Mega-constellation satellites on the horizon
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The trend towards smaller satellites has not only reduced the costs of building, launching and operating satellites, but has also enabled faster and more flexible deployment and made satellite mega-constellations feasible.

In recent years the space industry has undergone a dramatic transformation. Instead of launching few, complex, large and expensive spacecrafts, the trend is now towards the deployment of smaller, simpler and less expensive satellites. Due to the miniaturization of once-bulky satellite components, standardization, and substantially trimmed costs due to advances in design and manufacturing, the interest in small satellites (typically under 500 kilograms) has grown.

Low Earth Orbit (LEO) satellites are smaller than their Medium Earth Orbit and Geostationary Equatorial Orbit (GEO) counterparts and their orbits are much closer to Earth, so the rockets needed to launch them are also smaller and cheaper. Whereas, for example, a GEO-based high throughput satellites can be compared to the size and weight of a bus, a small LEO communication satellites is more like a motor-bike. The downside with LEO is that many satellites are needed to service a specific geographical area at any given time. LEO satellites orbit the Earth many times per day, so as each satellite flies over the coverage area, another one must follow behind it, ready to take over the operation (communication or monitoring) once the first satellite has passed the area. In turn, many ground stations are needed to communicate with all these satellites, orbital positions and frequencies, needing careful management to avoid interference.an advantage with LEO constellations is that they can provide true-global coverage including the polar areas.

Towards lightweight satellites

There are now several new initiatives based on mega-constellations of small satellites in LEO planned to be put into service during the next decade, starting with a focus on the satellites themselves. The most well-known frontrunners are OneWeb and StarLink, but many others aim to make similar systems, for example LeoSat, TeleSat(Canada) and Honyan (China). The new LEO systems should expect to face fierce competitions from O3b, looking to expand its network of satellites in MEO orbit and existing GEO-operators like Inmarsat and SES, continuing to invest in larger and increasingly powerful GEO-satellites.

Since a LEO-satellite’s altitude is just 3% of a GEO-satellite, the roundtrip delays will be much shorter, a significant benefit for real-time communication. For StarLink, SpaceX anticipates a latency of 25ms, which will be competitive with 5G and fixed broadband services and, at much less than the typical delays in GEO-systems with around 500ms, will enable better performance of interactive applications.  However, delivering real-time interactive broadband communication services with a large number of LEO satellites, travelling at high speeds over the horizon, requires significantly more complex networks and user terminals than GEO-systems. For example, the antennas need to the track the moving satellites, and the system needs to handle handover of communication sessions between satellites, whereas just one GEO satellite is required to serve its respective purpose.

LEO is not a new orbit for satellite communication, because the Iridium satellite constellation has already been running a global LEO-system with 66 satellites since 1998. However, this has been using a severely limited bandwidth, constraining user data rates and traffic capacity in the system. The new LEO-systems will use higher frequencies (Ku-band and Ka-band), thus offering a much-increased bandwidth, and will take advantage of the reduced launch costs and cheaper satellites that are available now. This will lead to massive increases in user data rates and system traffic capacity, at lower costs.

Both Oneweb and Starlink are claiming that their systems will start operations as early as 2020, however this will be limited to certain regions and market segments. The complete satellite constellations providing continuous broadband services to customers on a global basis are not likely to be in place before the latter half of the decade.

Miniaturization with a global impact

The trend towards miniaturization is also happening for Earth Observation (EO) satellites. Traditionally, institutional operators used advanced, expensive and complex satellites with multiple sensing technologies. Now, private players, often start-ups, are launching smaller and cheaper satellites, typically to perform a single function at lower cost.

Larger constellations and swarms of small satellites are used to improve surveillance capabilities, increase orbits, and fill the gaps between high-precision data provided by big satellites. Missions are emerging whereby small satellites become fractionated, so that each satellite performs a functional part of a total system such as imaging, processing and transmission.

