Degradation-Free Spectrometers for Solar Extreme Ultraviolet Irradiance Measurements: a Progress Report

Solar EUV observations will be made using two novel degradation-free EUV spectrometers which will be flown on a sounding rocket scheduled for launch during the summer of 2011. The two instruments, a rare gas photoionization-based Optics-Free Spectrometer (OFS) and a Dual Grating Spectrometer (DGS), are filter-free and optics-free. The OFS can measure the solar EUV spectrum with a spectral resolution comparable to that of grating-based EUV spectrometers. The DGS is designed to provide solar irradiance in a 9 nm band (FWHM) centered at 121.6 nm and a 4 nm band (FWHM) centered at 30.4 nm to overlap EUV observations from SOHO/SEM and SDO/EVE. The status of the upcoming sounding rocket flight (Judge 36.263US), as well as design improvements and results from laboratory tests of the instruments using a capillary discharge EUV photon source are presented. The spectrometers are being developed and demonstrated as part of the Degradation Free Spectrometers (DFS) project under NASA’s Low Cost Access to Space (LCAS) program and are supported by NASA Grant NNX08BA12G.