4 - QEO Spectrometers

ARL conducts applied research into atmospheric chemistry and transport processes, air-surface exchange, and numerical model development and evaluation. To advance this mission, ARL’s ASMD is collaborating with scientists at the Chemical Sciences Lab (CSL) to develop a cutting-edge 4-channel instrument capable of measuring NO, NO2, NOy, O3 in an air aircraft mission in collaboration with scientists at CSL.

The instrument is based on the state-of-the-art technique called broadband Cavity Enhanced Absorption Spectroscopy (CEAS). This development is essential for acquiring critical data to better understand the mechanisms of air pollution formation and atmospheric photochemical processes. The instrument will be developed and then be deployed on the NOAA Twin Otter aircraft in summer 2025 and will subsequently be utilized in AiRMAPS field studies in the years that follow.

This advanced system comprises a new set of four spectrometers, which form the core of the 4-channel NO/NO?/NOy/O? instrument. The development of this innovative tool is critical for enabling fast, precise measurements of nitrogen species (NO, NO?, and NOy) and ozone (O?). These measurements are essential for advancing our understanding of atmospheric chemistry and air pollution dynamics.

The spectrometers must meet the following requirements to ensure the instrument's performance and accuracy: Wavelength range: ~185-1100 nm (user configurations available within this range) Optical resolution (w/10 µm slit): 1.20-1.60 nm (FWHM) (preconfigured models) Integration time: 8 ms-60 minutes Dynamic range: 85000:1 (single scan) Signal to Noise Ratio (single scan):

1000:1 Buffering: stores up to 15,000 spectra Interfaces: USB; SMA 905;

RS-232 TEC: -40 °C to 50 °C Temperature (storage): -30 °C to 70 °C Temperature (operation): 0 °C to 55 °C Weight: less than 3 lbs We have identified Ocean Optics, Inc. as the vendor for spectrometers that meet the specified requirements. The selected models are high-sensitivity QEPro spectrometers (Model QEPro-UV250-200), which offer exceptional data collection rates. These spectrometers have been successfully utilized by NOAA/CSL and University of Alabama Huntsville in previous similar developments, demonstrating their reliability and suitability for this application. Ship to Address NOAA Air Resources Lab 5830 University Research Court College Park, MD 20740