Science Update
Co-investigators and Associates
Instrument Description
TIDE Data
Examples
TIDE/PSI Data Access
The TIDE/PSI investigation is designed to obtain mass-resolved observations of the velocity distribution of low energy or core plasmas of the magnetosphere, especially the polar regions. This includes the partial pressure, wind velocity and temperature of the principal ion species whose source lies in the terrestrial atmosphere and ionosphere, i.e. Hydrogen, Helium, Nitrogen, Oxygen, and molecules of these species and their compounds. Features of interest include the heating and outflow of terrestrial plasma into the magnetosphere, the circulation of this plasma within the magnetosphere, its acceleration by space storm processes, and the escape of terrestrial plasma out of the magnetosphere into the passing solar wind. Launch aboard the Global Geospace Science POLAR spacecraft is anticipated in late 1995.
TIDE views the plasma environment through seven independent energy analyzers that combine large collection area electrostatic mirrors with conventional retarding potential analyzers. The seven apertures are arranged in a fan to resolve polar angle relative to the spacecraft spin axis, while the spin of the spacecraft sweeps them through azimuth angle, providing nearly a full view of the sky. This permits the measurement of winds up to 300 km/s (750,000 mph) in arbitrary directions and temperature up to several million ¡K (300 electron Volts). After energy analysis, plasma ions are fed to a time-of-flight mass analyzer that clocks the speed of each ion detected, at known energy, and sorts ions accordingly.
The Thermal Ion Dynamics Experiment, with TOF
analyzer cover removed to expose the detector systems.
The Thermal Ion Dynamics Experiment as mounted on
the POLAR spacecraft. Note that the outer portion of the spacecraft is
removed.
The POLAR spacecraft inside the vacuum chamber for
thermal vacuum testing. TIDE is mounted at the upper right of the spacecraft
and is wrapped for protection.
PSI is a source of low energy Xenon ions and electrons that serves to "ground" the POLAR spacecraft electrically to the space plasma environment. Without PSI, the spacecraft would become positively charged in low density plasmas owing to emission of electrons by the photoelectric effect of sunlight on the spacecraft surfaces. This charge would prevent low energy ions from ever reaching the spacecraft or the TIDE apertures. Conversely, in the very hot plasmas that produce auroras, the spacecraft would become negatively charged by as much as several kiloVolts, potentially leading to harmful discharges. Operation of PSI will allow TIDE to view the low energy plasma and will protect the spacecraft from high voltage charging in hot plasmas.
The Plasma Source
Instrument source module.
The Plasma Source
Instrument as mounted on the POLAR spacecraft.
TIDE/PSI has been developed through the efforts of the following organizations:
The TIDE/PSI investigation science team also includes the following other organizations:
Space Plasma Physics Branch | Space Sciences Laboratory | Marshall Space Flight Center | NASA
Last Updated:
Tues. June 22, 1999