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IUE Guest Observer Badges No Longer Valid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
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).
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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Webmaster
Mr. James R. Caplinger, Computer
Sciences Corporation
Responsible NASA Organization/Official
Dr. Don West, IUE Operations Scientist