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README.md

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+# yksa-orbital
+
+Propagation for YKSA Django services. See [yksa_orbital/README.md](yksa_orbital/README.md)
+for the API, the backends and the sidecar contract — that document moved here
+with the code and is the reference.
+
+```
+yksa-orbital @ git+https://git.intra.yksa.space/web/yksa-orbital.git@v0.1.0
+```
+
+```python
+INSTALLED_APPS = [..., "yksa_orbital", ...]
+ORBITAL_PROPAGATOR_BACKEND = "sgp4"        # or "orekit"
+OREKIT_SERVICE_URL = "http://orekit:5000"
+```
+
+## Status
+
+Extracted from the `tle` repo, where it was already the right shape: a backend
+registry, a wire format and a config reader, with no Django models. It is used
+by `odms` today.
+
+`ops` and `tdas` still have their own propagation code
+(`ops/yksa_ops/orbits/propagate.py`, `tdas/yksa_tdas/location/propagate.py`) and
+should move onto this package next. Two things are missing before they can:
+
+- **`ops`** needs a `passes(station, satellite, window)` entry point. Its pass
+  prediction currently uses Skyfield, which this package does not wrap.
+- **`tdas`** needs the sub-satellite point and ECI/ECEF state vectors it computes
+  itself. Those the `sgp4` backend already provides, so that port is the
+  smaller of the two.
+
+Until both are done the estate still describes the same satellite through three
+code paths, which is the reason this package exists.
+
+The Orekit sidecar itself stays in `tle/services/orekit` — it is a container, not
+a Python package, and moving it is a deployment change rather than an extraction.