EARTH RESOURCES: CBERS

CBERS is the most high-profile international collaborative program developed by China. It is very much the achievement of one person: Renato Archer (1922-96), a naval officer and expert in nuclear energy who became a social democrat member of parhament during the 1960s and was then jailed by the military government. Many years later, he became Minister for Science and Technology, with responsibility for the Brazilian space agency, INPE. At a pohtical level, he believed in the importance of Brazil’s pursuing a foreign policy independently of Europe and the United States,

so, in December 1984, a Brazilian delegation was sent to Beijing to explore cooperation in space applications. Renato Archer himself traveled there in July 1986 to meet with the China Academy of Space Technology (CAST). Brazil had an active space program (sounding rockets, leading to its first satellite in 1993) and indeed had put efforts into trying to develop its own launcher (though with little success). Three areas of cooperation were explored: Earth resources, communications, and launchers. Chinese technicians visited Brazil in February 1987, where they presented the idea of a collaborative Earth resources program based on Zi Yuan and this was formally agreed on 6th July 1988 at a ceremony signed in Beijing by Brazilian President Jose Sarney.

The project was developed on a 70:30 China:Brazil basis, the total cost of the project being budgeted at between €330m and €345m. The project was called China Brazil Earth Resources Satellite and involved the building of two satellites, one in China, the second in Brazil. The first launch was scheduled for 1992, but suffered five years of delays, due mainly to political upheavals (Tiananmen, 1989, as well as domestic pohtics in Brazil). There were practical difficulties, too. The agreed working language was English, because most young Brazilian scientists had studied in American or European universities or institutes, but the much older Chinese scientists spoke only Chinese or Russian. CAST’s technical documentation was only in Chinese but, to develop an English text, “the Chinese secretaries did not know the English alphabet, so when they tried to work with it, just typing a few lines took hours” [11]. Happily, they found a Taiwanese-born Chinese and Portuguese­speaking geographer, Sherry Chou Chen, to bridge the gap.

CBERS weighed 1,450 kg and was a box 1.8 x 2 x 2.2 m, with one solar panel 2.6 m tall and 6.3 m long, able to generate 1.1 kW of power, while hydrazine powered the maneuvering jets. It was designed to cross the equator at 10:30 am every day, so as to set a standard point of reference for Sun angles on the targets observed, with a revisit pattern of 26 days. It was China’s first digital imaging satellite, overtaking the old “wet film” recoverable technology of the FSW series. CBERS was designed to enter an orbit of 774 km, 78.5°, similar to that of the Feng Yun 1, and provide detailed images of the Earth in five channels using Unear CCD cameras with a resolution of 20 m, able to tilt up to 32° to either side for oblique shots, swath 110 km, comparable to the French SPOT 4. CBERS was built to carry a multispectral infrared scanner (IRMSS) (resolution 20 m, swath 120 km) and a wide-field imager (WFI) (resolution 258 m, swath 890 km). The WFI was Brazilian – built, but the other components were made in China. The intention was to cover the country in narrow, medium, and wide resolution simultaneously. A data-collection system could pick up and retransmit information from unmanned inland stations and buoys.

CBERS was set for launch in September 1998 but, that July, the Chinese presciently announced that, due to incoming unfavorable weather, it would be delayed for a year. The first CBERS was eventually cleared for launch from Taiyuan on 26th September 1999 and its fuel tanks filled over the following three days. On the 30th, it was attached to its fairing. Nothing happened for the next two days, as launch workers had time off to observe the national holiday to mark the revolution

CBERS, following the well-established box-shaped design. Courtesy: INPE.

50 years earlier. Final integration took place over the 3rd to the 11th, after which the CZ-4B rocket itself was fuelled up. On 14th October, 400 technicians from both countries saw the launch and the rocket pitch over southward only 20 sec into its mission, heading over towards Laos. Twenty-two minutes and 40 sec after launch, CBERS 1 was ejected from the now bumed-out third stage and, 25 sec later, released a Brazilian subsatellite, SAC-1, or Scientific Applications Satellite 1. The successful deployment of both was soon confirmed by a ground tracking station at Nanning. By way of an endnote, the fuels left in the Long March 4B upper stage combusted accidentally on 11th March 2000, blowing the stage apart, scattering 300 fragments in orbit and spewing out a dust cloud of tiny fuel particles. Ironically, the Chinese had become increasingly aware of the problem of orbital debris and the Long March 4 was the first Chinese rocket fitted with a system of venting residual propellants to prevent this very situation from arising, obviously without much success.

