space Administration).
The FY-3 series provides global air temperature, humidity profiles, and meteorological parameters such as cloud and surface radiation required in producing weather forecasts, especially in making medium numerical forecasting.
The satellites monitor large-scale meteorological disasters, weather-induced secondary natural hazards and environment changes, providing geophysical parameters for scientific research on climate change and its variability, climate diagnosis and predictions.
The FY-3 series renders global and regional meteorological information for aviation, ocean navigation, agriculture, forestry, marine activities, hydrology and many other economic sectors.
The program was initially approved in 1998, while the engineering development of the first satellite began the following year. The collection of atmospheric data for intermediate – and long-term – weather forecasting and global climate research are the main aspects of the series.
The FY-3 series satellites are designed and developed by the Shanghai Aerospace Administration. The vehicle structure is a hexahedron of 4.4 m x 2.0 m x 2.0 m in the stowed configuration and 4.4 m x 10 m x 3.8 m in the deployed state.
The total spacecraft launch mass is estimated to be 2450 kg.
The satellite structure is based on a separated bay design, combined structure of center supporting cylinder and guest board for service module and propulsion module, and a combined structure of baffle plate and truss. Thermal control relies mainly on passive thermal control assisted by active thermal control.
The satellite features one solar panel mounted on one side of the satellite’s main body – making the span length of the satellite 10m in its flight configuration). The solar array is 22.464 m2 with an output power of 2.48 kW (EOL), average = 1100 W. Two NiCd battery units (36 cells) each of 50 Ah capacity provide power in ecliptic orbit phases.
The attitude control of the satellite employs three-axis stabilization (bias momentum control) with a pointing precision of 50 m on the ground. The ADCS (Attitude Determination and Control Subsystem) employs a star sensor for attitude sensing.
The FY-3 bus contains three major modules: a service module, a payload module, and a propulsion module. The spacecraft design life is three years.
The ground swath of the onboard optical-mechanical scanners is 3,000 km with a 250 m resolution in the High Resolution Picture Transmission (HRPT) mode. The satellite has two X-band transmitters (one real-time and one delayed) and an L-band transmitter (real-time).
The onboard data management computer, altitude and orbital control computer – and all the remote-sensing sensors – were connected via a MIL-STD-1553B data bus system, which allows autonomous management of data collection and calculating of orbital parameters by the onboard computers.
The instruments on board the satellites can be divided into three missions: sounding, ozone and imaging. The instruments used for sounding are the IRAS (Infrared Atmospheric Sounder), the MWTS (Microwave Temperature Sounder) and the MWHS (Microwave Humidity Sounder).
The IRAS is used to obtain atmospheric temperature profiles, atmospheric humidity profiles, to determine total ozone content, cirrus, aerosol, etc. The MWTS is used for atmospheric temperature profile, rainfall, cloud liquid water, surface parameters, etc. Finally, the MWHS is used for Atmospheric humidity profile, water vapor, rainfall, cloud liquid water, etc.
The instruments used for the ozone mission are the TOU (Total Ozone Unit) the SBUS (Solar Backscatter Ultraviolet Sounder). The TOU is used to determine the total ozone distribution, while SBUS is used for determining the ozone profile and the total ozone amount.
Finally, the instruments that are used for imaging are the VIRR (Visible and Infrared Radiometer), the MERSI (Medium Resolution Spectral Imager) and the MWRI Microwave Radiation Imager).
NSMC and CMA are responsible for receiving, processing the data of Chinese and foreign meteorological satellites, and distributing the data and information products to users for applications.
Other responsibilities include establishing the ground segment of the Chinese meteorological satellite observation system, conducting applied research in satellite meteorology, making plans and programs for developing Chinese meteorological satellite system based on the national requirements.
The FY-3 ground segment is comprised of five receiving stations. One of the stations is located in Kiruna, Sweden. The FY-3 data products will be transmitted via DVB-S (Digital Video Broadcast-Satellite).
