Space communications is something I am increasingly interested in.
Previously I worked in space communications satellite reliability, at Astrium Space (now Airbus Defence & Space).
This blog post will look at the various types of extra-terrestrial to earth communications, and how they will become increasingly important.
Deep Space Communications
The deep space communications network, isn’t one network.
Although the best known is probably the NASA Deep Space Network, there are a number of others.
For example the Russians and the Indians, have their own Deep Space Networks.
For this part of this blog post, we will focus on the NASA network.
The NASA Deep Space Network (DSN), has the following key functions:
- acquire telemetry data from spacecraft.
- transmit commands to spacecraft.
- upload software modifications to spacecraft.
- track spacecraft position and velocity.
- perform Very Long Baseline Interferometry observations.
- measure variations in radio waves for radio science experiments.
- gather science data.
- monitor and control the performance of the network.
The NASA DSN is based at three separate international locations.
The locations are:
The USA, at the Goldstone Deep Space Communications Complex
In Spain, at the Madrid Deep Space Communications Complex
In Australia, at the Canberra Deep Space Communication Complex
The strategic choice of ground station, is deliberate.
Each of the three ground stations is capable of covering 120 degrees of space.
Therefore, having three strategically placed international ground stations, gives 360-degree coverage of space, from the earth.
A primary 70 metre radio receiver dish is located at each centre, with secondary 34 metre dishes, which can be combined for backup purposes.
High Delay Rate Tolerant Networking (HDTN)
Integrated Radio Optical Communication (iROC)
Lunar LTE Studies
Space Telecommunications Radio System (STRS)
SDR – Software Defined Radio
Software Defined Radio (SDR) is a relatively new technology.
SDR differs from traditional radio communications hardware, in that much of the radio transceiver (transmitter / receiver) hardware blocks, are replaced by software.
The software runs on computer hardware.
The advantage of SDR based systems, is that the frequencies can be changed remotely in Space.
SDR incorporated into a communications satellite, allows remote changes, as future needs arise.
Traditional satellites had fixed hardware parameters, which could not be changed once launched into space.
This meant that communication satellites were ‘stuck’ on the frequencies that they left earth with.
SDR therefore increases operational flexibility, and can prolong the useful life of a communications satellite.