34th Solar Physics Division Meeting, June 2003
Session 17 Corona III
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[17.10] TRACE Image Flat Field and Sensitivity Corrections

R.W. Nightingale, T.D. Tarbell, C.J. Wolfson (LMSAL)

As of April 1, 2003, the TRACE instrument has been in orbit for 5 years. During this time the lumogen phosphor coating on the CCD has degraded due to the flux of extreme ultraviolet (EUV) photons. We have utilized flat field images obtained for the UV 1700 Å and broad-band white light (WL) channels, together with the synoptic disk center, and low-resolution ``dosimeter'' image data from throughout the mission, to correct for the degradation at all of the TRACE UV and EUV wavelengths. 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. By comparing the relative EUV sensitivity at different positions on the detector throughout the mission using images of the same active region at different pointings, we have calibrated the sensitivity changes and flat fields at the EUV wavelengths, including 171 Å and 195 Å. 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 images, to remove small artifacts intrinsic to the CCD and dust shadows common to certain channels. All these corrections have now 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. Plots of the time dependence of the sensitivity and examples of the flat field corrections, along with their use in TRACE_PREP.PRO, 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: nightingale@lmsal.com

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.