Scan Mirror Reflectivity Calibration for LEO Sensors
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Solution Overview
Problem
Low Earth orbit resource sensors with rotating, two-sided scan mirrors face performance degradation due to contamination over time, requiring effective calibration methods to maintain accurate data and imagery.
Innovation Solution
A scan mirror reflectivity calibration device that includes a light source assembly and detector assemblies to monitor and calibrate the mirrors by directing light onto the back side of the rotating two-sided scan mirror, detecting reflected light at various angles, positions, spectral bands, and polarizations, and storing reflectivity data for degradation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the scan mirror is made defect-free and both sides are made as close to identical as possible, then manufacturing precision is improved, but contamination over time degrades performance
Solution Approach 1:
The calibration device performs preliminary measurements of the scan mirror's reflectivity at multiple positions and angles before contamination significantly degrades performance. By establishing baseline data and monitoring changes over time, the system can detect early signs of contamination and adjust calibration parameters proactively, rather than waiting for performance degradation to occur
Solution Approach 2:
The system continuously monitors the scan mirror's reflectivity by comparing light intensity measurements taken at different positions and angles. This feedback mechanism allows the system to detect changes in mirror performance over time and automatically adjust calibration parameters to compensate for contamination, maintaining reliable operation despite degradation
2Productivity
If the scan mirror rotates continuously to scan earth surfaces, then productivity is improved, but the back side of the mirror becomes exposed to contamination
Solution Approach 1:
The calibration device uses the scan mirror's own rotation and positioning mechanisms to bring the back side of the mirror into position for measurement. The system leverages the existing rotational movement required for scanning operations to simultaneously perform calibration measurements, without requiring separate contamination prevention mechanisms or stopping the scanning process
3Measurement precision
If reflectivity is measured at multiple positions, angles, spectral bands, and polarizations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The calibration device uses a single light source and detector assembly that can measure reflectivity across multiple positions, angles, spectral bands, and polarizations by varying the mirror's orientation during rotation. This multi-functional approach allows comprehensive reflectivity characterization using one integrated system rather than requiring separate measurement devices for each parameter
Solution Approach 2:
The system dynamically adjusts the scan mirror's position and orientation during rotation to present different surfaces and angles to the light source and detector. By utilizing the mirror's rotational movement and varying its angular position, the system can measure reflectivity under multiple conditions sequentially, reducing the need for multiple static measurement configurations
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 continuous monitoring and calibration of the scan mirror's reflectivity over time, addressing contamination-induced performance degradation and ensuring accurate data collection by correlating reflectivity changes with position, angle, wavelength, and polarization.
Implementation Method 1
detect light that is emitted from the at least one light source assembly and that is reflected off of the back side of the rotating two-sided scan mirror
Data Source
AI summary
A scan mirror reflectivity calibration device is provided for monitoring and calibration of a rotating two-sided scan mirror. The scan mirror reflectivity calibration device can comprise at least one light source assembly operable to direct light onto a back side of a rotating two-sided scan mirror. The at least one light source assembly can be mounted outside a swept volume of the rotating two-sided scan mirror. The scan mirror reflectivity calibration device further comprises at least one detector assembly operable to detect light that is emitted from the at least one light source assembly and is reflected off of the back side of the rotating two-sided scan mirror. The at least one detector assembly can be mounted outside the swept volume of the rotating two-sided scan mirror.