Showing papers by "Jean-Marc Defise published in 2000"
TL;DR: In this article, the authors present the preflight photometric calibration of the Extreme-ultraviolet Imag- ing Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO), which consists of a Ritchey - Chretien telescope with multilayer coatings applied to four quadrants of the primary and secondary mirrors, several filters and a backside-thinned CCD detector.
Abstract: This paper presents the preflight photometric calibration of the Extreme-ultraviolet Imag- ing Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). The EIT consists of a Ritchey - Chretien telescope with multilayer coatings applied to four quadrants of the primary and secondary mirrors, several filters and a backside-thinned CCD detector. The quadrants of the EIT optics were used to observe the Sun in 4 wavelength bands that peak near 171, 195, 284, and 304 A. Before the launch of SOHO, the EIT mirror reflectivities, the filter transmissivities and the CCD quantum efficiency were measured and these values are described here. The instrumental throughput in terms of an effective area is presented for each of the various mirror quadrant and filter wheel combinations. The response to a coronal plasma as a function of temperature is also determined and the expected count rates are compared to the count rates observed in a coronal hole, the quiet Sun and an active region.
44 citations
18 Dec 2000
TL;DR: The CalRoc program was initiated to provide well calibrated, contemporaneous observations in support of the SOHO Extreme Ultraviolet Imaging Telescope (EIT) EIT as discussed by the authors.
Abstract: The ability to derive physical parameters of the Sun from observations by the Solar and Heliospheric Observatory (SOHO) Extreme Ultraviolet Imaging Telescope (EIT) greatly increases the scientific return of the mission. The absolute and time variable calibration of EIT therefore is of extreme interest. The NRL EIT Calibration Sounding Rocket (CalRoc) program was initiated to provide well calibrated, contemporaneous observations in support of SOHO EIT. These observations provide three benefits to the SOHO EIT data, absolute calibration points, temporal and spatial information of the EIT EUV response variability in flight via flat field information and clues to the physics of the degradation. Details of the bandpasses of the multilayered optics and the total telescope photometry are presented. Comparisons are shown with the contemporaneous images from SOHO EIT. Plans for the second CalRoc flight are discussed. Loss of reflectivity in the multilayer mirrors has been identified as a new component to the SOHO EIT and CalRoc degradation.
3 citations