Recent reports indicate that there was a close call between an Australian satellite and a suspected Chinese military satellite. In addition, the US government issued its first-ever fine for space junk. The Federal Communications Commission fined DISH Network, a satellite TV services company, $150,000 for a communications satellite that has been in space for over 21 years. This fine surprised many in the industry as it was not related to recent debris but rather the satellite’s failure to meet orbit requirements outlined in a debris mitigation plan.
While the EchoStar-7 fine is a first for the US, it likely won’t be the last. The number of active satellites in space is expected to increase by 700% by the end of the decade, leading to a more crowded space environment. This makes it increasingly important to monitor the tens of thousands of satellites and space debris. This has given rise to a new field called space domain awareness.
Satellites are typically found in three main orbits: low Earth orbit, medium Earth orbit, and geosynchronous orbit. Low Earth orbit is the most common and is home to at least 5,900 active satellites. Medium Earth orbit sits between 10,000 and 20,000km above Earth and is where important satellites like GPS are located. Geosynchronous orbit is at a very high altitude, upwards of 35,000km above Earth, and includes geostationary Earth orbit where satellites appear stationary from the ground.
In addition to active satellites, there is also a significant amount of space junk in orbit around Earth. Space junk includes disused artificial debris ranging from entire satellites to small fragments. Estimates suggest there are over 130 million pieces of space debris, with only 35,000 large enough to be routinely tracked.
Tracking these objects is crucial for space domain awareness. Ground-based tracking systems such as radar and optical sensors are used to detect and monitor objects in Earth’s orbit. Radar is effective for low Earth orbit, while optical sensors are needed for higher orbits. Multiple sensors around the globe are necessary for reliable and continuous space domain awareness.
Australia has a unique opportunity to contribute to space domain awareness due to its location. The country already hosts facilities for the US Space Surveillance Network on its west coast, where telescopes can operate in dark night skies. Australia is also working on a space domain awareness technology demonstrator funded by SmartSat CRC. This project combines expertise in observational astrophysics, data visualization, artificial intelligence, and space weather to monitor objects in orbit.
The recent fine issued for EchoStar-7 serves as a warning to other companies to ensure they meet debris mitigation plans. Inactive objects in orbit pose a collision risk and can contribute to the growing problem of space debris. To ensure the long-term use of Earth’s space domain, it is crucial to keep it safe for all.