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NASA's Transition Region and Coronal Explorer Mission Set to Study the Sun's Turbulent Upper Atmosphere

Donald Savage
Headquarters, Washington, DC                  March 19, 1998
(Phone:  202/358-1547)

Donna Drelick/Jim Sahli
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-8955)

RELEASE:  98-48

NASA'S TRANSITION REGION AND CORONAL EXPLORER MISSION SET TO 
STUDY THE SUN'S TURBULENT UPPER ATMOSPHERE 

    NASA's Transition Region and Coronal Explorer (TRACE) 
mission, scheduled for launch at 9:40 p.m. EST (6:40 p.m. PST) 
March 30, 1998, will greatly improve understanding of events in 
the Sun's atmosphere, including intense storms and flares, 
which can have an impact on power and communications systems on Earth.  

    The TRACE mission will join a fleet of spacecraft studying 
the Sun during a critical period when solar activity is 
beginning its rise to a peak early in the new millennium.  The 
Sun goes through an 11-year cycle from a period of numerous 
intense storms and sunspots to a period of relative calm and 
then back again.  The coming months in the Sun's cycle will 
provide solar scientists with periods of strong solar activity 
interspersed with periods when the Sun is relatively passive 
and quiet.  This will give TRACE the chance to study the full 
range of solar conditions, even in its relatively short planned lifetime. 

    TRACE will train its powerful telescope on the dynamic so-
called 'transition region' of the Sun's atmosphere, between the 
relatively cool surface and lower atmosphere of the Sun where 
temperatures are about 6,000 degrees Fahrenheit, and the 
extremely hot upper atmosphere called the corona, where 
temperatures are up to 16 million degrees Fahrenheit.  Using 
instruments sensitive to extreme-ultraviolet and ultraviolet 
wavelengths of light, TRACE will study the detailed connections 
between the fine-scale surface features and the overlying, 
changing atmospheric structures of hot, ionized gas, called 
plasma.  The surface features and atmospheric structures are 
linked by fine-scale solar magnetic fields.

    The power of the TRACE telescope to do detailed studies of 
the solar atmosphere makes this observatory unique among the 
current group of spacecraft studying the Sun. 

    "The spacecraft has roughly ten times the temporal 
resolution and five times the spatial resolution of previously 
launched solar spacecraft.  Its findings are eagerly awaited by 
the solar science community," said Dr. Alan Title, TRACE 
principal investigator from the Stanford Lockheed Institute for 
Scientific Research in Palo Alto, CA.  "We can expect to 
resolve some present mysteries of the Sun's atmospheric 
dynamics as well as discover new and exciting phenomena." 

    TRACE will be launched into a polar orbit to enable 
virtually continuous observations of the Sun, uninterrupted by 
the Earth's shadow for months at a time.  This orbit will give 
the mission the greatest chance of observing the random 
processes which lead to flares and massive eruptions in the 
Sun's atmosphere.

    The TRACE telescope is really four telescopes in one.  Its 
30-centimeter (12-inch) primary and six-centimeter (2-inch) 
secondary super-polished mirrors are individually coated in 
four distinct quadrants to allow light from different 
bandwidths (colors) to be reflected and analyzed.  An 
electronic detector collects images over a 231,000-by-231,000-
mile field of view, nearly 25 percent of the Sun's disk.  A 
powerful data handling computer enables very flexible use of 
the detector array including adaptive target selection, data 
compression and image stabilization. 

    "TRACE was completed on time, under budget, and met all 
performance goals," said Jim Watzin, Small Explorer project 
manager, NASA Goddard Space Flight Center, Greenbelt, MD.  "I'm 
really proud of this team.  They have produced a magnificent 
observatory in a manner that saved NASA nearly $9.7 million 
over the initial cost estimate."  TRACE, which costs $49 
million, is the third launch in the Small Explorer series of 
small, quickly developed, relatively low-cost missions.

    TRACE will be launched on an Orbital Sciences Corp., 
Dulles, VA, Pegasus-XL rocket released from an L-1011 jet 
aircraft at the Western Range, Vandenberg Air Force Base, CA.  
The launch window is open for 10 minutes.

    TRACE will be the first space science mission with an open 
data policy.  All data obtained by TRACE will be available to 
other scientists, students and the general public shortly after 
the information becomes available to the primary science team.  

    The TRACE telescope was designed and developed in 
cooperation between Lockheed Martin Corp. and Stanford 
University.  The spacecraft was designed and tested at Goddard, 
which manages the mission for the Office of Space Science at 
NASA Headquarters, Washington, DC. 

    Further information about the TRACE mission can be found on 
the Internet at:

          http://sunland.gsfc.nasa.gov/smex/trace

    TRACE science information can be found at: 

     http://www.space.lockheed.com/TRACE/welcome.html

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