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Updated: Jul 7, 2026
10:42
Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Summary
Atmospheric refraction causes mirages in infrared observations of ships at sea. A model involving temperature inversion and gravity waves explains observed horizon variations and extended visibility.
Area of Science:
- Atmospheric optics
- Infrared remote sensing
- Naval warfare technology
Background:
- Infrared (IR) observations of distant, low-elevation targets are affected by atmospheric refraction.
- Temperature gradients in the atmosphere commonly cause mirages, limiting visibility and distorting target appearance.
- Accurate tracking of seaborne thermal sources is crucial for naval operations.
Purpose of the Study:
- To analyze infrared image data of a seaborne thermal source affected by atmospheric conditions.
- To investigate the impact of atmospheric refraction and mirages on long-range IR observations.
- To develop a model explaining observed phenomena like horizon elevation variations and extended visibility.
Main Methods:
- Analysis of a 22-minute infrared image sequence recorded at the U.S. Naval Surface Warfare Center.
- Observation of a ship carrying a heat source moving towards the camera.
- Development of an atmospheric model incorporating temperature inversion and gravity waves.
Main Results:
- Observed quasi-periodic variations in horizon elevation.
- Documented extended range of visibility beyond typical limits.
- The data showed distortions consistent with atmospheric refraction and mirages.
- A model with a temperature inversion and a gravity wave reproduced the observed features.
Conclusions:
- Atmospheric refraction, particularly temperature inversions and gravity waves, significantly impacts long-range infrared observations of seaborne targets.
- The developed model provides a plausible explanation for mirages, horizon variations, and enhanced visibility observed in the infrared spectrum.
- Understanding these atmospheric effects is critical for improving the accuracy and reliability of naval infrared detection systems.
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