Fraczek Michael, Behrendt Andreas, Schmitt Nikolaus
EADS Innovation Works, Willy-Messerschmitt-Straße, 85521 München, Germany.
Opt Express. 2013 Jul 15;21(14):16398-414. doi: 10.1364/OE.21.016398.
A first laboratory prototype of a novel concept for a short-range optical air data system for aircraft control and safety was built. The measurement methodology was introduced in [Appl. Opt. 51, 148 (2012)] and is based on techniques known from lidar detecting elastic and Raman backscatter from air. A wide range of flight-critical parameters, such as air temperature, molecular number density and pressure can be measured as well as data on atmospheric particles and humidity can be collected. In this paper, the experimental measurement performance achieved with the first laboratory prototype using 532 nm laser radiation of a pulse energy of 118 mJ is presented. Systematic measurement errors and statistical measurement uncertainties are quantified separately. The typical systematic temperature, density and pressure measurement errors obtained from the mean of 1000 averaged signal pulses are small amounting to < 0.22 K, < 0.36% and < 0.31%, respectively, for measurements at air pressures varying from 200 hPa to 950 hPa but constant air temperature of 298.95 K. The systematic measurement errors at air temperatures varying from 238 K to 308 K but constant air pressure of 946 hPa are even smaller and < 0.05 K, < 0.07% and < 0.06%, respectively. A focus is put on the system performance at different virtual flight altitudes as a function of the laser pulse energy. The virtual flight altitudes are precisely generated with a custom-made atmospheric simulation chamber system. In this context, minimum laser pulse energies and pulse numbers are experimentally determined, which are required using the measurement system, in order to meet measurement error demands for temperature and pressure specified in aviation standards. The aviation error margins limit the allowable temperature errors to 1.5 K for all measurement altitudes and the pressure errors to 0.1% for 0 m and 0.5% for 13000 m. With regard to 100-pulse-averaged temperature measurements, the pulse energy using 532 nm laser radiation has to be larger than 11 mJ (35 mJ), regarding 1-σ (3-σ) uncertainties at all measurement altitudes. For 100-pulse-averaged pressure measurements, the laser pulse energy has to be larger than 95 mJ (355 mJ), respectively. Based on these experimental results, the laser pulse energy requirements are extrapolated to the ultraviolet wavelength region as well, resulting in significantly lower pulse energy demand of 1.5 - 3 mJ (4-10 mJ) and 12-27 mJ (45-110 mJ) for 1-σ (3-σ) 100-pulse-averaged temperature and pressure measurements, respectively.
构建了一种用于飞机控制与安全的短程光学大气数据系统新概念的首个实验室原型。测量方法已在[《应用光学》51, 148 (2012)]中介绍，该方法基于激光雷达探测空气中弹性和拉曼后向散射的已知技术。可以测量多种飞行关键参数，如气温、分子数密度和压力，还能收集有关大气颗粒和湿度的数据。本文展示了使用脉冲能量为118 mJ的532 nm激光辐射的首个实验室原型所实现的实验测量性能。分别对系统测量误差和统计测量不确定度进行了量化。对于在200 hPa至950 hPa气压变化但气温恒定为298.95 K的测量，从1000个平均信号脉冲的平均值获得的典型系统温度、密度和压力测量误差较小，分别为< 0.22 K、< 0.36%和< 0.31%。在946 hPa气压恒定但气温在238 K至308 K变化时，系统测量误差甚至更小，分别为< 0.05 K、< 0.07%和< 0.06%。重点关注了作为激光脉冲能量函数的不同虚拟飞行高度下的系统性能。虚拟飞行高度由定制的大气模拟腔系统精确生成。在此背景下，通过实验确定了使用测量系统所需的最小激光脉冲能量和脉冲数，以满足航空标准中规定的温度和压力测量误差要求。航空误差容限将所有测量高度的允许温度误差限制为1.5 K，将0 m高度的压力误差限制为0.1%，13000 m高度的压力误差限制为0.5%。对于100次脉冲平均温度测量，考虑到所有测量高度的1 - σ（3 - σ）不确定度，使用532 nm激光辐射的脉冲能量必须大于11 mJ（35 mJ）。对于100次脉冲平均压力测量，激光脉冲能量必须分别大于95 mJ（355 mJ）。基于这些实验结果，激光脉冲能量要求也外推到了紫外波长区域，对于1 - σ（3 - σ）100次脉冲平均温度和压力测量，分别导致显著更低的脉冲能量需求，即1.5 - 3 mJ（4 - 10 mJ）和12 - 27 mJ（45 - 110 mJ）。
