Project Overview

INSTRUMENTS

ORBITER: Remote Sensing Complement

Near-Infrared Mapping Spectrometer (NIMS): Makes measurements in the near-infrared region of the light spectrum to determine the composition, cloud structure and temperature of Jupiter's atmosphere. Designed to determine the mineral content and geochemistry of the surfaces of the Jovian satellites.

Photopolarimeter-Radiometer (PPR): Measures the intensity and polarization of the reflected sunlight in the visible part of the light spectrum. Used to study the temperature profile and cloud characteristics of Jupiter's atmosphere and to study the brightness, texture and temperatures of the satellites' surfaces.

Solid-State Imaging Camera (SSI)): The main imaging device on Galileo operating in the visible part of the light spectrum. Uses a CCD device to take pictures that are used to study the atmosphere of Jupiter and the geology of the Jovian satellites.

Ultraviolet Spectrometer (UVS): Measures light spectra from 1150 to 4300 Angstroms to determine the properties of the Jovian atmosphere, the surfaces of the Galilean satellites and the emission spectra of Io's torus. The instrument also studies the airglow and auroral emissions from the Jovian atmosphere.

ORBITER: Field and Particle Instruments

Dust detection instrument (DDS): Measures the mass and speed of small dust particles by sensing the impact products in electron and ion collectors. Studies the distribution of interplanetary dust and physical and dynamical properties of dust particles in the Jovian system.

Energetic Particles Detector (EPD): Measures the flux and the spectra of ions and electrons to provide spatial distributions and temporal fluctuations in the Jovian magnetosphere and the interplanetary space. Provides composition measurements for ions with energies exceeding 100 keV. Makes measurements in the range of 20 keV-3.4 MeV for ions and 15 keV-1.0 MeV for electrons. Uses two separate bi-directional solid-state detector telescopes mounted on a stepping platform.

Magnetometer (MAG): Measures the magnetic field of Jupiter, its magnetosphere, its satellites and the distortions of these fields by the interaction between the Jovian magnetosphere and the satellites. MAG will also characterize the interplanetary magnetic field and the magnetic fields of the asteroids.

Plasma Instrument (PLS): Measures the densities, temperatures, bulk velocities and composition of the low-energy plasma. The energy range for ions and electrons is 1.2 eV to 50 keV. The energies of the bulk of the plasma in the Jovian magnetosphere falls within the energy range of this instrument including the plasma in the cold and the hot torus of Io. Uses two sets of electrostatic spherical section analyzers. Has time of flight capability to determine the composition of ions.

Plasma Wave Subsystem (PWS): Measures the electric and magnetic fields in the frequency range of 5 Hz to 5.65 MHz. PWS will measure the intensities of the in-situ plasma waves in the Jovian magnetosphere and the radio waves emitted by Jupiter, the Earth and the Sun. Uses an electric dipole antenna to measure electric fields and a search coil magnetic antenna to measure the magnetic field.

Radio Science: Several investigators will use radio telecommunication subsystem to perform experiments involving celestial mechanics and relativity. Radio propagation investigations will probe the thermosphere, ionosphere and the magnetosphere of Jupiter. Radio occultation measurements will provide the density, pressure and temperature of the atmosphere as a function of height. Radio occultations will also provide measurements of the electron density versus height in the ionosphere.

Instruments on the Probe

Atmospheric Structure Instrument (ASI): Three type of sensors (temperature sensors, pressure sensors and a three-axis accelerometer) provide in-situ information on the structure of the Jovian atmosphere. Will yield information on the temperature and pressure levels at which the clouds form and help determine the radiative balance in the Jovian atmosphere.

Neutral Mass Spectrometer (NMS): Measures the composition of the neutral atmosphere by conducting atmospheric gases through an ionization region where ionization is achieved through electron impacts. The ion beam is passed through a quadrupole analyzer filter to transmit ions of a chosen charge to mass ration only. The ion beam is focused on a secondary electron multiplier ion detector. The instrument also measures the abundance of noble gases and more complex compounds by using a purification cell and two compound enrichment cells.

Nephelometer (NEP): Uses a transmitted laser beam to determine the scattering of light by atmospheric particles. The instrument is makes in-situ measurements of cloud structure and determine the character of the particles in the main clouds and in the atmosphere.

Energetic Particle Investigations (EPI): This experiment on the probe supplements the energetic particle (EPD) investigations on the orbiter. The instrument measures the fluxes of four different particle species (electrons, protons, alpha particles, and heavy ions A>2) in the innermost regions of the Jovian magnetosphere. Uses a detector assembly containing totally depleted circular silicon surface barrier detectors.

Lightning and Radio Emission Instrument (LRD): Uses a radio frequency antenna to measure the electromagnetic emissions and two photo diodes mounted behind fisheye sensors to directly detect lightning flashes. The instruments are used to verify the existence of lightning in the atmosphere of Jupiter. The radio frequency and optical data are sampled both in the time domain and in the frequency domain in the frequency range of 10 Hz to 100 kHz.

Helium Abundance Interferometer (HAD): Uses precision measurement of the refractive indices of the Jovian atmosphere by using a Jamin-Mascart double-path length interferometer over the atmospheric pressure range from 2.5 to 12 bars to accurately measure the relative abundance of helium to hydrogen. Determines the relative abundance of helium to a 0.1 percent accuracy.

Net Flux Radiometer (NFR): Optical radiation from Jupiter's atmosphere is allowed to enter the instrument through a diamond window where it is reflected through a Fabry optical system on to a detector assembly consisting of a six-element lithium tantalate detector array. Both upward and downward radiations are measured to determine the net flux of the radiation from Jupiter. The radiometer determines the radiation budget of Jupiter and helps in the detection of cloud layers in Jupiter's atmosphere.