CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Cassini ISS CALibration (CISSCAL)

The use of any instrument in making scientific measurements, be it a camera for collecting light, a scale for measuring mass, a straight edge for measuring length, or a clock for measuring the passage of time, requires that it be calibrated. Calibration is a process that tells you how to accurately relate the output of your instrument, like changes in electrical voltage or the changes in the length of a spring, to a physical entity like the number of photons of a particular energy or the amount of mass.

And so it is with the Cassini cameras. These complex and well-built imaging devices would be useless to us if we didn’t know how to translate the electrical signal coming out the back end into the absolute flux of electromagnetic radiation coming from the sources we image.

The calibration of the Cassini cameras has been a long and arduous process. It involves taking many images with the cameras of celestial sources whose absolute brightnesses at various wavelengths across the ultraviolet, visible and far-red regions of the electromagnetic spectrum have been determined over the years by other means. These calibration sources include Jupiter observed from the European Southern Observatory, the Saturnian moons Rhea, Dione, and Enceladus observed from the Hubble Space Telescope (HST) and the UK Infrared Telescope, and stars, like Vega, observed by HST and various Earth-based telescopes.

Here we post, for the convenience of those who wish to make scientific use of our images, the IDL software package CISSCAL written by the Cassini Imaging Team for calibrating the Cassini cameras, as well as all relevant data files and documentation. For details, see Porco, C.C. et al. (2004) Space Science Reviews 115, 363; West, R.A. et al. (2010) Planetary and Space Science, 58, 1475-1488; and the ISS Data Users Guide, provided below, which contains instructions for installing and using the software.

Cassini ISS Data User's Guide (updated: 2018-Sep-16):
·   iss_data_user_guide_180916.pdf
·   (remote PDS copy)

 
LINKS:

For the calibration software and support files (both required for calibration):

For the full calibration volume including sample images, ground calibration report, and support documentation:

·  Calibration Volume (web-browsable)   [CISSCAL can be found in the 'extras' directory]
·  Calibration Volume (tar/zip download file)   [CISSCAL can be found in the 'extras' directory]