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:

TRACE science information can be found at:

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