May 1996 Volume 4, No. 3
IUE DATA ANALYSIS CENTER NEWSLETTER
This is an electronic newsletter edited by the IUE Data Analysis Center (IUEDAC) intended to inform the numerous remote and local users of the IUEDAC software of recent software updates and project changes.
Unfortunately, the new system has imposed a few new operations constraints. All targets must have a bright (at least 8th mag) guide star within the field of view. Short, unguided exposures, as well as trailed exposures, are no longer possible. Observers are strongly urged to contact their VILSPA Contact RA to evaluate their targets for the remainder of the episode. Updated information is also available from the IUE hompages at
To simplify distribution, the Mac and PC procedure libraries are stored in compressed, self-extracting files located in the anonymous ftp account on archive.stsci.edu. See the IUEDAC web page for more information on downloading. No other programs are needed to extract the software. The Mac software is stored in a self-extracting archive file in ASCII format created using Compact Pro. The PC software is stored in a BINARY format self-extracting Zip file created using WinZip. The databases are stored in separate files since they require significantly more disk space. Installation instructions are included with both sets of files.
Users having difficulty accessing or installing the software should send e-mail to email@example.com. This work was completed under a grant from the NASA Astrophysics Data Program.
Note: RSI is offering a special educational discount on IDL for personal computers until the end of May. Contact RSI for more information.
NEWSIPS StatusWe have continued to process NASA SWP and LWP low dispersion data as they have become available. All 18th episode (and earlier) images are now releasable and are being processed through NEWSIPS. Sky background images are now being processed, but nulls and flat field images are not yet being processed.
Some images have not been processed because of missing database information or other problems. We are currently working on getting those images taken care of and processed. If you need images that seem unavailable, please contact Cathy Imhoff. She can check on them and in many cases fix the problem so that the images can be processed for you.
NEWSIPS Processing ChangeAs reported in the February 1996 DAC Newsletter, we have found that spectra which have been extracted using the SWET algorithm and only 2 nodes tend to yield fluxes which are too high. This may happen when the spectral data are very weak or when the image background is high.
We have decided to change the NEWSIPS production processing software to handle these images in a better way. If the SWET software yields a 2-node fit, the empirical cross-dispersion profile is NOT used. Instead the default profile (point source or extended, as appropriate) is used, centered on the empirical center line of the spectrum. This change should produce more reliable fluxes.
On a time available basis, we are reprocessing any 2-node images previously processed with NEWSIPS so that the data in the archive are uniformly extracted. Be aware that you may have retrieved the earlier version of the processed data and it may be affected by this change. To determine this, please check the processing history in the FITS header. Data processed after March 12, 1996, (Release 2.4.4) use the updated extraction. Data processed before this date and employing 2 nodes in SWET (see SWET section of the processing history - look for number of spline nodes and the statement "WARNING: LOW NUMBER OF SPLINE NODES") were extracted with the older technique.
Please contact Cathy Imhoff if you have questions or would like help in identifying affected data.
Dr. Terry Teays has agreed to assist the DAC staff on a consulting basis with some of the more technical work carried out by Rich. Mr. James Caplinger will assume several of the operations-related tasks done by Rich, while Mr. Randy Thompson will take on some of Rich's programing work.
Back to the IUE Data Analysis Center Page
Web CuratorMr. James Caplinger, Computer Sciences Corporation
Responsible NASA Organization/OfficialDr. Don West, IUE Operations Scientist