Short-range optical air data measurements for aircraft control using rotational Raman backscatter

Area of Science:

• Atmospheric remote sensing
• Optical physics
• Aviation technology

Background:

• Aircraft control and safety rely on accurate air data.
• Existing air data systems have limitations.
• Lidar-based techniques offer potential for novel air data sensing.

Purpose of the Study:

• To present the experimental performance of a laboratory prototype for a short-range optical air data system.
• To quantify systematic measurement errors and statistical uncertainties for key atmospheric parameters.
• To determine minimum laser pulse energy requirements to meet aviation standards for temperature and pressure measurements.

Main Methods:

• Developed a laboratory prototype for an optical air data system.
• Utilized lidar techniques detecting elastic and Raman backscatter from air.
• Employed a custom atmospheric simulation chamber to generate virtual flight altitudes.
• Quantified measurement errors and uncertainties using 532 nm laser radiation.

Main Results:

• Achieved small systematic errors: <0.22 K (temperature), <0.36% (density), <0.31% (pressure) under varying pressures.
• Achieved even smaller systematic errors: <0.05 K (temperature), <0.07% (density), <0.06% (pressure) under varying temperatures.
• Determined minimum pulse energy requirements: >11 mJ (temperature) and >95 mJ (pressure) for 100-pulse average at 1-σ uncertainty.
• Extrapolated lower pulse energy needs for ultraviolet wavelengths (1.5-3 mJ for temperature, 12-27 mJ for pressure).

Conclusions:

• The optical air data system prototype shows promising performance for measuring flight-critical parameters.
• The system can meet aviation standards for temperature and pressure with optimized laser pulse energy.
• Further development, especially in the UV spectrum, could significantly reduce energy requirements.