ON OBTAIE?NG LUNAR MISSlON LAUNCH OPPORTUNITIES

A general procedure for predicting launch opportunities for the RAE-B lunar orbiter mission is presented. It is shown that knowledge of the Earth-Moon distance and l w r phase and declination are sufficient to determine launch periods consistent with present mission constraints and to approximately predict launch, transfer, and arrival parameters such as park orbit coast time, the possibility of shadows in all phases of the mission, arrival energy, and the amount of sun-lit orbit time in the lvnar orbit. Constraints on RAE-B include bounds on the spin axis-Stm angle in the translunar tra-jectory, an upper limit on the arrival energy, and a minimum time for sunlight duration in lunar orbit. Presently, both posigrade and retrograde lunar orbits are being considered for the mission. Launch opportunities and trajectory char