Von: owner-sumer-soft@esa.nascom.nasa.gov [mailto:owner-sumer- soft@esa.nascom.nasa.gov] Im Auftrag von Schuehle Dr., Udo Gesendet: Montag, 25. April 2005 13:24 An: SUMER_SOFT Betreff: SUMER-SOFT: Detector-A defect The Detector-A of SUMER has a defect which appeared on 19 May 2004, affecting all images acquired after that date. A deterioration of the ADC in the time-to- digital converter box (TDC) has resulted in wrong addressing of the counts. This becomes apparent by missing lines, the counts being summed in the lines above. First, only line 207 was missing and counts appeared in line 208. Later, more lines blacked out. The counts are not lost but appear in one line, summing up the counts from maximal 64 lines below, which have zero counts. Presently only pixel rows up to 58 are still useable. The other rows can be used with a spatial resolution of 64 pixels (like “binning 64”). The defect concerns only the y-ADC, affecting the pixel rows, while the x-ADC is working correctly, leading to correct spectral information for all rows. The defect is progressing and, thus image corrections cannot be used as before and no standard routine can be provided. Most importantly, the flatfield correction cannot be used as before, because the odd-even pattern, usually contained in the standard flatfield image, has changed due to this defect. The odd-even pattern is now even stronger than before. It is therefore recommended either to use a spatial binning of two, or to determine the odd-even pattern from the data. To do this, all data of the observing period can be summed and the odd-even pattern can be determined from the row-sum of these data as a factor which every second line is above and every other is below the average. This factor must be the same for all rows, because it is assumed to be a digital nonlinearity that is affecting each second row in the same way. Then, this pattern can be expanded to an odd-even array to be multiplied to the image. After the odd-even correction, the usual flatfield procedure can be applied if necessary using the latest file “FF_*D_R_NOE.RST” from the flatfield directory (http://sohowww.nascom.nasa.gov/sdb/soho/sumer/calibration/flight/ff/). Udo Schühle, 25 April 2005-04-27