CAFE: a new, improved non-resonant laser-induced fluorescence instrument for airborne in situ measurement of formaldehyde

Abstract

Abstract. NASA Compact Airborne Formadehyde Experiment (CAFE) is a non-resonant laser-induced fluorescence instrument for airborne in situ measurement of formaldehyde (HCHO). The instrument is described here with highlighted improvements from the predecessor instrument, COmpact Formaldehyde FluorescencE Experiment (COFFEE). CAFE uses a 480 mW, 80 kHz laser at 355 nm to excite HCHO and detects the resulting fluorescence in the 420–480 nm range. The fluorescence is acquired at 5 ns resolution for 500 ns and the unique time profile of the HCHO fluorescence provides measurement selectivity. CAFE achieves a 1-sigma precision of 160 pptv (1 s) and 90 pptv (10 s) for [HCHO] = 0 pptv. CAFE has successfully flown on multiple aircraft platforms and is particularly well-suited to high altitude research aircraft or small air quality research aircraft where high sensitivity is required but operator interaction and instrument payload is limited.