Modulation and coding adjustment based on slant range characteristics for satellite downlinks

A satellite communications system adjusts a modulation and coding format for a downlink based on the slant range distance from the satellite to the receiving ground terminal. Modulation and coding formats are each associated with different sets of slant range distances. An estimated slant range from a satellite to a receiving ground terminal for a time period is determined, and the modulation and coding format associated with that slant range distance is identified. Data may then be transmitted by the satellite to the receiving ground terminal using the identified modulation and coding format for the time period. Additional factors may be considered in identifying the applicable modulation and coding format to be used.