There are numerous factors taken into consideration when planning the communications links between both the rover and the base station and the moon and the earth. Since video and data must be sent over the links, first and foremost a modulation scheme for digital transmission must be chosen. From there, the following parameters must be specified:
- Center Frequency
- Bandwidth
- Distance Transmitted
- Isotropic or narrow beamwidth
- Required SNR at receiver
- Possible Attenuation and Noise Sources
Finally, the link budget can be applied to determine the necessary antenna gain and transmit powers. The equation below is the link budget to be used.
The rain attenuation is obviously only applied to the link from the moon to the earth and can be described as follows:
The rainfall rate in the above expression represents the rate measured for .01% of the year which is typical for most models. The parameters k and alpha are frequency dependent regression coefficients and can be obtained from any satellite communications book.
