THE EXTREME ULTRAVIOLET EXPLORER ARCHIVE
        E. Polomski, J.J. Drake, C. Dobson, and C. Christian
                  Center for EUV Astrophysics,
           2150 Kittredge St., University of California,
                Berkeley, California  94720, USA

ABSTRACT

   The Extreme Ultraviolet Explorer public archive was created to handle the
storage, maintenance, and distribution of EUVE data and ancillary documentation,
information, and software.  Access to the archive became available to the
public on July 17, 1992, only 40 days after the launch of the EUVE satellite.
A brief overview of the archive's contents and the various methods of access
will be described.


1. INTRODUCTION

   The EUVE mission is expected to generate more than a Terabyte of data during
the lifetime of the satellite.  Public access to such a large data set necessi-
tates an expeditious and user-friendly archive interface.  The EUVE archive
plans to facilitate user access to mission-related data by employing a variety
of data retrieval mechanisms.
   The archive began supplying data to the public less than two months after
the launch of the satellite.  Archive data products presently include calibra-
tion target spectra, a catalog of past and future calibration targets, a pre-
liminary version of the EUVE Bright Source Catalog, extreme ultraviolet (EUV)
skymaps and images of extended sources, a list of approved guest observer
targets, a bibliography of EUVE publications, and C routines to calculate
interstellar medium transmission at EUV wavelengths.  All data are subject to
proprietary guidelines, which are outlined in a document available in the
archive.  As data rights deadlines expire, a more extensive set of spectra and
other EUVE data will become available to the public.


2. ARCHIVE ACCESS

   The scientific community may request publicly available data from the EUVE
archive via a variety of methods.  The archive may be accessed from an FTP site,
electronic mailserver, NASA's Astrophysics Data System (ADS), fax, and con-
ventional mail.
   Data may be retrieved from the archive FTP (file transfer protocol) site by
opening an FTP connection to ftp.cea.berkeley.edu.  At the Name prompt,
users should type anonymous and enter their complete e-mail address as a pass-
word.  The passwords used are logged, enabling us to keep a record of those
who have accessed the facility and to resolve any queries or problems more
promptly.  The FTP site is currently shared by the EUVE archive and the EUVE
Guest Observer Program:  information pertaining to both of these may be re-
trieved from the same site.  If you are unfamiliar with FTP, a list of available
commands may be obtained by typing help or ?.  To access the archive directory,
the user may change directory to pub/archive (cd pub/archive) and list the
contents of the archive by typing ls.
   Mailserver programs are more limited than FTP sites in terms of their data
transfer characteristics.  However, they can offer services, such as request
queuing and personal response processing, which FTP sites cannot.  Electronic
mail sent to archive@cea.berkeley.edu is processed by a mailserver program.
This program recognizes commands within the text of the e-mail message and
automatically returns data to the sender.  Mail messages which do not contain
commands are forwarded to archive personnel and are handled on an individual
basis.  A detailed description of EUVE mailserver commands may be obtained by
sending e-mail to archive@cea.berkeley.edu with a message containing the word
help on the first line of the main body of the text, not in the subject field.
A file containing information will be returned automatically.
   EUVE data may also be retrieved from NASA's ADS.  EUVE maintains an ADS node
and is actively participating in the system's development program.  ADS is a 
distributed database system for astronomical data.  It allows the requester to
perform database queries on remote databases by utilizing a query template.
Once data is retrieved, ADS users may manipulate and display it via a diverse
array of ADS tools.  Weiss and Good [1] present a recent overview of this sys-
tem.
   Questions regarding the ADS and user registration should be addressed

	ADS User Support
	Campus Box 389
	CASA
	University of Colorado
	Boulder, CO 80309
	Tel:  303-492-0466
or ads@cuads.colorado.edu

EUVE archive inquiries may also be addressed to the archive scientist, Dr.
Jeremy Drake, via conventional mail:

