Quasi-Optical Radar for Cloud Droplet Detection
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Solution Overview
Problem
Current LIDAR systems face difficulties in accurately characterizing multi-modal distributions of water droplet sizes in clouds, particularly when supercooled large droplets are present, leading to potential undetection and unsafe ice accretion on aircraft surfaces, which can alter aerodynamics and control.
Innovation Solution
A quasi-optical radar system that projects a divergent quasi-optical beam into the cloud atmosphere, allowing for a larger volume to be probed and enhancing the detection of sparse distributions of water droplets by using a system with a quasi-optical transmitter and receiver, and a cloud metric calculator to determine droplet density within the divergent projection volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If collimated LIDAR systems are used to measure cloud metrics, then the system can characterize mono-modal water droplet distributions, but the system fails to detect sparse super-cooled large droplets in multi-modal distributions
Solution Approach 1:
The patent changes the beam divergence parameter from collimated (small divergence) to uncollimated (large divergence) to transform the sampling volume characteristics. This parameter change allows the system to detect sparse SLDs while maintaining the ability to characterize overall droplet distributions, resolving the contradiction between measurement precision and detection reliability
Solution Approach 2:
The patent uses uncollimated LIDAR that probes a larger volume than necessary for mono-modal characterization, intentionally oversampling the cloud atmosphere. This excessive sampling action ensures that rare SLDs are detected while the data processing methods extract meaningful information about the dominant droplet population, solving the detection reliability problem
2Reliability
If uncollimated LIDAR systems are used to probe large cloud volumes, then the system can detect sparse SLDs, but the backscatter signal from SLDs is attenuated during signal averaging
Solution Approach 1:
The patent performs preliminary classification of backscatter signals into those originating from SLDs and those from the dominant droplet population. By identifying and separating SLD signals before averaging, the system preserves these rare but hazardous droplet detections while still benefiting from signal averaging for the dominant population, thus maintaining both reliability and measurement precision
Solution Approach 2:
The patent segments the backscatter signal analysis into distinct components: SLD contributions and dominant population contributions. This segmentation allows different processing strategies to be applied to each component, preserving SLD detection integrity while optimizing the signal-to-noise ratio for overall droplet characterization
3Device complexity
If collimated laser beams are used to sample cloud volume, then the beam projects a concentrated path, but the small field of view results in encountering few super-cooled large droplets
Solution Approach 1:
The patent inverts the conventional collimated beam approach by using an uncollimated beam with large divergence. Instead of concentrating the beam path, the system spreads the energy over a wide angle, transforming the sampling strategy from a narrow concentrated path to a broad dispersed volume, thereby encountering more SLDs while managing complexity through proven LIDAR technology
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
This approach enables the detection of even sparse distributions of water droplets, providing a continuous range-resolved backscatter signal and improving the accuracy of water droplet characterization, thereby enhancing the safety of aircraft by preventing ice accretion on unprotected surfaces.
Implementation Method 1
a quasi-optical receiver configured to detect a portion of the projected pulse of quasi-optical energy backscattered by the backscattering population of water particles
Data Source
AI summary
Apparatus and associated methods relate to determining, based on a detected portion of a projected pulse of quasi-optical energy backscattered by water particles within a divergent projection volume of a cloud atmosphere, properties of the backscattering water particles. The pulse of quasi-optical energy is projected into the divergent projection volume of the cloud atmosphere. The divergent projection volume is defined by an axis of projection and an angle of projection about the axis of projection. The portion of the projected pulse of optical energy backscattered by water particles within the divergent projection volume of the cloud atmosphere is received and detected. Various properties of the backscattering water particles, which can be determined from the detected portion of the projected pulse backscattered by water particles can include particle density and/or particle size.