High power transmitters
The distance of the radio waves that go from the vehicle to the ground station, is the same that the ones sent by the ground equipment have to travel, but in the opposite direction, which contain programs and/or orders for onboard computers.
But the spacecraft antennas are much smaller than the ones in Earth (its dimensions do not exceed three meters in diameter), and the sophisticated, very low noise receivers, used here in the Earth cannot be taken to space for reasons of weight limitation, power consumption, etc..
To compensate for these differences two combined strategies are used: the first one is to use high-power transmitters (up to 20 kW), and the second one is to slow the speed of the transmission of information.
Due to the statistical characteristics of the background noise, to increase the time of each unit of information the noise disturbance can be reduced with adapted filters, so the onboard receiver can make a better estimate of the noise signal.