that are differently polarized than the earth terminal antenna 110 in order to extend the period that ngso satellite 215 can illuminate ngso coverage area 235 a spot beam of ngso satellite 215 may continuously be steered over the ngso coverage area 235 and each ngso ground station within the ngso coverage area also tracks the serving ngso satellite as it moves across the ngso coverage area to ensure continuous coverage of ngso area 235 an ngso satellite constellation may have multiple ngso satellites so that at least one of the multiple ngso satellites will be visible at any time from the steerable antennas 225 of respective ngso ground stations antennas 225 may be mechanically steerable or active phased array ground terminal antennas ngso satellites are generally designed to have variable transmitter power level so that a constant power flux density over each service area is achieved for example the transmitter power of a spot beam illuminating a certain ngso coverage area is reduced when the ngso satellite is traveling directly at or near the top e g position a of the illuminated ngso coverage area and the transmitter power will be increased when the ngso satellite moves away from the coverage area 225 the transmitter power of ngso ground station antennas may also be increased to compensate for path loss when the ngso satellite moves away e g position b from the ngso coverage area or when fading events occur e g under rain or snow conditions the ngso satellite may interfere with the gso earth terminal 115 although its main antenna beam is pointed.