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IUE Project Electronic Newsletter

NASA-Goddard Space Flight Center (GSFC)

Vol. 5, No. 5 - May 1997


IUE Guest Observer Badges No Longer Valid

Please be advised that, effective May 1, 1997, badges issued to IUE Project participants for purposes of observation and analysis from 1978 through September 1996 will no longer be recognized for access to the Center. Access for individuals who visit the Center in the future for IUE data archiving proposes should be coordinated with the GSFC Security Office via memorandum.

Individuals who have been issued IUE badges may retain them as mementos of their long-standing association with the IUE Project and its many successes.

- Goddard Security Office


IUE Image Processing News

Processing of LWR Low-Dispersion Images: Possible Error at High FNs!

Recently, a problem with the noise model used in the extraction of some LWR low-dispersion spectra was uncovered. The problem occurs when the noise model is extrapolated to higher FN values than in the original data used to construct the noise model. In some cases, the extrapolated function decreases, incorrectly indicating that the noise decreases at higher signal levels. This extrapolation error affects the sigma values and, since they are used in the extraction, it can affect the flux levels that are derived where the spectrum is somewhat to very overexposed.

We are screening the LWR images to determine which ones are affected and will reprocess them with the corrected noise model. This change will be implemented in NEWSIPS Release 2.5.3, and the new noise model will be listed in the processing history as Version 1.1. For more information (e.g. whether your data are affected) please contact Cathy Imhoff (imhoff@iuegtc.gsfc.nasa.gov, or 301-794-1470).

Now Available: Updated SWP Sensitivity Degradation for 1993-1996

The SWP sensitivity degradation correction previously implemented in NEWSIPS was derived several years ago and extrapolated for data taken in the last few years of the IUE mission. Recent analysis by Matt Garhart has shown that the SWP camera sensitivity degraded at an increased rate, so that the current calibration underestimates the SWP fluxes by up to 5% in late 1996. Note that this affects both low- and high-dispersion data.

Matt has derived an update to the SWP sensitivity degradation correction, which has now been implemented into NEWSIPS processing. The update implements a linear correction with a larger slope for data from 1993 onward, defined to be continuous with the correction up to 1993 so that there is no "jump" in the fluxes for images taken before and after the new correction is applied. The details of this analysis will be published in the NASA IUE Newsletter and made available on the Web.

We have begun to reprocess all SWP low- and high-dispersion data from 1993 onward with the new sensitivity degradation correction. The new version of the data will be identifiable from the processing history NEWSIPS version (2.5.3 for SWP low dispersion, 3.1.1 for SWP high dispersion) as well as the processing date.

What about the LWP?

Testing shows that there is no need to change the sensitivity degradation correction. The extrapolation for later data works fine.

Coming Attractions: LWP High-Dispersion Processing

The LWP high-dispersion processing system is nearly ready. We hope to start processing images in the next 2 to 3 weeks. You are welcome to send us your requests for priority processing; however they will not be put into the system until processing begins. You can access the request form at:

http://hypatia.gsfc.nasa.gov/IUE/search/IUE_usrreq.html

Questions?

If you have any questions about IUE processing or the Final Archive, please feel free to contact me at imhoff@iuegtc.gsfc.nasa.gov, or at 301-794-1470. Thanks!

- Cathy Imhoff


IUEDAC Software Changes

01-Apr
A new version of the standard star help library was installed. The new version corrects typos found in the earlier version. In addition, the NEWSIPS versions of all SWP and LWP extracted spectral files have been requested from NDADS and added to the standard star archive on IUE.
01-Apr
The following experimental routines were implemented:
readmx
uses better splice points and optionally preserves uncalibrated data points.
ifitsrd
optionally stores output as an IDL structure.
iue3drow
new subroutine of ifitsrd.
usrreq
allows requesting NEWSIPS processing for all cameras and dispersions.
platform
supports DEC Unix systems.
uixplat
subroutine of platform.
11-Apr
A new version of the LMC extinction curve by Nandy, et al. was installed which corrects an error in one of the wavelength entries (discovered by Bram Boroson from Harvard).
16-Apr
New versions of the following programs were implemented:
ifitswrt
correct an error when input data array has more than 32,767 elements.
ismenu4, isnuflags.txt, iuelog.txt
include description of "raw image lost" flag.
25-Apr
A new version of iuefx was added to the experimental library which performs error checking on lists of images submitted using the optional file keyword.
30-Apr
New options were added to the following implemented routines:
asc_read
a /silent option prevents printing of non-error messages.
lblfix
a /nodelete option allows the plot window to remain displayed after the program ends.
06-May
A new version of asc_read was added to the experimental library which allows users to extract data as double precision rather than floating point numbers.
09-May
A new version of newcalib was implemented which includes the absolute flux calibrations for LWR low dispersion spectra extracted from the NEWSIPS SILO files. (The previous version was only compatible with LWP and SWP spectra.) Corrections were also made to newcalib which improve the agreement with NEWSIPS calibrations for SWP and LWP spectra by 2-3%.
- Randy Thompson

Final Archive Data From Anonymous FTP

The IUE Final Archive low dispersion extracted spectra are being made available via anonymous ftp at Goddard's Astrophysics Data Facility. To access this copy of the MXLO files, ftp to hypatia.gsfc.nasa.gov with the user name of anonymous and the password as your e-mail address.

The data will be found in the pub/iue/data/camera/image subdirectories, where camera is lwp, lwr, or swp, and image is the multiple of 01000 preceding the image number. For example,

swp00502.mxlo is in pub/iue/data/swp/00000/
swp07784.mxlo is in pub/iue/data/swp/07000/
swp24271.mxlo is in pub/iue/data/swp/24000/

All these file are in FITS format. For assistance with working with the data, please contact the IUE Data Analysis Center's staff (staff@iue.gsfc.nasa.gov).

Please note, these directories are still being filled. Over 90% of the Goddard SWP and LWP low dispersion data have been processed. VILSPA is processing the data obtained there and we must await the transfer from them of that data. LWR low dispersion processing has recently started. The data will be available via the NASA Data Archive and Distribution Service (http://ndads.gsfc.nasa.gov) before they are available on this site.

There are currently 17,588 LWP files and 30,924 SWP files available. No high dispersion data will be available from this anonymous ftp site due to disk space limitations. To obtain high dispersion data and the other low dispersion data types, please use the NDADS.

- Pat Lawton, ADF/UV Support


Mail Code Change

The Goddard mail code for the IUEDAC recently changed to Code 686.9. While the old code of 684.9 may be recognized for a while longer, we suggest that users employ the new code for mail delivery.

- James Caplinger


The IUE Electronic Newsletter, edited by James Caplinger, is primarily intended to inform the numerous remote and local users of the IUEDAC software of recent software updates, as well as let them know about news relating to the IUE project in general. If you want your name to be added to, deleted from, or changed on our distribution list, please send us e-mail to

news@iuedac.gsfc.nasa.gov

or send a postcard to:

IUE Data Analysis Center (IUEDAC)
Code 686.9, NASA-GSFC
Greenbelt, MD 20771


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