TIMED Solar EUV experiment

Abstract

The Solar EUV Experiment (SEE) on the NASA Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) mission will measure the solar vacuum ultraviolet (VUV) spectral irradiance from 1 to 195 nm. To cover this wide spectral range two different types of instruments are used: a grating spectrograph for spectra above 25 nm and a set of silicon photodiodes with thin film filters for the soft x-ray (XUV) below 35 nm. Redundant channels of the spectrograph and XUV photodiodes provide in-flight calibration checks on the time scale of a week, and annual rocket underflight measurements provide absolute calibration checks traceable to radiometric standards. Both types of instruments have been developed and flight proven as part of a NASA solar EUV irradiance rocket experiment. The SEE instrument is currently on the NASA TIMED spacecraft at the Johns Hopkins University (JHU) Applied Physics Laboratory (APL). The TIMED launch is planned for October 2000 as a two year mission.