Satellite Attitude Control in Survival Mode Without Local Time Knowledge
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Solution Overview
Problem
Existing satellite attitude control systems in survival mode for inclined low orbits require prior knowledge of local time, making them complex to implement, especially in non-sun-synchronous orbits, and necessitate different configurations for satellites in various orbits, which is impractical for large constellations.
Innovation Solution
A method for satellite attitude control in survival mode that uses a first control law to rotate the satellite around the X axis, ensuring the solar generator remains stationary and directed towards the sun, regardless of local time, using magnetic torquers and inertial actuators to maintain solar generator alignment with the sun, even in non-sun-synchronous orbits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the axis of survival angular momentum is predetermined as a function of local time to maximize solar generator insolation, then the average insolation on solar generators is maximized, but the control system becomes complex and requires a priori knowledge of local time
Solution Approach 1:
The patent extracts the dependency on local time knowledge from the control system by using a fixed predetermined axis for survival angular momentum that is independent of orbital local time. This removes the complexity of calculating and updating the axis based on varying local time conditions while still maintaining effective solar generator illumination through the natural orbital mechanics.
2Adaptability or versatility
If the axis of survival angular momentum varies with local time to adapt to drifting orbits, then solar generator performance is optimized, but the satellite requires different configurations for different orbits
Solution Approach 1:
The patent applies universality by designing a single fixed axis configuration for survival angular momentum that works across all orbital conditions including drifting orbits. This universal approach eliminates the need for different satellite configurations or pre-programmed local time data, allowing the same satellite design to be deployed in various orbits without modification.
3Use of energy by moving object
If the satellite regularly updates the axis of survival angular momentum to account for local time variation, then solar generator insolation is maximized, but the control algorithm becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-establishing a fixed axis for survival angular momentum before launch that remains constant throughout the mission. This preliminary configuration eliminates the need for complex real-time updates or calculations of the axis based on local time variations, simplifying the control algorithm while maintaining effective solar power generation through the satellite's natural orbital behavior.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable and adaptive attitude control for satellites in survival mode without prior knowledge of local time, ensuring continuous sunlight exposure for power generation across various inclined low orbits, simplifying configuration and operation for constellations.
Implementation Method 1
magnetic torquers capable of forming internal magnetic moments in a satellite reference frame
Implementation Method 2
inertial actuators capable of forming internal angular momentums in said satellite reference frame
Implementation Method 3
at least one solar generator, at least one solar sensor
Data Source
AI summary
A method for attitude control of a satellite in inclined low orbit in survival mode is disclosed, the satellite including at least one solar generator, at least one solar sensor, magnetic torquers capable of forming internal magnetic moments in a satellite reference frame having three orthogonal axes X, Y, and Z, and inertial actuators capable of forming internal angular momentums in the satellite reference frame. The at least one solar sensor has a field of view at least 180° wide within the XZ plane around the Z axis, the method including a step of attitude control using a first control law, a step of searching for the sun by means of the at least one solar sensor, when a first phase of visibility of the sun is detected, and a step of attitude control using a second control law.