CBERS-3 and 4
CBERS-3 & 4 (China-Brazil Earth Resources Satellite) - 2nd Generation Satellite Series
CBERS is a cooperative program of China and Brazil. In Nov. 2002, the governments of China and Brazil decided to expand the initial agreement by including another two satellites of the same kind, CBERS-3 and 4, as the second generation of the Sino-Brazilian cooperation effort. The planned cooperative CBERS-3&4 program of CAST and INPE employs enhanced versions of spacecraft and instruments. The specification of the project was agreed upon and closed in July 2004. A DDR (Digital Data Recorder) using solid state technology will be used to record all onboard imagery. 1) 2) 3) 4) 5) 6) 7) 8)
China/Brazil cooperative mission designations in China:
In China, the CBERS-3 & 4 satellites are referred to as ZY-1 FM3 & ZY-1 FM4 (Zi Yuan-1 Flight Models 3 & 4) with ZY-Yuan meaning "resource.".
- ZY-1 FM1 refers to the CBERS-1 spacecraft (launch Oct. 14, 1999)
- ZY-1 FM2 refers to the CBERS-2 spacecraft (launch Oct. 11, 2003)
- ZY-1 FM2B refers to the CBERS-2B spacecraft (launch Sept. 19, 2007).
Although the governments of China and Brazil had some preliminary discussions in the past to continue the CBERS satellite family with the missions of CBERS-5 and CBERS-6, there's no official agreement for CBERS-5 and 6 so far. The discussions about CBERS-5 and 6 will be held after the launch of CBERS-3.
Table 1: Comparison between CBERS-1/2/2B and CBERS-3/4 spacecraft series
Starting in 2004, Brazil changed its CBERS data distribution and access policies: 9)
• With CBERS-2, Brazil adopted an open data distribution policy, ensuring free access through the internet to its catalogue and to full resolution images.
• Online registration: any user can browse the catalogue, choose as many images as he wants, and download them for immediate use, with no cost, bureaucracy and working on a simple and fast catalogue system.
• The same policy was adopted for CBERS-2B and will be adopted for CBERS-3 when it is launched.
• The policy was also extended to neighboring countries under the footprint of the Cuiaba-Brazil ground station and archived at INPE's catalog.
Figure 1: Illustration of the CBERS-3 & 4 spacecraft (image credit: INPE, CAST)
The spacecraft consists of a hexahedron shaped structure divided in service and payload modules as shown in Figures 2 and 3. In the orbital configuration, the Z axis is pointed to nadir (Earth's surface). The cameras and antennas are mounted on the +Z side panel. The solar panel is mounted on the -Y side panel and rotates around the Y axis. The antennas, thrusters and attitude sensors, such as sun sensors, infrared Earth sensors, are mounted on other panels. 10)
AOCS (Attitude and Orbit Control Subsystem): The spacecraft is 3-axis stabilized keeping the imager pointed toward nadir. The AOCS includes star sensors, sun sensors, infrared Earth sensors, gyros, GPS receiver, a control computer, momentum wheels and a hydrazine propulsion system.
Thermal control is achieved mainly by passive means using thermal coating and multi-layer insulation blankets. Heat pipes and heaters are also used.
EPS (Electrical Power Subsystem): The EPS uses triple-junction GaAs solar panels, a shunt regulator, battery charge control, a battery discharge regulator, DC/DC converters and NiCd (Nickel Cadmium) batteries. The EPS can provide 2.30 kW to the spacecraft.
The nominal payload capability of the platform is ~1000 kg; the mass of the entire spacecraft is ~1980 kg. In its folded (launch) configuration, the dimensions are: 3.25 m in height and 3.35 m in diameter, compatible with a LM-4 class launch vehicle.
Figure 2: Illustration of the spacecraft structure (image credit: INPE, CAST)
Figure 3: Schematic view of the spacecraft bus along with its modules and instrument locations (image credit: INPE,CAST)
The OBDH (On-Board Data Handling) subsystem consists of a main computer and 7 remote terminal units to provide onboard data handling and the spacecraft monitoring and control functions.
