Algorithm Theoretical Basis Document (ATBD)#

Field	Value
Document	ATBD — Algorithm Theoretical Basis Document
DRD ref	EO-domain ATBD convention (no ECSS-E-ST-40C Rev.1 annex); algorithm constituent of the DPM, supporting the SRS
Container	Technical documentation — `docs/atbd/` (published); source in `compliance/drd/`
Project	`sar-processor` (gitlab.eopf.copernicus.eu/ipf/sar-processor)
Software criticality	Category C (ECSS-Q-ST-80C Rev.2 / ECSS-E-ST-40C Annex R)
Baselined at	PDR (Preliminary Design Review)
Status	Draft for SRR — skeleton

This ATBD records the theoretical and mathematical basis of every processing stage of sar-processor, the generic spaceborne SAR ground-segment forward processor. Algorithms are identified as ALG-<STAGE>-NN and traced from REQ-F-* (SRS) and into the SDD components. All algorithm content is TBD (PDR — pending SentiWiki S1 ingest); this issue fixes only the stage decomposition of the forward chain.

<1> Introduction#

Scope: L0 → L1 SLC → L1 GRD forward chain, sensor-agnostic formulation with per-sensor profile parameters; Sentinel-1 C-SAR is the reference for symbols, conventions and validation data. TBD (PDR).

<2> Applicable and reference documents#

Per SDP <2>; canonical technical reference: SentiWiki Sentinel-1 documentation set (vault-ingested). TBD (PDR).

<3> Conventions and symbols#

Radar geometry, slant/ground range, zero-Doppler convention, units. TBD (PDR).

<4> Processing stages#

Each stage section: purpose, inputs/outputs, mathematical description (ALG-*), accuracy and error budget, references.

<4.1> L0 decode (`ALG-L0D-*`)#

ISP extraction, decompression (FDBAQ/BAQ TBC), echo/annotation separation. TBD (PDR — pending SentiWiki S1 ingest).