NISAR satellite (NASA-ISRO dual-band SAR) has mapped Mexico City’s ground subsidence, reaching up to 25 cm/year, using L and S-band radar that penetrates clouds and vegetation.
Key Takeaways
NISAR uses L-band (24 cm wavelength) and S-band radar with SweepSAR technique, providing high-resolution, wide-swath imagery unaffected by clouds or vegetation.
Mexico City is one of the fastest subsiding capitals on Earth; measurements show up to 25 cm/year of ground movement.
Frequent revisit cadence enables sub-monthly change tracking, making it useful for near-real-time infrastructure monitoring.
The joint NASA-ISRO mission is the first dual-band global microwave imaging SAR mission, capable of fully polarimetric and interferometric data acquisition.
Hacker News Comment Review
Commenters with SAR background noted that InSAR subsidence mapping in urban areas is well-established; NISAR’s genuine advance is vegetation-penetrating L-band performance, not urban mapping per se.
Data quality concerns were raised: the published graphic shows unresolved acquisition-footprint striping that should have been ground-truthed against benchmarks before release.
The Angel of Independence monument prompted a structural discussion: its foundation uses thousands of wooden piles anchored to bedrock, explaining why it has not sunk with the surrounding street level.
Notable Comments
@spacewhales: “The new capabilities are mainly being able to do this in highly vegetated areas” – urban InSAR is intro-level; article overstates novelty.
@doodlebugging: flags visible WNW-ESE stripes in the lead graphic as unresolved processing artifacts that distort subsidence values along tracks.
