Instrument : Whole Sky Imager (WSI)

Note: wsi is currently inactive and/or retired.

Active Dates
1993.01.01 - 2004.01.10

Instrument Categories
Cloud Properties

Picture of the Whole Sky Imager (WSI)

General Overview

The whole-sky imager (WSI) is an automated imager used for assessing and documenting cloud fields
and cloud field dynamics. The WSI is a ground-based electronic imaging system that monitors the upper
hemisphere. It is a passive, i.e., non-emissive, system that acquires images of the sky dome through three spectral filters (neutral, red, and blue). From these sky images, we can assess the presence, distribution, shape, and radiance of clouds over the entire sky using automated cloud decision algorithms and related processing. The current WSI model (EO System 6) is capable of image acquisition under daylight, moonlight, and starlight conditions.

Output Value-Added Products

This instrument is an input to the following value-added products, which provide improved measurements or derived quantities.

  • wsicloudden : WSI: stationary (JPEG) images based on optical density retrieval
  • wsicloudspec : WSI: stationary (JPEG) images based on spectral retrieval
  • wsicloudsummary : WSI: cloud and aerosol info, classification summary data
  • wsicloudsummarygif : WSI: images (GIF) relating to cloud, aerosol summary data
  • wsifilesummary : WSI: images (GIF) and text representations of data existence

Output Datastreams

  • 02wsipartradjpg : WSI: stationary calibrated red or clear quicklook images (JPEG), 2-min intervals
  • 02wsipartradmpg : WSI: calibrated red or clear quicklook movies (MPEG), 2-min intervals
  • 10wsipartradjpg : WSI: stationary calibrated red or clear quicklook images (JPEG), 10 min intervals
  • 10wsipartradmpg : WSI: calibrated red or clear quicklook movies (MPEG), 10 min intervals

Primary Measurements

The following measurements are those considered scientifically relevant.


North Slope Alaska
NSAC1 Browse DataCentral Facility, Barrow AK
NSAC2 Browse DataCentral Facility, Atqasuk AK
Southern Great Plains
SGPC1 Browse DataCentral Facility, Lamont, OK
SGPL3 Browse DataBlackwell/Tonkawa Airport, OK
Tropical Western Pacific
TWPC1 Browse DataCentral Facility, Manus I., PNG
TWPC2 Browse DataCentral Facility, Nauru Island
TWPC3 Browse DataCentral Facility, Darwin, Australia


Douglas Sisterson
(630) 252-5836