Instrument Investigators Description Some Scientific Objectives

Visual and Infrared Imaging Spectrometer

An optical remote-sensing instrument

Investigator Team Lead: Robert Brown

Lunar and Planetary Lab, University of Arizona

VIMS consists of two telescopes designed to measure reflected and emitted radiation from atmospheres, rings, and surfaces. Each has a 32 microradian2 field of view.

Infrared channel, sensitive from 0.35 to 1.07 Ám, consists of a 23 cm aperture Cassegrain telescope, spectrometer grating, and 256-element linear indium antimonide array focal plane assembly. The instantaneous field of view is a single pixel; a two-dimensional image is created using a two-axis scanning mirror.

Visible channel, sensitive from 0.85 to 5.1 Ám, consists of a 4.5 cm aperture Shafer telescope, holographic spectrometer grating, and 256 x 512-pixel silicon CCD area array focal plane detector. Instantaneous field of view is an entire line of pixels; a single-axis scanning mirror produces a two-dimensional image.

VIMS' ability to move its mirrors to obtain spectra of different parts of target objects, without having to reposition the entire spacecraft to do so, makes it a "mapping spectrometer."

To map the temporal behavior of winds, eddies, and other features on Saturn and Titan, and study the composition and distribution of atmospheric and cloud species;

Determine the composition and distribution of the icy satellite surface materials;

To determine temperatures, internal structure, and rotation of Saturn's deep atmosphere;

Study the structure and composition of Saturn's rings;

Search for lightning on Saturn and Titan and for active volcanism on Titan, and observe Titan's surface.

All of Cassini's optical remote-sensing instruments, including VIMS, are rigidly mounted on the on the plus-X side of the spacecraft, with their apertures (seen with red aperture covers in the photograph) directed toward minus-Y. Detector electronics are cooled by passive radiation from dedicated radiator plates that face in the plus-X direction into deep, cold space. Pointing the optical instruments at their targets requires rotating the entire spacecraft.

More on VIMS

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