Multi-Axis Differential Optical Absorption Spectroscopy (CU MAX-DOAS)

The CU MAX-DOAS instrument measures scattered solar light at different elevation angles (0-180˚) above the horizon in order to quantify trace gases in the lower and free troposphere. The state-of-the-art CU MAX-DOAS is designed to have very low residual error in both the ultraviolet and visible spectral ranges, enabling the detection of trace gases (IO, BrO, HCHO, CHOCHO, NO2, O3, SO2, and HONO) in both pristine and polluted environments. Additionally, oxygen collision-induced absorption (O2-O2) is measured as a proxy for aerosol load.

Spheres Edition 8 2014, Article on Mercury

Ground Based MAX-DOAS

The ground-based CU MAX-DOAS (CU GMAX-DOAS) instrument has been deployed at stationary ground sites for time periods ranging from several weeks to several years, in order to capture temporal trends in trace gases and aerosols. To date, the CU MAX-DOAS has been deployed at Pensacola, FL (2009-2011); Pasadena and Fontana, CA for CALNEX 2010; Sacramento, CA for CARES 2010; Cape Cod, MA for TCAP 2012; Mauna Loa Observatory, HI (since 2017); and Maido Observatory, Réunion Island (since 2017).

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MAX-DOAS installed on a stationary platform EPA station Pensacola, Florida



The ship-based CU MAX-DOAS (CU SMAX-DOAS) instrument utilizes the MAX-DOAS technique onboard a sea vessel. Due to the constant movement (pitch & roll) of the ship, elevation angle pointing accuracy and stability are important factors in these measurements. The CU SMAX-DOAS telescope is designed to compensate for the ship's motion in real-time. The CU SMAX-DOAS has been deployed at VOCALS 2008, TAO 2009, TAO 2011, and TORERO 2012.

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MAX-DOAS is a multi-platform instrument designed to be installed in a variety of locations. Pictured above is the MAX-DOAS installed on the NOAA R/V Ka'imimoana