RF communications: The S-band is used for the TT&C functions providing two-way communications with the ground. The S-band antenna offers a near omni-directional coverage. The payload image data are downlinked in X-band by two TWTA transmitters. One of them has three carriers modulated in QPSK (Quadra-Phase Shift Keying): The on-board recorder has a capacity of 274 Gbit, capable to record data from all cameras.
Table 2: Summary of X-band downlink parameters (Ref. 10)
Launch: The CBERS-3 spacecraft (also referred to as Ziyuan I-03) was launched on December 09, 2013 (03:26 UTC) on a Long March -4B (CZ-4B) vehicle from the Taiyuan Satellite Launch Center, China. However, the CZ-4B vehicle malfunctioned during the flight and the satellite failed to enter orbit. - An investigation is underway to determine the cause of the failure. 11) 12) 13)
Orbit: Sun-synchronous orbit; altitude = 778 km; inclination = 98.5o; repeat cycle = 26 days, orbital period = 100.26 minutes; LTDN (Local solar Time on Descending Node) at 10:30 hours.
Figure 4: Photo of the CBERS-4 spacecraft (image credit: INPE)
Launch: The CBERS-4 spacecraft (also referred to as Ziyuan I-04) was launched on December 07, 2014 (03:26:04 UTC) on a Long March -4B (CZ-4B) vehicle from the Taiyuan Satellite Launch Center, China. The launch came one year after the loss of the CBERS-3 satellite that failed to reach orbit due to a malfunction of its Long March 4B rocket. 17) 18)
After the loss of the CBERS-3 satellite, Brazil and China agreed to speed up the development of its twin, CBERS-4, that was originally planned to fly in late 2015. Committed to shorten the gap in data caused by the launch failure, assembly of CBERS-4 was finished in early 2014 to allow several months of testing before the satellite was delivered to the launch site on October 17. Stacked atop the Long March 4B rocket last week, the satellite and its rocket underwent final testing activities ahead of launch day.
Orbit: Sun-synchronous orbit; altitude = 748 km; inclination = 98.55o; repeat cycle = 26 days, orbital period = 100.26 minutes; LTDN (Local solar Time on Descending Node) at 10:30 hours.
Sensor complement: (MUXCam, PanMUX, IRS, WFI, DCS)
The sensor complement of CBERS-3 & 4 represents an evolution with respect to the payload flown on the CBERS-1 &2 missions. Four cameras will be present in the payload module, with improved geometrical and radiometric performance.
Table 3: Basic characteristics of the CBERS-3 & 4 instruments
Note: * The PanMUX mirror may be used to revisit the same place within 3 days if necessary.
MUXCam (Multispectral Camera):
MUXCam is an INPE instrument designed and developed at Opto Eletrônica S. A., of Sao Carlos, Sao Paulo, Brazil. The objective is to provide imagery for cartographic applications. MUXCam is a multispectral camera with four spectral bands covering the wavelength range from blue to near infrared (from 450 nm to 890 nm) with a ground resolution of 20 m and a ground swath width of 120 km.19)
The MUXCam instrument consists of three equipments: RBNA, RBNB and RBNC. Figure 5 shows the RBNA equipment of the MUXCam instrument.
Note: RBNA is not an acronym, it is the code for the product tree. R stands for CBERS-3 and 4 mission, B is for the Space Segment, N is for MUX camera subsystem and A is for the optical head assembly.
• The RBNA provides image acquisition and is composed of the optical system (entrance mirror and lens assembly), optical housing and the focal plane assembly.
• The RBNB consists of the electronics responsible for the thermal control, the focus adjustment and the internal calibration system control.
• The RBNC subsystem is responsible for generating the CCD reading clocks, processing the CCD analog outputs to digital signal, and of data encoding into a serial data stream. This data is transmitted to the satellite.
Figure 5: Illustration of the MUXCam optical subsystem RBNA (image credit: Opto Eletrônica)
The CCD detector is a 4-line array, each line has 6000 pixels of size: 13 µm x 13 µm. Spectral thin films, deposited over a window that covers the photosensitive elements of the CCD, are responsible for the separation of the four spectral bands.
