The MARISAT-to-ship

-band signals used in maritime mobile satellite communications service are degraded by fading and scintillation at low elevation angles. These degradations are attributed to multipath effects arising from ionospheric, tropospheric, and/or sea surface diffractions. To characterize such degradations, measurements were made at the Southbury earth station and onboard the S.S. Mobil Aero while the ship was en route from Norfolk, VA, to Texas City, TX. Measurements include monitoring the carrier-to-noise ratio (

) of time-division multiplex/time-division multiple access (TDM/TDMA) voice carriers and measuring the bit error rate (BER) of 2400/1200 bit/s digital data transmissions through a voice channel. Results indicated that both

and BER are severely degraded at elevation angles below 5° due to propagation anomalies. Information useful for design considerations of future maritime communications systems is summarized.