Europa Clipper’s REASON and JUICE’s RIME instruments will be the first ice-penetrating radars flown to an icy moon with subsurface brine detection as an explicit science objective, and both missions cite Antarctic ice-shelf radar-sounding studies as their primary terrestrial heritage. That heritage, however, rests entirely on sparse, single-epoch airborne surveys, leaving open a basic question: how much does the timing of a single observation, or a handful of them, affect confidence in what is detected? We address this using a seven-year (2019–2025) Sentinel-1 C-band SAR time series across five Antarctic ice shelves, previously characterized for brine-consistent backscatter signatures with explicit confidence levels (strong at Nickerson, moderate at Sulzberger, none at Shackleton and Abbot, and inconclusive at Rennick, which is excluded from the quantitative analysis due to incomplete coverage from the 2021 Sentinel-1B satellite failure). Treating this record as an empirical baseline, we simulate both missions’ verified Europa flyby cadences — REASON’s 49-flyby two-campaign schedule (Cangahuala et al., 2025) and RIME’s two confirmed flybys on 2 and 16 July 2032 (Magnanini et al., 2024) — and report calibrated underestimation probabilities. RIME’s two-flyby sampling carries equal or higher underestimation risk than REASON’s denser cadence at every site and threshold tested, with the gap widest at the two sites with confirmed or probable brine signal (e.g., at a 0.5 dB threshold: 10.2% for REASON vs. 62.7% for RIME at Nickerson; 25.2% vs. 79.7% at Sulzberger). A secondary analysis of seasonal-contrast underestimation shows REASON’s cadence is not guaranteed to recover even the qualitative near-zero seasonal-contrast signature Dumpati (2026a) treats as a primary brine discriminator. A further finding indicates that cadence density is most protective for continuous, cyclical signals and comparatively unhelpful for noise-dominated, single-event variability — a distinction invisible to existing single-epoch heritage studies. These results provide mission teams with a quantitative, terrestrially-grounded basis for uncertainty in icy-world radar brine detections, independent of, and prior to, any frequency-calibrated translation between C-band backscatter and HF/VHF sounding reflectivity.
Data and code
All data and analysis scripts are openly available on Zenodo: https://doi.org/10.5281/zenodo.21114577
Currently waiting on the companion paper, which is under editor review.
Preprint: https://doi.org/10.22541/essoar.15005824/
Author: Shobha Mourya Dumpati, FGS, FRGS
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