Initial commit

yksa_orbital/backends/orekit.py

@@ -0,0 +1,276 @@
+"""Orekit propagation backend -- HTTP client to the sidecar service.
+
+Implements the same :class:`~odm.PropagatorBackend` seam as
+:class:`~yksa_orbital.backends.sgp4.Sgp4Backend`, but delegates the math to the
+Orekit sidecar (``services/orekit``) over HTTP. The stored OMM goes over the wire
+as a CCSDS message (see :mod:`yksa_orbital.wire`) and the JSON response maps back
+into a frame-agnostic :class:`~odm.StateVector`. Set
+``settings.ORBITAL_PROPAGATOR_BACKEND = "orekit"`` (and ``OREKIT_SERVICE_URL``)
+to make it the default -- nothing downstream changes.
+
+Requests carry only what this deployment means to override. The model itself
+lives in the sidecar's ``config.py`` and comes back through :meth:`model_config`;
+restating it here would be a second definition of the same thing.
+"""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+import httpx
+from django.conf import settings
+
+from odm import (
+    BackendBusy,
+    PropagationError,
+    PropagatorBackend,
+    StateVector,
+    parse_omm_epoch as _parse_iso,
+)
+from ..wire import omm_message, omm_messages
+
+#: Frames every state_at/ephemeris call needs: TEME is the seam's source of
+#: truth, ITRF supplies the Earth-fixed (ECEF) view.
+_CORE_FRAMES = ("TEME", "ITRF")
+
+#: Frames offered by the "show in frame" dropdown when this backend is active.
+DROPDOWN_FRAMES = ("TEME", "GCRF", "EME2000", "TOD", "ITRF")
+
+#: Route -> setting holding its timeout. A decay run is a minutes-long numerical
+#: propagation and an ensemble repeats it per realization, so neither can share
+#: the seconds-long budget the state/ephemeris queries use.
+_TIMEOUTS = {
+    "/decay": ("OREKIT_DECAY_TIMEOUT_S", 900),
+    "/decay_ensemble": ("OREKIT_ENSEMBLE_TIMEOUT_S", 7200),
+    # A download plus a file reload -- longer than the seconds-long state budget,
+    # shorter than a propagation.
+    "/refresh_space_weather": ("OREKIT_REFRESH_TIMEOUT_S", 120),
+    # Read on a page render for a caption. Fail fast and let the caller fall
+    # back rather than holding the response open.
+    "/config": ("OREKIT_CONFIG_TIMEOUT_S", 2),
+}
+
+
+def _service_url() -> str:
+    url = getattr(settings, "OREKIT_SERVICE_URL", "")
+    if not url:
+        raise PropagationError("OREKIT_SERVICE_URL is not configured")
+    return url.rstrip("/")
+
+
+def _timeout(path: str) -> float:
+    name, default = _TIMEOUTS.get(path, ("OREKIT_TIMEOUT_S", 30))
+    return float(getattr(settings, name, default))
+
+
+def _iso(dt: datetime | None) -> str | None:
+    if dt is None:
+        return None
+    return dt.astimezone(timezone.utc).isoformat().replace("+00:00", "Z")
+
+
+def _tuple3(seq) -> tuple[float, float, float]:
+    return (float(seq[0]), float(seq[1]), float(seq[2]))
+
+
+def _cartesian(states) -> list[dict]:
+    return [
+        {"epoch": _iso(sv.epoch), "r_km": list(sv.r_km), "v_kms": list(sv.v_kms)}
+        for sv in states
+    ]
+
+
+class OrekitBackend(PropagatorBackend):
+    name = "orekit"
+    display_frames = DROPDOWN_FRAMES
+
+    def model_config(self) -> dict:
+        """The simulation model the sidecar is flying (its ``GET /config``).
+
+        Read it rather than restating it: the model is defined in one place so
+        that two services' forecasts are comparable, and a client that keeps its
+        own copy has just made a second definition. See
+        :mod:`yksa_orbital.model_config` for the cached accessor callers want.
