Missing 'slantRange' dataset in NISAR GUNW files

[disilvestro]

Bug Report: KeyError for missing 'slantRange' dataset in NISAR GUNW files

Description of the problem

When running MintPy's prep_nisar.py, the function extract_metadata (called from load_nisar) fails with a KeyError because the dataset science/LSAR/GUNW/metadata/radarGrid/slantRange does not exist in my NISAR GUNW file, specifically slantRange. This causes the script to crash instead of handling the missing dataset gracefully.

Inputs:

• input_glob: /Users/giacomo/onedrive/scratch/nisar_download/Chiles/*.h5
• out_dir: /Users/giacomo/onedrive/scratch/nisar_download/Chiles
• start: '20251029'
• subset_lat: (0.65, 0.98)
• subset_lon: (-78.09, -77.76)
• update_mode: False

File being processed:
NISAR_L2_PR_GUNW_004_011_D_088_006_4000_SH_20251029T233018_20251029T233053_20251122T233019_20251122T233054_X05010_N_F_J_001.h5

Error message:

KeyError: "Unable to synchronously open object (object 'slantRange' doesn't exist)"

Members in /science/LSAR/GUNW/metadata/radarGrid:

- alongTrackUnitVectorX
- alongTrackUnitVectorY
- elevationAngle
- groundTrackVelocity
- heightAboveEllipsoid
- hydrostaticTroposphericPhaseScreen
- incidenceAngle
- losUnitVectorX
- losUnitVectorY
- parallelBaseline
- perpendicularBaseline
- projection
- referenceSlantRange
- referenceZeroDopplerAzimuthTime
- secondarySlantRange
- secondaryZeroDopplerAzimuthTime
- slantRangeSolidEarthTidesPhase
- wetTroposphericPhaseScreen
- xCoordinates
- yCoordinates

System information

• Operating system: macOS
• Python environment: conda
• MintPy version: 1.6.3.post26
• InSAR processor/product: NISAR GUNW