Seven hours later, CBERS was over Brazil and picked up by the main tracking station at Sao Jose dos Campos. In China, CBERS was tracked by stations in Beijing, Guanzhou, and Urumqi as well as the main mission control center in Xian which was responsible for on-orbit checkout. Data were sent down to the additional ground stations in Cuiaba and Alcantara. The initial orbit of CBERS 1 was 728­745 km, inclination 98.55° (polar), and period 99.6 min. Six days later, the satellite began to use its motor to gradually raise its orbit, in order to reach a perfect Sun – synchronous operating altitude. Over a month, in the course of 13 maneuvers, it

CBERS, showing narrow and wider swaths of its cameras. Courtesy: INPE. Tracking system: Cuiaba is the Brazilian station. Courtesy: INPE.

pushed its altitude to a circular orbit at 774 km, period 100.32 min, which it reached on 9th November, which enabled it to circle the Earth 14 times a day and revisit the same track over the ground every 26 days. CBERS carried out small but regular maneuvers to raise its orbit: whenever it fell to 100.315 min, the motor would fire briefly to lift it back up to 100.322 min. The wide-field instrument was reported to have failed after 177 days because of a short circuit.

A mission report four months later recorded that data were being collected for agriculture, forestry, water quality, urban planning, and environmental protection. Among the first commercial users of CBERS data were cellulose manufacturers (for information on eucalyptus trees) and government agencies trying to prevent slash-and – bum farming practices in the Brazilian jungle. In October 2001, the Space Mechanical and Electrical Research Institute in Beijing held a seminar to mark the first two years of the mission. CBERS 1 had sent back more than 200,000 images, of which 3,000 had been customized into publicly available CCD images. They had picked up anything from coal mine fires in Ningxia to landslides along the Yigong River in Bomi, Tibet. Its images were used by 1,200 operators in China and 3,000 in Brazil.

After four years, CBERS raised its orbit to 773-782 km, which became its retirement orbit. CBERS 1 operated for double its two-year planned lifetime, sending back over 8,000 images of China, covering 99% of the country. CBERS 1 retired in August 2003 but NASA reported that, on 18th February 2007, there was an accidental explosion of remaining propellant, which created another 60 pieces of debris [12].

CBERS 2 in assembly, this time in Brazil. Courtesy: Paolo Ulivi.

It was soon replaced by the 1,550-kg CBERS 2, built in Brazil and put into orbit by China on 21st October 2003. CBERS 2 carried the first Chuangxin (“creation”) micro-satellite, China’s smallest satellite to that point at only 88 kg (see below). CBERS 2 was technically similar to CBERS 1, with a high-resolution camera, wide – field camera, and multispectral camera, but there were improvements: downlink data volume was doubled and the revisit time shortened from 26 days to 13 days. The instruments were developed by the Beijing Institute of Space Mechanics and Engineering, all able to send images in real time. The multispectral CCD camera weighed 198 kg, had a focal length of 1.01 m, a spatial resolution of 5 m (10 m from the operating altitude of 778 km), and a side-look capability of 32°. The multi­spectral scanner weighed 135 kg, and had a focal length of 1.4 m and a resolution of 40 m. The light high-resolution CCD camera weighed 73 kg and had a focal length of 3.3 m. CBERS 2 concentrated on observing deforestation, land changes, natural disasters, pollution, and underground resources. CBERS 2 operated initially from 731-750 km and eventually raised its orbit to the same as CBERS 1. Its service Ufe took it to at least 2009.

CBERS 3 in orbit, continuing the box design and single panel. Courtesy: INPE.

Within a year, CBERS 2 was generating 2,100 images a week and had 15,000 individual users in 8,000 institutes and organizations. In its first three years, CBERS 2 built an image bank of over 150,000 pictures. The total number of CCD scenes distributed by May 2006 was 210,000, each CD having 145 MB. Users comprised private bodies and farms (51%), educational organizations (26%), and government bodies (23%). Typically, the CBERS catalog is downloaded 650 times a day.

