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FORMOSAT-5 Program Description Satellite Payloads Key Components


Program Description

FORMOSAT-5 program consists of Space, Ground, and Launch segments. In addition to the Falcon 9 launch vehicle, the Space segment is made up by Spacecraft Bus, Remote Sensing Instrument (RSI), and Scientific Instrument; Ground segment includes S-Band TT&C ground station, X-band Antenna System (XAS), Remote TT&C Station (RTS), Satellite Operations and Control Center (SOCC), and Image Processing Center (IPC). FOSMOSAT-5 program system configuration is shown below:


FORMOSAT-5 is the first space program that Taiwan Space Agency (TASA) takes full responsibility for the complete satellite system engineering design including payload(s). Mission of the program is shown as follows:

  • To build up Taiwan's self-reliant space technology on the remote sensing payload and spacecraft bus,
  • To develop the key components of the EO-type remote sensing instrument and spacecraft bus by integrating the domestic resources,
  • To continue to serve the global imagery users' community of FORMOSAT-2, and
  • To promote the space science experiment & research.

FORMOSAT-5 operates in a sun synchronous orbit at 720-km altitude with 98.28-degree inclination angle. Similar to FORMOSAT-2, an optical Remote Sensing Instrument (RSI), which provides 2-m resolution panchromatic (PAN, black & white) and 4-m resolution multi-spectral (MS, color) images, is the primary payload on FORMOSAT-5. The primary payload consists of one PAN band with 12,000 pixels and four MS bands with 6000 pixels each. In addition, a secondary payload, a scientific instrument, i.e., Advanced Ionospheric Probe (AIP), was developed by The National Central University (NCU). FORMOSAT-5 was launched by SpaceX Falcon 9 rocket on August 25, 2017 and both payloads are operating normally.




The basic characteristics of FORMOSAT-5 are similar to FORMOSAT-2 and shown below.

Characteristic Description
Category Remote sensing satellite
Weight About 450 kg (including payload and fuel)
Dimension Hexagonal, 2.8 m height, 1.6 m OD
Orbit altitude 720 km, sun-synchronous
Repeatability Every two days
Image Down Link Rate 150 Mbits/sec
Field of Regard 45° in pitch and roll axis
Period about 99 minutes
Mission Life 5 years
Attitude Pointing Accuracy ≦2 km in nadir direction for RSI imaging
Attitude Pointing Knowledge ≦ 390 m without GCP
Agility ≧24°/60 sec (Roll); ≧24°/60 sec (Pitch); ≧7°/60 sec (Yaw)
Ground Sampling Distance (GSD) 2m @ nadir (PAN), 4m @ nadir (Blue, Green, Red, Infrared)
Swath Width 24 km @ nadir
Contrast Transfer Function (CTF) ≧ 0.1(PAN)
≧ 0.2 (Blue, Green, Red)
≧ 0.16 (Infrared)
Signal-to-Noise Ratio (SNR) ≧83 (PAN); ≧95 (Blue); ≧95 (Green); ≧100 (Red);
≧100 (Infrared)
RSI Duty Cycle ≧8% per orbit
Image Data Storage ≧80 Gbits



FORMOSAT-5 carries an optical payload and a science payload to execute remote sensing mission and perform science research, respectively.

Optical Remote Sensing Payload

The Remote Sensing Instrument (RSI) is composed of Telescope and Electrical Unit (EU). The Telescope consists of Optics, Structure Module (SM) and CMOS Focal Plane Assembly (FPA). The specifications of RSI are listed as follows.

Items Specifications
Resolution 2m @ nadir (PAN), 4m @ nadir (Blue, Green, Red, Infrared)
Swath 24 km
Bands PAN, Blue, Green, Red, Infrared
Digitization 12 Bits
Storage ≧80 Gbits
Duty Cycle 8% per orbit
Orbit 720 km, Sun-synchronous
Contrast Transfer Function (CTF) ≧ 0.1(PAN)
≧ 0.2(Blue, Green, Red)
≧ 0.16 (Infrared)
Signal-to-Noise Ratio (SNR) ≧83 (Pan)
≧95 (Blue); ≧95 (Green); ≧100 (Red);
≧100 (Infrared)

Remote Sensing Instrument (RSI), has been jointly developed by TASA, NARLabs research centers (including ITRC and CIC), as well domestic organizations of NCSIST, AIDC, CMOS Sensor Inc., and Camels Vision Technologies in order to achieve the self-reliant development of remote sensing instruments and related key components and establish the technical energy of the self-made high-resolution optical payload.

Science payload

Advanced Ionospheric Probe (AIP) is provided by Institute of Space Science, National Central University (NCU) for the FORMOSAT-5 satellite as a science payload. The AIP is an all-in-one plasma sensor to measure ionospheric plasma concentrations, velocities, and temperatures over a wide range of spatial scales. The transient and long-term variations of ionospheric plasma can be monitored as seismic precursors associated with earthquakes.

