We describe the design and performance of a lightweight broadband cavity-enhanced spectrometer for measurement of NO₂ on uncrewed aerial vehicles and light aircraft. The instrument uses a light-emitting diode (LED) centered at 457 nm, high-finesse mirrors (reflectivity =0.999963 at 450 nm), and a grating spectrometer to determine optical extinction coefficients between 430 and 476 nm, which are fit with custom spectral fitting software and published absorption cross sections. The instrument weighs 3.05 kg and has a power consumption of less than 35 W at 25 ^∘C. A ground calibration unit provides helium and zero air flows to periodically determine the reflectivity of the cavity mirrors using known Rayleigh scattering cross sections. The precision (1σ) for laboratory measurements is 43 ppt NO₂ in 1 s and 7 ppt NO₂ in 30 s. Measurement of air with known NO₂ mixing ratios in the range of 0–70 ppb agreed with the known values within 0.3 % (slope $=\mathrm{0.997}\pm \mathrm{0.007}$; r²=0.99983). We demonstrate instrument performance using vertical profiles of the NO₂ mixing ratio acquired on board an uncrewed aerial vehicle between 0 and 110 m above ground level in Boulder, Colorado.

中文翻译：

---

用于无人驾驶飞行器 NO2 测量的轻型宽带腔增强光谱仪

我们描述了用于测量无人驾驶飞行器和轻型飞机上的 NO ₂的轻型宽带腔增强光谱仪的设计和性能。该仪器使用以 457 nm 为中心的发光二极管 (LED)、高精细反射镜（在 450 nm 处的反射率 = 0.999963）和光栅光谱仪来确定 430 和 476 nm 之间的光学消光系数，这与定制光谱相符拟合软件和公布的吸收截面。^{该仪器重 3.05 千克，在 25 ∘} C时功耗小于 35 W。 地面校准单元提供氦气和零气流，使用已知的瑞利散射截面定期确定腔镜的反射率。精度（1σ ) 对于实验室测量，NO _{2在 1 秒内为 43 ppt，NO 2}在 30 秒内为7 ppt已知 NO ₂混合比在 0–70 ppb 范围内的空气测量值与已知值在 0.3 %（斜率）内一致 $=\mathrm{0.997}\pm \mathrm{0.007}$; r ² =0.99983）。我们使用在科罗拉多州博尔德的地面以上 0 到 110 米之间的无人驾驶飞行器上采集的 NO ₂混合比的垂直剖面来展示仪器性能。