After a further four-year gap, CBERS 2B flew on the CZ-4B from Taiyuan on 19th September 2007 into an orbit of 736-741 km. It weighed 1,452 kg and was designed to send data on land use, agricultural production, and environmental protection. On 21st September, it climbed to its operational altitude of 773 km. CBERS 2B continued the high-resolution CCD camera and wide-field imager, but the IRMSS medium-resolution camera was replaced by a new high-resolution camera of 2.5-m resolution in the visible spectrum with a swath of 27 km and was able to swivel 4°. To improve pointing accuracy, the satelhte carried both satellite navigation (Global Positioning System (GPS)) and a star sensor. Within a year,

320.0 of its images had been downloaded from the internet worldwide. CBERS 2B ceased operations in April 2010 and Brazil put China under pressure to bring forward CBERS 3.

CBERS 3 is due by 2013, CBERS 4A by 2015, and 4B by 2017, with Brazil putting €230m into the program. CBERS 3 weighs 1,980 kg, can generate 2.3 kW of power, and is to be accompanied by a 500-kg observation mini-satellite, Amazonia. The number of cameras will be increased from three to five:

• a four-band panchromatic camera taking images of 5 and 10-m resolution, with a swath of 60 km and a swivel ability of 32°;

• a multispectral camera, 20-m resolution, with a swath of 120 km;

• an infrared multispectral camera taking images at 40 and 80-m resolution in four bands, with a swath of 120 km, all built in China;

• a four-band advanced WFI, resolution 73 m from 890 km, built in Brazil;

• a 20-m CCD camera, resolution 20 m, swath 120 km, also built in Brazil.

Overall, 50% will be made in Brazil, compared to 30% for CBERS 1-2. The satellites will have a design lifetime of three years. Transmission rates will treble from 100 mbps to 300 mbps. They will be followed by CBERS 5 and 6 with 1-m resolution to follow by 2020 and, later, CBERS 7 will be a Synthetic Aperture Radar satellite.

The CBERS series have had important results and outcomes for Brazil. In 1998, the Brazilian space agency, INPE, organized a team to prepare the dissemination and application of CBERS data. Regular workshops and “CBERS weeks” were held to discuss the results and outcomes. Applicants registered on INPE’s CBERS site, identified the ground area in which they were interested, and were then able to choose the images they wished to download. CBERS was able to provide a new agricultural map on a scale of 1:250,000 and the country is now covered in 172 new maps. Coloring could identify what crops were ready for harvesting or which had already been taken in: soy showed up as red before, but green afterward. A new vegetation map was made by the University of Vigosa. Land-ownership maps were developed, showing national parks and identifying individual private owners (to check against tax enforcement). Oil spills off the coast were detected.

One of the most important applications was in the area of deforestation, for the CBERS Wide Field Imager was able to image new areas of deforestation, trails, burning, and logging, especially when compared to earlier Landsat and SPOT photographs. On the east coast, only 7% of Atlantic forest remained. The first Landsat run in 1977 found a deforestation rate of 2.5%, the second run 7.5% in 1988, but CBERS data found a national deforestation rate of 18%, with

250.0 km2 being lost per year. Maps were handed over to law-enforcement agencies.

CBERS has been given high visibility by both countries and is considered by both to be a high point in their international scientific collaboration. This was symbolized

CBERS 3, showing the downward-pointing imaging platform. Courtesy: INPE.

when, in 2004, President Hu Jintao visited the national space research institute in Sao Paolo and planted a bellflower tree there. At one stage, China proposed that Malaysia join the CBERS program and have its own receiving station, but this does not appear to have been pursued. In a similar initiative, Venezuela signed a €100m agreement with China in 2011 for a 500-kg CAST2000 Earth observation satellite, VNRSS, for launch on Long March 4B and an order for a Turkish military reconnaissance satellite, Goturk, due to fly in 2012, presumably based on the same technology. The series is summarized in Table 6.4.

Table 6.4. CBERS series. CBERS1 14 Oct 1999 CBERS 2 21 Oct 2003 Chuangxin 1-01 CBERS 2B 19 Sep 2007 All on CZ-4B from Taiyuan.