Safely Removing Satellites: The Process of De-orbiting
Safely Removing Satellites: The Process of De-orbiting
Featured Telescope of the Day!
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.
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).
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 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.
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:
Drag Sails: These are deployable structures that increase the surface area of a satellite, allowing atmospheric drag to pull it out of orbit more quickly. Drag sails are especially useful for smaller satellites in LEO.
Ion Propulsion Systems: Some satellites use ion propulsion systems that provide precise control over the satellite's movement and allow it to de-orbit efficiently using minimal fuel.
Tethers: Electrodynamic tethers generate a current by interacting with Earth’s magnetic field, which creates drag and helps pull the satellite out of orbit.
Active Debris Removal (ADR): Several organizations are working on ADR systems that can capture and de-orbit non-functional satellites or space debris using robotic arms or harpoons. This could be essential for larger pieces of space junk that cannot be moved using onboard systems.
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.
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.
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:
Arduino Uno R3 Microcontroller Ideal for controlling various satellite components. Easy to program and widely used in DIY projects.
Raspberry Pi 4 Model B Perfect for running satellite operations and data management. Powerful and compact, used for space projects like Pi-Sat.
Adafruit Ultimate GPS Breakout – 66 channel A compact GPS module for real-time positioning and tracking. Great for satellite navigation and telemetry.
Sun Power Solar Cells Reliable small solar panels to power your satellite. Lightweight and efficient for CubeSat-sized projects.
XBee 3 RF Module Used for wireless communication between your satellite and ground station. Designed for long-range communication and low power consumption.
Tiny Circuits 9-Axis IMU (Inertial Measurement Unit) Essential for satellite orientation and stabilization. Measures acceleration, rotation, and magnetic field for accurate positioning.
Lipo Battery Pack 3.7V 10000mAh A reliable power source to store energy generated by solar panels. Lightweight and commonly used for small satellite projects.
CubeSat Structure Kit 3D-printed frame kits available for DIY satellite projects. A basic structure for housing your satellite's electronics.
TTGO LoRa SX1276 Module A radio communication module designed for long-range communication. Great for sending telemetry data from low Earth orbit.
MATLAB & Simulink Student Version Essential for simulating and testing your satellite’s functions, including orbit trajectories and control systems.
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
Assemble the CubeSat Structure Kit Begin by constructing the physical frame of your CubeSat. These kits usually come with lightweight, durable materials such as 3D-printed parts or aluminum. Ensure the structure has enough space for components like the microcontroller, battery, and sensors.
Step 3: Design the Power System
Install the Solar Panels (Pololu High-Power Solar Cells) Mount the solar panels on the exterior of your CubeSat. These panels will provide continuous power to your satellite in orbit. Ensure that they are positioned to maximize exposure to sunlight when in space.
Connect the Battery Pack (Lipo Battery Pack 3.7V 10000mAh) Wire the solar panels to the LiPo battery to store energy. The battery will ensure your satellite has power even when it's in Earth's shadow.
Step 4: Set Up the Onboard Computer
Install the Raspberry Pi 4 Model B This serves as the “brain” of your satellite. It will process data and control operations. Connect the Raspberry Pi to the CubeSat’s power system via the battery pack. Add a microSD card with your pre-written code and data management software for the satellite's mission.
Integrate the Arduino Uno R3 Microcontroller Use Arduino to handle real-time tasks, like managing sensors or communication. It’s a complementary system to the Raspberry Pi, which handles the overall mission, while Arduino handles specific control tasks.
Step 5: Attach Sensors and Modules
Install the GPS Module (Adafruit Ultimate GPS Breakout) Attach the GPS module to track the satellite’s position in orbit. Program the GPS to report position data to the Raspberry Pi for logging and telemetry.
Mount the 9-Axis IMU (Tiny Circuits IMU) This module measures acceleration, rotation, and magnetic fields to stabilize your satellite. Connect it to the Arduino for real-time orientation and attitude control.
Step 6: Communication System
Install the XBee 3 RF Module This module handles communication between the satellite and your ground station. Attach the antenna to the exterior of the satellite frame for optimal signal reception.
Integrate the TTGO LoRa SX1276 Module LoRa offers long-range communication and is ideal for sending telemetry data. Connect the module to the Raspberry Pi and program it to transmit data to Earth.
Step 7: Write and Upload the Software
Create Control and Data Processing Software On the Raspberry Pi, write code that controls the satellite’s mission—whether it's capturing images, logging GPS data, or transmitting data back to Earth. Use Python, MATLAB, or Simulink to create algorithms that simulate orbital functions and process sensor data.
Upload the Control Code to Arduino Use the Arduino IDE to upload code that manages real-time control systems, such as adjusting the satellite’s orientation using the IMU data.
Step 8: Testing and Simulation
Simulate the Satellite’s Orbit and Functionality Before launch, test your satellite’s functionality using MATLAB & Simulink. Simulate its orbit, test communication ranges, and monitor the power system. Place the satellite in a vacuum chamber (if available) to test how it will function in space conditions.
Test Communication and Power Systems Ensure that your communication modules are working by setting up a ground station and testing data transmission. Test the solar panels and battery pack to confirm they are providing adequate power.
Step 9: Launch Preparation
Coordinate with a Launch Provider Once your CubeSat is fully assembled and tested, work with a launch provider such as SpaceX or Rocket Lab for a ride-share launch. Ensure your satellite meets their size, weight, and regulatory standards.
Obtain Regulatory Approvals Depending on your location, you may need licensing from local or international space authorities (such as the FCC in the U.S.) to launch and operate your satellite.
Step 10: Launch and Operate
Launch the Satellite Your satellite will be deployed into orbit by the launch provider.
Operate the Satellite from the Ground Use your ground station to communicate with your satellite, receive telemetry data, and monitor its mission progress.
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.