Stamp of ACE Logo

Advanced Composition Explorer (ACE)

For the most recent news from ACE, go to the ACE Science Center website at:

The ACE Education and Public Outreach (E&PO) Committee has set up a page with ACE and other E&PO material on the web at:

As part of NASA's educational outreach program, ACE is participating in the Cooperative Satellite Learning Program (CSLP), and the ACE mission has been adopted by Old Bridge High School in Old Bridge, New Jersey.

The ACE project and NOAA developed and support the ACE Real Time Solar Wind (RTSW) monitoring capability. The intent is to provide 24 coverage of the solar wind parameters and solar energetic particle intensity. ACE's position a million miles upstream of earth may give as much as an hour's warning of CME's that can cause geomagnetic storms here at earth. See

Mission Description

The spacecraft is 1.6 meters across and 1 meter high, not including the four solar arrays and the magnetometer booms attached to two of the solar panels. At launch, it weighed 785 kg, which includes 189 kg of hydrazine fuel for orbit insertion and maintenance. The solar arrays generate about 500 watts of power. The spacecraft spins at 5 rpm, with the spin axis generally pointed along the Earth-sun line and most of the scientific instruments on the top (sunward) deck.

ACE Spacecraft 60kB GIF

ACE launched on a McDonnell-Douglas Delta II 7920 launch vehicle on August 25, 1997 from the Kennedy Space Center in Florida.

In order to get away from the effects of the Earth's magnetic field, the ACE spacecraft has travelled almost a million miles (1.5 million km) from the Earth to the Earth-sun libration point (L1). By orbiting the L1 point, ACE will stay in a relatively constant position with respect to the Earth as the Earth revolves around the sun.
Graphic of L1 location 23 kB GIF

The Advanced Composition Explorer (ACE) is an Explorer mission that was managed by the Office of Space Science Mission and Payload Development Division of the National Aeronautics and Space Administration (NASA). More on the ACE personnel, including scientific Co-Investigators can be found here.

The primary purpose of ACE is to determine and compare the isotopic and elemental composition of several distinct samples of matter, including the solar corona, the interplanetary medium, the local interstellar medium, and Galactic matter.
The nine scientific instruments on ACE are performing:

Return to ACE home pageReturn to ACE Home Page

Author and Curator: Eric R. Christian (
Responsible NASA Official: Tycho von Rosenvinge (
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    This file was last modified on Thursday, 15-Feb-2001 11:50:24 EST