In-flight calibration and performance of the Solar Extreme ultraviolet Experiment (SEE) aboard the TIMED Satellite

Abstract

Understanding both the absolute value and time variability of the solar extreme ultraviolet (EUV) spectral irradiance is necessary for understanding the structure and variability of the Earth’s thermosphere and ionosphere. Long-term measurement of the solar EUV irradiance requires a calibration scheme that addresses the following issues: (1) the calibration must be referenced to repeatable radiometric standards; (2) changes in calibration throughout the duration of the measurements must be tracked; and (3) the measurements must be validated with independent instruments and models. The calibration and performance of the TIMED Solar EUV Experiment (SEE), which has been measuring the solar EUV irradiance since early 2002, will be discussed in relation to these calibration objectives. The pre-flight calibrations of SEE are based on calibrated synchrotron sources at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF). The in-flight calibrations for SEE are based on redundant channels used weekly and annual suborbital rocket flights with the prototype SEE instruments that are calibrated before and after each launch at NIST SURF.