The Geography of Oxia Planum 02 CASSIS Data

This data set consists of the CaSSIS RGB data products acquired over the ExoMars Rover landing site in Oxia Planum. These data sets have been georeferenced and registered to the basemap mosaic as part of the scientific categorization of the landing site are being made available to scientific community to further the scientific investigation of the landing site.

Additionally, data for all CASSIS data cubes in the Oxia Planum region (as of 18/8/2021) will be available through the European Space Agency Guest Storage Facility (https://www.cosmos.esa.int/web/psa/psa_gsf). Each directory contains the data cube synthetic RGB image outputs from the ISIS pipeline at the University of Bern. This data set has not been georeferenced to the Oxia Planum basemap but each directory contains supporting map projection information.

This data set contains 3 directories:

02_a A synthetic RGB mosaic of CASSIS data. These data are provided with an equirectangular projection centred at 335.45°E

02_b Individual synthetic RGB images that where georeferenced to the OxiaBase map and used in mosaic (02_a). These data are provided with an equirectangular projection centered at 335.45°E

02_c 6 CASSIS Data cubes that were used in the scientific reconciliation of the Oxia Planum HiRISE mapping project.

Additionally all the data cube collected at Oxia Planum will be made available through the ESA guest storage facility www.cosmos.esa.int/web/psa/psa_gsf

The mosaic is named: OP = Oxia Planum, sRGB = synthetic RGB, Mosaic = indicates that this is a mosaiced data set, 4m = pixel size, April2021 = the date when the mosaic was made. We may make updates as more CASSIS data becomes available.

File name Description

CASSIS_OP_sRGB_mosaic_4m_april2021.tfw World file

CASSIS_OP_sRGB_mosaic_4m_april2021.tif Image data <- Open this data in GiS with the other supporting files in the same directory

CASSIS_OP_sRGB_mosaic_4m_april2021.tif.aux.xml Auxiliary symbology statistics

CASSIS_OP_sRGB_mosaic_4m_april2021.tif.ovr Image overviews

Naming convention: Each CASSIS image is named “MYww_xxxxxx_yyy_z” where; MYww = Mars year (e.g., MY35), xxxxxx = orbit number (e.g., 009394), yyy = distance around the orbit from 0 – 359, z = image mode (0 = single acquisition, 1 = stereo pair image 1, 2 = stereo pair image 2), RGB = synthetic RGB data, _r = georeferenced to the base layer and rectified.

File name (example) Description

MY34_001934_162_0_RGB_r.TFw World file

MY34_001934_162_0_RGB_r.TIF Image data <-Open this data in GiS with the other supporting files in the same directory

MY34_001934_162_0_RGB_r.TIF.aux.xml Auxiliary symbology statistics

MY34_001934_162_0_RGB_r.TIF.ovr Image overviews

These data are provided with the following projection: Equirectangular_Mars_Oxia_Planum, Projections = Equidistant_Cylindrical, Datum = D_Mars_2000 Spheroid, Central meridian = 335.45

The CaSSIS RGB products of this data set are standard products created by the University of Bern and University of Arizona available to the CASSIS science team.

The Colour and Stereo Surface Imaging System (CaSSIS; Thomas et al., 2017) instrument on the ESA Trace Gas Orbiter (TGO) continues to observe the ExoMars landing site (Figure 1). CaSSIS collects data with four filters (Infrared (IR); 950 nm, Near-Infrared (NIR); 850 nm, broad transmission, Panchromatic, filter (PAN); 650 nm and BLUE-GREEN; 475 nm), chosen to provide the camera with a limited multispectral capability sensitive to a variety of minerals (Tornabene et al., 2017). CaSSIS has a swath width of ~9 km and a rotation mechanism to permit stereo acquisitions. We use CaSSIS 3 or 4 band cubes for our scientific investigation of Oxia Planum. A mosaic of synthetic RGB products is presented on the main map. Synthetic RGB products use a combination of PAN and BLUE filter images whereby: The Red channel is the PAN filter mosaic, The Green channel is a combination of a low pass filter of the Blue and a high pass filter of the PAN, incorporating colour information from BLUE and spatial information of PAN. The Blue channel is a combination of PAN and BLUE-GREEN such that each pixel has a value of (2*BLU – 0.3*PAN). Each channel is individually contrast-enhanced to form the final product. As TGO operates in a non-sun synchronous orbit, surface overflights repeat every 36 days spanning a range of local times and seasons (table 2), individual images do not necessarily have appropriate viewing angles, lighting and atmospheric conditions conducive to the creation of a consistent mosaic data set. We will continue to update the database of georeferenced images as more appropriate images are collected by TGO.

Georeferencing and registration of the CaSSIS RGB data used an initial set of manual tie points to seed the automatically generating additional points. The CTX mosaic and CaSSIS data where rectified using the spline transformation. which optimizes for local accuracy but not global accuracy (Esri, 2020). This method provided good results for images with a range of viewing angles and accounts well for local adjustments needed for abrupt elevation changes.

Acknowledgment
The authors wish to thank the CaSSIS spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX programme. The instrument hardware development was also supported by the Italian Space Agency (ASI) (ASI-INAF agreement no. I/2020-17-HH.0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the University of Arizona (Lunar and Planetary Lab.) and NASA are also gratefully acknowledged. Operations support from the UK Space Agency under grant ST/R003025/1 is also acknowledged.