COMMUNICATIONS SUPPORT FOR LUNAR MISSIONS USING THE TDRS-II SYSTEM

The United States National Aeronautics and Space Administration's (NAS A's) Office of Exploration (OEXP) is evaluating potential scenarios fo r robotic and piloted missions to the Moon. This work is part of the O EXP effort to establish a human exploration program during the next ce ntury. For more than 4 years, NASA's Goddard Space Flight Center (GSFC ) has been performing systems engineering analysis for lunar explorati on scenarios. The GSFC studies have focused primarily on lunar communi cations, data systems, and operations. Two basic Earth-region communic ations architectures have been identified and seriously considered: gr ound terminal architectures, such as the Deep Space Network, and geosy nchronous relay satellite architectures, such as the Tracking and Data Relay Satellite II (TDRS II). The TDRS II, as currently specified, is a viable architecture and low-cost option - at least for early (1998 - 2005) lunar mission phases. Development of TDRS II, designed as a fo llow-on to the currently operating Tracking and Data Relay Satellite S ystem (TDRSS), is scheduled to begin soon. A major benefit of the TDRS II option is that the system as planned can provide substantial suppo rt to early lunar missions without modification.