OBSERVER: Space Situational Awareness — Europe’s Eyes on Space
OBSERVER: Space Situational Awareness — Europe’s Eyes on Space
evan
Mon, 17/03/2025 – 15:03
We rely on satellites more than we may realise—whether it’s for weather forecasting, global navigation, or critical communication systems. However, as our dependence on space-based technologies grows, so does the threat posed by the clutter of space debris surrounding Earth. Space Situational Awareness (SSA) is essential for ensuring the security of these assets, helping us track, monitor, and mitigate risks from both human-made debris and natural space objects. In this Observer, we explore how SSA is helping to protect our key space infrastructure and why it’s more important than ever.
Imagine a scenario in which, after years of meticulous planning, a cutting-edge satellite is finally launched into orbit. It carries advanced instruments designed to monitor the health of our planet, supporting efforts to better understand and protect our environment. Then, disaster strikes. A tiny fragment of space debris—no larger than a marble—smashes into the satellite at thousands of kilometres per hour. The impact severely damages one of its solar panels, cutting off power, and the mission is over before it even begins. While this scenario may seem hypothetical, it is grounded in reality. In 2016, a small, millimetre-sized fragment struck the solar panel of the European Union’s Copernicus Sentinel-1A satellite, causing a slight power reduction. Fortunately, it wasn’t mission-ending, and Sentinel-1A is still operational today.
When space debris threatens an operational satellite, ground teams can intervene, performing collision avoidance manoeuvres to temporarily move the satellite out of harm’s way. This happens more often than many realise. For those who work with Copernicus Sentinel data, missed data acquisitions—instances in which a satellite cannot deliver data over a specific region—are very familiar. These gaps can occur when satellites adjust their orbits to avoid collisions. For example, on Christmas Day 2024, the Copernicus Sentinel-2B satellite had to be repositioned to avoid a collision, which resulted in a temporary loss of data. Therefore, even without collisions, the increased number of manoeuvres needed in space affect the services on the ground.
While catastrophic collisions remain rare, the risk is steadily increasing. Thousands of satellites now orbit Earth, supporting everything from weather forecasting to global navigation. Many of these satellites operate in Low Earth Orbit (LEO)—altitudes below 2,000 km—because this is where they can gather high-resolution data with minimal communication delays. But as more satellites and debris accumulate, LEO is becoming dangerously overcrowded. According to reliable estimates, there are now more than 1 million pieces of debris larger than 1 cm drifting around Earth, most of which are in LEO. This debris includes inactive satellites, rocket fragments, and pieces from past collisions. With an increase in satellite launches—particularly from mega-constellations designed to provide global internet coverage—LEO is becoming more congested than ever, and the problem is growing worse.
Space-based technologies have become an integral part of our daily lives, and satellite data is used in a wide range of applications. In OECD countries, space-based systems already support more than half of the most critical infrastructure and services, such as transportation, energy, finance, food supply, and public safety.
To protect space operations and ensure the sustainability of Earth’s orbits, the EU Space Programme operates a Space Situational Awareness (SSA) component. SSA is made up of three subcomponents: Space Surveillance and Tracking (SST), Space Weather Events (SWE), and Near Earth Objects (NEO). These subcomponents monitor our space environment, providing information on potential hazards which enables satellite operators and decision-makers to safeguard infrastructure in space and on Earth and mitigate risks before they become serious problems.
Space Surveillance and Tracking (SST)
Space Surveillance and Tracking (SST) consists of a global network of sensor stations (governmental and commercial), including radars, telescopes, and laser-ranging stations, which continuously scan the skies. These sensors detect, track, and help catalogue artificial objects in orbit, collecting thousands of measurements every day. This data is then shared via a common European database and used by national operations centres, which combine this data with data from other sources for enhanced situational awareness. Based on these analyses, the EUSST Partnership (composed of 15 EU Member States) provides the key SST services of Collision Avoidance (CA), Re-entry Analysis (RE), and Fragmentation Analysis (FG), all designed to safeguard satellites and other space infrastructure. The outputs from the services are uploaded to the EU SST Portal, making it available to the SST users. The EU SST Front Desk and Portal are operated by The European Union Agency for the Space Programme (EUSPA).
