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STScI Archive News
| Space Telescope Science Institute | April 7, 1998 - Volume 3 |
The STScI Archive Newsletter disseminates information to users of the HST, IUE, Copernicus, EUVE and VLA-FIRST data archives supported by the STScI Archive. Inquiries should be sent to archive@stsci.edu.
| Contents | |
|---|---|
| Copernicus Archive Support at STScI | R. Thompson |
| EUVE Archive Support at STScI | P. Padovani |
| GHRS/FOS Status Report | S. Baum |
| HST User Survey | M. Donahue |
| Analysis of Apparent Velocities from NEWSIPS-Processed High Resolution IUE Data | M. Smith |
| IUE News | C. Imhoff / R. Thompson |
Ultraviolet spectroscopic data from the Orbiting Astronomical
Observatory (OAO-3) mission, also known as Copernicus, are now
available online from STScI. The Copernicus satellite, which
operated from 1972 to 1981, obtained Far-UV (900-1560 A) and
Near-UV (1650-3100 A) data for 551 targets.
The Copernicus data were originally delivered from Princeton to NSSDC
on magnetic tape in a project-specific format. As a result of a NASA
ADP grant awarded to PI George Sonneborn from Goddard Space Flight
Center, the Copernicus data was converted to FITS format disk files,
and contemporaneous U1 and U2 scans were coadded and stored as
separate quick-look binary table FITS files. Roughly 25,000 coadded
scan files are now available. Also archived were the data sets
described in the six Copernicus spectral atlas papers published by
Rogerson et al. between 1977 and 1989.
The Copernicus data sets and database files have now been transferred
to STScI and are accessible from the Copernicus web page at
http://archive.stsci.edu/copernicus .
Current resources and
capabilities include:
Inquiries about the access to the Copernicus archive should be sent
to
archive@stsci.edu.
Randy Thompson
Access to Extreme Ultraviolet Explorer (EUVE) data is now available
through STScI. EUVE, launched by NASA in 1992 and still operational,
covers the 70 - 760 Angstroms range, between the traditional UV and
X-ray bands.
EUVE has been managed, starting from the design and construction, to
the scientific mission and data archive, by the Center for Extreme
Ultraviolet Astrophysics (CEA) of the University of California,
Berkeley
(http://www.cea.berkeley.edu).
Due to reduced resources, CEA is now terminating support to the EUVE
archive. As a result of a collaborative effort between CEA and
STScI, the National Space Science Data Center (NSSDC), and the High
Energy Astrophysics Science Archive Research Center (HEASARC), the
latter three centers have agreed to take responsibility of the EUVE
archive. Namely, the science archive data (images and event files)
will be available both through STScI (
http://archive.stsci.edu/euve)
and HEASARC (
http://euve.gsfc.nasa.gov).
This is in keeping with the
nature of EUVE data, complementary to both optical/UV and X-ray
research, and with the fact that the optical/UV and X-ray communities
will benefit from using interfaces with which they are already familiar.
The data are currently held for network access at HEASARC (with links to
them from STScI and NSSDC). STScI will support the IRAF-based EUVE
software, after CEA completes the upgrade to IRAF V2.11. NSSDC, on the
other hand, will provide a permanent archive of the science and the
telemetry (raw) archive data
(http://nssdc.gsfc.nasa.gov).
The EUVE archive contains proprietary and non-proprietary observations
from the EUVE satellite from the beginning of the Guest Investigator
Program through the end of 1997. The data in the HEASARC EUVE archive
will be supplemented periodically with additional observations from CEA
as they are processed. They currently comprise a total of 26 GB of
compressed data on 244 distinct targets (including calibrations).
Access to EUVE data at STScI (
http://archive.stsci.edu/euve) is
available through the same WWW interfaces used for the Hubble
Data Archive. Links are provided for users to search the EUVE
catalog and retrieve the data, obtain help, and get information about
data analysis. Once the search is done, the user is presented with a
list of all datasets matching the query parameters. These can be
then retrieved via ftp from HEASARC by "clicking" on two hyperlinks
available in the "Data Files" column: EVT, which points to the event file,
and IMG, which points to the image file.
Inquiries about access to the EUVE archive should be sent as usual to
archive@stsci.edu.
Paolo Padovani
Major advances were made in the closeout calibrations for GHRS and
FOS this past year. For FOS there were improved sensitivities and
comprehensive flat field updates, and increased understanding of
wavelength accuracies. Recalibration and rearchiving of all the FOS
polarimetry data is planned for later this year. For GHRS there were
improved incidence angle corrections for the Large Science Aperture
in the medium resolution and echelle gratings, PSF characterization,
improved sensitivities for G140M, Ech-A, and Ech-B.
