Ground-based tracking and communications with spacecraft is a critical aspect of the space industry. It involves the use of specialized equipment and facilities on the ground to monitor the location, status and communicate with spacecraft in orbit. This information is used to ensure the safe and efficient operation of the spacecraft, as well as to plan and execute missions.

The main component of ground-based tracking is the network of ground-based tracking stations, which use radar, optical telescopes, infrared or other sensors to track the spacecraft and gather data on its position, velocity, and other characteristics. The data is then processed within mission control or “on-the-edge”, to determine the spacecraft's trajectory and plan future maneuvers.

Ground-based communications with spacecraft, often known as ground-stations, are typically composed of a set of equipment, including antennas, transceivers, and other electronic equipment, that are used to establish a radio link between the ground and the satellite. Ground-stations are used to send commands to the satellite, to upload new software or configuration settings, to receive data and telemetry from the satellite, and to monitor the health and status of the satellite.

Optical telescopes, infrared sensors and laser technology are common means of ground-based tracking of spacecraft. Planning the location of these types of ground-based tracking sensors and ground stations is important in order to optimise the following factors:

1. Line of sight: The ground-station must be located in an area where it has a clear line of sight to the spacecraft. This means that there should be minimal interference from clouds, atmospheric turbulence, buildings, or mountains.
2. Latitude and Longitude: The ground-station should be located at a latitude and longitude that will allow it to track the desired spacecraft over a significant portion of its orbit.
3. Accessibility: The ground-station should be located in an area that is easily accessible for maintenance, upgrades, and repairs.
4. Power and Communication: The ground-station should be located in an area where it has access to reliable power and communication infrastructure.
5. Cost: The cost of the ground-station location should be considered. Factors such as land lease, construction, and maintenance costs, as well as the cost of providing power and communication infrastructure, should all be taken into account.
6. Security: The ground-station should be located in an area that is secure and has minimal risk of vandalism or sabotage.
7. Networking: The ground-station should be strategically located within a larger network of ground stations to provide better coverage and redundancy.
8. International Regulations: The sensor should be located in an area that complies with international regulations and agreements related to space activities.

In evaluating the ideal location for ground-stations and sensors, trade-offs need to be made across the above factors according to the specific needs of a given mission. These trade-offs are typically made using data from simulations as optimising locations based on experiments are too expensive, difficult and risky. For example, the simulation tool, STK (Systems Tool Kit) can be used to simulate the orbit of a satellite and predict when it will be in view of a given location on the Earth. This can be used to identify potential locations for a ground station that will have a clear line of sight to the satellite. However, analysts often need to simulate the quality of their sensor observations of spacecraft e.g. rendering of the view observed of a spacecraft by an optical telescope in order to determine if a given location is suitable. Simulating quality of data is often beyond the capability traditional space simulation tools, requiring an integration with other tools which can be cumbersome. That's only the beginning though, with detailed design requiring an understanding of payload data storage, power consumption and thermal characteristics, and the list goes on.

At Nominal Systems, we're working hard to solve these problems by providing and all-in-one digital engineering solution for your team that is extensible and flexible. To make modelling your communication systems easier, we've included out of the box a range of digital models for you to develop on, such as:

• 6 degree of freedom propagation of multiple spacecraft with changeable geometry, reflectivity and other properties;
• Receiver, transmitter and data modules for performing link budget analyses with multiple spacecraft/ground-stations;
• Ground or space-based radar, optical and infra-red sensors using modern game-engines for visualisations;
• Electrical power consumption of ground and space segment through modular power nodes attached to components within the simulation;
• Accurate Earth terrain and topographical mapping;

Nominal Editor also provides the ability to visualize and analyse sensor and other data, making it easier for users to interpret and understand the information they are receiving. This is particularly useful in situations where data-driven decisions need to be made regarding critical infrastructure.

In summary, ground-based tracking and communications infrastructure is essential for the space industry, providing real-time monitoring, improved accuracy, enhanced mission planning, cost savings, data visualization, and automated decision making. Optimally locating ground-stations and sensors is critical for robust and efficient operations in space. As the sophistication of the ground-segment grows, so too must the tools used to plan and operate it. Together, this technology plays a crucial role in ensuring the safe and efficient operation of spacecraft and the successful execution of space missions.