Minimize RazakSat

RazakSat / MACSAT

MACSat (Medium-sized Aperture Camera Satellite) is a minisatellite Earth imaging mission, an international cooperative project between ATSB [Astronautic Technology (M) Sdn. Bhd.] of Kuala Lumpur, Malaysia, and SI (Satrec Initiative Co. Ltd.) of Daejeon, Korea. The major project funding is being provided by ATSB. The overall objectives are to demonstrate indigenous spacecraft design and manufacturing competence, to get involved in all aspects of high-resolution image observations and processing in a near equatorial LEO orbit (NeqO) for a number of applications in developing countries, and to develop technology for future missions. The cooperative agreement of ATSB with SI includes on-the-job training of ATSB engineers. The cooperative project started in 2000, a joint engineering team was formed in Nov. 2001. 1)

Note: The new name of MACSAT, namely RazakSat, was coined by Malaysia's Prime Minister Tun Mahathir Mohamad during his visit to ATSB on August 7, 2003 - in honor of the late Tun Abdul Razak Dato' Hussain, Malaysia's second Prime Minister. Hence, MACSat is the engineering name while RazakSat is the official name of the spacecraft.

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Figure 1: The RazakSat spacecraft in orbit (image credit: SI, ASTB)

Spacecraft:

RazakSat is a three-axis stabilized minisatellite of hexagonal shape (size envelope: 1200 mm diameter, 1200 mm height). The RazakSat bus structure, also referred to as the SI-200 bus (of KitSat-3 and STSat-1 heritage), consists of aluminum honeycomb decks, side panels, and solar panels (subsystems are stowed in module boxes). The S/C has a mass budget of 190 kg. Electrical power of ≥ 330 W (EOL) is provided by three deployable solar panels using triple-junction GaAs solar cells. A NiCd battery (3 x 6 Ah capacity) provides power during eclipse phases of the orbit. The PCM (POwer Conditioning Module) regulates +28 V bus power and generates +5 V / ±12 V regulated power from BCR (Battery Charge Regulator) and batteries.

An attitude pointing accuracy of ≤ 0.2º (2σ) is supported by the ADCS (Attitude Determination and Control Subsystem) for all three axes. Attitude is sensed by coarse and fine sun sensors, magnetometers, two star sensors (used during imaging operations), and a gyroscope. The coarse sun sensor is only used for initial attitude acquisition in the post-launch phase. ADCS actuators are two magnetorquers and four sets of reaction wheels (zero momentum stabilization). 2) 3) 4) 5) 6) 7) 8) 9) 10)

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Figure 2: Mechanical configuration of the RazakSat bus (image credit: SI, ATSB)

The spacecraft features in addition a body-pointing capability of up to ±30º in all directions and fiber optic gyros, thus providing a sufficient FOR (Field of Regard) for cross-track event monitoring as well as along-track stereo imaging. The C&DH (Command and Data Handling Subsystem) employs a mixture of star and distributed network architecture connected by serial links to an OBC.

The C&DH subsystem is comprised of one primary OBC, one secondary OBC, four TMCs (Telemetry and Command Modules), and a GPS receiver, providing accurate time and position information in real-time for a number of onboard services. All onboard communication uses the SLIP (Serial Line Internet Protocol) protocol, relaying IP packets over serial line point-to-point connections. The S/C design life is three years. 11)

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Figure 3: Launch configuration of RazakSat (image credit: SI, ASTB)

Spacecraft mass, power

190 kg, ≥ 330 W @ EOL (End of Life)

Spacecraft envelope

- 1200 mm diameter, 1200 mm height
- modular structure
- Passive & Active thermal control

EPS (Electrical Power Subsystem )

- GaAs/Ge solar cells on honeycomb substrate
- NiCd batteries (18 Ah)
- Peak Power Tracking (PPT) & constant current control
- Solar Power : >300 W @ EOL

ADCS (Attitude Determination & Control Subsystem)

- Three-axis stabilization based on four (reaction wheels)
- Pointing Accuracy : < 0.2º (2σ)
- Pointing Knowledge : 1 arcmin (2σ)
- Attitude sensing: CSS (Course Sun Sensor), FSS (Fine Sun Sensor), Magnetometer, Star Senors, Gyroscope

