1. Cassini
  2. Instruments and Data
  3. UVIS

Getting Started

1. Organization

  • UVIS archive data is organized into three groups by mission phase (cruise, Jupiter encounter, and Saturn tour). Within each phase, the UVIS archive consists of several multi-volume data sets, each based on a combination of observation type and target; each data set spans the entire phase.

  • The archive volumes contain UVIS data products: raw images, spectra, stellar occultations, and measurements of the relative abundance of deuterium and hydrogen. The archive also contains the associated pointing, navigation and spacecraft orientation information, instrument documentation, calibration files, calibration algorithms, representative software for handling the UVIS data files, and documentation necessary to produce higher level calibrated products.

  • UVIS produces four distinct data options from four separate operating channels. Each of these is identified using a reference abbreviation:

    • EUV - Extreme Ultra Violet spectrographic channel that produces images and spectra covering the range from 56 to 118 nm.

    • FUV - Far Ultra Violet spectrographic channel that produces images and spectra covering the range from 112 to 191 nm.

    • HSP - a solar blind CsI photocathode is used to observe high signal- to-noise ratio stellar occultation by rings and atmospheres

    • HDAC - A separate hydrogen deuterium absorption cell measures the relative abundance of deuterium and hydrogen from their lyman- alpha emission.

Note: The archive volumes are organized exclusively by date. This means that files from several channels and modes (and therefore associated with different UVIS data sets) can be interleaved in the same volumes and directories.

2. Directory and File Naming

On each volume, data are in subdirectories of the DATA directory.

  • Subdirectory names are chronological, based on the date of the observations contained in the subdirectory. Subdirectory names are in the form YYY_DDD, indicating the year and day of year of the observations.

  • File names are constructed using the UVIS channel ID and the approximate UTC time at which the observations in the file started. File names are in the form AAAYYYY_DDD_HH-MM, where:

AAA is one of the following UVIS channel IDs:

  * **EUV** \- Extreme Ultra Violet images and spectra (56 to 118 nm).
  * **FUV** \- Far Ultra Violet images and spectra (112 to 191 nm).
  * **HSP** \- solar blind CsI photocathode (stellar occulations).
  * **HDAC** \- hydrogen deuterium absorption cell.

YYYY_DDD_HH-MM is the approximate UTC time at which the observations in the file began.

3. Documentation

Cassini UVIS Data Users Guide

** Users are strongly encouraged to review a UVIS AAREADME.TXT file. ** This file appears in the root directory of every volume. (Some of the header information in the AAREADME.TXT files varies from one volume to the next, but the body of information in the files is the same.)

Further details of the UVIS archive volumes can be found in the “Software Interface Specification” (SIS) Document. This is a file UVIS-Archive-SIS.pdf, found in the DOCUMENT directory on each volume.

The CATALOG subdirectory on each volume contains a wealth of information about the UVIS instrument, team and data sets. See, in particular:

  • COUVIS_xxxx/CATALOG/UVISINST.CAT: Description of the UVIS instrument.
  • COUVIS_xxxx/CATALOG/INSTHOST.CAT: Description of the Cassini spacecraft.
  • COUVIS_xxxx/CATALOG/MISSION.CAT: Description of the Cassini mission.

Representative data set information (there are variations in the header information for the corresponding catalog files associated with each phase, but the contents are the same):

  • COUVIS_xxxx/CATALOG/SCALDS.CAT: Description of the UVIS calibration data set.
  • COUVIS_xxxx/CATALOG/SCUBEDS.CAT: Description of the UVIS cube data set.
  • COUVIS_xxxx/CATALOG/SSPECDS.CAT: Description of the UVIS spectrum data set.
  • COUVIS_xxxx/CATALOG/SSSBDS.CAT: Description of the UVIS solar stellar brightness data set.
  • COUVIS_xxxx/CATALOG/SWAVDS.CAT: Description of the UVIS image at one wavelength data set.

The file, COUVIS_0xxx/COUVIS_006xx/ERRATA.TXT, is in the root directory of each volume and documents any known anomalies or deviations from PDS standards contained in that volume.

Additional descriptions of the instrument can be found at the Cassini UVIS web page.

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