CBERS – China-Brazil Earth Resources Satellite

A Sino-Brazilian Cooperation for the monitoring and
study of the natural resources of our Planet

Brazil and China have continental territories with huge extent and plenty of natural resources, which undergo continual transformations of difficult following-up. The daily monitoring of these resources and transformations, both the natural as well as the man-made ones, is carried out with greater efficiency and economy when the Earth is observed from Space.

In a joint effort to develop capacity in the area of Earth Observation from Space, China and Brazil signed on July 6, 1988 an agreement for the development and launching of two remote sensing satellites. The ensuing program, known as China-Brazil Earth-Resources Satellite (CBERS), is coordinated by the China National Space Administration (CNSA) and the Brazilian Space Agency (AEB) and executed by the China Academy of Space Technology (CAST) and the National Institute for Space Research (INPE). CBERS program has experienced great success, with the successful launch and operation of the two satellites.

Given the success of the program, Brazil and China decided to give continuity to CBERS program and on November 22, 2002 signed new agreement for the manufacturing and launching of two new satellites – CBERS-3&4. with improved characteristics. CBERS-3&4 satellites will constitute the new generation of Chinese and Brazilian remote sensing satellites and will be launched in 2009 and 2011.

In order to avoid a data gap between CBERS-2 and CBERS-3, Brazil and China signed a complementary protocol on November 12, 2004 for manufacturing CBERS-2B satellite which was launched in 2007.

The CBERS program is a major success model of south-south cooperation in space technology between Brazil and China. CBERS is currently the only operational global land cover remote sensing program, with a data policy based on the public good and data continuity until 2015.

The Satellites
 
Every CBERS satellite is formed by the junction of two modules. The Payload Module carries the optical and electronic equipment used for earth observation and data collecting. The Service Module, in turn, carries vital equipment, such as energy supply, attitude control and telecommunications equipment, necessary for the in-orbit operation of the satellite.

CBERS-1

The first satellite, CBERS-1, was launched by the Chinese Long March 4B launcher, from the Taiyuan Launch Center, on October 14, 1999. Launch occurred at 11:15 AM (Beijing local time).


In CBERS-1 payload module there were 3 cameras, CCD Camera, IRMSS Scanner and WFI Camera, and a Transponder for the Brazilian Environmental Data Collection System.

CBERS-1 was integrated and tested at CAST’s facilities.

CBERS-2

CBERS-2 , technically identical to CBERS-1, was launched on October 21, 2003 from the Taiyuan Satellite Launch Center in China. The launch time was 11:16AM (Beijing local time). The CBERS-2 was integrated and tested at LIT, INPE’s Integration and Test Laboratory.

CBERS-2B

CBERS-2B, built to avoid interrupting the projects of thousand institutes and users of CBERS program, still belongs to the first CBERS generation, and is therefore almost identical to CBERS-1 and -2. However, some improvements were adopted. The main one concerns the payload, with the replacement of the IRMSS Scanner by a High-Resolution Panchromatic Camera (HRC). Additional improvements are a new on-board recording system, a GPS (Global Positioning System) and star sensor. Satellite integration and testing were performed at INPE, in São José dos Campos.

CBERS-2B was launched on September 19, 2007 (11:26AM, Beijing local time), also by a Long March 4B and from Taiyuan Satellite Launch Center.

CBERS-3 e 4

CBERS-3 and 4 satellites represent an evolution of CBERS-1 and 2. Four cameras will be present in the payload module, with improved geometrical and radiometric performance.

They are: PanMux Camera-PANMUX, Multi-spectral Camera-MUX, Infrared  Scanner-IRS and Advanced Wide Field Imaging Camera-AWFI.

Orbit

All CBERS satellites orbits are sun-synchronous, at a 778 km altitude. They perform about 14 revolutions a day and obtain a complete coverage of the Earth in 26 days.

The possibility of lateral pointing with the CCD camera, allied to the type of satellite orbit, makes it possible the production of stereoscopic pairs of any given region, with a 3-day interval between the images.      

