MAPPING: TANSUO AND TIANHUI

As the Chinese space program expanded in size in the early 2000s, ever more specialized subsets of missions emerged. A new, small, Earth resources satellite, Tansuo, was introduced in 2004 (“Exploration”) (the name “Shiyang” was also given, but this is a generic Chinese name for a test satellite). The first was launched on 18th April 2004 into polar orbit. This was the first time that there was a northward polar launch from Xi Chang, for hitherto all launches had been southward and, for the first time, a Long March 2C was used from Xi Chang. Its orbit was 600-615 km, 97.6°. The Tansuo series was essentially a set of pre­operational test missions to define a more permanent Earth resources and mapping system. Tansuo was a 204-kg high-resolution stereo imaging and mapping satellite built at the University of Technology in Harbin and the Photomechanical Institute of the Chinese Academy of Sciences in collaboration with the European company Astrium. It was China’s first terrain-mapping satellite, with a 10-m stereo-resolution camera with a 120-km swath.

Tansuo also deployed a 25-kg micro-satellite called Naxing, short for “Nami Weixing” or “micro-satellite”, and derived from the earlier small satellite Tsinghua 1 flown by Russia. Naxing was built by the University in Tsinghua as hands-on learning for engineers to develop microtechnology. China television showed pictures of the six-sided cylinder being ejected from Tansuo against the background of the Earth. Tansuo 2 was also launched on Long March 2C from Xi Chang on 18th November 2004 into a slightly lower orbit. Weighing 300 kg, it was announced as a mission to test new technologies for the surveying of land, resources, and geography, with six new systems for control, power, and orientation. Hereon, the series returned to the Jiuquan launch base.

Tansuo 3 was launched on 5th November 2008 and also deployed another mini­satellite, the second Chuangxin (see below). It went into a much higher orbit, 800 km high. Tansuo 3 was built by Harbin Institute of Technology, a 204-kg Earth

observation satellite with a CCD camera, while Chuangxin 1-02 was a small 88-kg store-dump satellite built by SAST which collected information on weather, hydrology, and natural disasters from remote stations. Results from the double mission were published in September 2011 by the National Commission for Disaster Reduction. According to the commission, the optical, infrared, and hyper-spectral sensors had provided rapid imaging data that helped rescue teams in no fewer than 70 natural disasters, notably the 2010 earthquake in Haiti. Tansuo 4 was again a double mission with Chuangxin 1-03 and also flew at 800 km. Tansuo 4 was built by the Harbin Institute again, but this time with the DFH SatelUte Co., and it may have been the larger CAST968 bus with a weight in the order of 400 kg.

We have few further details on these missions, or published images, but we do now have information on the current suite of Earth resources, environmental, and observational instruments from a description of the Beijing Institute of Space Mechanics and Electricity, originally institute 508 formed on 21st August 1958:

• Light and Small Infrared Area Camera, 8 kg, focal length 285 mm, used for monitoring fires, volcanoes, disasters, and the contours of deserts, with a resolution of 100 m;

• Wide Coverage Multi Spectral Imager for Ocean Monitoring, 18 kg, focal length 32 mm, swath 500 km, resolution 250 m from 798 km with four lens for acquiring data on ice, spills, and red tide;

• Wide Cover Multi Spectral Camera for Environment Monitoring, 34 kg, focal length 141 mm, resolution 30 m from 650 km, swath 700 km with two cameras;

• Large Area Staring Multi Spectral Camera, 130 kg, focal length 2 m, resolution 100 m from 24-hr orbit;

• Light Wide Coverage Scanner, 40 kg, focal length 1.3 m, swath 380 km, resolution 10 m from 1,300 km, for leakage detection, silting, riverbed pollution, and terrain observation;

• Push-broom Hyper-spectral Camera, 60 kg, focal length 41 mm, resolution 250 m from 800 km, with large field of view of agriculture, forestry, oceans, water, minerals, and environmental observations.

The first of a new type of satellite was launched on 24th August 2010: Tianhui, or mapping satellite, a CZ-2D used from Jiuquan in an orbit of 488-504 km, 94.5 min, 97.3°. The second carried a mapping camera with 5-m resolution and entered a similar orbit less than two years later. Both were crossing the equator at a similar time, 13:30 local time. It is possible that this new series benefitted from the earlier work undertaken by Tansuo and is an operational version, but the more powerful launcher suggests a heavier satellite. Outcomes do not yet appear to have been publicized. The series are summarized in Tables 6.6 and 6.7.