Mind The Gap: HiRISE Data Processing to Accommodate the Loss of CCD RED4

Abstract

The High-Resolution Imaging Science Experiment (HiRISE) [1] has been in operation on the Mars Reconnaissance Orbiter (MRO) since 2006 [2]. The HiRISE focal plane contains 14 CCDs, with 10 CCDs spanning the full swath in the red visible bandpass (RED0–RED9). Additionally, 3-band color can be obtained in the central ~20% of the swath width from four 'color' detectors that overlap the coverage of RED4 and RED5: two CCDs with near-infrared filters (IR10, IR11), and two CCDs with visible blue-green filters (BG12, BG13) [1,3] (Fig. 1). Although the instrument remains in good health [4], two of the RED CCDs have failed: RED9 in August, 2011, and RED4 intermittently since July, 2023 (MRO orbit ~79,500) [5]. The failure of RED9 did not impact imaging strategies as it is on the edge of the image; the HiRISE image swath merely became 10% narrower after RED9 failed. However, the RED4 CCD is in the middle of the image swath, leaving a problematic gap in the images. We present here the HiRISE team implementation of a substitution of the overlapping IR10 CCD for the missing RED4 data. IR10, which is aligned with RED4, presents similar data for dustier areas of Mars as the visible RED data.