Observation of the solar spectral irradiance from 200 nm to 870 nm during the ATLAS 1 and ATLAS 2 missions by the SOLSPEC spectrometer

The SOLSPEC instrument was built to measure the solar spectral irradiance f rom 200 nm to 3000 nm. The instrument participated in the three ATLAS missi ons. It consists of three spectrometers, which measure the solar spectral i rradiance in the ultraviolet, visible and infrared domains. The ultraviolet and visible solar spectra obtained during the ATLAS 1 mission have been pr esented elsewhere. Measurements during the second flight are presented in t his paper. Most of the ATLAS 1 results are confirmed by the ATLAS 2 measure ments, but some improvements are obtained in certain wavelength domains owi ng to better calibration procedures and selection of measurements. The data gathered during the first two flights by the SSBUV, SUSIM and SOLSPEC spec trometers are compared and discussed.