A low elevation angle propagation measurement of 1.5-GHz satellite signals in the Gulf of Mexico

The current maritime L-band (1.5-GHz) mobile satellite communications service (MARISAT) is not available for communications paths below
10\deg
elevation angles because fading and scintillation at low elevation angles introduce signal degradations. These are attributable to scattering, diffraction, and multipath effects arising from ionospheric, tropospheric, and/or sea surface irregularities. To obtain a better understanding of the above-mentioned signal degradations, propagation measurements were made in the Gulf of Mexico with a MARISAT terminal on board the SS Mobil Aero for elevation angles from ship to satellite in the
15\deg
to
0\deg
range. Results indicated that mean signal strength was severely attenuated with remarkably increased fluctuations at elevation angles below
5\deg
. Characterizations of signal strength and peak-to-peak fluctuations of the L-band signal as a function of elevation angles are presented.