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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[55.05] Ultraviolet Flat Fields, Sensitivity Changes, and Their Removal from TRACE Images

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

As of April 1, 2002, the TRACE instrument has been in orbit for 4 years. During this time the lumogen phosphor coating on the CCD has degraded due to the flux of extreme ultraviolet (EUV) photons. Flat field images have been obtained for the UV 1700 Å, 1216 Å, and broad-band white light (WL) channels. Normalized flat field responses have been calculated for each of these channels throughout the mission to date. Recent 1700 Åimages show up to about a 30 % reduction in sensitivity near the center of the CCD relative to the edges. Analyzing these flat fields together with the synoptic disk center images throughout the mission, the flat fields and sensitivity changes over time for all 5 UV channels have been determined. The 1700 Åflat field images serve as the basis for the lumogen loss corrections in all UV channels (but not WL). A set of time dependent power and multiplier parameters have been determined from fitting these flat fields to the mission synoptic data for the various UV wavelengths. The WL flat field images have not changed within ±1.5 % over the mission to date. The WL flat fields are also used in the corrections for all UV images, to remove small artifacts intrinsic to the CCD and dust shadows common to certain channels. All these corrections have been implemented as an update into the SolarSoft (SSW) routine TRACE_PREP.PRO, and normally are automatically applied to the images after the dark pedestal and current corrections. Examples of these corrections applied to images over time will be presented.

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: ngale@lmsal.com

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