Very Low Earth Orbit (VLEO) is defined as the region of space located approximately 100 – 450 kilometers above the Earth’s surface. Satellites operating in this region come with a set of unique advantages and challenges.
Advantages of VLEO
Reduced Power Draw: Because of the proximity to Earth, VLEO satellites require less power for operations like data transmission, which in turn reduces the overall power requirements of the satellite.
Improved Resolution: VLEO satellites can offer higher resolution imagery than their higher-altitude counterparts due to their closer proximity to the Earth.
Lower Latency: The closer proximity to Earth also results in lower latency in communication, which can be crucial for certain applications.
Natural Deorbiting: The high atmospheric drag at VLEO altitudes can naturally deorbit most objects within weeks, reducing the accumulation of space debris.
Cost Effectiveness: Deploying satellites to VLEO is significantly easier and cheaper than into higher orbits. Smaller, lighter platforms using cheaper payloads in VLEO can perform as well as larger, more expensive platforms in conventional Low Earth Orbit (LEO).
Challenges of VLEO
High Atmospheric Drag: The environment of VLEO causes high atmospheric drag on spacecraft, requiring regular propulsion to maintain an orbital altitude.
Damage and Erosion: The higher density of atomic oxygen in VLEO compared to higher orbits results in more damage and erosion to spacecraft surfaces.
Reduced Coverage and Accessibility: A satellite in VLEO will have reduced coverage and accessibility due to a smaller coverage footprint by the sensors, a restricted elevation angle, and reduced communication windows with ground stations.
Applications of VLEO
Very Low Earth Orbit (VLEO) offers unique advantages that make it attractive for several types of applications. Here’s a list of some major applications for VLEO:
|Communication||One of the primary advantages of VLEO is the reduced latency in communication compared to satellites in higher orbits. This is because the time it takes for a signal to travel to and from a satellite decreases as the altitude of the satellite decreases. Therefore, VLEO is of great interest for building next-generation satellite communication networks.|
|Earth Observation||Due to its proximity to the Earth, VLEO is an excellent location for satellites tasked with Earth observation. Satellites in VLEO can capture high-resolution images and data which can be used in various applications like environmental monitoring, disaster management, urban planning, and military surveillance.|
|Space Debris Monitoring||Given the increasing concern over space debris, VLEO can be used to monitor and track space debris. As we continue to launch more satellites into space, tracking and managing space debris has become increasingly important for ensuring the long-term sustainability of space activities.|
|Scientific Research||VLEO provides a unique environment for a variety of scientific experiments and research. This can range from studying the Earth’s atmosphere to conducting gravitational experiments, and to investigating the behaviors of various materials and technologies in the space environment.|
Examples of Past and Planned VLEO Missions
The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission of ESA remained at an altitude of 240-280 km from 2009 to 2013 with the help of xenon-fueled electric thrusters.
The SLATS (Super Low Altitude Test Satellite) of JAXA (Japan Aerospace Exploration Agency), with a mass of approximately 400 kg, was flown at an altitude of approximately 200 km from 2017-2019, and was powered with xenon thrusters.
Since November 1998, the ISS (International Space Station) resides at altitudes of around 400 km. Cargo vehicles and onboard thrusters help the ISS to maintain its orbit in VLEO.