The global ozone monitoring by occultation of stars (GOMOS) instrument on ENVISAT: Requirements, design and development status

GOMOS is a medium resolution spectrometer designed to measure the concentrations of, and monitor the trends in, stratospheric ozone with very high accuracy and to observe other atmospheric trace gases. Using the star occultation technique, GOMOS combines the features of self-calibration, high vertical resolution and good global coverage. Due to its high sensitivity down to 250 nm, which is one of its main design drivers, GOMOS can measure ozone profiles from 15 km to 90 km. Accessible altitude ranges, accuracies and global coverage are optimum on the night side. In addition, it can measure atmospheric turbulence, which is of interest for understanding the vertical exchange of energy in the Earth's atmosphere. The main mission, instrument and the equipment requirements and their implications on the design and technology choices are presented. The GOMOS design has been completed and validated and the hardware and software development is currently in its final stage with the flight model equipment in manufacturing. Equipment and subsystem level tests performed have all confirmed so far that the design meets and even exceeds the requirements with respect to several parameters.