The Army has a well established requirement for satellite communications (SATCOM) OTM, in order to support the needed level of near real-time, tactically-relevant information on a non-contiguous battlefield. The US Army CERDEC Space and Terrestrial Communications Directorate is doing relevant research and development in order to provide the best SATCOM OTM technology for transition to the Warfighter. Systems being developed support multi-band operation with both MILSATCOM and commercial frequency bands at the data rates required within the stringent confines of available size, weight, power and production cost. The technologies employed in order to meet these requirements include mechanical, phased array, and hybrid antenna architectures. The Army development community needs a way to independently and rigorously test these and other SATCOM OTM antenna systems. The US Army CERDEC SATCOM OTM Lab located at Aberdeen Proving Ground, MD will meet this need. The SATCOM OTM Lab will support a multitude of development and testing capabilities, but will focus on measuring acquisition and tracking performance. The lab will utilize two methods to comprehensively support OTM testing. First, test vehicles will be instrumented and driven over applicable cross country road courses at APG while operating over active satellites. Second, a motion simulator will be utilized to implement testing over live satellites and in a laboratory environment to simulate operation over the full range of elevation angles. The technical concepts behind this approach to achieve a comprehensive technical capability will be discussed. Technical challenges and trades being conducted will also be addressed. Applicability to Joint certification for operation over MILSATCOM satellites will be included.