+        """
+        return self._get("/config")
+
+    def _get(self, path: str) -> dict:
+        try:
+            resp = httpx.get(_service_url() + path, timeout=_timeout(path))
+        except httpx.HTTPError as exc:
+            raise PropagationError(f"Orekit sidecar unreachable: {exc}") from exc
+        if resp.status_code >= 400:
+            raise PropagationError(f"Orekit sidecar error {resp.status_code}")
+        return resp.json()
+
+    def _post(self, path: str, payload: dict) -> dict:
+        try:
+            resp = httpx.post(
+                _service_url() + path, json=payload, timeout=_timeout(path),
+            )
+        except httpx.HTTPError as exc:
+            raise PropagationError(f"Orekit sidecar unreachable: {exc}") from exc
+        if resp.status_code >= 400:
+            try:
+                detail = resp.json().get("error", resp.text)
+            except Exception:  # noqa: BLE001
+                detail = resp.text
+            if resp.status_code == 503:
+                # The sidecar keeps a worker free for interactive queries and
+                # turns heavy work away rather than queueing it. Distinct from a
+                # 400 so the caller retries instead of storing a failed run.
+                raise BackendBusy(detail)
+            raise PropagationError(f"Orekit sidecar error {resp.status_code}: {detail}")
+        return resp.json()
+
+    def _run(self, path: str, omm: dict, spacecraft: dict, options: dict) -> dict:
+        """Shared payload assembly for the decay and ensemble routes."""
+        payload = {"message": omm_message(omm)}
+        for source in (spacecraft, options):
+            payload.update({k: v for k, v in source.items() if v is not None})
+        at = payload.get("at")
+        if isinstance(at, datetime):
+            payload["at"] = _iso(at)
+        return self._post(path, payload)
+
+    def state_at(self, omm: dict, at: datetime | None = None) -> StateVector:
+        return _state_from_response(self._post("/state", {
+            "message": omm_message(omm),
+            "at": _iso(at),
+            "frames": list(_CORE_FRAMES),
+        }))
+
+    def ephemeris(
+        self, omm: dict, start: datetime, stop: datetime, step_s: float,
+    ) -> list[StateVector]:
+        data = self._post("/ephemeris", {
+            "message": omm_message(omm),
+            "start": _iso(start), "stop": _iso(stop),
+            "step_s": float(step_s), "frame": "TEME",
+        })
+        element_epoch = _parse_iso(data.get("element_epoch"))
+        return [_ephemeris_point(p, element_epoch) for p in data.get("states", [])]
+
+    def transform(self, states, frame_in, frame_out):
+        frame_in = frame_in.upper()
+        frame_out = frame_out.upper()
+        if frame_in == frame_out:
+            return list(states)
+        data = self._post("/transform", {
+            "frame_in": frame_in,
+            "frame_out": frame_out,
+            "states": _cartesian(states),
+        })
+        return [
+            StateVector(
+                epoch=_parse_iso(res.get("epoch")) or src.epoch,
+                frame=frame_out,
+                r_km=_tuple3(res["r_km"]),
+                v_kms=_tuple3(res["v_kms"]),
+                element_epoch=src.element_epoch,
+            )
+            for src, res in zip(states, data.get("states", []))
+        ]
+
+    def fit_tle(self, states, frame, template_omm):
+        return self._post("/fit_tle", {
+            "states": _cartesian(states),
+            "frame": frame.upper(),
+            "template_message": omm_message(template_omm),
+        })
+
+    def decay(self, omm: dict, spacecraft: dict, **options) -> dict:
+        """Propagate to re-entry (see ``services/orekit/decay.py``).
+
+        Minutes-long, so it is only ever called from Celery.
+        """
+        return self._run("/decay", omm, spacecraft, options)
+
+    def decay_ensemble(self, omm: dict, spacecraft: dict, **options) -> dict:
+        """P10/P50/P90 lifetimes over resampled solar cycles.
+
+        This is :meth:`decay` repeated once per realization, so it costs tens of
+        minutes. Never call it from a request path.
+        """
+        return self._run("/decay_ensemble", omm, spacecraft, options)
+
+    def refresh_space_weather(self, *, force: bool = True) -> dict:
+        """Pull the current CSSI (and, if configured, MSAFE) file over the deployed
+        one on the sidecar. Returns the sidecar's status dict; a failed download
+        is reported there, not raised, so a scheduled refresh never errors on a
+        transient network problem.
+        """
+        return self._post("/refresh_space_weather", {"force": bool(force)})
+
+    def fit_drag(self, elements: list[dict], **options) -> dict:
+        """Fit a ballistic coefficient from an element history.
