isce-framework / isce-framework/isce3

Ionospheric correction with IMAGEN for half-swath acquisitions

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@seongsujeong is already working on this.

Since Sep 26, 2025.

bug
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Python
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Description

NISAR uses TEC data in IMAGEN format, which is a JSON file that the total TEC and top TEC are sampled on near-range and far-range location at ionospheric piercing points (IPPs). The IMAGEN production makes use of look angles to compute the IPPs, and the angles are based on the full swath.

The issue is that some NISAR acquisitions are done in half-swath. The current implementation of the ionospheric delay LUT2d computation (here) brings the near-range and far-range value from the input RSLC's radar grid. Therefore, processing half-swath data with IMAGEN (i.e. assuming full swath acquisitions) will cause an issue because the assignment of the LUT's x grid is incorrect.

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