Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

The MAX-DOAS instrument measures solar stray light at different elevation angles (0-180˚) above the horizon in order to quantify trace gases in the lower troposphere. The state of the art CU MAX-DOAS is designed to have a very low residual error in both the UV and Visible spectral ranges, allowing the detection of trace gases in low concentration in both pristine and polluted environments (i.e. IO, BrO, HCHO, CHOCHO, NO2, and HONO). Additionally, the oxygen collision pair (O4) is measured and used as a proxy for the determination of aerosol load.

Spheres Edition 8 2014, Article on Mercury

Ground Based MAX-DOAS

The ground-based CU -MAX-DOAS (GMAX-DOAS) has been utilized in a geostationary mode, where measurements last for time periods ranging from several weeks to several years, in order to capture temporal trends in the measured parameters for the particular environment in which the instrument is located. To date, the CU-GMAX-DOAS has been deployed at ground based sites such as: Pensacola, FL (2009-2011); Pasadena and Fontana, CA for CALNEX 2010; Sacramento, CA for CARES 2010; and Cape Cod, MA for TCAP 2012.

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



Ship based MAX-DOAS (SMAX-DOAS) applies the MAX-DOAS technique to measurements on a ship. Due to pitch and roll of the ship it has the challenge of stably holding the elevation angles at their certain positions with respect to the horizon. The CU MAX-DOAS device is able to measure the movement of the ship, and its telescope compensates for it accordingly in real-time. It has been deployed on the following measurement campaigns: VOCALS 2008, TAO 2009, TAO 2011, and TORERO 2012.

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