-a paper/poster presentation for
Mosaic and the Web International Conference '94
Behram Antia,
Carol Christian, Kuei Chen
Center for EUV Astrophysics (CEA)
University of California at Berkeley
2150 Kittredge St.
Berkeley, California
94720-5030
Abstract
The Extreme UltraViolet Explorer (EUVE) satellite is NASA's most
recent Explorer-class astrophysics mission. This orbiting observatory is
the first to examine the whole extreme ultraviolet portion of the spectrum;
it covers from approximately 50-760 Angstroms. The Center for EUV
Astrophysics (CEA) at
the University of California at Berkeley, is responsible for the archival
and dissemination of the missions raw and processed data products.
The Archive group at CEA has endeavoured to provide an wide range of
data, documentation, software and services online to the astronomical
community and the world via NCSA's Mosaic. The ability to access/distribute
our data and data products has changed dramatically in just the last year
with Mosaic as our WWW interface. We can now provide some very sophisticated
services to allow users to reprocess, preview and retrieve data remotely.
For example, user's can request that our system build
a data file for a particular EUV source, with their specifications of
position on the sky and field of view. They can then view and/or retrieve the
final product for further analysis. The implications of this type of
accessibility are wide-ranging; from all levels of science and astronomy
education to multiwavelength astronomical research. We will discuss our
current implementation and our plans on expanding our web site with new
information and services.
Introduction
The burgeoning growth of the Internet has caused a fundamental change in the
way information or activities are made available by providers and used by
"consumers". The single service that has caused a dramatic increase in
information traffic in the last couple of years is the World Wide Web and
its premiere exploration tool Mosaic.
The powerful and sophisticated access that the Internet provides
to many specialized, geographically diverse, data sets and the parallel
abilities to communication with colleagues, has increased the pace of
scientific research enormously. While at the same time becoming a means
of general education and amusement. The multimedia capabilities of the
web have greatly enhanced all of these aspects for the estimated
30 million users.
As an example, just a few short years ago, the launch of a two
hundred million dollar satellite into orbit, which performs exceptionally
well for years, opening up one of the last frontiers of observational
astronomy, would not have been as easily accessible to the scientific and
Internet communities. The original mission requirement is that the data be
deposited with NASA's National Space Science Data Center. In addition,
CEA developed portable IRAF tools and distributed CD-ROM's.
However, the new Internet tools we have to work with have changed the
thinking quite dramatically.
During the mission, we will accumulate about 330 Mb of telemetry per day
for several years, and a large group of researchers processes and analyzes
this data. The CEA is then faced with the task of making the data, derivative
products, explanatory material and software available to the scientific
community. The CEA has also responded to the new NASA strategy
to formulate mechanisms to offer mission data in a more
public arena, such as the K-12 community and academic
institutions conducting informal education programs.
The EUVE team at Berkeley is committed to making the mission a
truly public one. The political climate at NASA heavily favours this,
and the agency is leading the way for government agencies in the areas
of public access to information, streamlining governing processes and
coordination, and enhancing the exchange and development of ideas. CEA
is one NASA affiliate that has made this policy come alive with our
web site.
Mission and Data Product Overview
The Extreme UltraViolet Explorer (EUVE) satellite is the latest in a very
successful series of astrophysics missions conducted by NASA. This class of
observatory includes such splendid examples such as the International
Ultraviolet Explorer (IUE) and the Cosmic Background Explorer (COBE).
EUVE was launched on June 7th, 1992, from Cape Canaveral, Florida,
into a near-Earth (550 km) orbit. The orbiting observatory is the first
to examine the extreme ultraviolet portion of the spectrum; it covers
from approximately 50-760 Angstroms. The EUVE satelitte has two phases
of operation. The first phase was an imaging "survey" of the entire sky.
The second (and present) phase is the pointed observation, at particular
objects of interest, collecting spectra. The two phases result in two
fundamentally different types of data.
One type of data is essentially an image or map of the
entire sky, the other -the spectra, can be
used to study the physics and chemistry of
individual objects in detail.