Off-axis imaging capability

Up to ± 30º \[body pointing to extend FOR (Field of Regard)\]

C&DH (Command & Data Handling Subsystem)

- Two on-board computers
- Telemetry and command interface modules
- Analog telemetry channels: up to 90
- Digital telemetry channels: up to 120

TT&C subsystem

- 9.6 kbit/s / 1.2 kbit/s S-band TT&C uplink
- 38.4 kbit/s / 9.6 kbit/s / 1.2 kbit/s S-band TT&C downlink

Image transmission

30 Mbit/s (X-band)

Mission design life

> 3 years

Table 1: Key features of the RazakSat spacecraft

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Figure 4: View of the reaction wheel (left) and the fiber optic gyro (image credit: SI, ASTB)

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Figure 5: View of the magnetometer controller (left) and magnetometer (image credit: SI, ASTB)

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Figure 6: Block diagram of RazakSat (image credit: (image credit: SI, ASTB)

RF communication is provided in S-band (TT&C) at data rates of 1.2, 9.6 and 38.4 kbit/s (use of AX.25 protocol), FSK modulation. In addition, there is an X-band downlink for imagery transmission at 30 Mbit/s using the RazakSat packet frame protocol (QPSK modulation). A single IRPS (Image Receiving and Processing Station) in Kuala Lumpur with a 7 m diameter antenna dish is used to receive the imagery and to control the spacecraft.

Orbit: Non-sun-synchronous NeqO (Near Equatorial LEO) circular orbit, altitude = 685 km (nominal), inclination = 7.5 - 9º. The near-equatorial orbit provides a high degree of temporal resolution (repeat coverage) for Malaysia and other equatorial countries.

Launch: The RazakSat spacecraft was launched on July 14, 2009 (UTC) on a Falcon-1 vehicle of SpaceX (Space Exploration Technologies, El Segundo, CA). Secondary small payloads are: InnoSat of three Malaysian universities (Universiti Sains Malaysia, Universiti Teknologi Malaysia and Universiti Malaysia Perlis), and a CubeSat developed by ATSB. 12)

Note: the launch was initially planned for late 2005 but due to the long delays and the launch failure of Falcon-1 on March 24, 2006 (maiden flight) the launch of RazakSat had to be postponed for a considerable amount time.

The launch site is the “Reagan Test Site” in the Kwajalein Atoll (part of the Republic of the Marshall Islands) in the Western Pacific. The Kwajalein Atoll is made up of nearly 100 coral islands surrounding a 2,300 km2 lagoon. The launch site is located at about 9.99º N latitude and 167.6º E longitude. The Kwajalein Missile Range (KMR) is a US military range and launch site (since World War II) for missiles and, occasionally, Pegasus and Falcon-1 launched small satellites.


Sensor complement: (MAC)

MAC (Medium-sized Aperture Camera):

MAC is a high-resolution multispectral pushbroom imager featuring five linear CCD detector arrays aligned in parallel in its focal plane assembly (FPA). MAC consists of two subsystems: EOS (Electro-Optical Subsystem) and PMS (Payload Management Subsystem). The EOS includes a modified 300 mm aperture Ritchey-Chretien telescope (with two aspheric aluminum mirrors and two spherical correction lenses), the FPA (Focal Plane Assembly), and SPU (Signal Processing Unit). The mirrors are made of low-expansion glass, (Astro-Sital), the lenses are made of BK7 (a quality optical glass of Schott).

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Figure 7: Layout of the MAC telescope optics (image credit: SI)

The telescope's structural elements employ different materials such as Super Invar, Invar, aluminum, stainless steel and titanium to protect the optical elements during launch and to maintain the optical performance during operation. Heaters are implemented to raise the telescope temperature when looking into deep space. The heaters are controlled by the PMS, their average power consumption is about 9 W.