+
+        Cheap next to :meth:`decay` -- a linear fit plus one orbit of density
+        evaluations -- so it uses the ordinary timeout.
+        """
+        payload = {"messages": omm_messages(elements)}
+        payload.update({k: v for k, v in options.items() if v is not None})
+        return self._post("/fit_drag", payload)
+
+    def space_weather(
+        self, start: datetime, stop: datetime, **options,
+    ) -> dict:
+        """Observed daily F10.7 / Ap between two dates.
+
+        As cheap as :meth:`fit_drag` -- a provider lookup per day, no
+        propagation -- so it uses the ordinary timeout.
+        """
+        payload = {"start": _iso(start), "stop": _iso(stop)}
+        payload.update({k: v for k, v in options.items() if v is not None})
+        return self._post("/space_weather", payload)
+
+    def state_in_frames(
+        self, omm: dict, at: datetime | None = None, frames=None,
+    ) -> dict:
+        """Multi-frame state for the coordinate-system dropdown.
+
+        The sidecar's ``/state`` payload already matches the
+        :meth:`PropagatorBackend.state_in_frames` contract, so nothing
+        downstream special-cases Orekit.
+        """
+        return self._post("/state", {
+            "message": omm_message(omm),
+            "at": _iso(at),
+            "frames": list(frames or DROPDOWN_FRAMES),
+        })
+
+
+def _state_from_response(data: dict) -> StateVector:
+    states = data.get("states", {})
+    teme = states.get("TEME")
+    if not teme:
+        raise PropagationError("Orekit response missing the TEME state")
+    itrf = states.get("ITRF") or {}
+    geodetic = data.get("geodetic")
+    return StateVector(
+        epoch=_parse_iso(data.get("epoch")),
+        frame="TEME",
+        r_km=_tuple3(teme["r_km"]),
+        v_kms=_tuple3(teme["v_kms"]),
+        ecef_km=_tuple3(itrf["r_km"]) if itrf.get("r_km") else None,
+        ecef_v_kms=_tuple3(itrf["v_kms"]) if itrf.get("v_kms") else None,
+        geodetic=_tuple3(geodetic) if geodetic else None,
+        element_epoch=_parse_iso(data.get("element_epoch")),
+        warnings=list(data.get("warnings") or []),
+    )
+
+
+def _ephemeris_point(point: dict, element_epoch: datetime | None) -> StateVector:
+    ecef = point.get("ecef_km")
+    ecef_v = point.get("ecef_v_kms")
+    geodetic = point.get("geodetic")
+    return StateVector(
+        epoch=_parse_iso(point.get("epoch")),
+        frame="TEME",
+        r_km=_tuple3(point["r_km"]),
+        v_kms=_tuple3(point["v_kms"]),
+        ecef_km=_tuple3(ecef) if ecef else None,
+        ecef_v_kms=_tuple3(ecef_v) if ecef_v else None,
+        geodetic=_tuple3(geodetic) if geodetic else None,
+        element_epoch=element_epoch,
+    )

yksa_orbital/backends/sgp4.py

@@ -0,0 +1,217 @@
+"""SGP4 propagation backend.
+
+Ported from the sibling ``yksa_tdas`` service's ``location/propagate.py`` (pure
+``sgp4`` + stdlib ``math``, no numpy). Builds a ``Satrec`` straight from the
+stored canonical OMM dict via :func:`sgp4.omm.initialize` -- no TLE-line
+round-trip -- propagates to the requested instant, and fills the TEME state plus
+Earth-fixed (ECEF) and WGS84 geodetic views on the :class:`StateVector`.
+
+The TEME->ECEF rotation uses GMST only (no polar motion / nutation); a future
+Orekit backend will provide rigorous frames. That approximation is fine for the
+sub-km display accuracy this service targets.
+"""
+
+from __future__ import annotations
+
+import math
+from datetime import datetime, timedelta, timezone
+
+from sgp4 import omm as sgp4_omm
+from sgp4.api import SGP4_ERRORS, Satrec, jday
+from sgp4.propagation import gstime
+
+from odm import PropagationError, PropagatorBackend, StateVector, parse_omm_epoch
+
+WGS84_A_KM = 6378.137
+WGS84_F = 1.0 / 298.257223563
+WGS84_E2 = WGS84_F * (2.0 - WGS84_F)
+EARTH_ROT_RAD_S = 7.292115e-5
+
+
+#: Frames the pure-Python backend can transform between (GMST rotation only).