CEA is
the scientific base for the mission, controlling the science payload,
while NASA's Goddard Space Flight Center controls the spacecraft. CEA is
unique in this regard, it is a separate entity that controls data processing
and handling, and storage of the mission data. The tools and techniques we
have developed are therefore also unique to this facility.
EUVE is the only mission to have all of the telemetry
on an optical disk jukebox constantly available on-line.
The data from the survey mission was proprietary to the Berkeley science
team for a period of one year and the spectroscopic data given to Guest
Observers also carries the same exclusivity. After these periods expire,
the data is "released". Since the mission is ongoing, new data and data
products are continually added to the archive of public information.
This has been a driving force in the creation in our web site; the
realization that the data set is dynamic and evolving. The data products
from the survey that we make available include:
- source catalogs -- Two catalogs of the survey results have been
published in the literature:
"The Extreme Ultraviolet Explorer Bright Source List" (Malina, et al. 1994)
"The First EUVE Source Catalog" (Bowyer, et al. 1994).
For the confirmed detected sources contained therein, these
catalogs furnish coordinates, approximate count-rates and
optical identifications (where available).
-
skymaps -- The survey skymaps are packaged as sets of binned raw
photon
(~1.3' resolution) and exposure (~10' resolution) maps for each
survey band pass, of which there are four.
-
pigeonholes -- An EUVE "pigeonhole" is a file which contains the
time-tagged photon event information within a small radius
(typically 0.4 degrees) of a given location on the sky.
Though the raw data from the survey portion of the mission will not change,
the form that the derived data products take will. The spectral observations
are also made available online in a limited fashion at the moment, but
mostly through supplementary media including CD-ROM. The integration of
services is a goal that will be discussed.
The CEA Web Site
The revolution in communication that is the World Wide Web and its associated
browsers, was not something envisaged in the early eighties as the mission
hardware and software were being prepared. The CEA web site was inaugurated
in Sept. 1993 and has expanded significantly since. The Archive group has
shifted its focus of data storage and access to a web-based one. It has
superceeded the expansion of our mailserver, ftp site and gopher services,
though all still exist and will continue to do so. The web site now contains
a wide variety of data, software, and documentation for many varied aspects
of the mission. Each group, or major unit, that comprises the whole of CEA
has contributed their unique information to the site. This in fact is a
reason why the local Mosaic site gets so heavily used. Besides being an area
for testing and creation, interdepartmental work is actively carried out
and information shared. The whole project benefits from the accessibility
to each individual units work.
Overview of Structure
There are several areas of active development at the Center for
EUV Astrophysics (CEA):
Types of Services
The particular area of focus in this paper will be the Archive. The structure
of the web site reflects the major offerings: data, software and services
and documentation are the links at the top level. As previously mentioned,
the types of data products
are all available here. Some are interactively created as per user request,
and others are static, but ever increasing in volume. We have incorporated
many forms for information retrieval because we can then offer data that
is built on the specifications of the researcher.
The ability to generate
a particular image of a piece of the sky
(skymap)
is of great value to those who
wish to study the broader characteristics of a region. Instead of confining
them to data products as we feel they should be presented, the raw data and a
processing tool is offered and the onus of the scientific validity is shifted.
Thus a user
can request a particular region that matches an image she has for the xray sky
for example. The ability to study astronomical objects in many differing
wavelengths is of key importance, and systems such as the European Space
Information System
(ESIS)
and the Astrophysics Data System
(ADS)
aim to provide exactly this ability.
Pigeonholes are also created
by the user using a Mosaic form. These are essentially photon-event lists
for particular sources and can be used to study luminosity and to derive
light curves for example. The pigeonhole for a source in the extreme
ultraviolet can be then combined with other data from optical, xray,
infrared etc. measurements and a clearer overall picture of an objects
properties emerges. In order not to alienate those users inconvenienced
with insufficient bandwidth, we have kept the clickable maps and images
to within reason. Several of our services rely on inlined or external gif
images, but we have not made it a necessary condition for using our site.
