Communicating with Mars during periods of solar conjunction

A reliable communications link between Mars and Earth will be required during the initial phase of the human exploration of Mars. The direct communications link can easily be realized during most of the 780-day Earth-Mars synodic period, except when this link encounters increased intervening charged particles during superior solar conjunctions. The effects of solar charged particles are expected to corrupt the data signals to varying degrees. During superior solar conjunctions of interplanetary spacecraft, flight projects routinely scale down or suspend operations by invoking command moratoriums, reducing tracking schedules, and progressively lowering data rates. The actual operations scenarios will vary between flight projects and from conjunction to conjunction. This paper presents results of a study conducted to determine to what extent and by what techniques communications may be maintained throughout Mars-Sun-Earth superior conjunction periods that could occur during early human Mars exploration missions. Using a number of techniques discussed in this paper, it should be possible to maintain some degree of communication throughout all of the superior conjunctions occurring between 2015 and 2026, except for one occurring in 2023, in which actual occultation of the signal source by the Sun´s disk occurs.