6.5 General Arrangement and Design Drivers

As can be concluded from the requirements section, the communications subsystem is intimately connected to the payload and command and data handling subsystems, the orbit, and the ground segment. Regardless of the mission, there’s a power system and command and data handling system to support the power and data needs of the communications system. There’s a radio receiver, transmitter, and likely an antenna and amplifier.

The antennas need unobstructed access to the space environment. The internal electronics, like the amplifiers, filters, diplexers, receivers, etc. typically collect on a dedicated communications board. This board is connected to the central computer that is controlled by the command and data handling system. The communications board typically has all the coding and modulation onboard to process raw signals. This processing can also happen on the central computer.

^{Deep Space Network: A Discussion on NASA’s Vital Lifeline to Spacecraft. Video by NASA/JPL}

The ground segment is not the spacecraft bus communications specialist’s responsibility but coordinating with the ground segment lead is. For context, typically, NASA and other large agencies have a network of ground stations, like the Deep Space Network, that cover a range of frequencies and offer continuous coverage. Smaller groups, like universities or companies, must provide their own ground station network or purchase access to a network. A fantastic community to tap into and contribute to is the SatNOGS community-operated ground station network. By involving amateur radio operators all over the world, small satellites that wouldn’t get the time of day on the Deep Space Network can get information back. Building and operating ground stations, like spacecraft, have become more and more feasible for DIY enthusiasts.