Safely Removing Satellites: The Process of De-orbiting

In the age of rapid advancements in space technology, the challenge of safely de-orbiting satellites is gaining critical importance. As thousands of satellites are deployed to serve global communications, Earth observation, and scientific missions, managing the end-of-life stage for these satellites is a priority to prevent space debris and ensure long-term sustainability in Earth’s orbits.

This article explores the detailed process of de-orbiting satellites, how engineers plan for their safe removal after their operational life, and the technologies used to mitigate the growing threat of space debris.

What is Satellite De-orbiting?

De-orbiting refers to the deliberate process of safely removing a satellite from its orbit, either by directing it to burn up upon re-entry into Earth’s atmosphere or by relocating it to a graveyard orbit. When satellites reach the end of their operational life or become non-functional, they must be de-orbited to prevent collisions with other space objects, which can create dangerous debris clouds and hinder future space missions.

This process has become essential as the population of artificial objects in orbit grows with the rise of satellite constellations, like SpaceX’s Starlink, adding hundreds or even thousands of satellites into low-Earth orbit (LEO).

Importance of De-orbiting Satellites

Space debris, also known as orbital debris, includes defunct satellites, spent rocket stages, and fragments from collisions or disintegration. According to NASA, there are more than 27,000 pieces of space debris larger than 10 cm currently being tracked, and millions of smaller fragments are unaccounted for. These objects pose a collision risk to active satellites and crewed spacecraft.

The Kessler Syndrome is a scenario in which the density of objects in low-Earth orbit becomes so high that collisions between objects generate more debris, causing a cascade of destruction. This amplifies the importance of carefully planned satellite de-orbiting.

The De-orbiting Process: Step by Step

The de-orbiting of satellites follows a well-defined process, and the method chosen depends on the altitude of the satellite and its purpose. Below are the steps typically involved:

1. End-of-Life Planning

Satellite missions are typically planned with an end-of-life strategy to account for how they will be removed from orbit once their functionality expires. This includes calculating fuel reserves needed for a controlled de-orbit or determining an alternative disposal method, such as moving the satellite into a graveyard orbit.

Most satellites in low-Earth orbit are de-orbited within a few years after the end of their mission, while satellites in geostationary orbits may be moved to graveyard orbits to free up valuable space.

2. Lowering Orbital Altitude

In a controlled de-orbit, the satellite’s onboard propulsion system is used to gradually lower its altitude until atmospheric drag causes it to re-enter the Earth’s atmosphere. For low-Earth orbit satellites, this is the most common method.

This process must be calculated with great precision, as an uncontrolled re-entry could result in parts of the satellite reaching Earth's surface, potentially causing damage.

3. Atmospheric Re-entry and Burn-Up

For many satellites in LEO, the de-orbiting process involves re-entering the Earth's atmosphere at high speeds, where the intense heat caused by friction with atmospheric particles will cause the satellite to burn up, disintegrating into harmless fragments.

This is the ideal scenario, as it ensures that no satellite debris falls to Earth, reducing risks to human life and property. Satellites designed to de-orbit in this manner often include materials that are meant to fully burn up on re-entry.

4. Relocation to a Graveyard Orbit

Satellites in higher orbits, such as those in geostationary orbit (approximately 36,000 km above Earth), cannot be safely de-orbited due to their distance from the Earth. In such cases, they are moved to a graveyard orbit, which lies about 300 km above geostationary orbit.

This graveyard orbit is a designated area for non-functional satellites, where they are stored indefinitely to avoid interference with active satellites. To move a satellite to this orbit, engineers use any remaining fuel to propel it to this altitude once it has completed its mission.

5. Passivation

Passivation is the process of depleting a satellite’s remaining energy sources, including fuel, batteries, and pressurized tanks. This ensures that the satellite does not explode due to internal pressure or stored energy, which would create additional debris.

6. Tracking and Monitoring

Even after de-orbiting, satellites are tracked using ground-based radar and optical systems to ensure they are safely removed from orbit. Satellites that are left in orbit to eventually decay naturally must be monitored to ensure their path remains predictable and does not pose a collision risk to other objects.

Key Technologies for De-orbiting

Several innovative technologies are being developed to improve satellite de-orbiting processes, especially with the rise of small satellite constellations. Some of these technologies include:

Legal and Regulatory Framework

International space agencies and organizations, such as the United Nations Office for Outer Space Affairs (UNOOSA), have developed guidelines for satellite de-orbiting to promote the safe and responsible use of outer space. The Inter-Agency Space Debris Coordination Committee (IADC) provides recommendations for limiting the creation of space debris and ensuring that satellites are removed from orbit within 25 years of mission completion.

Many countries now require satellite operators to submit detailed end-of-life de-orbiting plans before launching their spacecraft.

Conclusion

The de-orbiting of satellites is a critical process to ensure the safety and sustainability of space operations. As space activity increases and the number of satellites in orbit continues to grow, managing the end-of-life phase for these spacecraft will become even more essential.

By implementing advanced de-orbiting techniques, leveraging innovative technologies, and adhering to international guidelines, the global space community can mitigate the risks of space debris and ensure that future generations can continue to benefit from space exploration and satellite services.

Recommended products for building a satellite

If you're planning to build a satellite at home, here are some top products you can purchase online to get started with a small satellite project, like a CubeSat:

These products, along with open-source satellite kits, can give you a solid foundation to design and assemble a small satellite for educational or hobbyist purposes!

Building a fully functional satellite using the listed products is an exciting and complex project. Here's a step-by-step guide to help you assemble these components into a working satellite, such as a CubeSat:

Step 1: Define Your Satellite’s Mission

Before assembly, decide what your satellite will do. Whether it’s Earth observation, communication, or scientific experiments, defining the mission will help you choose the right sensors and equipment.

Step 2: Build the CubeSat Frame


Step 3: Design the Power System


Step 4: Set Up the Onboard Computer


Step 5: Attach Sensors and Modules


Step 6: Communication System


Step 7: Write and Upload the Software


Step 8: Testing and Simulation


Step 9: Launch Preparation


Step 10: Launch and Operate

Building a satellite at home is an ambitious yet achievable goal for hobbyists, engineers, and students. With these components, proper planning, and the right mission objectives, you can contribute to space research and innovation right from your home.