Don Savage Headquarters, Washington, DC May 31, 1995 (Phone: 202/358-1547) Jim Sahli Goddard Space Flight Center, Greenbelt, MD (Phone: 301/286-0697) RELEASE: 95-80 NASA'S X-RAY TIMING EXPLORER SHIPPED TO LAUNCH SITE The X-ray Timing Explorer (XTE) spacecraft is being shipped to its launch site in Florida today from the Goddard Space Flight Center in Greenbelt, MD. When it is launched this August, XTE will gather data about X-ray emitting star systems and other sources within the Milky Way galaxy and beyond. The satellite has completed its environmental testing program and is being flown to the Cape Canaveral Air Station launch site by an Air Force C-5 aircraft from Andrews AFB in Maryland. The 6,700-pound (3,045-kilogram) spacecraft currently scheduled for launch August 31 aboard a Delta II Expendable Launch Vehicle was integrated and tested at Goddard, which is managing this mission. After several months of preparing the X-ray observatory for flight in Florida, XTE will be launched into a 360-mile (580-km) low-Earth orbit. Spacecraft engineers and scientists from the three XTE instrument teams gathered at Goddard this month for a final rehearsal of mission operation activities before shipping the spacecraft to the launch site. The instruments are being provided by science and engineering teams at Goddard, the University of California at San Diego, and the Massachusetts Institute of Technology. "It is great to see the whole spacecraft shipped to the Cape after several years of pulling the different pieces together," said Dale Schulz, Project Manager for the XTE mission in Goddard's Flight Projects Directorate. "XTE will carry three instruments for studies of the variable X-ray sky: the Proportional Counter Array, the High Energy X-ray Timing Experiment and the All Sky Monitor. A two-year prime mission is scheduled, with extended operations for four to five years possible," said Dr. Jean Swank, project scientist for the XTE at Goddard. "XTE will carry out in-depth timing and spectral studies of X-ray sources across a wide range of X-ray energies to answer questions about collapsed compact stars -- white dwarfs, neutron stars, and black holes, and about very large black holes in quasars and galaxies," she said. "The X-ray sky is highly variable. Suddenly an obscure faint star lost in the crowd can become the brightest X-ray source in the sky, revealing where a black hole is likely to be found. Neutron stars emit beams of X-rays that sweep across our view as the stars rotate. XTE is tuned to watch the action and study it. These data will allow us to study the strongest gravitational and magnetic fields that we think exist in the universe," she said. Observations of specific targets to be studied with XTE will be proposed by scientists from the United States and abroad. Selected observations will be implemented by scientists at the XTE Science Operations Center (SOC) at Goddard. XTE will transmit data via two of NASA's Tracking and Data Relay Satellites, which will then relay the data to a ground station in White Sands, NM, and then to the SOC. Scientists can monitor observations from the SOC. Data are sent to their home institutions for detailed analysis. Goddard manages the X-ray Timing Explorer for the Office of Space Science at NASA Headquarters in Washington, DC. - end - EDITOR'S NOTE: For additional information about the mission, information about XTE is available on the World Wide Web at the following Internet address: http://heasarc.gsfc.nasa.gov/docs/xte/xte.html NASA press releases and other information are available automatically by sending an Internet electronic mail message to domo@hq.nasa.gov. In the body of the message (not the subject line) users should type the words "subscribe press- release" (no quotes). The system will reply with a confirmation via E-mail of each subscription. A second automatic message will include additional information on the service. Questions should be directed to (202) 358-4043.