Inertial sensors are used on-board satellites and spacecraft to provide measurements of the attitude of the system with respect to inertial baselines.
They are often used in conjunction with other attitude sensors, such as sun sensors or star trackers, to give additional readings for ongoing attitude determination.
In this article you can see an overview of the main forms of inertial measurement attitude sensors along with details on various systems available on the market today.
Contents
- About inertial attitude sensing
- Accelerometers
- Gyroscopes
- Inertial Measurement Units (IMUs)
- Further reading
About inertial attitude sensing
Inertial sensing units are used in space systems to determine the motion and orientation of the satellite or spacecraft with respect to an inertial reference frame.
Inertial sensors can measure attitude without relying only on external reference points or resources, such as signals from ground stations, the starscape, or the Earth’s horizon.
Commercial products are available in 3 main configurations:
- A single-axis gyroscope or accelerometer
- An Inertial Reference Unit (IRU) with 3 orthogonal gyroscopes
- An Inertial Measurement Unit (IMU) with 3 orthogonal gyroscopes and 3 orthogonal accelerometers
The sections below include a selection of inertial sensors available on the global market today.
You can click on the links to open pages with more detail on each system. From these pages you can submit requests for quotes, documents, or further information by the supplier, and we’ll handle the request for you (find out more about how this works here).
If you want to shortcut this process, or need some assistance refining either your specific inertial sensor or more general attitude determination requirements, you can instead submit an open tender and our expert procurement team will get back to you ASAP.
Accelerometers
Accelerometers measure velocity changes of the system as it travels through space, usually by analyzing the movements of an internal mass relative to it’s casing.
When evaluating accelerometer options it is very important to consider the acceptable values for the input and output acceleration ranges, as well as the minimum measurable acceleration.
You should also ensure that any accelerometers are compatible with gyroscopes if these are also being used to determine angular changes of the spacecraft.
The AMU is composed of four accelerometers disposed on a regular tetrahedron. It includes an accelerometer adaptation electronic board with four electrically independent channels connected to each Fibre Optic Gyro (FOG) Electronic Module (FEM) of the Gyro Electronic Unit (GEU) by an electrical harne
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request infoGyroscopes
Gyroscopes use a spinning wheel as a fixed reference point to determine angular momentum changes.
If the overall system’s attitude changes, the wheel adjusts, and the extent to which it does so can be used to measure the spacecraft’s new orientation.
In satellites, a gyroscope is usually available as either a Microelectromechanical System (MEMS) Gyro or a Fiber Optic Gyro (FOG). FOGs typically offer superior performance but are heavier and require more power.
The NewSpace Systems NSGY-001 Stellar Gyro is a gyro system that propagates a spacecraft's attitude from a known initial condition, without drift, while sufficient stars are common across frames. The image-based rotation estimates can complement a set of MEMS rate gyroscopes to maintain a high accuracy attitude estimate at low angular rates (where MEMS gyroscope drift is most severe).
The GranStal Solutions GS-SFA-311A - Fiber Optic Gyroscope is a 3-axis FOG that outputs angular velocity and attitude data in the three orthogonal axes of the carrier via an RS422 interface. The FOG module has been designed as a lightweight system in a small physical volume and has achieved flight heritage.
Inertial Measurement Units (IMUs)
Inertial Measurement Units (IMUs) are combined, integrated units containing a combination of accelerometers, gyroscopes, and magnetometers.
The system can have varying Degrees of Freedom (DoF) depending on requirements, along with in-built redundancy with additional sensors or innovative setups.
The performance of the individual sensors is important for overall attitude accuracy and the integration and interoperability between sensors is important to ensure seamless measurements.
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Further reading
- Attitude sensors
- Accelerometers
- Gyroscopes
- Inertial Measurement Units (IMUs)
- Sun sensors
- Star trackers
- Satellite components
