July 28, 1997 Donald Savage Headquarters, Washington, DC July 23, 1997 (Phone: 202/358-1547)
Lynn Jenner Goddard Space Flight Center, Greenbelt, MD (Phone: 301/286-0454)
ADVANCED COMPOSITION EXPLORER SET TO STUDY MATTER FROM SUN, MILKY WAY AND BEYOND
The Earth is constantly being bombarded by a stream of accelerated particles arriving not only from the Sun, but also from interstellar and galactic sources. The study of these energetic particles by NASA's Advanced Composition Explorer (ACE) observatory will contribute to the understanding of the formation and evolution of the solar system as well as the astrophysical processes involved.
The space science observatory is scheduled for launch on a Delta II rocket at 10:39 a.m. EDT August 25, from Launch Complex 17 at the Cape Canaveral Air Station, FL.
"The Advanced Composition Explorer observatory is designed to sample the matter that comes near the Earth from the Sun, from the apparently, but not actually, empty space between the planets, and from the Milky Way galaxy beyond the solar system," said Don Margolies, ACE Mission Manager at NASA's Goddard Space Flight Center, Greenbelt, MD.
"While previous missions have studied these particles, the instruments on ACE have a collecting power 10 to 1,000 times greater and will be at least 100 times more sensitive than anything we've ever flown," Margolies said. "We will be able to study known phenomena in much greater detail than previously possible, and discover new ones to give us a better understanding of the interaction between the Sun, the Earth, and the galaxy."
The Advanced Composition Explorer has six high-resolution particle detection sensors and three monitoring instruments. It will sample low-energy particles of solar origin and high-energy galactic particles. The observatory will be placed into an orbit at the L1 libration point, which is almost a million miles (or 1.5 million kilometers) away from the Earth, about 1/100 the distance from the Earth to the Sun.
The ACE payload includes four brand-new, state-of-the-art spectrometers. They are the Cosmic Ray Isotope Spectrometer; Solar Isotope Spectrometer; Solar Energetic Particle Ionic Charge Analyzer; Ultra-Low-Energy Isotope Spectrometer. In addition, there are four spare instruments from other NASA missions that, with appropriate modifications, are being flown on ACE. They are the Solar Wind Electron, Proton, and Alpha Monitor; Solar Wind Ionic Charge Spectrometer; Electron, Proton, and Alpha Monitor; and a Magnetometer. An additional instrument, the Solar Wind Ion Mass Spectrometer, is a newly built copy of a previously flown instrument.
Also onboard are two secondary instruments, the Spacecraft Loads and Acoustic Measurements, designed to measure spacecraft environments during the first five minutes of launch, and the Real Time Solar Wind experiment, which will provide real- time data to the National Oceanic and Atmospheric Administration (NOAA). NASA and nine universities in the U.S. and Europe built the instruments.
The ACE spacecraft's instruments and experiments will work together to add to our understanding of solar events ranging from "solar storms" to the origin and evolution of solar and galactic matter.
The scientific goal of the ACE mission is to measure accurately 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.
ACE also has an Earth applications goal. It will provide NOAA's Space Environment Center, Boulder, CO, with continuous real-time solar wind "space weather" information, which will give an advance warning (about one hour) of geomagnetic storms that can affect electric power grids, Earth-orbiting spacecraft, and radio communications on Earth.
The 1,730-pound observatory was built by the Johns Hopkins Applied Physics Laboratory, Laurel, MD, where its instruments were integrated. ACE was tested at the Applied Physics Laboratory and at Goddard.
The science payload was provided under the direction of the Payload Management Office at the California Institute of Technology, Pasadena, CA. Flight operations will be conducted from Goddard; the Science Center is located at Caltech. The ACE mission is managed by the Explorer Program at Goddard for the Sun-Earth Connections Program in the Office of Space Science, NASA Headquarters, Washington, DC
An ACE Project website can be found at the following URL:
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