GEOSYNCHRONOUS WEATHER SATELLITES

For the Chinese, the next stage was to operate a weather satelhte in geosynchronous orbit. Called the Feng Yun 2, this would complement the Feng Yun 1 series. The concept was that Feng Yun 2 would send back constantly scanning pictures of China and the western Pacific from its high vantage point 36,000 km out, while Feng Yun 1 and 3 would send back detailed weather maps from their lower, regular 100-min passes over China from an altitude of 900 km. Locations set for the new series were 86.5°E and 105°E. The original program envisaged two experimental and then operational satellites, with three and five channels, respectively. Chief designer of the imaging system was Tong Kai (1931-2005), a graduate of the Leningrad Institute of Telecommunications Engineering, who later went on to the navigation satelhte project. Construction of ground systems began in 1988 and was completed in 1994.

Geosynchronous meteorological satelhtes are expensive, requiring a big launcher and high operating standards. However, the vantage point of 36,000 km can provide quality weather coverage of large land masses around the clock. The United States operated their first geosynchronous metsat in 1974 (Synchronous Meteorological Satellite 1), Japan and Europe in 1977 (Himawari and Meteosat, respectively), and Russia not until 1994 (Elektro).

Feng Yun 2 was a drum-shaped satellite, 4.5 m tall, with a diameter of 2.1 m and a weight of 1,380 kg. It carried a five-channel Visible and Infrared Spin Scan Radiometer, which transmitted a visible picture of 2,500 lines and 1,250-m resolution every 30 min, infrared images of 2,500-m resolution, and water vapor images of 2,500-m resolution to stations in China and Melbourne, Australia, made by the Institute for Technical Physics in Shanghai. It was intended to provide cloud, temperature, and wind maps. It was designed by SAST, developed by the Shanghai Aerospace Technology Research Institute of the China Aerospace Corporation, and built in the Hauyin machinery plant. Service life was three years, the last to fly in 2013 before the FY-4 came in. The FG-36 solid-fuel apogee motor was designed to achieve the final insertion: it was 1.53 m long, 900 mm in diameter, 729 kg in weight, with a thrust of 44 kN or 289 sec ISP.

The Feng Yun 2 series got off to a disastrous start. When Feng Yun 2-1 was being loaded with propellant in the processing hall at Xi Chang launch site on 2nd April 1994, the satelhte exploded, killing one technician and injuring 31 others. The satellite itself, valued at over €88m, was a write-off and it took over three years to redesign the propellant tank system so as to make sure this accident would never happen again.

The replacement Feng Yun 2-1 was eventually launched on the Long March 3 rocket from Xi Chang on at 9:00 pm Beijing time on 10th June 1997. Twenty-three minutes after launch, the hydrogen-powered third stage fired to send it on its way to its permanent position at 105°E, with a scheduled lifetime of three years. It also carried a solar x-ray spectrometer and space particle detector. By September, it had completed its full range of systems testing and was ready for handing over to the state meteorological administration. Its instruments were calibrated against those of Feng Yun 1-3 using, as a ground-based reference point, Qinhai Lake.

Feng Yun 2-1 lasted until 10th April 1998, only six months of full operations, when it was lost. Ground controllers managed to regain control at the end of the year, but the resumption was limited to six images a day. Contact was off and on during the year, good images being returned from time to time. In March 2000, meteorological operations with the satellite appear to have ended and the satelhte was moved to 86°E by the end of April. Station-keeping maneuvers continued there so it must have still returned some data. It was taken out of orbit on 1st September 2006.

The gap in operations did not last for long, for a replacement satellite, Feng Yun 2-2, was lofted into orbit by Long March 3 on 25th June 2000, soon arriving at 2-1’s old station, 105°E. A month later, following on-orbit testing, the imaging systems were turned on by the National Satellite Monitoring Centre. Twenty-five minutes later, after they had completed a full scan of the Earth, full disk images in color, infrared, and water vapor came flooding into the center, showing clouds swirling over south-east Asia, a clear view of southern Australia, and tropical storm Tembin menacing Japan. Resolution was as sharp as 5 km, which, from 36,000 km out, was good. Three images in each format were, from thereon, sent to the monitoring center every 25 min. Feng Yun also collected and retransmitted data

from automatic weather platforms at sea. Feng Yun 2-2 was even designed to monitor solar radiation, carrying a solar x-ray spectrometer and space particle detector to monitor solar activity and charged particle radiation. It was taken off orbit on 7th October 2006 when it was moved to 123°E and began drifting [6].

Feng Yun 2-3 was launched to 105°E on 19th October 2004, with visible and infrared equipment to watch ocean conditions, fog, hailstorms, sandstorms, and fires. It was declared operational the following May and was described as the first operational version. It was the first Feng Yun to use the CZ-3A, the 3 having been retired. Feng Yun 2-4 was launched on CZ-3A on 8th December 2006 to form a pair with 2-3 but at 86.5°E. The next Feng Yun, 2-5, was launched on CZ-3A on 23rd December 2008, entering transfer orbit after 24 min. At this stage, the series, which had a relatively simple numbering system, began to get complicated. First, the Chinese began to applying lettering, so that the missions were called 2A, 2B, etc. Second, it was announced that the December 2008 launch was 2-6, not 2-5 as expected – a move designed to acknowledge the loss of the first intended mission (now 2-1). Whatever the number, Feng Yun 2-5 was unusual in that the CZ-3A final stage was reignited after 1,500 sec to take the stage out of orbit, a debris mitigation measure.

China reported that, as a result of the Feng Yun system, the country had received advance warnings of typhoons, been able to take flood diversion measures, brought ships back to port ahead of storms, harvested crops before bad weather, and controlled river flows through dams. They had enabled China to estimate crop growth from vegetation and moisture indices, map land use and desertification, and provide data on urban hot spots, smog and dust, algal blooms, forest pests and diseases, pollutants, and even the ozone hole over the Antarctic. By 2006, China had over 100 receiving stations for Feng Yun data. That year, it signed an agreement for eight countries to take the data – Peru, Thailand, Bangladesh, Thailand, Pakistan, Mongolia, Iran, and Indonesia. An information dissemination system was established, called FengyunCast, for domestic and foreign users in Asia and Australia (Europe has EumetCast and the Americans have GeonetCast).

The Feng Yun 4 series will replace the “2” series from the mid-2010s, with 10 visible and infrared channels and microwave sounder. Locations will be 86.5°E and 107°E and six will be launched in 2013-20. The “4” series will have optical and microwave sounders to enable the compiling of three-dimensional maps of atmospheric temperature and humidity, supplemented by four instruments: solar x-ray imager, extreme ultraviolet imager, solar x-ray radiometer, and extreme ultraviolet radiometer. China’s objective is to have an integrated system of FY-3s and FY-4s by 2020 providing data on the atmosphere, hydrosphere, biosphere, lithosphere, and cryosphere, with morning and afternoon FY-3s and a three-satellite system of radar rain measurers. The series is summarized in Table 6.2.