The FPA uses five identical linear CCD detector line arrays on a single PCB (Printed Circuit Board), without any beam splitters or optical butting. Each CCD line array has 8,192 active pixels with a pixel size of 7 µm. SPU is responsible for power provision to the FPA, operation of detectors, processing and formatting of video signals and the transmission of digital image data. 13) 14) 15) 16) 17)

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Figure 8: View of the FPA layout (image credit: ASTB, SI)

The PMS includes TPU (Thermal Power Unit) and MMU (Memory Management Unit). MMU features two MSM (Memory System Module) in cold redundancy, responsible for the overall management of MAC (32 Gbit of data storage). Two different processors are being used for each MCM: TS68EN360 and XPC860. They synchronize the imaging operation to the signal from the RazakSat GPS receiver. MAC calibration: in-orbit radiometric calibration (relative calibration of the FPA) is being performed on a periodic basis requiring the view of special ground targets. 18)

Parameter

Value

Parameter

Value

Spectral channels

- 1 (PAN),
- 4 (MS)

GSD (Ground Sampling Distance)

- 2.5 m (PAN)
- 5.0 m (MS)

IFOV (PAN)

3.65 µrad

IFOV (MS)

7.30 µrad

PAN band (nm)

510-730

Swath width, (FOV)

≥ 20 km, (1.675º)

MS bands (nm)

450-520, 520-600, 630-690, 760-890

MTF @ Nyquist frequency

- PAM×> 8%,

- MS > 15%

SNR

≥ 50

Signal quantization

8 bit

Data storage capacity

32 Gbit

Signal gain

Programmable

Instrument mass
Instrument size

- 42.1 kg
- Optics : 450 mm dia. x 755 mm
- Electronics : 320 x 215 x 162 mm

- Peak power
- Standby power

- 63 W (all heaters on)
- 12.8 W

Table 2: Specification of the MAC imager

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Figure 9: Illustration of the MAC instrument (image credit: SI)

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Figure 10: Illustration of the MAC imager (image credit: SI)

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Figure 11: Block diagram of the MAC instrument (image credit: SI, ASTB)

Applications of MAC imagery:

Panchromatic data:

• Urban development, urban or rural boundary studies infrastructure mapping

• Insurance assessment

• Stereo mapping for forestry use, agriculture application

• Monitoring of shipping routes and coastal monitoring, oil spill detection

• Logistics planning, terrain analysis

• Disaster response

Multispectral data:

• Infrastructure mapping, real-estate planning, land cover and land use

• Assessing hazards & damage

• Geology mapping, structural interpretation, range & water resources

• Coastal monitoring, pollution monitoring, management of marine ecosystem

• Detecting mines & missiles, monitoring refugee movements

• etc.


1) B. J. Kim, S. Park, E. E. Kim, H.-S. Chang, W. Park, J. Seon, M. Ismail, A. Rasheed, A. S. Arshad, “MACSAT - A Mini-Satellite Approach to High Resolution Space Imaging,” Proceedings of the AIAA/USU Conference on Small Satellites, Logan UT, Aug. 11-14, 2003, SSC03-VI-8

2) E. E. Kim, Y.-W. Choi, H. S. Yang, M.-S. Kang,, A. Rasheed, H. Nasir, R. Rosdi, A. H. Hai, I. Ismail, A. S. Arshad, et al., “Development of Engineering Model of Medium-sized Aperture Camera System,” 4th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April, 7-11, 2003

3) Information and spacecraft illustration kindly provided by Ahmad Sabirin Arshad and by Ismail Maszlan of ATSB, Kuala Lumpur, Malaysia

4) http://www.satreci.com/eng/products/products_01.htm

5) H. Lee, “A Low-Cost Attitude Determination and Control Simulation for the Functional Verification of Embedded Control Software,” 2004 KSAS-JSASS Joint Symposium on Aerospace Engineering, Seoul, Korea, Nov. 18-19, 2004

6) N. M. Yusoff, “RazakSAT - Technology Advent in High Resolution Imaging System for Small Satellite,” Proceedings of the 26th ACRS (Asian Conference on Remote Sensing), Hanoi, Vietnam, Nov. 7-11, 2005

7) H, J, Chun, B. J. Kim, H. S. Chang, E. E. Kim, W. K. Park, S. D. Park, A. S. Ashard, “RazakSAT - A High Performance Satellite Waiting for Its Mission in Space,” Proceedings of the 20th Annual AIAA/USU Conference on Small Satellites, Logan, UT, Aug. 14-17, 2006, paper: SSC06-IV-6

