Coregistration of CTX images to HRSC Global Datasets

 

The current approach for ortho-rectifying images taken by the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) uses MOLA data as a global reference ([1]), but this approach is imprecise, specifically at the equator, due to the large difference in spatial resolution between the two datasets (6 vs 463 m/pix).  Automatic point matching of image pixels to DTM pixels are not reliable, therefore usually the CTX pixels are matched to imagery datasets which are themselves controlled to MOLA, such as the THEMIS IR dataset ([2]).

The HRSC team is working on creating global mosaics of bundle-block-adjusted digital terrain models (DTMs) and corresponding image mosaics with better internal photogrammetric precision than the 50 m used as the grid size, and less deviation from MOLA profile heights, aimed to be finished by the end of 2023. 

This abstract presents our progress in using a new approach, by using HRSC DTMs as the global reference for CTX image rectification instead of MOLA, which involves using the HRSC ortho-image for co-registration of CTX images and applying brightness correction before combining all images of a quadrangle together to form a seamless mosaic which is then exported as a single image file. 

 

The workflow and processing is performed using modern pixel registration techniques, the USGS’ ISIS system, a database management system, and high-performance computing, and results in significantly less pixel offsets compared to the previous approach.

References[1] J. L. Dickson et al., LPSC 49, #2480. [2] S. J. Robbins et al., LPSC 52, #2066. 

Acknowledgements: This work is supported by the German Space Agency (DLR Bonn), grant 50OO2204, on behalf of the German Federal Ministry for Economic Affairs and Climate Action. We thank the HPC Service of FU for computing time.