In one instance, the archive has a form for generating and displaying
model
spectra in the EUV based on a series of parameters (such as electron
density and temperature) chosen by the user. The form is the interface to a C
program that generates the model spectra and delivers the data file and/or
image in real-time.
In addition to data and interactive software, we have a great deal of
supporting documentation for the mission online, including an indexed
Bibliography of refereed papers, We also have several movies,
animations and many images of all types available.
Supplementary Services
While the web based delivery of all our data is certainly an admirable
goal, it is at the moment, technically prohibitive. We therefore also
deliver data and data products on 8mm tape and CDROM. Of course,
we have complete descriptions and order forms available through NCSA's Mosaic.
The CDROM delivery of data sets is currently a practical solution since
one entire data set for a single Guest Observer target pointing can be
several hundred Mb.
Future Developments and Enhancements
In the near term, CEA will be streamlining the user interface to make it
more intuitive, as we add more and more data, services and documentation.
The addition of our editorial archive of ~600 papers (from refereed journals)
on EUV astronomy is a formidable task, but progress is being made.
We also continually update the publically released Guest Observer targets.
As more and more information comes online, it needs to be coupled with
intelligent search engines of various types. We are currently creating
source catalogue search utilities and will be indexing all the papers
as an example. For astronomers out there, we will also have a fully featured
coordinate conversion utility online soon.
The quickly evolving software will soon enable a whole new suite of
services to users of CEA's web site. For example, we envision secure data
delivery to Guest Observers, real-time analysis tools for our data products,
and possibly remote scheduling and autonomous satellite operations being
conducted over the web. Also, the ability to present distance learning
sessions for all educational levels is actively being pursued. The
interactivity and multimedia nature of the web cannot be emphasized enough
when considering the possibilities for education.
The nature of the web has enabled a whole new operational method
for our entire project, and this, we hope, will be a model for other
NASA missions and indeed any large collaborative experiment that are
envisioned. Even now, CEA is testbedding many of the tools and techniques,
including web-based ones, that future satellite missions will be able to
draw upon.
Conclusion
We have tried to show in this paper, the underlying philosophy at the CEA of
data distribution, distributed services and computing, as well as demonstrate
the types of services and data products currently offered. We are constantly
learning in order to improve these, and look forward to working on new
techniques and methods in the future.
The Center for EUV Astrophysics at the University of California at Berkeley,
has endeavored to create a web site that is fully featured and provides
the best possible information delivery system for astronomers and anyone
wishing to learn more about our universe...
This work supported in part by NASA contracts.NAS5-29298 and NAS5-30180.
Author Info
Behram Antia
Center for EUV Astrophysics (CEA)
University of California at Berkeley
2150 Kittredge St.
Berkeley, California
94720-5030
I am a Research Associate at the Center for EUV Astrophysics (CEA), which is
a department of the University of California at Berkeley.
EUVE is a project I've been with for 2.5 years as a
member of the Data Analysis and Archive groups. The Data Analysis Science
Support (DASS) group researches calibration of the EUVE instrumentation and
provides data processing and analysis to Berkeley scientists at CEA. We also
perform science investigations utilizing imaging and spectroscopic data
from EUVE. The Archive group is responsible for the storage, maintenance
and especially the distribution of EUVE data and ancillary documentation,
information and software, including maintaining the CEA node of ADS.
I have been involved with CEA's web site since its inception in Sept '93,
and am now particularly responsible for the Archive portion. My role in the
Archive web site involves writing forms and scripts to handle user requests
and data/info orders as well as disseminating and organizing the wide variety
of data we are making publically available. In my spare time, oh nevermind,
I never have any...
My co-authors on the paper/poster
presentation are the managers of the Data Analysis and Archive groups
(Brett and Carol), fellow Research Associates Bill and Kuei Chen.
Home Pages are here:
Brett Stroozas/
Bill Boyd/
Carol Christian
Please feel free to contact me with any questions you may have regarding
our mission and/or our web site. For your convenience, you can use my
Mosaic email form. or directly mail
behram@cea.berkeley.edu