Application of earth-observation satellites to disaster monitoring

The small satellite constellation for environment and disaster monitoring and forecasting (SSCEDMF) is an important component of China's earth-observation satellite system. SSCEDMF is being deployed in two stages. On 6 September 2008, two optical satellites, Huan Jing (HJ)-1-A and B, were successfully launched. Each carries three main sensor types, including wide-coverage CCD cameras, IR sensors (IRSs), and a hyperspectral imager. Both HJ-1-A and B carry dual CCDs that image four bands with a spatial resolution of 30m. Each image is 360km wide. HJ-1-A also carries a hyperspectral imager capable of imaging 115 bands from 0.45 to 0.95μm with average spectral and spatial resolutions of 5nm and 100m, respectively, and 50km image width. HJ-1-B carries a four-band IRS with two near-IR and one mid-IR band, each with 150m resolution, and one thermal band of 300m resolution.

China's National Committee for Disaster Reduction (NCDR) and the National Disaster Reduction Center of China (NDRCC) are responsible for satellite operations and management. From September 2008 to February 2010, NCDR and NDRCC organized sessions at educational and other institutions to carry out on-orbit test and disaster-reduction application capacity assessment.

Figure 1. Huan Jing-1 winter mosaic image of China.

Figure 2. Ice-lake risk mapping.

In March 2010, the satellites were declared operational. To satisfy the government's disaster-management needs, NCDR and NDRCC established two work patterns, one for routine daily operations and another for emergency response. Separate teams were established for data processing and applications of the CCD, hyperspectral imager, and IRS instruments. Background parameters and disaster vulnerability assessments are obtained during routine daily operations. When disasters occur, we activate the ‘Working procedure for emergency response with space-technology application against unexpected natural disasters.’ A satellite-observation plan is created to obtain disaster-area images as quickly as possible.

Figure 3. Snow monitoring.

Figure 4. Dynamic fire monitoring and assessment of Australia.

The HJ-1-A/B satellites provide wide coverage at high frequency. Data from the satellites is used today for natural-disaster forecasting, monitoring, and assessment. Imagery has been used to asses China's severe drought, large-area snow disasters, wildfires, floods, typhoons, large-area landslide and debris flows, earthquake recovery, desertification, and for observations of plant disease and insect-pest outbreaks. The satellites have also imaged large forest fires in Australia, earthquake damage in Haiti and Chile, and the oil spill in the Gulf of Mexico.

Figure 5. Drought monitoring and assessment in China's western Liaoning province.

Figure 6. Dynamic oil-spill monitoring in the Gulf of Mexico on (a) 11, (b) 13, and (c) 19 May 2010.

NARCC has recorded HJ-1 image mosaics of China at 30m resolution every season since September 2008 (see Figure 1). Other applications include disaster risk mapping, snow, drought, and fire monitoring and assessment. Figures 2 and 3 illustrate dynamic ice-lake monitoring of the Yarkant river in the Xinjiang Uygur autonomous region and snow-cover monitoring in the wake of a severe snow disaster in October 2008, respectively, while Figure 5 shows the drought monitoring and assessment product for China's western Liaoning province during a severe drought in the summer of 2009. On 6 February 2009, an extremely serious forest fire began in southeastern Australia, affecting several major cities including Melbourne. Figure 4 shows the fire-tendency analysis^1,2 based on HJ-1-B IRS data from 16 to 23 February. On 22 April 2010, an oil platform sank in the Gulf of Mexico, leading to a major oil spill (see Figure 6). Environmental-hazard monitoring remains a key application of the NARCC program.