Aurora 4000 POLAR NEPHELOMETER Aerosol particles in the atmosphere directly influence the earth’s radiative balance by absorbing and scattering the solar radiation and indirectly, by changing the cloud’s microphysical properties. The phase function, defined as the amount of light scattered as a function of the scattering angle, is a key parameter to accurately model the influence of the aerosol scattering on the earth’s radiative balance. Polar nephelometers provide this measurement. The Aurora 4000 is the first commercially available polar nephelometer in the world. The instrument provides more specific light scattering measurements for up to 18 angles between 10° and 170°, with customised resolution. This extra measurement provides comprehensive data allowing a greater characterisation of aerosol scattering than the basic backscatter measurement. BENEFITS • High powered multi-wavelength LED light-source increases measurement accuracy • Higher flow available via the external pump option for common inlet cases • Raw measurement counts available for customised data analysis • Single light source and detector used for each sector measurement • Simplified fully automatic and scheduled calibration (zero and/or span) using internal valves, ideal for remote locations • Simplified automatic calibration using internal valves, ideal for remote locations • Robust instrument for unattended operation. • 12 VDC operation (60 watts maximum, 15 watts nominal) • Automatic optical reference calibration • Fully integrated package including; internal sample pump, sample heater, internal calibration valves, zero air pump and data logger • Internal sample heater with temperature or RH control, which can be enabled by the user to eliminate the effects of humidity (RH: < 30 to < 90 % ). LED vs flash lamp • Our LED light source is guaranteed not to fail within 3 years and often exceeds five years • Heat generated by the LED light source is a fraction of that generated by a flash lamp, minimising changes in sample RH • LEDs emit light at a specific wavelength eliminating the need for band pass filters • An LED light source uses the same light path for each wavelength ensuring consistency of measurement, eliminating the need for multiple PMTs and maximising light intensity. It uses the same three wavelength technology as the Aurora 3000 but also automatically measures the amount of light scattered in different angular sectors by varying its backscatter shutter position. The Aurora 4000 simultaneously measures at 525 nm (green), 450 nm (blue) and 635 nm (red), using the now proven LED light source (Mueller, 2010), to enable wide and in-depth analysis of the interaction between light and aerosols.