8) B. J. Kim, “RazakSat - A Near Equatorial Earth Observation Minisatellite,” May 2007, Daejon, Korea, URL: http://csplab.kaist.ac.kr/lecture/SatRec2007/lecture_notes/EE807_070531.pdf

9) Ahmad Sabirin Arshad, “Small Satellite Technology Developments in Malaysia,” Information Exchange Meeting for Small Satellite Development, 11th Session of the Asia-Pacific Regional Space Agency Forum (APRSAF-11), November 2, 2004, Canberra, Australia, URL: http://www.aprsaf.org/data/p_saprsaf_data/repo_ap11cd/ss_info/6_SS_Malaysia.pdf

10) Norhizan Hamzah, “Malaysian Space Technology: Current Towards Future,” Proceedings of Map Asia, Aug.18-20, 2008, Kuala Lumpur, Malaysia, URL: http://www.gisdevelopment.net/proceedings/mapasia/2008/plenary2/ma08_NorhizamHamzah.pps

11) Byungjin Kim, Salem Al Marri, Norhizam Hamzah, “SI-200 Mini-Satellite Platform for Earth Observation Missions,” Proceedings of the 60th IAC (International Astronautical Congress), Daejeon, Korea, Oct. 12-16, 2009, IAC-09.B1.1.3

12) “SpaceX Successfully Launches Satellite Into Earth Orbit,” July14, 2009, Space Travel, URL: http://www.space-travel.com/reports/SpaceX_Successfully_Launches_Satellite_Into_Earth_Orbit_999.html

13) Ee-Eul Kim, Y.-W. Choi, Eugene D. Kim, S.-K. Jeong, M.-S. Kang, H. Md. Nasir , Md. Rushdan Md. Rosdi, Asma Hani Ad. Hai, “Integration and Testing of a High-Resolution Camera for Small Satellites,” RAST 2005 (Recent Advances in Space Technology), Istanbul, Turkey, June 9-11, 2005

14) Y.-W. Choi, E. D. Kim, M.-S. Kang, S.-K. Jeong, S.-U. Yang, J. Kim, Ee-Eul Kim, S.-D. Park, H.-S. Yang, M. Ismail, A. S. Arshad, “Pre-Flight Performance Characterization of RazakSAT Medium-sized Aperture Camera (MAC),” Proceedings of SPIE Conference `Optics & Photonics 2005,' Vol. 5882, San Diego, CA, USA, July 31-Aug. 4, 2005

15) E. D. Kim, Y.-W. Choi, M.-S. Kang, E.-E. Kim, H.-S. Yang, A. A. Rasheed, A. S. Arshad, “Medium-sized Aperture Camera for Earth Observation,” Proceedings of the 5th International Conference on Space Optics, March 30 - April 2, 2004, Toulouse, France

16) Ee-Eul Kim, Young-Wan Choi, Ho Soon Yang, Myung-Seok Kang, Seong-Keun Jeong, Seung-Uk Yang, Jong-Un Kim, “Development of Engineering Model of Medium-Sized Aperture Camera System,” 4th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 7-11, 2003, IAA-B4-0701, URL: http://www.dlr.de/iaa.symp/Portaldata/49/Resources/dokumente/archiv4/IAA-B4-0701.pdf

17) Ee-Eul Kim, Young-Wan Choi, Myung-Seok Kang, Seong-Keun Jeong, “Development of Earth Observation Sensors for Small Satellites in SaTReC Initiative,” 5th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 4-8, 2005, URL: http://www.dlr.de/iaa.symp/Portaldata/49/Resources/dokumente/archiv5/0705P_Ee-EulKim.pdf

18) Ng Su Wai, Adhwa Amir Tan, Jessica Wong Soo Mee, Maszlan Ismail, Mustafa Din Subari, “Preflight Radiometric Calibration of RazakSAT,” Proceedings of the 4th International Conference on Recent Advances in Space Technologies (RAST 2009), Istanbul, Turkey, June 11-13, 2009


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.