false-color composite image, constructed from data obtained by VIMS, shows the glow of auroras streaking
out about 1,000 kilometers (600 miles) from the cloud tops of Saturn's south polar region.
See Volume 1-Mission Overview, Science Objectives and Results
for full science report. The technical report is in other volumes archived at the Jet Propulsion Lab.
Mission Science Highlights and Science Objectives Assessment
provides a brief overview of the mission
The Visible and Infrared Mapping Spectrometer (VIMS) was designed to generate spectral maps of the Saturn system at visible
and near-infrared wavelengths. It was also frequently used to record the occultation of stars by Saturn and its
moons, as well as by Saturn's rings. VIMS was assembled at NASA's Jet Propulsion Laboratory (JPL) for the Cassini
Mission to Saturn. Its components were supplied by JPL, the Agenzia Spaziale Italiana in Italy and France's Centre
Nationale de la Recherche Scientifique.
Scientific objectives of VIMS include the following:
- Determine the distribution of the gases and aerosols in Saturn's atmosphere and their time variability
- Study Saturn's atmospheric dynamics, including the characterization of its ammonia clouds
- Map the radial, azimuthal and vertical distribution of the material in Saturn's rings
- Discern the mineralogical composition and surface properties of the particles comprising Saturn's rings
- Constrain and identify the mineralogical properties of Saturn's icy satellites, including the non-icy contaminants
found across the system
- Map the composition and geology of Titan's surface
- Determine the distribution of the gases and aerosols in the atmosphere of Titan and their variability with time
- VIS: Visible-spectrum spectrometer
- IR: Infrared spectrometer
- Often the two spectrometers were operated together, and data was merged into a single data cube spanning the
full wavelength range. During data processing, each of the main detector channels can be separated out.
VIMS Instrument Characteristics*
* values taken from Tables I and II in Brown
et al. (2004) in
Space Science Reviews
a 0.3 - 1.0 by special command
b in normal mode (five spectral pixel binning); 1.46 nm spectral resolution in high-resolution mode
|Spectral Range (µm)
|Spectral Sampling (nm)
|# of Bands
|Instantaneous Field of View (mrad)
||0.17 x 0.17
||0.25 x 0.5
|Effective IFOV (mrad)
||0.5 x 0.5 (3 x 3 sum)
||0.5 x 0.5 (1 x 2 sum)
|Total FOV (mrad)
||32 x 32 (64 x 64 pixels)
||32 x 32 (64 x 64 pixels)
The design of the VIMS instrument was largely based on the Near-Infrared Mapping Spectrometer (NIMS) which flew on the Galileo
mission to Jupiter. Both the VIMS and NIMS benefited from the long history of imaging spectrometers that preceded
them. VIMS incorporated two channels to cover its full wavelength range. The Italian-built VIMS Visual Channel
(VIS) recorded light at wavelengths between 0.35 and 1.05 µm in 96 individual spectral channels, with a spectral
resolution of 7.3 nm. The VIMS Infrared Spectral Region Component (IR) which was built by JPL, picked up in the
near infrared at 0.85 µm and extended the coverage of the VIMS instrument out to 5.1 microns with 256 spectral
channels, at a spectral resolution of 16.6 nm. Separate telescopes collected light for each spectrometer, and each
spectrometer operated in a variety of observational modes. However, they were usually operated together in compatible
modes to generate a single data cube spanning the full wavelength range available to both portions of the instrument.
In addition to its standard imaging mode, with data-cube sizes up to 64x64 pixels, VIMS was able to operate in continuous
LINE-mode (used for close Titan flybys and some radial ring scans) and in POINT-mode (for stellar occultations).
The instrument also contained an off-axis solar port which was used to obtain spectra of the Sun for calibration
purposes and to monitor solar occultations by Titan, Saturn and the rings.
The engineering details of the VIMS instrument and the science objectives it was built to address are described in further
detail in the
Space Science Reviews
Brown et al. (2004)
Data Search Tools
about searching for VIMS images of rings, or for close encounters with moons using the OPUS
and the Image Atlas search tools listed below.
OPUS search engine allows for an interactive search of the VIMS data in the PDS archive based on a wide
variety of search parameters, including observation geometry and target.
PDS Imaging Atlas is another image-search tool with VIMS data, where parameter search and thumbnail evaluation
Master Schedule is a time-ordered listing of observations by all instruments. This may help find data based
on particular events, however the OPUS tool and Image Atlas linked above will be much simpler to use in most
Event Calendar is an interactive event-finding tool that can be used to search for data associated with
- Catalogs of VIMS
Stellar and Solar Occultations Observations are available. They include information on the latitudes and ranges of Titan
and Saturn occultations, as well as the radial coverage and opening angle of ring occultations
Browse Raw Data Products
Derived Data Products
VIMS Rings Occultation Data
- The Occultation Data is a set of peer-reviewed data sets located at the PDS Ring-Moon Systems Node
- The data contains reduced and calibrated optical depth profiles for Saturn's rings derived from VIMS stellar
occultation observations at the Rings Node.
- The data includes radial profiles at 1 and 10 km resolution derived from more than 60 VIMS occultations.
Analyzing VIMS Data
Processing VIMS Data
- The ISIS 3 is a software package can be used to process VIMS data.
- Users should use these
Step-by-Step Instructions for cartographic and science data if they wish to create their own products.
(Note: this applies only to imaging and LINE-mode data, and not to occultation data, though the format of the
raw data is the same in all cases)
IR Pixel Timing
VIMS-IR Pixel Timing
- VIMS was used in modes that were not a part of the initial instrument design. The VIMS infrared channel used
an articulating secondary mirror to produce a raster scan of the scene being observed.
- Users who wish to construct geometry for individual pixels within the scan must deal with characteristics of
the VIMS internal clock.
- The VIMS-IR Pixel Timing linked above is a white paper which has been generated and the resulting refinement
has been included in the ISIS 3 software.
VIMS Final Report of Radiometric Calibration 1/25/2018
The VIMS instrument underwent shifts in the wavelength calibration of the spectrometer since the mission launch. Large shifts occurred
during the Jupiter fly-by in 2000, followed by a period of stability until Saturn orbit insertion. Small shifts
occurred throughout the orbital tour until the end of mission in September 2017. The wavelength shifts require
a time-dependent radiometric calibration technique to be deployed to preserve radiometric accuracy. The final report
covers unresolved issues, quantifies the time-dependent wavelength shift, and described a compensatory scheme that
provides an accurate calibration for both specific intensity and intermediate frequency for the VIMS measurements
made throughout the Cassini Mission.
Other Useful Products and Resources for Interpreting the Data
The VIMS team has archived operational details for each observation, including command and mode data. These archives are
These files require knowledge of mission planning to be useful to the user.
IOI Files: Instrument command files used to acquire data for specific requests 126 MB TXT file
Requests: Observation details (e.g. primary bv, secondary bv) for each observation - 5.6 MB CSV file
SFOFs: Short forms generated for each observation - 350 MB TXT file