Table 4: Requirements of the MUXCam optical subsystem
Figure 6 presents the layout of the optical system developed. The optical system consists of a refractive system with 14 components: an entrance mirror, a window, 11 fixed lenses and a moving lens. The total length of the optical system is 653 mm. The weight of the optical components (excluding the mirror) is about 4.7 kg and the system is athermal in the temperature range from 0oC to 40oC. Figure 7 exhibits the manufactured optical system aligned in its optical housing and during optical test.
Figure 6: MUXCam collecting lens system with focal adjust lens (image credit: Opto Eletrônica)
Figure 7: MUXCam collecting lens with focus adjust lens assembled in alignment stage (image credit: Opto Eletrônica)
The entrance mirror must be manufactured with high superficial quality. Figure shows the schematic mounting draw and a picture of the mirror before it received the reflexive coating.
Figure 8: Illustration of the MUXCam entrance mirror (image credit: Opto Eletrônica)
PanMUX (Panchromatic and Multispectral Camera):
The instrument is a CCD pushbroom camera that provides panchromatic images with 5m GSD (Ground Sample Distance) and three band multispectral images with 10 m GSD. The camera has a swath width of 60 km and a side-viewing capability of ±32o. The PanMUX has focal plane adjustment and on-orbit calibration capabilities.
Table 5: Spectral bands of PanMUX camera
IRS (Infrared System) or IRMSS-2 (Infrared Multispectral Scanner-2):
IRS (CAST) is of IRMSS heritage. IRS is an imager with 4 spectral bands. The spatial resolution is halved with regard to IRMSS.
Table 6: Spectral band of the IRS instrument
WFI (Wide-Field Imager):
WFI (also referred to as WFI-2) is an advanced version of the instrument of INPE flown on CBERS-1, and -2, featuring 4 spectral bands with a ground resolution of 64 m at nadir and a ground swath of 866 km. The WFI instrument on CBERS-3 provides also an improved spatial resolution in comparison with the previous WFI sensors on board of the CBERS-1 and CBERS-2 satellites (260 m on previous missions), maintaining, however, its high temporal resolution of 5 days.
This camera will be used for remote sensing of the Earth and it is a imed to work at an altitude of 778 km. The optical system is designed for four spectral bands covering the range of wavelengths from blue to near infrared and its FOV (Field of View) is ±28.63o, which covers 866 km, with a ground resolution of 64 m at nadir. WFI has been developed through a consortium formed by Opto Electrônica S. A. and Equatorial Sistemas. 20)
Table 7: WFI requirements
The optical system development and the performance analyses (including optical system MTF, distortion, polarization sensitivity and stray-light) was executed using ZEMAX® software. Figure 9 shows the refractive optical system of each optical channel with 10 elements. The first element is a window aimed to work as a shield for thermal and radiation protection of the optical channel.
Figure 9: WFI collecting lens system (image credit: INPE)
Figure 10: Illustration of the WFI instrument (image credit: INPE)
DCS (Data Collection System):
Beside the cameras, CBERS 3&4 will have the DCS (Data Collection System) and the SEM (Space Environment Monitor). The DCS is provided by INPE and the SEM is provided by CAST (Chinese Academy of Space Technology).
