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Introduction to CAPS

Cassini-Huygens is the fourth spacecraft to visit the planet Saturn, following Pioneer 11 (1979), Voyager 1 (1980), and Voyager 2 (1981). It is also the first to be placed in orbit around Saturn. The spacecraft consists of two primary components: (1) The Cassini spacecraft, designed to orbit Saturn; and (2) the Huygens probe, designed to be dropped into the atmosphere of Saturn's largest moon Titan and land on its surface.

Launched in 1997, Cassini-Huygens began its journey with gravitational assist flybys of the planets Venus (1998 and 1999), Earth (1999), and Jupiter (2000). It arrived at Saturn and was placed into orbit around Saturn on July 1, 2004. The Huygens probe detached from Cassini on Christmas Day 2004, and descended through Titan's atmosphere to the ground three weeks later, on January 14, 2005. Since that time, the Cassini spaceraft has continued orbiting Saturn, collecting data on the planet Saturn, its rings, its moons, and its magnetosphere.

Cassini carries on-board a whole host of scientific instruments for studying the Saturn system. One instrument is called the Cassini Plasma Spectrometer. or CAPS. CAPS consists of three sensors, all mounted on a common scanning platform:

1. the Electron Spectrometer (ELS), which measures the flux of electrons as a function of energy/charge and aperture entry direction. Its energy range is 0.7 eV to 30 keV.
2. the Ion Beam Spectrometer (IBS), which measures the flux of positively charged ions of all species as a function of energy/charge and aperture entry direction. Its energy range is 1 eV to 50 keV.
3. the Ion Mass Spectrometer (IMS), which provides species-resolved measurements of the flux of positively charged atomic and molecular ions as a function of energy/charge vs. aperture entry direction. Its energy range is 1 eV to 50 keV.

The CAPS team at the NASA Goddard Space Flight Center analyzes data from the Ion Mass Spectrometer in order to better understand the plasma environment of Saturn's magnetosphere and its moons. The team has been particularly interested in studying the plasma environment of Saturn's largest moon Titan.