Collision Avoidance (CA) assesses the risk of potential collisions between satellites or between satellites and space debris. When a potential high-risk event is detected, the system generates alerts, giving satellite operators the time they need to adjust their satellites’ orbits and avoid a collision. Currently, over 550 satellites are registered with the EU SST Collision Avoidance Service, and about one high-risk event is detected each week. In some weeks, this can rise to two or three events, highlighting the increasing congestion of the orbits around our planet.
Re-entry Analysis (RE) tracks objects which might re-enter Earth’s atmosphere. While most of this debris burns up upon re-entry, larger objects will sometimes not burn up entirely and pose risks to populated areas. Last month, for example, debris from a Falcon 9 rocket landed in Poland. By predicting when and where objects will re-enter, RE helps authorities prepare and issue warnings if necessary, reducing the threat posed by larger fragments.
Fragmentation Analysis (FG) monitors in-orbit collisions, break-ups, or malfunctions. When a satellite or other object breaks apart, this service helps determine how much debris was created and where it is headed. It also assesses the potential risks posed by the fragments to other operational satellites. This capability is crucial for managing the aftermath of a fragmentation event, which can result in a cascade of smaller debris creating further hazards.
Space Weather Events (SWE)
Space weather events are natural fluctuations in the solar atmosphere and surrounding space environment that can impact space-based and Earth-based systems. These include radiation storms, solar flares, and geomagnetic disturbances—phenomena which can disrupt electrical systems in satellites orbiting Earth and affect critical infrastructure on the ground. A well-known manifestation of space weather is the Aurora Borealis, or Northern Lights, which are caused by magnetic storms triggered by solar activity.
However, not all space weather events are as beautiful and benign as the Northern Lights. Some can have severe consequences which can impact critical infrastructure. For example, in March 1989, a powerful solar storm affected Earth’s magnetic field, inducing currents in the power grid and causing a nine-hour blackout in Quebec, Canada. Similarly, in October 2003, a solar storm disrupted high-voltage power transmission systems in southern Sweden. Over the years, numerous other solar storms have interfered with satellite navigation, communications, and even aviation systems.
This is where Space Weather Events (SWE), the third subcomponent of Space Situational Awareness (SSA), plays an important role. SWE focuses on tracking, assessing, and predicting space weather events, helping to protect satellites in orbit.
Through SWE, the EU is supporting research for the development of advanced space weather models and forecasting tools aimed at improving early warning systems. These efforts include testing and validating new forecasting capabilities, which will lay the groundwork for a space weather service covering spacecraft operations and tracking. Such a service will help stakeholders to prepare for and mitigate potential disruptions caused by space weather events.
Near Earth Objects
While human-made space debris is a significant concern, natural space objects such as asteroids and comets also pose substantial risks to satellites. Some near-Earth Objects (NEOs) follow trajectories which bring them dangerously close to Earth, increasing the likelihood of collision with operational satellites.
The EU’s NEO initiative aims to improve Europe’s capabilities to monitor and expand our knowledge on these natural objects. NEOs are space rocks—comets and asteroids—which approach Earth or travel in close proximity to our planet. These objects played a major role in the early evolution of Earth and continue to enter the Earth’s atmosphere regularly, posing a risk to both space assets and potentially to life on Earth itself.
In recent years, the EU has increased its efforts to track and study NEOs. Understanding the physical characteristics of these objects, such as their composition and trajectory, is crucial. The EU is working on developing a European catalogue which details the physical properties of NEOs and will serve as an important resource for scientists and decision-makers.
Additionally, the EU promotes networking among facilities and research centres across Europe. This collaboration is further strengthened by an annual conference, at which experts discuss the latest developments and strategies for improving NEO monitoring.
Another component of this initiative is to study potential fast-response space missions for NEO reconnaissance (to better understand the characteristics of the object) and NEO deflection in relation to bigger international NEO impact exercises.
Through these efforts, the EU is not only improving its ability to characterise the different NEOs but is also working towards developing the necessary technologies to address the risks they pose. The goal is to ensure that Europe is well-prepared to protect both its space assets and, when necessary, take action to safeguard the planet from potential threats posed by space rocks.
By tracking, monitoring, and mitigating risks from space debris, space weather, and near-Earth objects, SSA is ensuring the safety and sustainability of space operations and helping to protect citizens and the services we rely on every day.
Thu, 20/03/2025 – 12:00
