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International Ultraviolet Explorer Prepared to Receive its Final Command

Douglas Isbell
Headquarters, Washington, DC              September 30, 1996
(Phone: 202/358-1753)

Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-5566)

RELEASE: 96-194

INTERNATIONAL ULTRAVIOLET EXPLORER PREPARED TO RECEIVE ITS FINAL COMMAND

     After nearly 19 years of operation, NASA's International 
Ultraviolet Explorer (IUE) spacecraft will receive its final 
"shutdown" -- marking the end of one of the longest and most 
productive missions in the history of space science.  

     "The decision to shut down a hardy veteran like IUE was 
not an easy one," said Dr. Wesley Huntress, Associate 
Administrator for Space Science at NASA Headquarters, 
Washington, DC.  "However, we have to balance our available 
budgetary resources with an increasing number of productive 
space science missions that require operational support.  IUE 
has been incredibly productive over its long lifetime."

     Originally designed for a three-year life, the 
observatory and its spectrographic instruments enable studies 
of astronomical and cosmic phenomena that emit ultraviolet 
radiation, which is blocked from ground-based telescopes by 
Earth's atmosphere.  IUE has been controlled from NASA's 
Goddard Space Flight Center, Greenbelt, MD, for the past two decades.  

     "IUE was a pioneering research spacecraft for observing 
the ultraviolet spectrum," said Dr. Yoji Kondo, IUE project 
scientist at Goddard.  "Many of the scientists that use the 
Hubble Space Telescope and other space-based observatories 
today began by studying the ultraviolet with IUE." 
 
     Some of IUE's most recent research includes observations 
of Comet Hyakutake during March 1996.   Scientists using IUE 
tracked and observed the nucleus of Comet Hyakutake for five 
days, obtaining exposures of up to five hours in duration 
that provided new insights into the chemical processes taking 
place inside the comet.  The comet was found to be ejecting 
ten tons of water every second as it passed near the Sun.  
Astronomers also were able to confirm that the "break up" 
event of March 24 involved only a small piece of the comet, 
Kondo said.

     IUE has contributed to many branches of astronomical 
research over the years, ranging from studies of objects in 
the Solar System to observations of distant galaxies.  This 
includes the historic first identification of the star that 
exploded and became known as Supernova 1987A.

     Goddard has operated the IUE in three-way collaboration 
with the European Space Agency (ESA) and the Particle Physics 
and Astronomy Research Council (formerly the British Science 
Engineering and Research Council) of the United Kingdom since 
the spacecraft's launch on Jan. 26, 1978.   IUE has been 
operated in a real-time mode similar to ground-based 
observatories, and was the only geosynchronous scientific 
satellite observatory capable of working continuously 24 
hours per day.

     More than 2,000 guest observers from all corners of the 
world, including astronomers from North and South America, 
Europe, China, India, Russia, Africa, and Australia, have 
used the observatory at Goddard and through the ESA control 
site in Spain.  Approximately 3,500 scientific articles based 
on IUE observations have been published in peer-reviewed 
journals -- the largest number for any satellite observatory 
thus far.  In addition, more than 500 doctoral students have 
used IUE results in their dissertations, clearly 
demonstrating the importance of the IUE project to the 
education of the next generation of astrophysicists.

     "IUE has contributed significantly to astronomical 
science over the years.  Yet its ultimate legacy will be the 
final data archive, which will be completed by the end of 
1997," Kondo said.  "Using newly developed software, 
additional scientific information will be gleaned from more 
than 100,000 astronomical observations that are currently 
being reprocessed.  This data archive will be stored for 
future reference and will remain an important resource for 
astrophysical studies for many years to come."

     As part of NASA's continuing budget reduction efforts, 
day-to-day science control of the IUE was fully transferred 
to ESA on Oct. 1, 1995, thus combining the NASA and ESA IUE 
science programs, although Goddard maintained responsibility 
for the daily operational maintenance of the spacecraft.  It 
was jointly decided by NASA and ESA that final shutdown would 
occur on Sept. 30, 1996.

     A past winner of the U.S. Presidential Award for Design 
Excellence, IUE has been used as a central facility in many 
multiwavelength observations, an important modern approach to 
astrophysical research.  The spacecraft has been used in 
conjunction with ground-based telescopes and other space 
observatories, including the Compton Gamma Ray Observatory 
and the Hubble Space Telescope.

     More information on IUE and other related astrophysics 
missions is available on the Internet at URL:

       http://iuewww.gsfc.nasa.gov/iue/iue_homepage.html

                       -end-

Editor's note:  A more detailed list of IUE scientific 
highlights is available from the NASA Goddard Public Affairs 
Office at 301/286-8955.