Number 26, May 2003
Content: 1) Error in the Application of the FUSE Flux Calibration for post June 2002 data 2) FUSE Cycle 5 NRA to be released in late June, 2003 1) Error in the Application of the FUSE Flux Calibration for post June 2002 data We have discovered an error in the way that the flux-calibration is applied in the CalFUSE pipeline. This problem affects data taken after June 2002. A corrected algorithm has been devised and implemented. The FUSE Science Operations Team performs regular observations of flux calibration targets to monitor the sensitivity of the instrument. For reasons of work load and pipeline stability, not all of these observations are used to produce flux calibration files for the CalFUSE pipeline. This is in part due to the fact that very little change has been seen in the sensitivity over the first part of the mission. The latest set of time-dependent flux-calibration files were released in June of 2002. Analyses now indicate that the FUSE sensitivity has decreased by 1 to 7%, depending on the channel, since that time. We have been begun work on a new set of flux-calibration files that will reflect these changes; we expect to release them by June 2003. For data obtained between the dates of two flux-calibration files, the pipeline interpolates between the two calibration files. For data obtained after the most recent calibration file, however, the pipeline has been deriving its flux-calibration by linearly extrapolating from the last two calibration files. This is an error; the program should simply use the most recent flux-calibration file. Our two latest flux-calibration files are dated March 2002 and June 2002. Therefore, the problem affects all exposures obtained after 06/19/2002. Two segments, LiF 1B and LiF 2A, are particularly affected, because the last two sensitivity curves for these segments differ by about 10%. Moreover, the flux error grows linearly with time. The effects are less significant for other segments, and it affects only the FLUX and ERROR arrays, not COUNTS and CNTSERR. We have developed a number of tools to correct this error. These tools, together with more information on this error, are available from the web page, "An Error in the Application of the FUSE Flux Calibration" at the following URL: Among the available correction tools is a new version of the CalFUSE pipeline, CalFUSE v2.4, containing the corrected algorithms. This is available at: ftp://fuse.pha.jhu.edu/fuseftp/calfuse/ We are currently installing CalFUSE v2.4 into the default processing stream. All data processed after May 6 will be processed with the new pipeline version. We are also dedicating an extra CPU to reprocessing the affected data sets as quickly as possible. We estimate that this will be completed within a month of the present date. 2) FUSE Cycle 5 NRA to be released in late June, 2003 We would like to remind you that the NRA for FUSE Cycle 5 observations is planned to be released in late June 2003. The proposal deadline will be in mid-September with cycle 5 observations starting on April 1, 2004.
The Observer's Electronic Newsletter is published by the FUSE project and is aimed at the FUSE user community.
Editor: B-G Andersson, FUSE Guest Investigator Officer.
The FUSE Project is managed by Johns Hopkins University's Center for Astrophysical Sciences in Baltimore, MD, for NASA's Goddard Space Flight Center. The FUSE Principal Investigator is Dr. Warren Moos, the FUSE Project Manager at JHU is Mr. J.B. Joyce, and the NASA Project Scientist for FUSE is Dr. George Sonneborn.
Further information about the FUSE Guest Investigator Program can be obtained from: Dr. George Sonneborn; email@example.com
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