Don Savage, Jim Sahli

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


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


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,