Why Are LEO Satellites Small?
Low Earth Orbit (LEO) satellites, typically operating at altitudes ranging from 160 to 2,000 kilometres (99 to 1,200 miles) above Earth, have become a cornerstone of modern space operations. These satellites are widely utilised in various applications, including Earth observation, broadband internet, and IoT connectivity. One defining characteristic of LEO satellites is their relatively small size compared to their counterparts in higher orbits, such as geostationary (GEO) satellites. But why are LEO satellites designed to be small? This article explores the engineering, economic, and operational factors that contribute to the compact nature of LEO satellites.
1. Shorter Operational Lifespan
LEO satellites have shorter operational lifespans compared to GEO satellites, typically ranging from 5 to 10 years.
Atmospheric Drag: LEO satellites encounter atmospheric drag, which gradually decreases their altitude and shortens their lifespan unless corrective manoeuvres are executed
Planned Obsolescence: Rapid advancements in technology often render satellite hardware outdated within a few years. Operators prefer smaller satellites that can be more affordably replaced with newer models.
Cost Efficiency: A shorter lifespan reduces the need for overengineering, enabling smaller, simpler designs that are optimised for short-term use.
The emphasis on frequent upgrades and replacements drives the trend toward smaller, more agile satellites.
2. Reduced Power Requirements
Operating in LEO significantly reduces the power demands on satellites, enabling compact designs.
Proximity to Earth: Being closer to the planet allows LEO satellites to use lower-power transmitters for communication with ground stations, thereby reducing the need for large solar panels or batteries.
Smaller Payloads: Many LEO satellites carry lightweight, specialised instruments designed for specific tasks, such as imaging or data relay, which consume less power.
The lower energy requirements enable LEO satellites to rely on smaller power systems, contributing to their compact design.
3. Advances in Miniaturisation
Technological advancements in miniaturisation have revolutionised satellite design, particularly for LEO missions.
COTS Components: The use of Commercial Off-the-Shelf (COTS) electronics has enabled the integration of advanced capabilities into smaller, more compact packages.
CubeSats and SmallSats: Standardised small satellite platforms, such as CubeSats, a class of nanosatellites that use a standard size and form factor, have become popular for Low Earth Orbit (LEO) missions. Measuring as small as 10 cm³ (1U), these platforms demonstrate how miniaturisation has enabled highly compact and functional designs. Small spacecraft, also known as SmallSats, focus on spacecraft with a mass of less than 180 kilograms, approximately the size of a large kitchen fridge. Even with small spacecraft, there is a wide variety of sizes and masses that can be differentiated.
Efficient Sensors: Modern sensors and processors deliver high performance with reduced size, weight, and power (SWaP) requirements, making them ideal for LEO missions.
Thanks to miniaturisation, LEO satellites can perform complex tasks without the need for large, bulky hardware. This is a testament to the efficiency of their design, as it enables high performance with reduced size, weight, and power (SWaP) requirements.
4. Lower Launch Costs
The cost of launching satellites into orbit is directly tied to their size and weight.
Ride-Sharing Opportunities: Smaller satellites can take advantage of ride-sharing missions, where multiple satellites are launched on the same rocket, significantly reducing costs.
Dedicated Launchers: Companies like Rocket Lab and Astra specialise in launching small satellites, catering specifically to the growing demand for LEO missions.
Frequent Deployments: The smaller size allows operators to deploy prominent constellations cost-effectively, as seen with Starlink and OneWeb.
The economic advantage of smaller satellites aligns perfectly with the cost-sensitive nature of LEO missions. Smaller satellites can take advantage of ride-sharing opportunities, dedicated launchers, and frequent deployments, all of which contribute to cost reduction in LEO missions.
5. Constellation-Based Architecture
Many LEO missions involve deploying constellations of satellites rather than relying on a single large platform.
Distributed Capabilities: Instead of a single massive satellite, constellations comprise numerous small satellites that work together to provide global coverage and redundancy.
Scalability: Constellations enable incremental deployment, allowing operators to scale their networks over time.
Risk Mitigation: A failure of a tiny satellite has minimal impact on the overall network, whereas the loss of a large satellite in higher orbits would be catastrophic.
The reliance on constellations encourages the use of smaller satellites that are easier and cheaper to produce and deploy.
7. Easier End-of-Life Management
Dealing with space debris is a growing concern, and smaller satellites offer advantages in end-of-life management.
Natural Deorbiting: Atmospheric drag in LEO ensures that small satellites naturally re-enter and burn up within a few years, reducing long-term debris risks.
Deorbit Mechanisms: Many small satellites are equipped with simple deorbit devices, such as drag sails, that ensure compliance with guidelines for mitigating space debris.
The ease of managing smaller satellites at the end of their mission life contributes to their appeal for LEO operations.bodies.
6. Faster Production and Deployment Cycles
Smaller satellites have shorter development cycles, enabling rapid production and deployment.
Streamlined Manufacturing: The simplicity of small satellite designs enables efficient production processes, often utilising automation and 3D printing.
Agility in Deployment: Operators can quickly respond to emerging needs, such as disaster monitoring or IoT connectivity, by deploying small satellites in a matter of months.
The ability to produce and launch small satellites quickly is particularly valuable in dynamic industries where flexibility is key.
8. Specialised Mission Objectives
LEO satellites are often designed for specific, focused objectives, enabling smaller, mission-specific designs.
Earth Observation: High-resolution cameras and sensors for environmental monitoring or disaster response require precise but compact instrumentation.
Communication: LEO satellites for broadband internet or IoT use lightweight transceivers optimised for targeted coverage areas.
Scientific Research: Many small satellites are used for scientific experiments, requiring only the minimal payload necessary to achieve their research goals.
The targeted nature of LEO missions allows satellites to be tailored for efficiency and compactness.
9. Innovative Propulsion Systems
LEO satellites benefit from the development of compact and efficient propulsion systems.
Electric Propulsion: Miniaturised electric propulsion systems, such as ion thrusters, are ideal for small satellites, providing efficient station-keeping and orbit adjustments.
Chemical Propulsion Alternatives: Smaller satellites often use simpler cold-gas or monopropellant thrusters, reducing size and complexity.
Compact propulsion systems enable small satellites to perform necessary manoeuvres without adding excessive weight.
10. The Role of NewSpace Philosophy
The NewSpace movement emphasises innovation, cost reduction, and accessibility, aligning well with the use of small satellites in LEO.
Startups and Universities: Many small satellite missions are led by startups or academic institutions, which prioritise cost-effective designs.
Commercial Applications: The commercialisation of space has driven demand for small, affordable satellites that can rapidly deliver value.
NewSpace initiatives have revolutionised the satellite industry, fostering the growth of small satellite missions.
Conclusion
The small size of LEO satellites reflects a confluence of technological, economic, and operational factors. Their short operational lifespans, reduced power requirements, and reliance on miniaturised technologies enable efficient and cost-effective designs. Furthermore, their use in constellations, faster production cycles, and alignment with NewSpace philosophies have cemented their role as a cornerstone of modern space operations.
As the demand for global connectivity, Earth observation, and IoT services grows, the importance of small LEO satellites will continue to rise. With advancements in propulsion, materials, and onboard systems, the capabilities of these compact satellites will only expand, ensuring their vital role in shaping the future of space exploration and technology.