Showing papers by "J. Lang published in 2007"
TL;DR: The EUV Imaging Spectrometer (EIS) as mentioned in this paper is a two-element, normal incidence design with a backside-illuminated, thinned CCD, which has a significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2 -5 s exposure times in the brightest lines.
Abstract: The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona and upper transition region emission lines in the wavelength ranges 170 – 210 A and 250 – 290 A. The line centroid positions and profile widths will allow plasma velocities and turbulent or non-thermal line broadenings to be measured. We will derive local plasma temperatures and densities from the line intensities. The spectra will allow accurate determination of differential emission measure and element abundances within a variety of corona and transition region structures. These powerful spectroscopic diagnostics will allow identification and characterization of magnetic reconnection and wave propagation processes in the upper solar atmosphere. We will also directly study the detailed evolution and heating of coronal loops. The EIS instrument incorporates a unique two element, normal incidence design. The optics are coated with optimized multilayer coatings. We have selected highly efficient, backside-illuminated, thinned CCDs. These design features result in an instrument that has significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2 – 5 s exposure times in the brightest lines. EIS can scan a field of 6×8.5 arc min with spatial and velocity scales of 1 arc sec and 25 km s−1 per pixel. The instrument design, its absolute calibration, and performance are described in detail in this paper. EIS will be used along with the Solar Optical Telescope (SOT) and the X-ray Telescope (XRT) for a wide range of studies of the solar atmosphere.
1,050 citations
TL;DR: In this article, the authors used the measurement of line ratios to monitor and validate the calibration over the first six years of observation, using branching ratios and line ratios independent of the electron temperature and density, line ratios dependent on electron temperature or density.
Abstract: The scientific return from an extreme-ultraviolet spectrometer depends on the accuracy and precision of its radiometric calibration. For the Coronal Diagnostic Spectrometer on SOHO, radiometric calibration started pre-launch in the laboratory and continued after launch by making comparison measurements of the same area of the Sun with calibrated sounding rocket payloads and also by intercalibration with the SUMER instrument on SOHO. The present work uses the measurement of line ratios to monitor and validate the calibration over the first six years of observation. As well as using branching ratios and line ratios independent of the electron temperature and density, line ratios dependent on electron temperature or density have also been used successfully to validate and monitor the calibration. The results indicate that, within the uncertainties, the radiometric calibration has been validated and maintained over the first six years of observations apart from three specific wavelengths, 338.98 A, 315.0 A, and 311.8 A. Problems with lines at 608.4 A, 303.4 A (seen in second order), 335.4 A, and 360.7 A are attributed to difficulties with the burn-in correction.
7 citations