Students and Educators: Precollege

ACE Spacecraft was launched in August, 1997

ACE: Studying Energetic Particles

The Earth is constantly bombarded with high-speed particles coming not only from the sun, but also from outside of the solar system. Studying these energetic particles can help us understand the origin and evolution of our solar system. The Advanced Composition Explorer (ACE) spacecraft carries nine instruments that can collect and measure these particles 10 to 1,000 times better than previous spacecraft. From ACE, scientists on Earth will receive information about the solar wind such as its velocity, temperature, and composition.

The ACE Spacecraft was launched in August 1997. Its primary mission is to observe energetic particles within the solar system. The mission lifetime is two to five years.

Solar flares, Geomagnetic storms

ACE will orbit the sun very near the Earth (approximately 1/100th of the distance from the Earth to the Sun). From here, it will be able to determine which particles hit the Earth. This information will help scientists to better understand phenomena such as solar flares. ACE will also be able to warn us of encroaching geomagnetic storms that disrupt communications and are hazardous to astronauts.

"Where did I come from?"

This question is usually one about life, but behind it are scientific questions about the material of which we are made, the elements in the atoms and molecules of our bodies. The answer to the question, "Where did the matter we are made of come from?" is not so easy to find. Some could be satisfied with an answer such as "We are made of the same elements that are found on the Earth we live on." But where did that material come from?

The Earth is but one planet in the solar system, and most of the solar system material is inside the Sun. How can we find out what the Sun is made of? Where did the Sun come from? One can even go further and ask, "What is the galaxy made of?" There is a whole series of related questions that are involved in understanding the cycles the matter goes through as the universe and the structures within it evolve.

Measuring particles of history

Science has barely scratched the surface in examining the actual source of the particles traveling through space around us. The mix of particles that ACE will measure is the result of a complex history. The ability of the ACE's nine instruments to measure a wide range of particle types and energies at the same time and location is what will enable scientists to separate the many processes the matter has undergone on its way to ACE.

Putting the puzzle pieces together

The prime purpose of ACE is to study the composition of several distinct sources of matter; the Sun and solar system, the local interstellar space, and the galaxy as a whole. This, in turn, will lead us to a better understanding of the origin of the elements, and the subsequent evolutionary processing of matter (how it has changed since it was created). Along the way, ACE will learn more about particle acceleration and transport in the universe, information needed to separate the changes in composition during the particles' travel. Learning the differences in composition between the solar wind and the Sun will help answer questions about how the solar corona is formed and how solar wind is accelerated. All of these interesting problems are part of the larger question "Where did we come from?" ACE is one piece of the enormous puzzle.

As new information becomes available, from both spacecraft and Earth-based instruments, the picture becomes clearer. Theories are upheld or upset, and new theories take their place. ACE provides an abundance of information to further our understanding of the way our solar system, galaxy, and universe were created and how they continue to evolve.