System Overview

Below is a general illustration of what to expect at the end of this design project:

First thoughts

The first step to do when approaching such a topic is to identify the different technical areas of a system design and their mutual interactions. A satellite communications system can be divided into two main technical areas:

- the communications system

- orbital mechanics

The communications system

The communication system is responsible for conveying data between the probes, the satellite and Earth. Once the requirements of the system are set, the first approach will be to determine link budgets. There are two link budgets, one for the probes-satellite link, and another for the satellite-Earth link. A link budget will allow us to choose modulation and encoding schemes. It is also closely related to the power subsystem on board.
We have been provided data on Neptune’s atmosphere gases composition and their respective absorption factor. This information will contribute immensely to the link budget assessment. We will see that the total absorption is not negligible deep inside in the planet’s atmosphere.

Orbital mechanics

Although orbital mechanics are of the specialty of aerospace engineers, one should not forget that the locations of the satellite and probes at some time as well as their relative velocities are extremely important towards the maintenance of a successful communication system. For instance, neglecting a Doppler effect or moving out of the line of sight might lead to critical loss of data as well as many years of space travel wasted. Therefore, both the communications engineer and the aerospace engineer should work together to find the best solution for the system. Questions might include: what type of orbit should the satellite have? How far from Neptune? How is that reflected on the free space path loss? Where would the probes be relative to the satellite at any given time? All those questions will be answered throughout the project.