NASA Missions: Advanced Composition Explorer

Overview

The Advanced Composition Explorer (ACE) monitors particles with origins from the sun, planets, stars, and galaxies. These particles are observed at energies ranging from solar wind ions to galactic cosmic ray nuclei.

A continuous stream of accelerated particles, not only from the Sun but also from interstellar and galactic sources, bombards the Earth. The investigation of these powerful particles will advance our knowledge of the astrophysical processes involved in the formation and evolution of the solar system. With a collecting power 10 to 1000 times greater than previous or planned experiments, the Advanced Composition Explorer (ACE) spacecraft samples low-energy solar particles and high-energy galactic particles with six high-resolution sensors and three monitoring instruments. ACE conducts measurements over a wide range of energy and nuclear mass, under all solar wind flow conditions, and during both large and small particle events, including solar flares, from a vantage point about 1/100 of the distance between the Earth and the Sun.

NASA's ACE spacecraft

Over brief time intervals, ACE offers solar wind data that is nearly real-time. When predicting space weather, ACE can give a one-hour head start on geomagnetic storms that could overwhelm power grids, interfere with communications on Earth, and endanger astronauts.

Measurement and comparison of the chemical composition of various samples of matter, including the solar corona, solar wind, and other populations of interplanetary particles, the local interstellar medium (ISM), and galactic matter, is the main goal of ACE. Even though these goals have made great progress, new opportunities have arisen as a result of the solar cycle's changing conditions. As NASA's and the Sun-Solar-System Connection (S3C) Theme's goals change, new observations, theoretical advancements, missions, and other factors have also created new difficulties. One of these is gaining the scientific knowledge required to predict space weather in the years to come, when people will begin to leave Earth's magnetosphere for the first time.

In Depth

NASA's Advanced Composition Explorer (ACE) spacecraft was created to study spaceborne energetic particles from the Sun-Earth L1 Lagrange point, about 870,000 miles (1.4 million kilometers) from Earth, The spacecraft was specifically launched to look into the material that the Sun ejected in order to determine the similarities and interactions between the Sun, Earth, and the Milky Way galaxy.

Additionally, ACE offers up-to-date information on the space weather as well as geomagnetic storm advance warning. The nine instruments that make up ACE have a collecting power that is 10–10,000 times greater than anything that has ever been launched.
A month after launch, ACE reached apogee and then entered a Lissajous orbit near the L1 point. On January 21, 1998, the spacecraft was deemed operational. As of 2015, it was still measuring solar energetic particle intensities and providing near-real-time 24/7 coverage of solar wind parameters.
Since all of the instruments on ACE are still operational as of mid-2017, the mission could theoretically last until around 2024 with the exception of the SEPICA instrument (data from which were no longer received after February 4, 2005).

Scientific Instruments in ACE spacecraft:

• Solar Wind Ion Mass Spectrometer (SWIMS) and Solar Wind Ion Composition Spectrometer (SWICS)
  
• Ultra-Low Energy Isotope Spectrometer (ULEIS)
• Solar Energetic Particle Ionic Charge Analyzer (SEPICA)
•  Solar Isotope Spectrometer (SIS)
• Cosmic Ray Isotope Spectrometer (CRIS)
• Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM)
• Electron, Proton, and Alpha-Particle Monitor (EPAM)
• Magnetometer (MAG)
• Real Time Solar Wind Experiment (RTSW)