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.

Operations News

As we mentioned in the last Newsletter, IUE lost one of its gyros in early March as a result of improper commands sent by the Goddard Sigma 5 ground computer. The one gyro system was loaded into the spacecraft and ground system, and VILSPA has been able to largely resume science operations. The new system was sufficiently stable to allow IUE to observe Comet C/Hyakutake in late March, allowing observers to monitor its rate of water production (among other items) prior to the comet's perihelion passage. This rate showed a seven-fold increase over a five-day period at that time, suggesting a high rate of dust and gas ejection. Further details are available in IAU Circulars #6355 and #6370, and from VILSPA's Hyakutake page at http://www.vilspa.esa.es/iue/hyakutake.html.

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

http://archive.stsci.edu/iue/iue.html (Goddard)

and

http://www.vilspa.esa.es/iue/iue.html (VILSPA)

IUE Data Analysis Software for Personal Computers

The IUEDAC IDL software (which includes roughly 450 programs) is now available for distribution for Power Macintosh computers, and Personal Computers running Windows 3.1. Several databases are also available including the recently expanded IUE merged observing log, the IUE FES table, the Bibliographic Reference database (which catalogs papers published using IUE data), and a table of IUESIPS configuration entries.

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 archive@stsci.edu. 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.

IUE Image Processing News

NEWSIPS Status

We 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 Change

As 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.

cli

User-Developed Software

Hey, we're not proud! Who can afford to be nowadays? If you have developed software to analyze IUE data that you think might be useful to other users, and if you have an interest in making this code more generally available, the DAC would like to hear from you! We are considering establishing a subdirectory specifically for such contributed code. IUE has traditionally benefitted greatly from this kind of user input. Please contact Randy Thompson or Jim Caplinger.

ra/jc

IUE Vax Anonymous FTP Account Moved

Because of problems with disk drive IUE$DKB0, the anonymous ftp account on the IUE VAX computer has been moved to disk IUE$DKA200. Users accessing this account using the DECnet COPY command will need to specify the new disk drive when accessing files. Users connecting via ftp will not see any changes.

Staff Changes

Dr. Richard Arquilla recently left the IUEDAC staff to begin work with Flight Dynamics under another contract. We wish him the best in his new position.

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.

The End and A Beginning

This issue marks the last DAC Newsletter formally dedicated solely to DAC-related issues. Future Newsletters will have a broader scope covering the Goddard side of the IUE project as a whole. Dr. Terry Teays has agreed to assume the burden of editing future editions of the Newsletter, which will still be distributed on a (more or less) monthly basis. The addresses given at the top should still be used by subscribers for Newsletter-related messages.

Editor: Mr. James Caplinger
Contributors: Dr. Richard Arquilla; Dr. Cathy Imhoff; Mr. Randy Thompson

Back to the IUE Data Analysis Center Page

Web Curator

Mr. James Caplinger, Computer Sciences Corporation

Responsible NASA Organization/Official

Dr. Don West, IUE Operations Scientist