<title>In-orbit performances of the EIT instrument on board SOHO and intercalibration with the EIT Calroc Sounding Rocket program</title>

Abstract

The Extreme UV Imaging Telescope (EIT) instrument is operating on-board the SOHO spacecraft since January 1996. EIT is providing EUV observations of the solar corona in four narrow channels: 171, 195, 284 and 304 Å. Due to continuous exposure to the EUV solar irradiation, the instrument performance is continuously evolving. The backside thinned detector is showing important changes in its overall response and local damages of EUV highly exposed areas. These performance modifications can be characterized through several observation analyses that are discussed in this paper. Two major effects are identified: contamination on the detector surface and charge mobility changes in the CCD produced by the EUV irradiation. To restore the instrument response, bakeouts are regularly planned as well as specific observation sequences that are used to characterize the detector damages. An overview of the instrument response behavior is presented in this paper. To cross calibrate this instrument, the spare components of the EIT program were assembled in a new structure used as the EIT Calroc Sounding Rocket instrument. The Calroc flight successfully occurred in October 97 and gathered very useful data that provide additional means to cross calibrate the EIT-SOHO instrument. The Calroc results and their use to improve the EIT-SOHO data are discussed. This sounding rocket mission demonstrated good correlations of the performance monitoring analyses on the EIT-SOHO with the diagnostic deduced from the Calroc observations.

Superlattice-doped silicon detectors: progress and prospects

“…Solar EUV radiation caused the loss of over 80% of EUV responsivity, and also led to instabilities that severely compromised photometric accuracy (see Figure 2). 17,18 An investigation of the damage mechanisms revealed that most of the degradation was caused by EUV-induced surface damage, which formed trap states and led to local charging of the native oxide on the exposed detector surface. The surface damage could only be partially annealed, and the resulting instabilities could not be adequately corrected, prompting the European Space Agency to fly a duplicate instrument on a sounding rocket for recalibration and diagnosis.…”

CORONAL MASS EJECTION INDUCED OUTFLOWS OBSERVED WITHHINODE/EIS

“…This correction is based on the assumption that the coordinate information of SOHO/EIT observations is reliable. According to the report of the instrument (Delaboudinière et al 1995) and its on-orbit performance (Defise et al 1998), this is a good assumption.…”

Solar VUV measurements obtained by SOHO instruments and their radiometric calibration

“…The ground-based programme of EIT provided a complete calibration of the system (Defise et al, 1995), but time constraints during the integration schedule and difficulties in combining it with the priority scheme of the large synchrotron facility Super-ACO at Orsay, as well as the substitution of a new detector after the endto-end test (using silicon diodes calibrated at NIST) reduced the validity of the pre-flight characterization (Defise et al, 1998). Consequently, Dere et al (2000) suggested formal relative combined standard uncertainties at the end of the laboratory calibration of 60 %, 70 %, and 75 % for the 19.5 nm, 28.4 nm, and 30.4 nm channels, respectively.…”

“…They have been used for deriving SOHO EIT flat-field information (Defise et al, 1998), and provided input for the degradation correction.…”