Abstract

<span>Satellite link design, link margin and services at lower bands of satellite spectrum has been facing the challenges of meeting the demands for higher bandwidth requirements. Satellite operators and service providers are been compelled to migrate to the use of higher frequencies above 10 GHz. These higher frequencies were discovered to be vulnerable to atmospheric degradation creating the challenge of service availability especially for tropical rain zones with higher rainfall intensities and longer rain event durations. This study strive to evaluate the profile of rainfall and the monthly and annual variability to improve the design parameters of satellite propagation. Two yeas rainfall measurement campaign was conducted in Abuja at Nigcomsat-1R ground station with a view to understanding the characteristics of Abuja rain. The location of the site is on lat. 9.06o N and lon. 7.48o E. Tipping bucket rain gauge was used for point rain rate and 1.8 m VSAT antenna was installed to monitor the rain induced attenuation on satellite broadband signal. The results shows a huge variability between month to month as well as annual average between 2016 and 2017. The performance of broadband satellite service was found to largely to depend on the quality of the carrier power above the system noise rather than bandwidth capacity or the receive signal level while higher attenuations are associated with higher rain intensities and the slant path effects.</span>

<span lang="EN-GB">The utilisation of higher frequency bands above 10 GHz by the satellite industries to provide the bandwidth (BW) required for broadband multimedia services, video conferencing, direct-to-home TV programmes and IP data requires the understanding of atmospheric losses and good link planning for satellite-to-earth links. The trade-off between the service availability, data rate and BW determine the type of modulation scheme and error corrections to be employed. These services also depend on the link performance under adverse atmospheric conditions, especially rain-induced attenuation. In this research, study measurements were conducted on space-to-earth satellite links using the beacon narrowband and broadband IP carrier signals of a Nigcomsat-1R satellite operating at 42.5°E. A VSAT receiving terminal at a latitude of 7.4°N, longitude of 9.04°E and altitude of 334 m above sea level was utilised to quantify the rain-induced attenuation of both the beacon and broadband signals during rain events. The measurements were then compared with the link performance under clear sky conditions. The performance revealed that, when compared with the broadband signal, the induced rain attenuation on beacon signal presented a disparity in the responses, resulting in significant variations of 10.14 dB in the carrier-to-noise ratio (C/N) and 17.42 dB in the received signal level at a Ku-band frequency of 12.518 GHz. These observations were also compared with the Crane global rain map and ITU-R P.618-12. Both models disagreed with the measurement values for Abuja, Nigeria.</span>

Images of the earth’s surface captured by radiometric detectors on air-borne (satellite) sensors were employed in geologic reconnaissance survey. They were used to study rock units, pattern and trends of geologic structures on the surface in 2D. Multispectral resolution Landsat-8 Operational Land Imager (Landsat-8 OLI), have nine spectral band with spatial resolution of 30 m (bands 1 to 7, and 9) and 15 m for band 8. The aim of this research is to discriminate lithological units/complexes and delineate fractures (lineaments), hence, only bands 2 to 7 were used for this study. This technique was used to discriminate existing lithological units and identify major and minor extensive geologic structures within the study area. These selected bands were selected, grouped and combined (Band Combination (BC)) and processed for interpretation using applicable Software Packages. Hence, for each procedure and maximum clarity in the output of results, three bands were combined for each analytical process. Bands 4,3,2; 6,5,4; 7,5,3 were combined for Natural Colour Composite (NCC), False Colour Composite (FCC) and Principle Component Analysis (PCA) respectively. The results revealed two distinct lithological Complexes due to their similarities in appearance and differences in mineralogical compositions. SRTM-DEM was used to highlight the topography showing the lowest relief at the northeast and the highest relief at the south east. More so, elongated ridges of intermediate-high reliefs were exposed at the southern part of the study area trending NW-SE. A lineament map and Rose plot shows dominant trend of fractures to be NNW-SSE, NW-SE, N-S,

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