1) Information provided by Luiz A. Bueno of INPE, Sao José dos Campos, Brazil
2) Space Technology Activities at INPE," UK-Brazil Workshop on Space Science Technology, Oct. 29 - Nov. 1, 2007, Sao José dos Campos, SP, Brazil
3) Antonio Machado e Silva, Frederico Liporace,Marcelo Santos, "CBERS: a Reference in the Brazilian Space Program," JACIE 2007 (Joint Agency Commercial Imagery Evaluation) Workshop, March 20-22, 2007, Fairfax, VA, USA, URL: http://calval.cr.usgs.gov/JACIE_files/JACIE07/Files/112Siilva.pdf
4) Frederico dos Santos Liporace, "CBERS Program Update," 10th Annual JACIE ( Joint Agency Commercial Imagery Evaluation) Workshop, March 29-31, 2011, Boulder CO, USA, URL: http://calval.cr.usgs.gov/JACIE_files/JACIE11/Presentations/WedAM/920_Liporace-JACIE_11.025.pdf
5) Hilcéa Ferreira, "Benefits of data sharing:The CBERS program," Symposium on the Data Sharing Action Plan for GEOSS and the Benefits of Data Sharing, Beijing, China, November 02, 2010, URL: http://www.codata.org/GEOSS/CBERS.pdf
6) José Epiphanio, "CBERS: A partner for controlling deforestation and degradation," REDD Meeting, Feb. 4, 2009, URL: http://www.dpi.inpe.br/REDD_Workshop/Jose_Epiphanio.pdf
8) Frederico Liporace, Leila Fonseca, José Dias de Matos, "Brazilian EO Satellite Program Update," Proceedings of the 11th Annual JACIE (Joint Agency Commercial Imagery Evaluation ) Workshop, Fairfax, Va, USA, April 17-19, 2012,URL: http://calval.cr.usgs.gov/wordpress/wp-content/uploads/Liporace_brazil_eo_update.pdf
9) José Carlos N. Epiphanio, Rozane Fonseca Silva, "Earth Observation in Brazil: CBERS Data Distribution and Impact of Open Data Policy," Proceedings of the 49th Session of UNCOPUOS-STSC (UN Committee on the Peaceful Uses of Outer Space-Scientific and Technical Subcommittee), Vienna, Austria, Feb. 6-17, 2012, URL: http://www.oosa.unvienna.org/pdf/pres/stsc2012/2012ind-04E.pdf
10) Information was provided by Janio Kono of INPE [Instituto de Pesquisas Espaciais (National Institute of Space Research)], Sao José dos Campos, S.P., Brazil
11) "China-Brazil satellite fails to enter orbit," Space Daily, Dec. 09, 2013, URL: http://www.spacedaily.com/reports/China-Brazil_satellite_fails_to_enter_orbit_999.html
12) Rui C. Barbosa, "Brazil's CBERS-3 spacecraft lost following Chinese failure," NASA Spaceflight.com, December 9, 2013, URL: http://www.nasaspaceflight.com/2013/12/chinese-long-march-4b-cbers-3/
14) "China and Brazil to launch CBERS 3 satellite in November 2012," URL: http://www.aerospace-technology.com/news/news128337.html
15) "Brazil, China To Postpone Joint Satellite Launching To 2011," Space Travel, Feb. 16, 2010, URL: http://www.space-travel.com/reports/Brazil_China_To_Postpone_Joint_Satellite_Launching_To_2011_999.html
16) "Brazil and China carry out joint tests on Cbers-3 satellite before its launch this year," March 29, 2011, URL: http://www.macauhub.com.mo/en/2011/03/29/brazil-and-china-carry-out-joint-tests-on-cbers-3-satellite-before-its-launch-this-year/
18) Patrick Blau, "Chinese Long March 4B Rocket successfully launches CBERS-4 Satellite," Spaceflight 101, Dec. 7, 2014, URL: http://www.spaceflight101.com/long-march-4b---cbers-4-launch-updates.html
19) E. G. Carvalho, L. C. N. Scaduto, A. L. Soares, A. G. Santos, S. Evangelista, D. Rebolho, A. R. Santos, A. Castellar, L. A. Azeka, W. M. Souza, R. G. Modugno, R. Cartolano, L. F. Vales, A. T. Malavolta, S. Barbalho, F. S. Santos, L. Candeloro, D. Segoria, M. A. Stefani, J. C. Castro Neto, "The Brazilian Multispectral Camera (MUX) for the China-Brazil Earth Resources Satellite - CBERS-3 abd -4," ICSO 2010 (International Conference on Space Optics), Rhodes Island, Greece, Oct. 4-8, 2010, URL: http://congrex.nl/icso/Papers/TPosters/14_carvalho.pdf
20) L. C. N. Scaduto, E. G. Carvalho, R. G. Modugno, R. Cartolano, S. H. Evangelista, D. Segoria, A. G. Santos, M. A. Stefani, J. C. Castro Neto, "The Brazilian Wide Field Imaging Camera (WFI) for the China-Brazil Earth Resources Satellite - CBERS-3 & 4," ICSO 2010 (International Conference on Space Optics), Rhodes Island, Greece, Oct. 4-8, 2010, URL: http://congrex.nl/icso/Papers/TPosters/53_scaduto2.pdf
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).