High-rate communications from Mars has significant but manageable challenges during the timeline 2020 to 2030. MRO sends data on X-band at rates as high as 5.3 Mbps. MRO could have been designed to send data at much higher rates than 5.3 Mbps over most Mars-Earth distances were it not for bandwidth limitations at X-band (ref. 3-1). The bandwidth issue is less severe at Ka-band. The deep space allocation for Ka-band is 500 MHz, compared with 50 MHz at X-band. This section discusses the various assumptions and challenges foreseen for a high rate Ka-band downlink. These assumptions and challenges include spacecraft constraints, ground station configuration, weather and atmospheric implications, solar conjunction, spectrum constraints, and the extreme variation in Earth-Mars distance.