Interface Requirements Document (IRD)

Interface Requirements Document (IRD)#

Project: Sentinel-2 MSI Synthetic L0 reconstruction generator (s2_msi_raw_generator) — runs S2B L1B backwards through the exact inverse of the operational L0→L1B radiometric chain to reconstruct L1A → L0plus (CCSDS-122 ISP) → Synthetic L0, validated against the reference ESA L0 img. · DRD: ECSS-E-ST-40C Rev.1 Annex C (IRD). The interface requirements are owned by the SRS (single source, REQ-IF-NNN); this IRD collects and contextualises them without duplicating their normative text. The interface designs satisfying them are controlled in the ICD.

1. Introduction#

1.1 Purpose#

Identify every external interface of the CSCI, state which requirement governs it and where its design is controlled. The system context and actors are described in the SSS §2.1.

1.2 Convention#

Requirement IDs below are references into the SRS §5 (and, for interfaces introduced by the S2 L1B reverse chain run, SRS §3.4b); the SRS text is normative. ICD anchors (ICD-IF-*) name the controlling design section in the ICD.

2. Interface inventory#

Interface

Direction

Governing requirement (SRS)

Design control (ICD)

L1A/L1B product input (EOPF Zarr)

in

REQ-IF-001

ICD §Interfaces (input)

Synthetic L0 RAW product output (canonical + open container)

out

REQ-IF-002, REQ-FUNC-042

ICD-IF-L0

Operational GIPP (S2A S2A_OPER_GIP_* XML)

in

REQ-IF-003

ICD §Interfaces (GIPP)

Compressed ISP payload / CCSDS-122 codec stream

internal ↔ out

REQ-FUNC-092

ICD-IF-C122, ICD-IF-ISP

Product file naming (EOPF PSFD §3)

out

REQ-FUNC-091

ICD-IF-NAME

Calibration-database ADFs (spectral.zarr, cal-DB)

out

REQ-FUNC-039

ICD §ADF outputs

Public S3 bucket fetch (anonymous, verified GET) — pulls the S2B L1B that seeds the reverse chain

in

REQ-FUNC-093 (S2 L1B reverse-chain fetch/validation)

ICD §Data sources

msi-processor handoff (open-container L0 + ADFs)

out

REQ-FUNC-042, SYS-03

ICD-IF-Synthetic L0; processor ICD

3. Interface requirements#

3.1 Product interfaces#

  • REQ-IF-001 (SRS §5) — input: EOPF L1A/L1B Zarr, measurements/d{DD}/b{xx}/img / …/DD{nn}/B{xx}/l1a_raw_image.

  • REQ-IF-002 (SRS §5) — output: EOPF L0 Zarr v2, 156 measurement arrays + quality masks + ISP + STAC / sensor-configuration / provenance metadata.

  • REQ-FUNC-042 (SRS §3.3) — the additional open-container L0 form ingested by the msi-processor l0_decode unit.

3.2 Data-carrier interfaces#

  • REQ-FUNC-092 (SRS §3.4b) — CCSDS-122-lossless payloads in CCSDS space packets, with a bit-exact ground decode (read_l0_isp_dn).

  • REQ-FUNC-091 (SRS §3.4b) — EOPF PSFD §3 file naming, round-tripping through naming.parse_psfd_name; underivable fields fall back to documented, flagged defaults.

3.3 Auxiliary-data interfaces#

  • REQ-IF-003 (SRS §5) — operational GIPP JSON ingest (REQOG/RDEPI/BLIND/RPARA/RCRCO).

  • REQ-FUNC-039 (SRS §3.4) — ESUN spectral.zarr calibration-database ADF in the schema the processor’s toa unit consumes.

4. Validation#

Each interface requirement carries its verification method and evidence in the SRS and the traceability matrix. The primary interface-level validation on S2 data is the reverse chain itself: the Synthetic L0 RAW img compared to the reference ESA L0 img, with the 10/20 m bands agreeing to ≤~4 DN. The supporting interface checks — CCSDS-122 / L0plus bit-exact ground decode (decode(L0plus)==L1A, REQ-FUNC-092), PSFD naming round-trip (REQ-FUNC-091), and EOQC on both L0 forms — are reported in the S2 L1B validation.