Constraints on Lower Atmosphere Clouds from Perturbation Images Using the Huygens’ Probe Descent Imager and Spectral Radiometer (DISR)

English Abstract:

The Huygens Probe landed on the surface of Titan in early 2005 after separation from the Cassini spacecraft upon which it resided during its seven-year journey to the Saturn system. During its descent within the Titanian atmosphere, Huygens captured hundreds of still images using its three visual imagers, contained within the DISR instrument.

Following Huygens’ landing, DISR continued to take images of the same scene of the surface for approximately an hour. At first glimpse these post-landing visuals may appear to be redundant; but in actuality they provide a rare opportunity to observe subtle changes within Titan’s atmosphere when calibrated and compared with each other. Of the three imagers of DISR, only the Side Looking Imager (SLI) offered a view above the horizon once Huygens touched down on Titan. Our analysis will be restricted to data from this instrument.

For each image we isolated the pixels above the horizon, then radiometrically calibrated and co-added the images to increase the signal to noise ratio. Mean frame subtraction was performed on image sets which accentuated the differences between adjacent images following histogram stretching. The resulting image sets were animated in a loop to observe anomalies and patterns of interest for further analysis and to calculate the magnitude of the radiometric variation across the sky.