Carina Schumann, University of the Witwatersrand, Johannesburg, South Africa, Hugh G.P. Hunt, University of the Witwatersrand, School of Electrical and Information Engineering, Johannesburg, South Africa, Marcelo M Saba, INPE National Institute for Space Research, S. Jose Dos Campos, Brazil, Susan Jane Webb, Univ Witwatersrand, Johannesburg, South Africa and Tom Warner, Z T Research, Rapid City, SD, United States