SunSpace (www.sunspace.co.za) is a commercial company that was set up in the wake of the successful launch by the University of Stellenbosch of the SunSat low-earth orbiting satellite. The company was established in 1999 and operates from a science park in the proximity of Stellenbosch University.
The connection with SunSat is obvious, as almost half of the board members were involved with this project. The managing director is Bart Cilliers and the board includes Professors from the University, including Gideon de Wet and Garth Milne.
The development of SunSat was hampered by financial constraints but local companies in the electronics industry contributed generously. CSIR for example, provided the electro-optical payload while the magnetometer was from Hermanus Magnetic Observatory. A complete system was also supplied to Korea for a similar experiment called 'Kitsat'.
SunSpace decided to capitalise on its unique (and proven) subsystems and manufacture these to sell to the creators of other micro-satellites. The sub-systems and payloads offered include the imager, a deployable boom, the magnetometer, reaction wheels, the Star Tracker, the VHF/UHF communications system and the realtime view finder. It is useful to look at some of these in more detail.
The multispectral scanner payload ground resolution varies from 4 m to 10 m with the swathe covered varying from 48 to 100 km. In panchromatic mode, the resolution varies from 2 to 5 m at an altitude of 600 km.
A new generation autonomous Star Tracker was built on the experience from previous satellite missions. The sensor is used for accurate 3-axis attitude information in realtime, and provides unbeatable performance for small satellites. The Star Tracker uses a sensitive matrix CCD sensor and has a single star position accuracy of 22 arc seconds, with a boresight pointing accuracy of 15 arc seconds. It can identify all stars with magnitudes greater than about six.
The SunSpace reaction wheels provide small satellites with 3-axis control torques and 3-axis momentum exchange capability. Integration of reaction wheels and gyroscopes enables 3-axis control of the spacecraft's inertial rates. Each reaction wheel has built-in electronics for controlling both the wheel and the gyroscope. The new generation reaction wheels and gyroscopes have been flight qualified.
Earth observation satellites are normally pre-programmed to image specific target areas on Earth. Cloud cover and off-pointing errors often mean that the selected targets are not recorded. These problems can be solved (if the satellite ground station is within the footprint) by using an on-board TV camera (the View Finder) with narrow and wide fields of view. This provides feedback to the ground station which can then steer the main imager towards the required target area.
The current SunSpace magnetometer is based on the flight heritage of two satellites, SunSat and Safir-II. It consists of a 3-axis fluxgate sensor with an analog processing board, the magnetometer normally mounted on an extended arm. The output of the magnetometer is three analog signals with a scale factor of 12 nT/mV, the measurement range being ±60 000 nT ±2%.
In terms of these sub-systems, SunSpace provided Korea with the multispectral scanner for the Kitsat satellite, a Star Camera and deployable boom for Australia's FesSat-1 micro satellite that was launched in 2002. Sun Space also supplied Germany with a 3-axis fluxgate magnetometer for use in its Safir-II satellite.
In regard to satellites, SunSpace has developed a range of these, including MxSat, MMSat, SMISat, Sunspace-180, and three medium satellites. A satellite development toolkit is also available that allows new entrants to build their own micro-satellite.
The SunSpace-180 is an interesting example as it is based on the flight heritage of SunSat and the Greensat imager (Greensat being South Africa's satellite that was part of a programme to launch military systems. The complete launch site and rockets etc, were destroyed under pressure from America). Two Greensat satellites complete with imager, are intact, as well as is the special Houwteq premises. The 180 offers ground resolutions of 5 m colour and 2,5 m panchromatic at an altitude of 600 km. The mass of the payload can vary between 120 kg and 180 kg depending on the final configuration. The dimensions of the satellite are 720 x 685 x 685 mm.
SunSpace is also involved in a number of other international satellite programmes, including the multisensor micro satellite imager (MSMI) in collaboration with Belgium with the NRF providing local financial support. One of the longer term objectives of this programme is the use of South African satellites in an African/international constellation and growing the export of small satellite platforms and payloads to international clients. The MSMI will be equally suitable as an auxiliary payload on larger satellites.
Late in 2005, government announced its intention to develop space science within the country and announced a project to develop and launch the country's second satellite. The satellite will operate in low-earth-observation (LEO) mode and will be able to take high-resolution pictures of any area in South Africa. The programme, which will receive government funding of R26 million, will be carried out by SunSpace in collaboration with the University of Stellenbosch. The ZA-002 programme is capable of being carried out by South Africa and in the longer term, the satellites could be deployed as a constellation of observation platforms for Africa. The ZA-002 will be used for a variety of applications, ranging from telecommunication to the monitoring of water supplies and crop development, and over the longer time frame, be able to view environmental degradation.
With a staff in excess of 40 people, mostly highly skilled engineers and technicians, the company is now approaching critical mass and hopefully will convey to the world that South Africa is still in the satellite business.
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