+_SGP4_FRAMES = ("TEME", "ITRF")
+
+
+class Sgp4Backend(PropagatorBackend):
+    name = "sgp4"
+    # SGP4 natively yields TEME; the GMST rotation gives an Earth-fixed view.
+    display_frames = ("TEME", "ITRF")
+
+    def transform(self, states, frame_in, frame_out):
+        frame_in = frame_in.upper()
+        frame_out = frame_out.upper()
+        if frame_in == frame_out:
+            return list(states)
+        if frame_in not in _SGP4_FRAMES or frame_out not in _SGP4_FRAMES:
+            raise PropagationError(
+                f"sgp4 backend only transforms between {_SGP4_FRAMES}; "
+                f"got {frame_in!r}->{frame_out!r} (use the orekit backend for more)"
+            )
+        out = []
+        for sv in states:
+            if sv.epoch is None:
+                raise PropagationError("state needs an epoch to rotate frames")
+            jd_ut1 = _jd_of(sv.epoch)
+            if frame_in == "TEME":  # TEME -> ITRF
+                r, v = _teme_to_ecef(sv.r_km, sv.v_kms, jd_ut1)
+            else:  # ITRF -> TEME
+                r, v = _ecef_to_teme(sv.r_km, sv.v_kms, jd_ut1)
+            out.append(_replace_frame(sv, frame_out, r, v))
+        return out
+
+    def state_at(self, omm: dict, at: datetime | None = None) -> StateVector:
+        sat = _satrec_from_omm(omm)
+        element_epoch = _epoch_of(sat)
+        when = at if at is not None else element_epoch
+        if when is None:
+            raise PropagationError("OMM has no usable epoch and no target time given")
+        return _state(sat, when, element_epoch)
+
+    def ephemeris(
+        self, omm: dict, start: datetime, stop: datetime, step_s: float,
+    ) -> list[StateVector]:
+        if step_s <= 0:
+            raise PropagationError("step must be positive")
+        if stop < start:
+            raise PropagationError("stop must be on or after start")
+        sat = _satrec_from_omm(omm)
+        element_epoch = _epoch_of(sat)
+        out: list[StateVector] = []
+        t = start.astimezone(timezone.utc)
+        stop = stop.astimezone(timezone.utc)
+        step = timedelta(seconds=step_s)
+        # Guard against runaway loops; callers cap this via OEM_MAX_POINTS.
+        while t <= stop + timedelta(microseconds=1):
+            out.append(_state(sat, t, element_epoch))
+            t += step
+        return out
+
+
+def _satrec_from_omm(omm: dict) -> Satrec:
+    sat = Satrec()
+    sgp4_omm.initialize(sat, _normalise_for_sgp4(omm))
+    return sat
+
+
+def _normalise_for_sgp4(omm: dict) -> dict:
+    """Return a copy whose EPOCH matches sgp4.omm's strict ``...%S.%f`` parser.
+
+    Stored epochs occasionally lack fractional seconds (or carry a trailing
+    ``Z``); sgp4.omm.initialize only accepts ``%Y-%m-%dT%H:%M:%S.%f``.