Applications

The CBERS satellites are equipped with camera for earth observation in different spectral bands. Each satellite also carries a transponder for data collecting, in support to the operation  of the Brazilian Environmental Data Collecting System. The CBERS-3&4 satellites will be equipped with a more sophisticated payload than the on onboard CBERS-1&2 satellites.

The family of remote sensing satellites CBERS brought to Brazil significant scientific advances. This significance is attested by the over 15000 users from more than 1500 organizations registered as active CBERS users, also by the 300000 CBERS images, distributed at the approximate rate of 250 every day.

Its images are used in important areas, as fire control in the Amazon Region, water resources monitoring, urban growth, land use, education and several other applications.

CBERS is fundamental for large national and strategic projects, like PRODES - Amazon annual deforestation rate evaluation, DETER – Amazon deforestation real time detection and CANASAT - monitoring of sugar-cane areas, among others.

The application potential of a given sensor is established as a function of its spatial resolution, temporal resolution, and spectral and radiometric characteristics. In order to maximize the results to improve the cost/benefit ratio one should consider the trade-off between the application needs and the sensors characteristics. Following are indicated some applications for each camera although the possibility of applications is very ample.

The Medium Resolution Imaging Camera (CCD), with its medium spatial resolution – 20 meters – in four spectral bands plus one panchromatic band, is suited for observation of phenomena and objects whose details are important. As it has a field of view of 120Km, it is suited for city and region studies. Given its temporal frequency of 26 days, it supports the analysis of phenomena whose duration is compatible with its temporal resolution. This temporal resolution can be improved as the CCD has the capacity of side view. Its bands are located in the spectral zone of the visible and near infrared, which allow good contrast between vegetation and other type of objects.

Here follows some potential CCD applications to be pointed out:

• Vegetation: identification of forest areas, forest alterations in parks, forest reservations, native or man-made forests, area quantification, recent fire scars.
• Agriculture: identification of agricultural fields, area quantification, monitoring of agricultural development and expansion, quantification of central pivots, support for crop forecasting, various inspections.
• Environment: identification of anthropic anomalies across water channels, reservoirs, forests, urban surroundings, roads; analysis of natural recurrent events, compatible with camera resolution, mapping of use of land, urban sprawling.
• Water: Identification of water-continent borders, coast studies and management, reservoir monitoring.
• Cartography: as this camera has sideways pointing of 32º east and west, in few steps, it enables the acquisition of stereoscopic images for a proper cartographic analysis. This feature also makes possible the acquisition of images of a certain area in a terrain in shorter intervals, which is useful for the monitoring of dynamical phenomena.
• Geology and soil: support for soil survey and geology.
• Education: generation of support material for educational activities in geography, environment and other subjects.

The IRMSS (Infrared Multispectral Scanner), present in CBERS-1 and -2, camera has two spectral bands in the medium infrared region and a panchromatic band with a 80 meters spatial resolution, plus one band in the thermal infrared region with 160 meters. Its applications are the same as those of the CCD camera with proper adaptations. Additional applications are:

• Analysis of phenomena that present surface temperature modifications.
• Generation of state region mosaics.
• Generation of image charts.

The WFI (Wide Field Imager) is able to image large territorial extensions, 890km wide. This characteristics makes WFI very interesting for observing phenomena whose magnitude or interest lie in the macro-regional or state scale. As a function of this wide spatial coverage, its temporal resolution has a gain – it can generate images of a certain region with a less than five days interval. Here follow some of its applications:

• Generation of state region and national mosaics.
• Generation of vegetation indexes for monitoring purposes.
• Monitoring of dynamical phenomena like agricultural harvests, persistent fires.
• Alert system, where a WFI image can serve as an indication for the acquisition of higher resolution images of the CCD or IRMSS cameras.
• Joint operation with other world data collecting systems of low to medium resolution.

The HRC (High-Resolution Panchromatic Camera) scans a relatively narrow strip - 27km- and with high resolution, of 2.4m pixel dimension. The operation mode is based on a 130 days revisit. In this fashion it will be possible to obtain at least two complete coverages of the country per year. This camera will not be able to provide stereoscopy. Among its applications, one may mention the following:

• Detailed national or regional mosaics.
• Update of thematic maps.
• Urban growth for county planning.
• Urban and intelligence applications.