In January 1998, the Data Handbook Volume II for the Legacy
Instruments, including FOS and GHRS, was published. It is available
upon request through the
STScI help desk or from the WWW page
(http://www.stsci.edu/documents/dhb/web/DHB.html).
GO and archival support for both spectrographs continues at a good
pace. With the formal completion of the closeout calibrations,
support for STIS, FOS, and GHRS has been amalgamated into a single
functional entity at STScI, the Spectrographs Group, where we
continue to provide support and calibration analysis for the legacy
spectrographs as well as for STIS, our operational HST spectrograph.
FOS and GHRS researchers should direct any questions they might have
to
help@stsci.edu, and their questions will be forwarded on to the
Spectrograph Group for answering. We regularly describe new
calibration and software information for FOS and GHRS in the HST
Spectrographs Space Telescope Analysis Newsletter (STAN) and we
encourage those working with FOS and GHRS to be sure to subscribe to
that STAN, which is also available at
http://www.stsci.edu/instruments/stis under "Documents". The FOS and
GHRS WWW Instrument pages
(
http://www.stsci.edu/ftp/instrument_news/FOS/topfos.html and
http://www.stsci.edu/ftp/instrument_news/GHRS/topghrs.html
respectively) are also kept up to date and should be an important
resource for archival researchers.
Stefi Baum
We conducted a user survey regarding Guest Observer services,
including proprietary data access, media experiences and preferences,
and use of recalibration resources. We invited 460 observers from
Cycles 5 to the present as well as all authorized users to
participate in our survey. We received 114 responses, which we have
used to form our plans regarding future data media options, paper
products, and a new ``on-the-fly'' recalibration service for HST
data. We received a number of helpful comments and suggestions. We
describe a partial list of results here. We determined some general
recalibration patterns for the WFPC2, STIS and NICMOS instruments.
Electronic retrieval of data is popular with GOs, and CDROMs were
popular as a future media choice. User needs are very important to
us, so we are grateful to everyone who participated in this survey!
Thanks for taking the time to participate. You will be hearing more
about future STScI user services, including ``on-the-fly''
recalibration, over the next 6 months.
Megan Donahue
The recent addition of NEWSIPS-processed echellograms to the IUE
archives permits the analysis of apparent radial velocities (RVs) via
cross-correlation techniques, both with respect to old-generation
(IUESIPS) processings and relative to different instruments. We
report here on a comparison of apparent RVs, mainly for the
short-wavelength (SWP) camera with respect to time, wavelength,
aperture-type, and cameras. We also compare RVs from IUE data
relative to RVs from the Copernicus and Orfeus missions. (See also
http://archive.stsci.edu/iue/newsips/radvel/.)
Although residual zeropoint errors still exist for NEWSIPS SWP data,
both with respect to apparent RVs from images from the LWP and LWR
cameras and relative to RVs derived from optical studies, most
NEWSIPS-processed SWP images are to be greatly preferred over IUESIPS
data because of their far greater stability with time. Differences
in apparent RVs from large- and small- aperture images arise for all
three cameras for bright stars because of a systematic centering
error used by the IUE Project to guide on bright stars. The Large
Aperture - Small Aperture difference amounts to -5 to -6 km/s for SWP
images. In addition, RV differences for individual large-aperture
images can sometimes be large due to centering errors.
One of the most interesting systematics found in our study is an
apparent wavelength-dependent difference in NEWSIPS SWP images, both
with respect to IUESIPS processings and the Copernicus atlas of tau
Sco. This systematic is robust and is likely to arise from a 1990
revision of the laboratory wavelengths of the PtNe calibration source
used by IUE and GHRS. This fact may have broad implications for
comparisons of velocities from datellite data before and after this
date.
Myron Smith
Cathy Imhoff
Although the IUE Data Analysis Center (IUEDAC) officially closed
October 8th, 1997, there is continued support for the IUEDAC software
and documentation from STScI. IUEDAC users will also continue to be
supported and questions regarding IUEDAC software or IUE data
analysis can be sent to
archive@stsci.edu.
See the IUEDAC page at
http://archive.stsci.edu/iue/iuedac.html for information on
retrieving the software and documentation. The latest IUEDAC
software modifications are listed at URL:
http://archive.stsci.edu/iue/rdafnews.html
The latest IUEDAC Users Guide was updated on February 5th, 1998, and
is online at
http://archive.stsci.edu/iue/manual/dacguide/ and can be
downloaded in either Postscript (guide.ps), LateX (guide.tex), or PDF
(guide.pdf) format.
Randy Thompson
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subscription.
Access to Copernicus Data
EUVE Archive Support at STScI
GHRS and FOS Data: Status Report
HST Archive Survey 1998
Analysis of Apparent Velocities from NEWSIPS-Processed High Resolution IUE Data
IUE NEWS
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