is a microsatellite developed and built by the NTU(Nanyang Technological University
Nanyang Technological University is one of the two largest public universities in Singapore with the biggest campus in Singapore and the world's largest engineering college. Its lush 200-hectare Yunnan Garden campus was the Youth Olympic Village of the world's first 2010 Summer Youth Olympics in...
) in collaboration with Defence Science Organisation
Defence Science Organisation is the defence research agency of Singapore. It was setup in 1972 by the late Dr Goh Keng Swee to conduct research on future warfare. Three engineers were handpicked by Dr Goh to form the Electronics Test Centre . With the progressive expansion of its R&D scope, the...
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
The objective of the X-SAT mission is to demonstrate technology in support of high-resolution imaging capabilities and to analyze and implement onboard parallel processing algorithms, thereby demonstrating improved mission achievements for generally downlink-limited small satellite imaging missions.
The purpose of X-Sat is :
- Earth observation and imaging for environmental applications such as monitoring of forest fires and ocean red tides, with a 10 m resolution multispectral (three spectral bands in the visible and near infrared spectrum) instrument as a primary payload.
- Satellite-based data acquisition/distribution and messaging using mobile terminals.
The satellite carries three payloads, namely the imaging system IRIS, the communication platform ADAM, and the parallel computer PPU for image processing. Further research experiments using the communication and navigation instruments on-board will be conducted to investigate atmospheric question and communication related issues.
The camera is built by SatReCi and designed as a push-broom scanner with three individual scan lines in the green (520 nm – 600 nm), red (630 nm – 690 nm), and near-infrared (760 nm – 890 nm) wavelength range. The three linear detectors consists each of
5000 active elements, which were all manufactured on the same wafer and subsequently
coated with different interference filters to select the appropriate spectral characteristic.
The design provides a high degree of band-to-band alignment, i.e. 0.1 pixels. The provided spatial resolution will be 10 m for the nominal altitude of 685 km, thus enabling a
swath width of 50 km. The optics were designed as a variant of the Mangin telescope
with a primary and secondary mirror as well as two correction lenses and has an aperture
diameter of 120 mm. Internally the IRIS is equipped with a redundant signal processingand control module, which pre-processes the image data for the storage in the 8 Gbit
large memory module. Note that this bulk storage module is entirely under the control of
the IRIS and independent from the earlier mentioned RAM-Disk.
The instrument is a two-way low data rate communication link using UHF  to acquire
oceanographic data, e.g. temperature, salinity, and water pressure from autonomous,
operating buoys that drift in the open sea. Further applications are in aeronautics, search
and rescue missions as well as in land-based data collection. For the downlink of the
gathered information to the individual ground receiving station the satellite’s S-band
transmitter is utilised.
Parallel Processing Unit
The third payload is the PPU that will provide processing of acquired imagery on a parallel architecture. The objective is to increase the mission’s benefits by enabling unsupervised data processing in space and therefore easing the bottleneck of transmission to
the ground receiving station. The computer consists of four fully connected radiationhardened Xilinx Virtex FPGAs with each of it hosting four processing nodes (PN). In
addition, spare processor nodes are kept available in case a regular PN will become inoperative due to the environmental conditions. Every node comprises a StrongArm
processor that is clocked at 100 MHz and 64 MByte of local memory (SDRAM). The
choice for this processor was determined through its 0.35 mm manufacturing process,
i.e. the relatively small sensitivity to radiation, and the provided performance energy
ratio of 115 MIPS / 200 mW.