This is the first report about the development of INMARSAT-C Satellite communication terminal. We analyze the existing Inmarsat-C terminal and examine each rules(IMO rule, domestic rules) about terminal. With that result, we design the basic hardware and software of terminal. This report consists of ; 1) the contents of the overall of operating situation and resources of INMARSAT-C system as like operation of communication system, communication channels and services 2) the contents of the specification of Inmarsat-C terminal hardware and software and the rules of IMO and Type approval 3) the design of basic hardware and reserch of signal modulation/demodulation using Viterbi algorithm 4) the design of software algorithms and functions focused in korean situations.