Initial commit

yksa_orbital/wire.py

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+"""Render a stored OMM dict as the CCSDS message the Orekit sidecar consumes.
+
+The sidecar takes CCSDS messages, not TLE lines, so nothing on this path
+truncates an epoch to eight digits or drops a mass. This module is the single
+place that turns ODMS's stored GP dict into one.
+"""
+
+from __future__ import annotations
+
+from odm import OmmRecord, PropagationError, as_omm_kvn
+
+#: CCSDS defines MEAN_MOTION_DOT as the *first derivative* of the mean motion,
+#: while TLE line 1 carries half of it -- and Space-Track's OMM output copies
+#: the TLE field across unchanged, so that is the convention in our stored data.
+#: Orekit reads the spec. Doubling here keeps the element set Orekit reconstructs
+#: identical to the one we hold, and is confined to this wire format: the OMM we
+#: publish to users stays byte-compatible with Space-Track's.
+_NDOT_TLE_TO_CCSDS = 2.0
+
+#: Orekit's OMM parser rejects an SGP4 message missing any of these, and
+#: upstream feeds do sometimes omit the bookkeeping ones. They do not affect
+#: propagation; the values only have to be present and well-formed.
+_SGP4_DEFAULTS = {
+    "EPHEMERIS_TYPE": 0,
+    "CLASSIFICATION_TYPE": "U",
+    "ELEMENT_SET_NO": 999,
+    "REV_AT_EPOCH": 1,
+    "BSTAR": 0.0,
+    "MEAN_MOTION_DOT": 0.0,
+    "MEAN_MOTION_DDOT": 0.0,
+}
+
+_REQUIRED = ("EPOCH", "MEAN_MOTION", "ECCENTRICITY", "INCLINATION")
+
+
+def omm_message(omm: dict, *, object_name: str = "") -> str:
+    """One stored OMM dict as CCSDS KVN, ready to POST to the sidecar."""
+    if not isinstance(omm, dict):
+        raise PropagationError(f"expected an OMM dict, got {type(omm).__name__}")
+    missing = [key for key in _REQUIRED if omm.get(key) in (None, "")]
+    if missing:
+        raise PropagationError(
+            f"OMM is missing {', '.join(missing)}; cannot build a CCSDS message"
+        )
+
+    fields = dict(omm)
+    theory = str(fields.get("MEAN_ELEMENT_THEORY") or "SGP4")
+    if theory.upper().startswith(("SGP", "SDP")):
+        for key, default in _SGP4_DEFAULTS.items():
+            if fields.get(key) in (None, ""):
+                fields[key] = default
+        fields["MEAN_MOTION_DOT"] = (
+            float(fields["MEAN_MOTION_DOT"]) * _NDOT_TLE_TO_CCSDS
+        )
+
+    return as_omm_kvn([OmmRecord(
+        omm=fields,
+        object_name=object_name or str(fields.get("OBJECT_NAME") or ""),
+        object_id=str(fields.get("OBJECT_ID") or ""),
+        originator="ODMS",
+        mean_element_theory=theory,
+    )])
+
+
+def omm_messages(omms: list[dict]) -> list[str]:
+    return [omm_message(omm) for omm in omms]