Possible use of microwaves for interplanetary communication

The power required for one way radio communication to various planetary bodies has been calculated at various freqencies with a view to choosing a suitable frequency for interplanetary communication. On the basis of ionospheric and external noise considerations, a ¿radio frequency window¿ higher than 100 mc has been selected for such systems. Transmission loss considerations including free space attenuation, molecular absorption in the path, antenna gains etc have led to the conclusion that frequencies in the S band of microwave region are best suited for establishing radio contact with other planets.