© Electronic Systems Laboratory 1999
by Buchan Milne
WWW:sunsat.ee.sun.ac.za
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These publications date from the beginning of the project and can be retrieved via www, ftp or email depending on its availability. Send email to sunsat@firga.sun.ac.za for papers not available on ftp or www.
This paper describes the science payloads and experiments of the SUNSAT microsatellite which is to be launched in 1997. A very modular satellite mechanical structure has enabled the addition of addtional experiments at a late stage of the program. The design and performance measurements of the engineering and technology payloads (a 15 m resolution imager and an accurate ADCS system) are reported. The science payloads including an accurate GPS receiver, laser retroreflectors, a magnetometer and school experiments is described, indicating that a very complex microsatellite was developed as the first venture into space by a South African university.
This paper describes the total system configuration, flight model components and pre-flight tests of the SUNSAT microsatellite which is to be launched in 1997. A very modular satellite mechanical structure has been constructed and environmentally tested. The performance measurements of the communication payloads (VHF, UHF, S and L band communications systems) are reported. The operation of the attitude determination and control system and other bus systems is briefly described, indicating that a very complex microsatellite was developed as the first venture into space by a South African university. A major spin-off from the programme is an established electronics systems laboratory where students can gain multidisciplinary engineering experience on a challenging project.
The SUNSAT Micro Satellite Program:
Technical performance and limits of imaging micro satellites
Sias Mostert, Thys Cronje and Francois du Plessis
This paper examines the technical performance of the SUNSAT micro satellite bus, which is supporting the high resolution imager (HRI) payload on the micro satellite which is scheduled for launch in December 1998. A number of existing remote sensing satellites are investigated to determine some key parameters by which a micro satellite remote sensing mission should be evaluated. The SUNSAT 1 HRI instrument is then evaluated in this context and future possible missions suggested which is suitable for micro satellite missions.
Ground Voltage and Current Cancellation
by Co-axial Cable.
Garth W. Milne, 1998 South
African Symposium on Antennas and Propagation/Microwave Theory and
Techniques.
The most frequent use of co-axial cable is to prevent electrical noise entering signals being passed between equipment. Ground voltage differences are common and add in series with the signal voltage. The screen of co-axial cable grounded at both ends induces a voltage in the inner conductor which cancels higher frequency ground voltage differences, starting from a break point of typically 2kHz. The signal current also produces a flux external to the screen, which induces a loop current through the screen and earth path which opposes the earth current. Signal currents above 2kHz thus increasingly return through the screen, in spite of a lower impedance ground path. An equivalent circuit explains the phenomena and the extreme sensitivity of co-ax and oscilloscope probes to short pigtail leads. Experiments are described and data presented which justify the theory. Remarks are made on end connections, cable trays, and feeding power lines via co-ax.
EMC and RFI problems and solutions on the SUNSAT Micro-satellite, GW Milne, JJ Roux, E Jansen, JA Koekemoer and PPA Kotzè. 1998 South African Symposium on Antennas and Propagation/Microwave Theory and Techniques.
Fault tolerance in Sunsat satellite. Pieter Bakkes and Sias Mostert. AIAA Computing in Aerospace 9 Conference, San Diego, CA, USA, 1993.
Development of a reliable telecommand system for microsatellite applications. Tielman F. Botha and Dave M. Weber. AIAA Computing in Aerospace 9 Conference, San Diego, CA, USA, 1993.
SUNSAT Imaging , Present and Future. Du Plessis Francios E and Milne Garth W. IEEE Smallsat Conference, October 1994.
Development of the SUNSAT Groundstation. Jordaan~Louis en~Wilhelm~James. Spacecon 94, 11 September 1994.
Sunsat, Stellenbosch University and SA-AMSAT Remote Sensing and Packet Communications Microsatellite. Garth Milne et al. Proceedings of the Conference on Small Satellites 7, Utah, USA, 1993.
Use of Helical Resonators for High-selectivity filter's on SUNSAT's 2m up/down links. Milne~GW Jansen~E. SA AMSAT Spacecon Conference, Johannesburg, August 1993.
SUNSAT microsatellite communication payload. Roux JJ. SA AMSAT Spacecon 94, September 1994.