The HEAD-1 satellite:
The HEAD-1 is the first satellite in the Skywalker Constellation. The satellite has a launch mass of 45 kg and sports 3-axis stabilization. HEAD-1 will be operational for two to three years.
The HEAD-1 satellite applies highly integrated “Smart” satellite platform, equipped with the world advanced AIS (Automatic Identification System) payload system, including the sensitive AIS receiver and beam-complementary, ground-fully-covered AIS receiving antenna, which has good detection rate for the ship’s high-density and medium density areas.
In average, it can decode 2 million messages from no less than 60,000 ships per day.
HEAD Aerospace is headquartered in Beijing, China, with its subsidiaries in the Netherlands, Italy, France and Hong Kong, and operate globally.
As the main user and sole operator of “HEAD-1” satellite, HEAD Aerospace will carry out the commercial operation based on its AIS system after satellites launching.
It will complete the coverage of global sea area and key river course, realize the position tracking, navigation and AIS data extension applications of global vessels, and serve in China and coastal countries along the “21st century Maritime Silk Road” maritime, ports, shipping, fisheries, finance, insurance and other government departments and agencies.
The Skywalker Constellation will be composed of 30 satellites with different buses for different applications with multiple sensor capabilities. The satellites are to be deployed in Sun-synchronous orbits and Low Earth orbits, and will use a modern ICT infrastructure for data processing, machine learning, automation and data access, providing a secure end-to-end data environment (from space to end-user).
The constellation will benefit of international collaboration for frequency allocation, ground segment, data distribution, market exploration, etc.
Launch Vehicle and Launch Site:
With its main commonality matched to the Long March 4B, the first stage has a 24.65 meter length with a 3.35 meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of first stage is 193.330 kg). The CZ-4C is the only Chinese launch vehicle with a restartable N2O4/UDMH third-stage.
Improvements on the CZ-4C included an improved third-stage powered by an YF-40A engine with restart capability; a propellant management system on the third-stage; remotely-operated automated launch control system that integrated various functions previously carried out separately, including launch control, system testing, data transmission, telemetry, and power supply; a new flight computer with better calculation performance and a smaller size power supply; and a new guidance system with GPS input.
The rocket adopted a different launch checkout procedure to that of its predecessors. Instead of being tested in a horizontal position before being erected on the launch pad, the rocket could be assembled and tested vertically on the launch pad at the same time, reducing the launch preparation time by a third.
The vehicle is equipped with a YF-21B engine capable of a ground thrust of 2,971 kN and a ground specific impulse of 2,550 Ns/kg. The second stage has a 10.40 meter length with a 3.35 meter diameter and 38,326 kg, consuming 35,374 kg of N2O4/UDMH.
It includes a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).
The third stage has a 4.93 meter length with a 2.9 meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40A engine capable of a vacuum thrust of 100.8 kN and a specific impulse in a vacuum of 2,971 Ns/kg.
Situated in the Kelan County in the northwest part of the Shanxi Province, the Taiyuan Satellite Launch Center (TSLC) is also known by the Wuzhai designation. It is used mainly for polar launches (meteorological, Earth resources and scientific satellites).
The launch center has two single-pad launch complexes, a technical area for rocket and spacecraft preparations, a communications center, a mission command and control center, and a space tracking center.
The stages of the rocket were transported to the launch center by railway, and offloaded at a transit station south of the launch complex. They were then transported by road to the technical area for checkout procedures.
The launch vehicles were assembled on the launch pad by using a crane at the top of the umbilical tower to hoist each stage of the vehicle in place. Satellites were airlifted to the Taiyuan Wusu Airport about 300km away, and then transported to the center by road.
The TT&C Centre, also known as Lüliang Command Post, is headquartered in the city of Taiyuan, It has four subordinate radar tracking stations in Yangqu (Shanxi), Lishi (Shanxi), Yulin (Shaanxi), and Hancheng (Shaanxi).
The launch of the Long March 4C (Y21) rocket from the LC9 launch complex was the first launch from Taiyuan in 2017.