Aug 16, 2021
Ground Station 101
A standard mission with an aim to collect one sort of space data uses three operational components: space, ground, and user segments. This time, we will focus on the ground component, showcase its use cases, and how it communicates with the space segment (orbital satellites).
Ground Stations are also known as Earth stations or simply “antennas”. They are basically radio devices designed to establish communication with one or multiple satellites.
Although one might think it takes years to launch a fully functioning satellite into LEO (Low Earth Orbit), this is no longer the case. Satellites have become ridiculously easy to procure — in fact, they can be ordered online and assembled in a matter of weeks. Many data companies have used this opportunity to start collecting Earth Observation (EO) data, or images and sensor data of our home planet captured by satellites. The more satellites in LEO available to snap Earth, the more meaningful insights we can get about what’s going on.
But before users here on Earth can gain these insights, the raw data must first be received by a ground station, then processed into datasets that actually make sense.
Let’s take a closer look at the visual explaining what processes do we have to take for space data to reach the end-user.
Ground System
The ground system, or ground segment, is responsible for collecting and distributing the most valuable asset of the mission — the data itself.
Using the proper ground system is a key to mission success. Whether the goal is to monitor the atmosphere, weather patterns, crops, missile silos or marine traffic, a satellite up there can certainly collect the right data. But it is the ground system that manages the conversion of this data into insights.
An example science satellite mission would typically have the following elements within the ground system architecture:
- Ground Station: Receives raw data from satellites and transmits commands to them. The process of receiving is called downlink; the process of sending commands to the satellite is called uplink.
- Mission Operations Center (MOC):
- Commands the spacecraft through uplink;
- Monitors spacecraft performance;
- Requests and retrieves data through downlink; - Science Operations Center (SOC):
- Generates and disseminates science data products
- Determines science operations be relayed to the MOC - Data Storage and Network: Handles the data exchange between the MOC, the SOC and the stations, or forwards it to users
One of the key issues of ground segments today is that every agency or enterprise, especially established ones, operate very disparate ground segment architectures that may differ significantly from this model. This makes them poorly interoperable, which is why more standardized architectures are needed to streamline data acquisition and open up new market opportunities.
What are the primary elements of a Ground System?
Do not confuse Ground System and a Ground Station, as those are two completely different terms. Ground System uses a number of Ground Stations as a part of the whole ecosystem to fetch data more reliably and quickly.
- Ground Stations are used for telemetry, tracking, and communicating with spacecraft. The core components of a ground station are an antenna and a hardware stack underneath, usually a collection of transceivers, servers and other items that pass the data down the pipeline.
- Ground Station Networks are a seamlessly connected grid of Ground Stations.
- Control Centers are used for spacecraft operations management.
One of the main things we should keep in mind is that ground stations communicate within line of sight. This means that the satellite must be within the station’s horizon to send its signals effectively — it can’t be on the other side of the planet and transmit. The station’s location is typically selected to be optimal for the orbit of the satellite. The location determines how frequently the station can receive satellite data and how long each of these contacts (or “passes”) can be.
Ground Station Network
By connecting more than one ground station into a network, you increase the number of contact opportunities with a targeted satellite. If the user/client is looking for some real-time information collected by a satellite in orbit, relying on multiple ground stations is a must.
As more ground stations are added to the network, it becomes more difficult to manage. The MOC must therefore increasingly rely on automation and orchestration of contacts to keep the flow of data smooth and predictable.
How do Ground Stations communicate with Satellites?
Ground services may either communicate with satellites Direct-to-Earth (DTE) or space relay. Basically, in DTE communication, Ground Stations communicate with the satellite directly.
Unlike a traditional ground network that goes direct from a “client” satellite to a ground station on the ground, a space relay networks consist of communication satellites that relay data from the “client” satellite down to a ground station.
The drawback of relays is that ground stations achieve a lower data rate. DTE provides a much higher rate since the ground station is connected directly to the satellite.
In either case, communication occurs over radio frequency (RF) or optical signals, each having distinct advantages and disadvantages. RF communication is somewhat simpler to set up, but uplink is burdened by each country’s rigid regulation on radio transmission licensing. Laser communication can offer high data rates and is not subject to any regulation, but its major drawback is that even light cloud cover will prevent the optical ground station from establishing contact with the satellite.
What’s the price of running a Ground Station? How does GSaaS make a change?
Depending on the operating frequency, the size and type of antenna as well as supporting equipment (such as Low Noise Amplifiers (LNA), transceivers, etc.), a number of factors drive the cost of a ground station. We’re talking five to six-digit figures.
Until recently, most agencies and companies used to build their own stations and storage infrastructure. Since regular Ground Stations are costly to set up and maintain — especially in different countries — there has been an interest in “renting” Ground Station capacity. The business of leasing existing stations to space enterprises, in combination with a cloud platform, is called a Ground Station as a Service (GSaaS). GSaaS services allow agencies, enterprises and even individual users to rent third-party station capacity, effectively outsourcing much of the Ground System.
A lot of amateur space enthusiasts are making fully operational DIY ground stations. Can you make one too?
The best part, however, is that you don’t have to spend an entire fortune to communicate with an orbital satellite. For a modest budget in the range of $500 — $5,000, most people can assemble an adequate ground station for testing and even some limited commercial uses. One of the most prominent non-commercial networks is SatNOGS, which has a growing open-source community and provides great information on setting up your own station in the open frequencies. These stations are excellent to get involved with amateur radio communities and figure out the basics of satellite communication, and an excellent learning source.
In case you’re interested in building a ground station to receive an Automatic Picture Transmission (APT) from active National Oceanic and Atmospheric Administration (NOAA) satellites, click on the link.
The NOAA satellites are Low Earth Orbit (LEO). Each satellite circles the Earth approximately every 100 minutes so it’s relatively easy to get a decent amount of contacts daily. The images transmitted by NOAA satellites are produced by the satellite’s primary scanning instrument called the Advanced Very High Resolution Radiometer (AVHRR). The instrument is designed to detect five channels of radiant energy from the surface of the Earth ranging from the visible spectrum to the near-infrared and infrared or thermal spectra. As the satellite passes over a given part of the earth, the AVHRR sensors collect and transmit data automatically.
The future is clear for the space data industry. Why?
As we mentioned, commercial Ground Stations are not exactly cheap to maintain or set up. Many agencies, businesses, and individuals will become increasingly reliant on GSaaS to replace legacy infrastructures, set up new data networks, and monetize their data products more rapidly.
While large cloud-based players like AWS Ground Station and Azure Orbital seem set to dominate this trend, a number of other providers are already active. But it’s our solution, HomePort, that will make an impact by creating the first decentralized network of ground stations with customizable pipelines and access to decentralized marketplaces where everyone can participate.
HomePort, armed with the Ephemeris Protocol, will create a radically new infrastructure for satellite data that will change the way communities, enterprises, agencies, and users tap into the space economy.
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HomePort website: homeport.network/technology/
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