GNSS Sky Visibility Planning and Dilution of Precision Analysis for EOS Ground Station Selection for Nigeria Space Programme

The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nigeria and other parts of the globe, similar to the Indian Remote Sensing (IRS) model will enhance global telecommand, precise EOS tracking, data transmission, and distribution of NigeriaSat data, which will enhance global-scale data awareness, usage and higher financial returns for Nigeria. This study, therefore, attempts the application of Global Navigation Satellite System (GNSS) sky visibility planning and dilution of precision analysis technique to select the optimal location for EOS ground station(s) in Nigeria. The Nigerian Geodetic Network (NigNet) GNSS Continuously Operating Reference Stations (CORS) RINEX data of February 2012 and Trimble Total Control (TTC) software were used for the determinations of the baselines and positions of the 11 available CORS. The technique of GNSS sky visibility planning and dilution of precision (DOP) was adopted because signals from satellites behave in a similar pattern in the atmosphere, so poor visibility in GNSS signals in a particular observation window translates relatively to poor orbit definition signal for an EOS. Based on Jon's rating of DOP values [1= ideal; 2-3 = excellent; 4-6 =good; 7-8= moderate; 9-20=fair; 21-50= poor)], the DOP values for the stations across Nigeria can be adjudged to range between excellent and good for ground receiving stations. However, the overall results showed that GEMB on ellipsoidal heights of 1795.7857m has the most suitable DOPs and sky visibility plan for ground receiving sites followed by CGG Toro (916.7853m) and RAMPOLY Maiduguri (702m). The sky visibility analysis showed the availability of an average of 9 GPS and 2 GLONASS constellation satellites to receivers at elevation angles of 10°-15° between 6:00hrs and 24:00hrs daily across Nigeria. The approach of OS ground receiving station suitability analysts demonstrated in this study is recommended for the Nigerian.