Small satellites could allow near real and real time satellite imagery, making it feasible for global corporations to monitor all their assets at the same time and generate high-resolution visual data for individual companies, governments, or those trading on global financial markets. The advantages in deploying small satellites for EO include lowered business entry barriers and faster deployment due to the reduced costs and improved surveillance capability made possible by constellations and swarms. And there will be a swarm. Prior to 2012, less than 100 satellites were being launched into LEO orbit. Since then, there has been a surge in activity, leading to a launch rate of more than 400 for 2017-2018, with an estimated further 7000 ready for launch in the next 10 years1.

However, despite the proliferation of small satellites there will still be a need for larger, high precision satellites, to be used also a baseline/reference for small satellite data quality assurance. Further, there is a huge potential in combining high-precision data from larger satellites with new data streams from small satellites, to create new insights and unlock value for a variety of stakeholders.

The need for information from high-precision satellites is growing, because of society’s need for continuous information over large territories. This need can only be met by reevaluating traditional solutions. Provision of low-cost ubiquitous broadband will enable and accelerate IoT in different industries, and particularly impact industries that rely on mobile assets and operate beyond coverage of earth-bound broadband networks for example aviation, maritime and offshore industries. Spreading connectivity to unserved areas and doing it with ample bandwidth at low-cost will make huge impact for the affected areas and users. Even for areas and users that are already served, the new LEO-systems will introduce more capacity and drive prices down due to competition.

Space agencies, like National Aeronautics and Space Administration (NASA), European Space Agency (ESA), , Russian Federal Space Agency (Roscosmos), Italian Space Institute (ASI), Indian Space Research Organisation (ISRO), China National Space Administration (CNSA), Japan Aerospace Exploration Agency (JAXA) and German Aerospace Center (DLR), are leading the world in EO by developing cutting-edge spaceborne technology to gather different types of data from the planet, and in turn support policy-making for a more sustainable future.

Beyond barriers: an orbital view of the planet’s health

The data acquired by EO satellites can be used to classify images (such as water, rivers, forest, infrastructures, ships and other assets) and to generate geophysical variables characterizing for example vegetation, water and air quality. Data and insights into areas such as ocean monitoring and pollution detection are vital to better understanding the Earth systems and ecological changes.  EO satellites therefore serve an essential role through the continuous, global data they provide.

However, there are many hurdles that need to be overcome when building a mega-constellation of small satellites. Firstly, the project needs to be fully financed, then regulatory approvals must be acquired, and frequencies coordinated to ensure safe coexistence with other satellite systems. Then the project relies on regular, timely and economical launches of its many satellites. It will not be possible commence service until a large portion of satellites are launched and operational. The cost and complexity with development of user equipment also contributes to the technical risk, due to advanced antennas modem design and satellite handover functionality. Many start-ups, companies and investors underestimate these hurdles, and jump into space business without grasping the complexity of coordinating the action of hundreds of satellites, their system architecture and ensuring service continuity.

Once a mega-constellation is up and running, it won’t be without its hurdles yet. The growing number of small satellites orbiting Earth presents some unique challenges. For communication satellites the radio resources need to be carefully managed, to avoid interference not only between the new LEO systems, but also legacy systems in other orbits operating in the same or adjacent frequency bands.  Additionally, space junk and debris pose a serious risk to small satellites in LEO orbit, calling for countermeasures such as collision detection, collision avoidance and removal strategies at the end-of-life, adding to the system cost. Regulations and standards are lacking, which implies an uncertainty for existing as well as new players. A general concern is that many small satellites are not equipped with propulsion systems and thus cannot perform any collision avoidance or end-of-life disposal manoeuvres, thus imposing risks for other satellites in the same orbit.

Still, when these hurdles are overcome then EO mega-constellations can both provide a unique, orbital view of our planet’s health and open up new economic and social opportunities.

Contributors

DNV GL is grateful to Gordon Campbell, Director, Science, Applications and Future Technologies Department, Directorate of EO Programmes at the European Space Agency (ESA) and Dag Anders Moldestad Senior Advisor at the Norwegian Space Agency for the valuable discussions.

Main author: Steinar Lag

Contributor:Barbara Scarnato

Editor: Tiffany Hildre

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