TIMED Solar EUV Experiment

The Solar EUV Experiment (SEE) on the NASA Thermosphere, Ionosphere, Mesosp here, 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 spec trograph 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 t he spectrograph and XUV photodiodes provide in-flight calibration checks on the time scale of a week, and annual rocket underflight measurements provi de absolute calibration checks traceable to radiometric standards. Both typ es of instruments have been developed and night proven as part of a NASA so lar EUV irradiance rocket experiment. The SEE instrument is currently on th e NASA TIMED spacecraft at the Johns Hopkins University (JHU) Applied Physi cs Laboratory (APL). The TIMED launch is planned for October 2000 as a two year mission. (C) 2000 Elsevier Science Ltd. All rights reserved.