Navigation Overview

This page sketches the navigation-pipeline architecture and the per-image data flow. The chapters that follow drill into each subsystem.

System architecture

RMS-NAV is organised around six cooperating subsystems:

1. DataSet — handles image-file access and organisation across mission archives.

2. ObsSnapshot and its per-instrument subclasses — wrap an oops observation and supply backplanes, extended-FOV accessors, and per-instrument metadata.

3. NavModel — generates the predicted appearance of one part of the scene (stars, a body, or rings) and emits NavFeature instances ready for technique consumption plus Annotations for the summary image.

4. NavTechnique — consumes feature subsets and produces a NavTechniqueResult (offset, covariance, calibrated confidence, diagnostics).

5. NavOrchestrator — the top-level driver that runs the two-pass pipeline and reconciles per-technique results via ensemble(), returning a single NavResult.

6. nav.annotation — composes per-NavModel annotations into the summary-PNG overlay.

Data flow

1. nav_offset (or another CLI driver) constructs a DataSet and yields one ImageFile at a time.

2. The matching ObsSnapshotInst subclass reads the file via from_file().

3. build_models_for_obs() walks the NavModel registry and constructs per-image instances applicable to the observation.

4. The NavOrchestrator builds a NavContext, gathers features and per-NavModel annotations, gates features by reliability, runs every feasible prior-free technique (pass 1), ensembles the pass-1 results to derive a prior, runs prior-required techniques against that prior (pass 2), and ensembles the union.

5. build_metadata_dict() projects the resulting NavResult into a JSON-friendly metadata block.

6. navigate_image_files() writes the metadata JSON and the summary PNG. The PNG’s annotation overlay is composed upstream by combine() over the per-NavModel annotations the orchestrator collected; the driver composites that overlay onto the contrast-stretched source image and writes the bytes.

The detailed class hierarchy and inheritance graph is at Class Hierarchy.