RELEASE NO: 97-119

ACE MISSION STATUS REPORT #2

The Advanced Composition Explorer (ACE) is heading away from Earth at about twelve hundred miles per hour. Its current distance from Earth is 516,876 miles (833,000 kilometers). After a successful launch from Cape Canaveral Air Station in Florida on Aug. 25, 1997, NASA's latest spacecraft is enroute to its final destination approximately 1 million miles from Earth.

"The spacecraft continues to perform quite well. It has operated beyond our expectations at this point," said Don Margolies, mission manager for the ACE project at the Goddard Space Flight Center in Greenbelt, Md. Goddard is managing the ACE project for the Office of Space Sciences at NASA Headquarters in Washington, D.C.

"Next on our agenda is to perform an orbit shaping maneuver on Sept. 11. This maneuver is designed to keep the spacecraft's Sun-Earth-vehicle angles within specifications,Ó said Margolies.

A complete checkout of all spacecraft subsystems was completed during the first few days of flight, and a mid-course correction was performed Aug. 26. The spacecraft thrusters were fired for six minutes and thirteen seconds, instead of the nine minutes expected, saving fuel. Additionally, the Flight Operations Team at Goddard successfully completed a maneuver, Sept. 2, designed to keep the high gain antenna pointed toward the Earth. Antenna pointing corrections will be made every five to six days.

To date, eight instruments have been activated with the remaining instrument to be turned on by Sept. 6. Although some instruments are already returning science data to the ACE Science Center, scientists expect to start formal science operations by the end of January 1998, when the spacecraft reaches the L1 libration point (1 million miles from Earth). All scientific data will be received at Goddard and forwarded to the ACE science Center, at California Institute of Technology, for analysis.

ACE is one of NASA's fleet of spacecraft developed by the Explorer Program, located at Goddard. The scientific goal of the ACE mission is to accurately measure the composition of several different types of matter, including particles coming from the Sun, the very thin gas between the planets, the even thinner gas just outside the solar system, and matter from distant parts of the galaxy. The particles that ACE measures are moving very fast, up to 3.5 million miles per hour, and are atomic and subatomic. As part of NASA's Space Physics program the data gathered by ACE will be studied and compared with data collected from other missions, past and present, to give us a better understanding of the interaction between the Sun, the Earth, and the galaxy.

Information about the ACE mission is available on the Internet at the following location:

ACE: http://www.gsfc.nasa.gov/ace/ace.html

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