Pre-Launch Calibration of the Bidirectional Reflectance Distribution Function (BRDF) of Ultraviolet-Visible Hyperspectral Sensor Diffusers
Abstract
:1. Introduction
1.1. Overview
1.2. Description of BRDF
2. Experiment
2.1. Equipment for Calibration
- Solar simulator
- 2.
- Five-dimensional mobile station
- 3.
- Standard diffuser
2.2. Calibration Setup
- The centers of these two surfaces must be perpendicular to their respective planes, with a consistent distance of approximately L, in accordance with the standard irradiance calibration.
- This involves transitioning the UVS operational mode to “earth mode” to initiate observations of a designated point beneath the Earth’s surface. Adjustments are made to align the line connecting the center of the Earth port with the center of the diffuser to create a 30° angle with the normal of the diffuse reflector plate. Before commencing the calibration process, the light source is activated and allowed to stabilize for ten minutes.
- To capture comprehensive data, the rotation of the payload turntable begins, starting from the edge of the payload field of view (FOV) and progressing in 0.5° intervals until the instrument completes a full FOV scan. Ten observations are collected for each rotation position.
- Following this, the payload’s operational mode is transitioned to “solar mode”, and the onboard diffuse reflective plate is configured to “calibration 1” mode. The test apparatus is setup according to the provided diagram, ensuring that the front surface of the light source outlet aligns parallel to the sun port’s surface.Equal distances must be maintained between the optical stimulus and the onboard diffuser, both in the irradiance mode and the radiance mode, through careful adjustments.
- The angles are set to β = 26.45° and α = 0, and 50 data frames are acquired. α measurements start from −4°, adjusting in 1° increments up to +4°, with images captured at each α angle. Starting at 14.95°, β is measured in 1° increments up to 37.95°, and α is recorded at each β angle. Finally, the onboard diffuse reflector calibration board is transitioned to calibration 2 mode, and the test procedure is repeated to conclude the BRDF calibration for both onboard diffuse reflector boards.
3. Results and Discussion
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Index | Characteristics | ||
---|---|---|---|
Scientific objectives | O3, SO2, NO2, BrO, O3 profile, Aerosol, Cloud, etc. | ||
Channel | UV1 | UV2 | UVIS |
Spectral range/nm | 250–300 nm | 300–320 nm | 310–495 nm |
Spectral resolution/nm | ~1 | 0.5 | ~0.6 |
Field of view | 112° | ||
Spatial resolution | 28 km × 21 km (at nadir) | 7 km × 7 km (at nadir) | 7 km × 7 km (at nadir) |
SNR | >50 | >200 | >200@ UV >1000@ VIS |
Wavelength calibration accuracy | 0.05 nm | 0.05 nm | 0.05 nm |
BRDF calibration accuracy | 3% |
UV1 | UV2 | VIS | |
---|---|---|---|
Source non-uniformity | 1.5% | 1. 5% | 1.5% |
Standard diffuser plate uncertainty | 1% | 1% | 1% |
UVS non-stationarity | 0.42% | 0.42% | 0.47% |
Source non-stationarity | 1% | 1% | 1% |
Solar simulator distance error | 0.5% | 0.5% | 0.5% |
Total | 2.162% | 2.162% | 2.173% |
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Mao, J.; Wang, Y.; Shi, E.; Wang, J.; Yao, S.; Zhu, J. Pre-Launch Calibration of the Bidirectional Reflectance Distribution Function (BRDF) of Ultraviolet-Visible Hyperspectral Sensor Diffusers. Appl. Sci. 2024, 14, 7278. https://doi.org/10.3390/app14167278
Mao J, Wang Y, Shi E, Wang J, Yao S, Zhu J. Pre-Launch Calibration of the Bidirectional Reflectance Distribution Function (BRDF) of Ultraviolet-Visible Hyperspectral Sensor Diffusers. Applied Sciences. 2024; 14(16):7278. https://doi.org/10.3390/app14167278
Chicago/Turabian StyleMao, Jinghua, Yongmei Wang, Entao Shi, Jinduo Wang, Shun Yao, and Jun Zhu. 2024. "Pre-Launch Calibration of the Bidirectional Reflectance Distribution Function (BRDF) of Ultraviolet-Visible Hyperspectral Sensor Diffusers" Applied Sciences 14, no. 16: 7278. https://doi.org/10.3390/app14167278