Tianhui (Sky Drawing)
Tianhui (TH, “Sky Drawing”) is an Earth-observing mission using optical, radar, gravity, and magnetism sensors to obtain geo-information about the Earth. The programme plans to launch up to 9 satellites of 6 different types to obtain quantitative survey of the Earth’s land, sea, gravitational and magnetic field. These satellite will form a space-based Earth-observing network to conduct both basic survey of the globe as well as detailed survey for key areas or in response to an emergency.
Name:...............Tianhui (TH) Discipline:.........Imaging / optical Type:...............Government / military No. of missions:....3 First mission.......2010 Last mission........2015 Sponsor agency......PLA / China Tianhui Satellite Centre Contractor(s).......CAST (prime) CIOMP (electro-optical payload)
China first began its research on the transmission-type three-line array stereo-topographic CCD camera technology n the 1980s under the 863 Programme (China State Hi-Tech Research and Development Initiative). The development of the indigenous stereo-topographic CCD camera began in 1996. A prototype of the three-line array stereo-topographic camera was tested on the Shiyan Weixing 1 engineering experiment satellite launched in April 2004.
The stereo-topographic mapping satellite programme was initiated in June 2005, and the development of the Tianhui 1 mapping satellite began in 2006. China TianHui Satellite Centre, a department under the Navigation and Survey Bureau of the Central Military Commission (CMC)’s Joint Staff Department, was established in 2007 to be responsible for the Tianhui satellites’ development, operation, and data processing and distribution.
Tianhui 1 (TH-1) is a stereo-topographic mapping satellite developed by China SpaceSat Co. Ltd., a commercial branch of China Academy of Space Technology (CAST), with the development commencing in 2005. The satellite is similar in roles and capability to Ziyuan 3, but features a different electro-optical mission payload developed by Changchun Institute of Optics, Fine Machinery and Physics (CIOMP) of the China Academy of Sciences (CAS).
Tianhui 1 is equipped with a three-line array panchromatic camera with a spatial resolution of 5 metres, a panchromatic CCD camera with a spatial resolution of 2 metres, and a multi-spectral imager with a spatial resolution of 10 metres. The swath width of the cameras is 60 km. The satellite operates on a 500 km polar orbit inclined at 97.3°, and could cover all areas on the Earth surface between 80°N and 80°S latitude every 58 days.
The satellite is based on the CAST2000 bus, with an orbital mass of around 1,000 kg. To achieve accurate quantitative survey of the Earth, the satellite requires long-duration, high-precision three-axis stabilisation in orbit, which is achieved by integrating three star sensors directly with the electro-optical mission package, coupled with GPS input. GPS coordinates data are also transmitted to ground station to be overlaid with the satellite imagery in further data processing.
Satellite bus:......CAST2000 Mass:...............1,000 kg Dimensions:.........N/A Solar panel span:...N/A Orbit:..............500 km Inclination:........97.3º Stabilisation.......3-axis Designed life.......3 years