AAS 200th meeting, Albuquerque, NM, June 2002
Session 55. Solar Data Analysis and Calibration
Display, Wednesday, June 5, 2002, 10:00am-7:00pm, SW Exhibit Hall

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[55.04] Extreme Ultraviolet Flux and Sensitivity Changes in TRACE Images

T.D. Tarbell, R.W. Nightingale (LMSAL)

During the TRACE mission, the sensitivity of the instrument in both UV and EUV channels has changed. This was expected from pre-flight measurements of the effects of EUV flux on a lumogen-coated CCD detector similar to the TRACE flight CCD. A mission-long record of EUV flux on the CCD has been maintained using low-resolution ``dosimeter'' images. The correlations between EUV flux and UV sensitivity suggest that most of the change can be attributed to the detector and not to reductions in optical throughput. The techniques for UV calibration described in our accompanying poster have not been successful for the EUV channels. The Kuhn-Lin algorithm for deriving flat fields fails due to the very high contrast and temporal variability of TRACE EUV images. The synoptic images have not yet yielded useful information either, due to low fluxes in quiet sun and intermittency and variability among active regions. However, it is possible to measure the relative EUV sensitivity at different positions on the detector throughout the mission, using images of the same active region at different pointings. By comparing these with the dosimeter images and UV results, a preliminary calibration of sensitivity changes and flat fields in 171 Åand 195 Åhave been derived. Examples of corrected images are shown.

This work was supported by the TRACE project at LMSAL (contract NAS5-38099).

The author(s) of this abstract have provided an email address for comments about the abstract: tarbell@lmsal.com

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.