+    """
+    fields = dict(omm)
+    epoch = fields.get("EPOCH")
+    dt = parse_omm_epoch(epoch)
+    if dt is not None:
+        fields["EPOCH"] = dt.astimezone(timezone.utc).replace(tzinfo=None).strftime(
+            "%Y-%m-%dT%H:%M:%S.%f"
+        )
+    return fields
+
+
+def _epoch_of(sat: Satrec) -> datetime | None:
+    try:
+        jd = sat.jdsatepoch + sat.jdsatepochF
+        unix = (jd - 2440587.5) * 86400.0
+        return datetime.fromtimestamp(unix, tz=timezone.utc)
+    except Exception:  # noqa: BLE001 -- defensive; a bad epoch just yields None
+        return None
+
+
+def _state(sat: Satrec, when: datetime, element_epoch: datetime | None) -> StateVector:
+    when = when.astimezone(timezone.utc)
+    jd, fr = jday(
+        when.year, when.month, when.day,
+        when.hour, when.minute, when.second + when.microsecond / 1e6,
+    )
+    err, r, v = sat.sgp4(jd, fr)
+    if err != 0:
+        raise PropagationError(SGP4_ERRORS.get(err, f"sgp4 error {err}"))
+
+    r_ecef, v_ecef = _teme_to_ecef(r, v, jd + fr)
+    geodetic = _ecef_to_geodetic(r_ecef)
+    return StateVector(
+        epoch=when,
+        frame="TEME",
+        r_km=(r[0], r[1], r[2]),
+        v_kms=(v[0], v[1], v[2]),
+        ecef_km=r_ecef,
+        ecef_v_kms=v_ecef,
+        geodetic=geodetic,
+        element_epoch=element_epoch,
+    )
+
+
+def _jd_of(when: datetime) -> float:
+    """Full Julian date (UT1≈UTC) for a UTC datetime."""
+    when = when.astimezone(timezone.utc)
+    jd, fr = jday(
+        when.year, when.month, when.day,
+        when.hour, when.minute, when.second + when.microsecond / 1e6,
+    )
+    return jd + fr
+
+
+def _replace_frame(sv: StateVector, frame: str, r, v) -> StateVector:
+    """Copy ``sv`` with a new frame label and position/velocity.
+
+    When the target is the Earth-fixed frame, mirror the rotated state into the
+    ECEF convenience fields so geodetic-dependent conversions keep working.
+    """
+    ecef_km = r if frame == "ITRF" else sv.ecef_km
+    ecef_v_kms = v if frame == "ITRF" else sv.ecef_v_kms
+    return StateVector(
+        epoch=sv.epoch,
+        frame=frame,
+        r_km=tuple(r),
+        v_kms=tuple(v),
+        ecef_km=ecef_km,
+        ecef_v_kms=ecef_v_kms,
+        geodetic=sv.geodetic,
+        element_epoch=sv.element_epoch,
+        warnings=list(sv.warnings),
+    )
+
+
+def _teme_to_ecef(r, v, jd_ut1):
+    """Rotate TEME position/velocity to Earth-fixed (ECEF) via GMST."""
+    theta = gstime(jd_ut1)
+    cos, sin = math.cos(theta), math.sin(theta)
+    x = cos * r[0] + sin * r[1]
+    y = -sin * r[0] + cos * r[1]
+    z = r[2]
+    vx = cos * v[0] + sin * v[1] + EARTH_ROT_RAD_S * y
+    vy = -sin * v[0] + cos * v[1] - EARTH_ROT_RAD_S * x
+    vz = v[2]
+    return (x, y, z), (vx, vy, vz)
+
+
+def _ecef_to_teme(r, v, jd_ut1):
+    """Inverse of :func:`_teme_to_ecef`: Earth-fixed (ECEF) -> TEME via GMST."""
+    theta = gstime(jd_ut1)
+    cos, sin = math.cos(theta), math.sin(theta)
+    x = cos * r[0] - sin * r[1]
+    y = sin * r[0] + cos * r[1]
+    z = r[2]
+    # Undo the Earth-rotation term, then the rotation, to recover TEME velocity.
+    a = v[0] - EARTH_ROT_RAD_S * r[1]
+    b = v[1] + EARTH_ROT_RAD_S * r[0]
+    vx = cos * a - sin * b
+    vy = sin * a + cos * b
+    vz = v[2]
+    return (x, y, z), (vx, vy, vz)
+
+
+def _ecef_to_geodetic(r) -> tuple[float, float, float]:
+    """ECEF (km) -> WGS84 geodetic latitude/longitude (deg) and altitude (km)."""
+    x, y, z = r
+    lon = math.atan2(y, x)
+    p = math.hypot(x, y)
+    lat = math.atan2(z, p * (1.0 - WGS84_E2))
+    alt = 0.0
+    for _ in range(8):
+        sin_lat = math.sin(lat)
+        n = WGS84_A_KM / math.sqrt(1.0 - WGS84_E2 * sin_lat * sin_lat)
+        alt = p / math.cos(lat) - n
+        lat = math.atan2(z, p * (1.0 - WGS84_E2 * n / (n + alt)))
+    return math.degrees(lat), math.degrees(lon), alt