The anticipated data specification of the geophysical parameters measured by the AIP is shown in the following table:

Geophysical parameters Range Sensitivity Accuracy
Ion composition 3 % ~ 100 % 1 % 10 %
Ion concentration 4×102 ~ 1.2×107 cm-3 1 % 10 %
Ion velocity ±3.2 km/s (cross-track)
±5.0 km/s (ram)
±10 m/s
±100 m/s
±50 m/s
±200 m/s
Ion temperature 500 ~ 10,000 K ±50 K ±200 K

Key Components

Five components have been jointly developed by TASA and the domestic research organizations or outsourced to the domestic suppliers under FORMOSAT-5 Program. They are Command and Data Management Unit (CDMU), Power Control and Distribution Unit (PCDU), RSI Electronic Unit (RSI EU), CMOS-type Focal Plane Assembly (CMOS FPA), and Flight Software (FSW). All components have been delivered and integrated on the satellite.

Power Control and Distribution Unit (PCDU)

Space-grade PCDU is developed by TASA and NCSIST. TASA defined the component requirements based on system requirements. NCSIST performed circuit design and PCB manufacturing. TASA and NCSIST executed the functional testing and environmental testing to qualify the PCDU for space application. This is the first critical component integrated to FORMOSAT-5 satellite to provide all power supply required for all components and subsystems.

The main characteristics of PCDU include to deploy solar panels, to provide satellite electrical power, to maintain battery power in the range of 21-35V for heaters and CDMU, to output power at +5.2V+/-0.26V@50W and +/-15V+/-0.75V@30W for electrical components, to provide satellite safety and recovery capability during emergency, and to incorporate more than 17 circuit modules, more than 100 electrical power channels and 38 Solar power control paths.

PCDU is composed of the following PCBs:

Command and Data Management Unit (CDMU, or On-Board Computer, OBC)

CDMU can control attitude, maintain orbit, process health data, execute command, handle remote sensing and science data, regulate power, manage on-board time and recover from failure. It can survive under the extreme radiation, high-temperature and low-temperature space environment to achieve 0.94 reliability for orbit operation over 5 years and satisfy TASA space-grade on-board computer requirements.

CDMU flight model has passed severe validation of space environmental tests. It has been integrated on the FORMOSAT-5 satellite to validate functions of the other components and subsystems (except RSI). TASA has performed the subsystem specification development, circuit design, digital circuit simulation, FPGA firmware development and PCB circuit layout in house while CSIST supported the PCB manufacturing and structure fabrication. Finally, TASA and CSIST performed the space environment testing together, including EEE parts life tests, radiation qualification, components thermal vacuum testing, vibration testing, chock testing and EMC testing to qualify the CDMU for space applications.

The circuit design is based on the several guidelines, i.e. module, back-up and high reliability design, safe mode management on satellite failure, large operational margin, and noise inhabitation capabilities. Main characteristics of CDMU includes 20 MIPS operation capability with fault tolerant LEON3 CPU, 25 Mbps high data communication, 8Mbps down link rate,128kbps up link rate, on-board up to 6 science payloads with 3Gbits science data storage capacity and in-orbit FSW patch capability.

PCDU is composed of the following PCBs:

RSI Electronic Unit (RSI EU)

Space-grade RSI EU is developed by TASA, Camels Vision Technologies and CSIST. TASA is responsible to system design, and space qualified EEE parts procurement & qualification. Camels Vision Technologies is responsible to the SSR detailed design, SSR Electrical Ground Support Equipment and Elegant Bread Boards. NCSIST is responsible to the detailed design, fabrication, assembly, function tests and delivery of the RSI EU.

RSI EU is a control and data processing unit of RSI payload to ingest the CMOS FPA image data at 480 Mbps for PAN or MS channel, to compress data in wavelet transform, to store up to 128Gbits SSR, and to output at 150Mbps with X-band downlink. Other characteristics include file management, isolation of bad memory and power saving mode at idle status. The flight model of RSI EU has been completed the final environmental tests and delivered. It has been installed on the satellite and passed the comprehensive test.

Outlook and inside of RSI EU are as follows.

RSI is composed of the following PCBs:

CMOS-type Focal Plane Assembly(CMOS FPA)

CMOS FPA is developed by COMOS Sensor Inc. (CSI) while TASA and CIC validate the performances of the component. It senses five spectral bands including panchromatic, blue, green, red, and near infrared. On flying over the earth surface, the sequential data of linear sensors are accumulated, stored and down-linked to the ground. The data are processed as an image which shows the stripe of earth surface in 24 km wide with 4 meter multi-spectral and 2 meter panchromatic resolutions.

Outlook of CMOS Type FPA is ahown below.

CMOS FPA is an innovative CMOS image sensing device with the core sensor CMOS IC. The IC is a single chip with size of 120mm × 23.2 mm stitching four system-on-chips (SoC). Each SoC is composed of five image sensing lines. The MS image sensing lines consisting of 6,000 pieces of 20μm pixels while the PAN image sensing line consisting of 12,000 pieces of 10μm pixels. The chip has passed radiation survivability and high energy particle survivability tests. The best sensor IC has been selected for the flight CMOS FPA. The flight model of CMOS FPA has been completed the final environmental tests and delivered. It has been installed on the satellite and passed the comprehensive test.

The IC chip without and with package are shown below.