Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)


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4STAR has made several test flights on the PNNL G1, and its full capabilities are still being developed. When it achieves those full capabilities, we expect that, in addition to AATS-like direct-beam measurements of aerosol optical depth (AOD) and water vapor, 4STAR’s sky-scanning capabilities will permit the first airborne AERONET-like retrievals of such aerosol properties as SSA, complex refractive index, shape, and multimodal size distribution. Its zenith-viewing mode will permit retrievals of cloud optical thickness and cloud particle effective radius (when combined with a measurement of upwelling flux at two solar wavelengths), and its spectrometric resolution will permit improved aerosol-gas separation (hence improved aerosol retrievals) and possibly retrievals of additional gases. For SEAC4RS, 4STAR is offered as an option to replace AATS-14 on the DC-8 after initial science flights by AATS-14 during the Southeast Asia deployment. 4STAR has the sun-tracking capabilities of AATS and adds sky-scanning and zenith-viewing capabilities, all with spectrometers replacing the individual photodiodes of AATS-14.
Group/Instrument Description

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