2.2.1 Sigma-Nought (σ°) Calibration

[Yuvraj198920]

As a SAR scientist
I want to apply sigma-nought calibration to SLC data
So that I can compare backscatter across products and time

Acceptance Criteria:

• Calibration LUT read from quality/calibration/sigma_nought
• Interpolation to burst resolution
• Calibration formula implemented per ESA doc
• Output in dB scale (-80 to 0 dB typical)
• Available as virtual band or via -oo CALIBRATION=SIGMA_NOUGHT
• Matches SNAP output within ±0.5 dB
• Performance: < 5s for full burst

Definition of Done:

• Calibration results validated against SNAP
• Integration tests pass
• Documentation with formula included

Tasks:

1. Parse sigma-nought LUT from Zarr
2. Implement 2D interpolation (scipy algorithm in C++)
3. Implement calibration formula
4. Create virtual band for calibrated data
5. Benchmark and optimize
6. Write validation tests vs SNAP