In this paper we describe a unique spectrometer that has been developed and tested over 10 years at Lauder, New Zealand. The spectrometer in question, UV2, makes alternating measurements of global UV and direct sun UV irradiance. After an assessment of the instrument performance, we compare the ozone and aerosol optical depth derived from UV2 to other independent measurements, finding excellent agreement suggesting that UV2 could supersede these measurements, particularly for ozone.