ROSAT Status Report: Oct 8 1997
TCDLT2 problem in converted REV0 & REV1 German Events files Now Fixed!
A problem has been detected with some ROSAT events files in the data archive. The problem is that the TCDLT2 keyword is negative in some files.
The affected files are the German Rev1 sequences, specifically, the events files which have been converted to US fits format. The German Rev 1 datasets are easily identified as they are those with directory names like wp600185, and the converted events files have names like wp600185.fits (i.e. no n00, ao1 etc trailing the sequence name, and no _bas in the filename, those are all later versions of ROSAT data, and unaffected).
The list of German Rev1 sequences in the archive can be found below along with the value of the TCDLT2 keyword in each case, a negative value indicating that the sequence was affected. About 10% of German Rev1 sequences have a correct value for TCDLT2. If you have retrieved Rev 1 German data in the past you can check the TCDLT2 keyword in the second extension of the events file to see if your data are affected. 302 observations were affected, as of Oct 8 1997.
The TCDLT2 keyword specifies how DEC changes across the field, from the reference pixel. The flip in sign means that if you make an image from the events file with software which uses this keyword, like xselect, then the resulting image has the Y-direction inverted, i.e. the DEC increases in the wrong direction. This Y-flip obviously results in an incorrect position derivation for sources in the image.
The problem has been traced back to an early version of a conversion program, which reformatted German _events.tfits files into w*_seq.fits files. As this is isolated to the events conversion program, there is no problem with other data files in the affected sequences. Most notably the "standard" SASS images in the same dataset (the _im1, _im2 etc files) are OK. The WGACAT database is also unaffected, and source positions in that database are correct, even for "affected" sequences.
The "US-formatted" REV0 & REV1 German events files which contained
incorrect values of the TCDLT2 keyword have been corrected as of Oct 15
1997. Any archive users who have obtained versions of these files prior
to Oct 15 1997 should retrieve the corrected versions. Note that the
original (unconverted) versions of the events lists (i.e. the
w*_events.tfits files) were not affected by this problem and so do not
need to be replaced.
If you have any questions please email rosathelp@athena.gsfc.nasa.gov
NOTE: No HRI sequences are affected by this problem.
A list of the corrected files follows.
wp100010.fits wp100130.fits wp110016.fits wp110127.fits wp110167.fits wp110589.fits wp110602.fits wp130371.fits wp130372.fits wp130374.fits wp140296.fits wp140310.fits wp140317.fits wp140318.fits wp140319.fits wp140321.fits wp140322.fits wp140326.fits wp141856.fits wp141858.fits wp141867.fits wp141878.fits wp141879.fits wp141880.fits wp141889.fits wp150044.fits wp160030.fits wp160085.fits wp180001.fits wp180002.fits wp200156.fits wp200157.fits wp200158.fits wp200159.fits wp200160.fits wp200161.fits wp200162.fits wp200175.fits wp200196.fits wp200198.fits wp200199.fits wp200200.fits wp200209.fits wp200211.fits wp200216.fits wp200220.fits wp200228.fits wp200235.fits wp200236.fits wp200237.fits wp200238.fits wp200241.fits wp200411.fits wp200412.fits wp200423.fits wp200433.fits wp200437.fits wp200438.fits wp200452.fits wp200604.fits wp200612.fits wp200617.fits wp200618.fits wp200619.fits wp200622.fits wp200636.fits wp200659.fits wp200701.fits wp200703.fits wp200715.fits wp200851.fits wp200853.fits wp200856.fits wp200861.fits wp200862.fits wp200864.fits wp200866.fits wp200867.fits wp200869.fits wp200872.fits wp200888.fits wp201077.fits wp201078.fits wp201079.fits wp201082.fits wp201092.fits wp201107.fits wp201113.fits wp201114.fits wp201119.fits wp201122.fits wp201123.fits wp201139.fits wp201144.fits wp201145.fits wp201177.fits wp201179.fits wp201182.fits wp201183.fits wp201228.fits wp201234.fits wp201241.fits wp201248.fits wp201249.fits wp201262.fits wp201263.fits wp201267.fits wp201268.fits wp201272.fits wp201279.fits wp201288.fits wp201292.fits wp201294.fits wp201295.fits wp201296.fits wp201305.fits wp201311.fits wp201312.fits wp201313.fits wp201325.fits wp201368.fits wp201371.fits wp300033.fits wp300035.fits wp300036.fits wp300038.fits wp300040.fits wp300041.fits wp300068.fits wp300164.fits wp300176.fits wp300217.fits wp300219.fits wp300267.fits wp300292.fits wp300293.fits wp300294.fits wp400039.fits wp400041.fits wp400054.fits wp400178.fits wp400312.fits wp400322.fits wp400323.fits wp400329.fits wp500041.fits wp500043.fits wp500045.fits wp500048.fits wp500052.fits wp500056.fits wp500057.fits wp500058.fits wp500062.fits wp500122.fits wp500193.fits wp500201.fits wp600058.fits wp600066.fits wp600079.fits wp600100.fits wp600185.fits wp600188.fits wp600195.fits wp600196.fits wp600204.fits wp600296.fits wp600297.fits wp600298.fits wp600299.fits wp600300.fits wp600301.fits wp600303.fits wp600305.fits wp600306.fits wp600308.fits wp600309.fits wp600311.fits wp600312.fits wp600316.fits wp600317.fits wp600318.fits wp600319.fits wp600321.fits wp600322.fits wp600323.fits wp600327.fits wp600329.fits wp600330.fits wp600334.fits wp600335.fits wp600336.fits wp600338.fits wp600339.fits wp600340.fits wp600341.fits wp600342.fits wp600346.fits wp600354.fits wp600355.fits wp600356.fits wp600358.fits wp600359.fits wp600360.fits wp600361.fits wp600362.fits wp600366.fits wp600371.fits wp600374.fits wp600375.fits wp600378.fits wp600415.fits wp600417.fits wp600419.fits wp600437.fits wp600448.fits wp600462.fits wp700138.fits wp700145.fits wp700151.fits wp700164.fits wp700170.fits wp700173.fits wp700180.fits wp700186.fits wp700201.fits wp700216.fits wp700226.fits wp700227.fits wp700229.fits wp700262.fits wp700468.fits wp700496.fits wp700498.fits wp700508.fits wp700516.fits wp700528.fits wp700535.fits wp700536.fits wp700538.fits wp700552.fits wp700553.fits wp700557.fits wp700577.fits wp701034.fits wp701038.fits wp701045.fits wp701048.fits wp701050.fits wp701055.fits wp701063.fits wp701068.fits wp701072.fits wp701087.fits wp701093.fits wp701129.fits wp701139.fits wp701140.fits wp701144.fits wp701150.fits wp701153.fits wp701174.fits wp701179.fits wp701195.fits wp701200.fits wp701207.fits wp701213.fits wp701217.fits wp701219.fits wp701233.fits wp701234.fits wp800073.fits wp800096.fits wp800162.fits wp800174.fits wp800184.fits wp800333.fits wp800339.fits wp800340.fits wp800341.fits wp800345.fits wp800353.fits wp800365.fits wp800369.fits wp800385.fits wp800390.fits wp800393.fits wp800401.fits wp800403.fits wp800411.fits wp800415.fits wp800416.fits wp900026.fits wp900143.fits wp900201.fits wp900212.fits wp900220.fits wp900222.fits wp900223.fits wp900228.fits wp900233.fits wp900425.fits
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