Space Traffic Management: The Growing Challenge of Collision Avoidance
Did you know that the number of collision avoidance maneuvers reported by Starlink doubles every 6 months? Read about how startups are helping to keep satellites safe in orbit
Issue 90. Astronauts 11 452. Featuring insights from N42.5, a space situational awareness and space traffic monitoring company.
Living in a city, I seldom pay attention to the night sky. This year, while at a remote seaside location, I was fortunate to witness a clear sky, free from city light pollution. To my surprise, I observed at least four satellites at any given moment, a stark contrast to six years ago when I had a similar opportunity. Back then, spotting one satellite was noteworthy. This rapid increase in visible satellites highlights the booming interest in space operations, driven by market opportunities and disruptive technologies.
Currently, there are thousands of satellites in orbit, and this number is projected to reach 100,000 by 2030. Consequently, this growth has led to a significant increase in space debris. According to the European Space Agency (ESA), there are over 40,500 pieces of debris larger than 10 cm, about 1,100,000 pieces between 1 and 10 cm, and an estimated 130 million pieces smaller between 1 mm and 1 cm. Impacts with debris in the centimeter size range can disable an operational spacecraft. On the other hand, collisions with debris in the millimeter size range can cause localized damage or disable specific subsystems of a functioning spacecraft.
Because of the multitude of both active spacecraft and debris, satellites rarely can stay passive in their orbit. In numerical terms, the number of collision avoidance maneuvers reported by Starlink doubles every 6 months. In 2022, Space Ambition discussed the dangers of space debris, such as high-speed collisions, and the potential for cascade effects like Kessler Syndrome, a chain reaction that could potentially render space activities and the use of satellites infeasible for generations (a good impression of such event is well depicted in the movie “Gravity”). We also explored potential solutions, including onboard propulsion for maneuverability, improved shielding, refined payload separation, and debris tracking systems. In this article, we will focus on the business opportunities surrounding the tracking and avoidance of objects in orbit, or, in other words, situational awareness.
Components of Successful Situational Awareness:
1. Detecting Danger
The first step in situational awareness is detecting potential hazards. This is achieved using radars or optical telescopes, which can be ground-based or space-based. Typically, both telescopes and radars can track objects as small as 1 cm in low Earth orbit (LEO) or about 10 cm in geostationary orbit (GEO). Projects like Odin Space (raised ~$0.8M since 2020) aim to manage the risk of colliding with sub-centimeter (down to ~0.1 mm) debris, although here the company aims to monitor the density of small objects rather than tracking each of them individually.
2. Calculating Orbits and Collision Probabilities
Detecting objects is not enough. A piece of space debris might be thousands of kilometers away from your satellite on a different orbit, but after several revolutions around the Earth, their paths might intersect, leading to a collision. Therefore, it is crucial to calculate orbits and collision probabilities accurately. Although orbits follow classical mechanics and should be deterministic (in other words, calculable with high precision), uncertainties arise due to data measurement errors. Radars and telescopes measure the coordinates and velocities of objects with slight inaccuracies. Moreover, calculation errors exist, as the calculations may not precisely account for Earth's gravitational field (Earth is not a perfect ellipsoid), solar wind pressure, or the orientation and shape of debris. Additionally, magnetic storms affect the state of the upper layers of Earth's atmosphere, causing their expansion and contraction. This increases or decreases friction for the objects in the orbit and affects the trajectory. These factors lead to the accumulation of uncertainties with time.
This is why it is essential to update space object data regularly. Knowing about the launch of new satellites and tracking their orbits is not enough; data on all spacecraft and debris and their current positions must be constantly refreshed. The United States Space Command's publicly accessible SATCAT catalog normally has a one-week delay for most of its objects, which is sufficient. Commercial companies in the field of situational awareness strive to update their data every 2-3 days. Despite the availability of standardized calculation methods, most small satellite operators lack the resources to independently perform comprehensive calculations and account for all collision probabilities.
Therefore, they delegate this task to specialized companies. These companies track specific customer satellites and calculate the optimal way to avoid collisions when necessary. The challenge here is how to adjust the orbit without making the situation worse (not shifting to an orbit that poses a higher risk of collisions after a few revolutions), without using excessive fuel, and without moving to a less functional orbit. This is a complex task, which is why it often makes sense to outsource it to specialized Space Situational Awareness (SSA) and Space Domain Awareness (SDA) companies, most of which are from the USA and Europe.
Many of these companies offer software-only solutions, with the largest player being Privateer (raised $56.5M since 2021), founded by Apple co-founder Steve Wozniak. Among the companies developing hardware-based solutions for space traffic monitoring, most of their hardware is ground-based. Notable firms in this category include LeoLabs (raised $111M since 2016), Slingshot Aerospace (raised $118.9M since 2017), and ExoAnalytics (a defense company on the market since 2008).
As the N42.5 team found, some players aim to monitor the situation from the orbit:
Some companies, such as Digantara and Vyoma, are like us in creating their own satellite constellations to monitor space traffic, including debris. However, many SSA and SDA companies involved in satellite development focus on inspection and often have ties to the defense and military sectors. Examples include True Anomaly, Astroscale, and Northstar.
At N42.5, we are developing a constellation specifically for space traffic monitoring, tracking the movement of satellites and space debris in orbit. Unlike inspection-focused companies, our mission is to create the most comprehensive and independent catalog of space objects, including satellites and debris as small as 1 cm. Our constellation can be deployed in LEO, GEO, and even Lunar and Martian orbits as traffic there increases. Our goal is to be the leading provider of precise data, ensuring safer space traffic for all those with assets in different orbits.
3. Managing Space Debris Disposal
The next level involves monitoring the disposal of space debris. Various international guidelines and agreements, such as the Inter-Agency Space Debris Coordination Committee (IADC) guidelines, aim to mitigate space debris. These include measures like passivation (depleting all onboard energy sources post-mission), re-entry techniques to ensure satellites burn up in the atmosphere, and designing satellites to minimize debris generation. Read more in the coming articles of our continuing series on space laws. Satellite constellation operators are currently only concerned with managing debris and their satellites post-mission if they contain hazardous materials like nuclear substances. However, this is a financial issue. Over time, more fuel will be needed for collision avoidance, and satellites will become heavier and thus more expensive. It is anticipated that operators of orbital constellations will soon feel the impact of this problem on their budgets.
As the number of satellites in Earth's orbit continues to grow, the challenge of managing space debris becomes increasingly critical. Effective situational awareness, including accurate detection, maneuvering, and debris disposal, is essential to avoid potential collisions and ensure the long-term sustainability of space operations. Companies and international organizations must work together to develop and implement strategies that address these challenges. By staying informed and proactive, we can navigate the complexities of space debris and protect valuable assets in our increasingly crowded orbits. If you have any ideas to share, please reach out to us at hello@spaceambition.org.