This dataset contains the investigator-selected Key Parameters from the Polar Visible Imaging System (VIS). The VIS key parameter data set is a survey of auroral activity provided by a series of single images showing a significant area of the auroral zone at visible wavelengths. An auroral image of 256 x 256 pixels is produced approximately every 24 seconds dependent on the integration time and filter selected. Some coordinate information is included for viewer orientation. Coordinates are calculated for a grid of 18 x 18 points corresponding to one pixel out of every 15 x 15 pixel block. In addition, a rotation matrix and a table of distortion-correcting look direction unit vectors are provided for the purpose of calculating coordinates for every pixel.

To facilitate viewing of the images, a mapping of pixel value to a recommended color table based on the characteristics of the selected filter is included with each image.

A relative intensity scale is provided by the uncompressed count table of variable 27. Approximate intensity levels in kiloRayleighs are given in the intensity table of variable 28. The VIS site at http://eiger.physics.uiowa.edu/~vis/software contains information on the availability of more precisely calibrated intensities.

The data set also contains various imager-related parameters, plus spacecraft position and velocity vectors, spin axis unit vector, and the sun position unit vector, all in GCI coordinates. Times are given in both the CDF-standard Epoch and the ISTP-standard Time_PB5.