	Dr. Jeremy Drake
	The Center for EUV Astrophysics
	2150 Kittredge Street
	University of California
	Berkeley, CA
	94720 USA
or by fax (510-643-5660).[1em]


3. ARCHIVE EXPANSION

   By early summer of 1993, the archive will have expanded to incorporate se-
veral new services.  Several new catalogs will be released on ADS, including the
EUVE Bright Source List, as well as updates to the calibration target list and
the ROSAT Wide Field Camera Bright Source List.  The addition of a "spectrum-
server" to the EUVE ADS node will enable a user to position a mouse cursor on
the name of an EUVE target and automatically display and retrieve its spectrum.
   The EUVE mailserver will be expanded to include additional commands, as well
as a new ISM server facility to calculate interstellar medium absorption from
a remote site.  This facility is a prototype of a service which is planned for
future implementation, whereby the user can submit input data for a variety of
on-line programs using electronic mail.  These programs will expand user access
to EUVE data to include those users who have no access to the FTP facility and,
in addition, allow interface with proprietary software.  The ISM server will
enable a user to send input values  within an e-mail message to the ISM exe-
cutable located in the EUVE archive.  The server will automatically return out-
put values to the sender in electronic mail.
   The archive will release the first EUVE CD-ROM, less than a year after
launch, at the June 1993 meeting of the American Astronomical Society in
Berkeley.  CD-ROM media enable one to distribute and access complete libraries
of information at very low cost.  CD-ROMs have many advantages over traditional
data storage media such as magnetic tape:  they can store  up to 700 megabytes
of data, or almost 500 floppy discs, and have much more rapid access times
than magnetic tape.  In addition, in contrast to magnetic media, CD-ROM media
are not susceptible to X-rays, moderate heat or magnetic fields [2] [3].
   In recent years, CD archivists have expressed concern over the predicted
lifetime of CD-ROM media.  Although some writers have suggested lifetimes as
little as 10 years, most vendors believe that CD media will endure for 25
years, possibly longer than the hardware needed to read them [3] [4]! The CD's
longevity appears to be related to quality of manufacture.  If the edge of the
disc is not properly sealed, oxygen may reach the metal surface and corrupt
the media [5].  However, some companies are proposing new standards for testing
CD-ROMs that are expected to result in discs that will endure for more than
1000 years [5].
   The EUVE CD-ROM will contain spectroscopic data from in-orbit calibrations,
the EUVE IRAF data reduction software package, a sample raw spectrum of the
star AT Mic, a preliminary version of the EUVE Bright Source List, C routines
to calculate interstellar medium transmission, EUV skymaps, images of extended
EUV sources, and various mission-related tables and text documents.  Future
archive plans include the purchase of CD recorder hardware and software that
will enable CDs to be produced in-house.  As guest observer and survey data
rights begin to expire in early summer of 1994, this data will be incorporated
into the EUVE archive and will be accessible to the public from CDs.  As many
as 50 EUVE CD-ROMs may be created in the next 3.5 years.
   The EUVE archive is still in the initial stages of rapid growth  and expan-
sion.  The archive plans summarized above indicate the variety of methods by
which the scientific community will be able to access data.  It is hoped that
the archive will provide an efficient and  user-friendly means of accessing
EUVE data for the lifetime of the mission and beyond.


REFERENCES

1. J.R. Weiss and J.C. Good "The NASA Astrophysics Data System", in Databases
	and On-line Data in Astronomy, ed. M.A. Albrecht and D. Egret, Dor-
	drecht:  Kluwer, p. 139 (1991).
2. T. Thomaidis, Redlands Daily Facts, May 11, 1992.
3. Plain Talk:  CD-ROM Lifetime, 3M Optical Recording internal publication,
	1992.
4. J. Udell, BYTE, February, p. 116 (1993).
5. B. Fox, New Scientist, 134 (1815), 19 (1992).