Absolute calibration of the Colour and Stereo Surface Imaging System (CaSSIS)

Pre-landslide topographic reconstruction in Baetis Chaos, mars using a CaSSIS Digital Elevation Model

“…First, the framelets were mosaicked into a single 257 image making use of the attached Spice Kernels 258 (Acton, 1996). Such framelets are already 259 radiometrically calibrated (Thomas et al, 2022) used in Conway and Balme (2014) and de Haas et al (2015) using three levels of complexity to test the fidelity of each reconstruction: i) a semi-automatic method; ii) a manual method that is informed by the morphology of the terrain surrounding the landslide; and iii) a manual method that is informed by the morphology of the terrain surrounding the landslide and applies a terrain tilt to improve the reconstruction of the deposits. Each additional step should represent an improved, better reconstruction, but as the complexity increases, the computation time does as well, from a few minutes with method 1 to several hours with method 3.…”

In-flight radiometric calibration of the ExoMars TGO Colour and Stereo Surface Imaging System

“…Fortunately, the issue is not severe for CaSSIS images of Mars as the maximum excess signal is only one to two DN at the maximum exposure time of 1.5ms. Nevertheless, this effect must be taken into account when imaging other objects with longer exposure times, such as reference stars for absolute calibration purposes (Thomas et al, 2022).…”

“…The observed change in focus is the result of the thermal expansion of the carbon fiber structure of the telescope. The images of photometric reference stars and Jupiter were also analysed to refine the absolute photometric calibration of the instruments (Thomas et al, 2022).…”

“…We find this procedure more precise and reliable than having to rely on a dark current rate. See Thomas et al (2022) for additional details.…”

“…The entire dataset was reprocessed with the revised values and distributed during the first half of 2022. Thomas et al (2022) detail this analysis and provide a set of multiplicative correction factors to solve this issue. The relative error on the absolute radiometry is currently estimated at 2.8%.…”