The Mobile User Objective System (MUOS) is designed to replace UHF SATCOM with enhanced capacity and performance, modern crypto and modern protocols. The MUOS waveform is being ported to a number of software defined radios (SDRs) that will soon be fielded and capable of utilizing the MUOS network of geosynchronous satellites and ground transport. Once these radios are in place, the process of moving existing and adding new applicationsover to MUOS will need to begin.To support the transition of legacy applications to MUOS, W5 proposes to build an off-satellite MUOS application test bed.The test bed will utilize W5's Mighty MUOOS simulator and expand its capabilities to support analysis and validation of tactical data link (TDL) data over MUOS.