Graham McIntire
622edee180
Classifies every contact's likely non-LOS propagation mechanism and persists the result on contacts.propagation_mechanism. Mechanism is determined in priority order: 1. user_declared_prop_mode (ADIF PROP_MODE from the operator log) 2. EME — moon-ephemeris check, ≥2m band, >1800 km path 3. aurora — Kp≥5 + high-lat path, 50-432 MHz 4. sporadic-E — foEs × 5 ≥ band_mhz, 400-2500 km path 5. meteor_scatter — ±3 days of a shower peak, VHF/UHF 6. rain_scatter — common-volume radar heavy rain, 5-11 GHz ≤800 km 7. tropo_duct — HRRR native_best_duct ≥ band or ducting_detected 8. line_of_sight — ≤50 km path 9. troposcatter — default Persisted via MechanismClassifyWorker (queue: :mechanism, unique on contact_id). Submit-time enqueue path includes :mechanism by default; BackfillEnqueueWorker cron now handles :mechanism alongside existing types so prod continuously backfills any contact with propagation_mechanism_status in (:pending, :queued, :failed). Also added :radar to the cron's type list so common-volume radar backfill runs automatically rather than only via `mix radar_backfill`. New modules: - Microwaveprop.Propagation.MoonEphemeris — Meeus low-precision moon position, accuracy ±1° — enough for the mutual-visibility EME test - Microwaveprop.Propagation.MechanismClassifier — plug-in priority chain over the evidence map - Microwaveprop.Workers.MechanismClassifyWorker — assembles inputs from HRRR / native profiles / common-volume radar / solar_indices / ionosonde + calls the classifier ADIF importer now reads PROP_MODE into user_declared_prop_mode so operator-tagged mechanisms (EME/ES/MS/RS/AS/AUR) become ground truth.
130 lines
3.9 KiB
Elixir
130 lines
3.9 KiB
Elixir
defmodule Microwaveprop.Propagation.MoonEphemeris do
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@moduledoc """
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Approximate moon-position calculation for EME classification.
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Accuracy target: ±1° — enough to decide "is the moon above the horizon
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for both stations right now?" which is the EME feasibility test. We
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use Jean Meeus's low-precision algorithm (Astronomical Algorithms,
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chapter 47), good to ~10' over historical amateur contact timestamps.
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No external ephemeris table — pure math so it works for any date.
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"""
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@deg_to_rad :math.pi() / 180.0
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@rad_to_deg 180.0 / :math.pi()
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@doc """
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Returns the moon's altitude above the horizon in degrees for a given
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observer lat/lon and UTC timestamp. Negative means the moon is below
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the horizon (not reachable).
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"""
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@spec altitude_deg(number(), number(), DateTime.t()) :: float()
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def altitude_deg(lat, lon, %DateTime{} = ts) do
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{ra, dec} = moon_ra_dec(ts)
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gst = greenwich_sidereal_hours(ts)
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# Local hour angle in degrees
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lst_deg = :math.fmod(gst * 15.0 + lon, 360.0)
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hour_angle = lst_deg - ra * 15.0
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lat_r = lat * @deg_to_rad
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dec_r = dec * @deg_to_rad
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ha_r = hour_angle * @deg_to_rad
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sin_alt =
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:math.sin(lat_r) * :math.sin(dec_r) +
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:math.cos(lat_r) * :math.cos(dec_r) * :math.cos(ha_r)
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sin_alt |> max(-1.0) |> min(1.0) |> :math.asin() |> Kernel.*(@rad_to_deg)
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end
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@doc """
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`true` if the moon is above the horizon at the given observer + time.
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"""
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@spec above_horizon?(number(), number(), DateTime.t()) :: boolean()
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def above_horizon?(lat, lon, %DateTime{} = ts), do: altitude_deg(lat, lon, ts) > 0.0
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# — private math helpers below —
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# Returns {right ascension (hours), declination (deg)} of the moon.
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defp moon_ra_dec(%DateTime{} = ts) do
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jd = julian_day(ts)
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t = (jd - 2_451_545.0) / 36_525.0
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# Mean orbital elements (Meeus §47, degrees).
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l_prime = 218.3164477 + 481_267.88123421 * t
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d = 297.8501921 + 445_267.1114034 * t
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m = 357.5291092 + 35_999.0502909 * t
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m_prime = 134.9633964 + 477_198.8675055 * t
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f = 93.2720950 + 483_202.0175233 * t
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# Longitude correction (leading term only — 6.289°).
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lambda =
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l_prime +
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6.289 * sin_deg(m_prime) -
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1.274 * sin_deg(2 * d - m_prime) +
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0.658 * sin_deg(2 * d) -
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0.186 * sin_deg(m)
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# Latitude (β) leading term.
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beta = 5.128 * sin_deg(f)
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# Obliquity of the ecliptic.
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eps = 23.439 - 0.0000004 * (jd - 2_451_545.0)
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# Convert ecliptic (λ, β) → equatorial (α, δ).
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lam_r = lambda * @deg_to_rad
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beta_r = beta * @deg_to_rad
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eps_r = eps * @deg_to_rad
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sin_alpha = :math.sin(lam_r) * :math.cos(eps_r) - :math.tan(beta_r) * :math.sin(eps_r)
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cos_alpha = :math.cos(lam_r)
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alpha_r = :math.atan2(sin_alpha, cos_alpha)
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sin_delta =
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:math.sin(beta_r) * :math.cos(eps_r) +
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:math.cos(beta_r) * :math.sin(eps_r) * :math.sin(lam_r)
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delta_r = :math.asin(sin_delta)
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ra_hours = :math.fmod(alpha_r * @rad_to_deg / 15.0 + 48.0, 24.0)
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dec_deg = delta_r * @rad_to_deg
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{ra_hours, dec_deg}
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end
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defp julian_day(%DateTime{year: y, month: m, day: d, hour: h, minute: mi, second: s}) do
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{y2, m2} =
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if m <= 2 do
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{y - 1, m + 12}
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else
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{y, m}
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end
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a = div(y2, 100)
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b = 2 - a + div(a, 4)
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jd_day =
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Float.floor(365.25 * (y2 + 4716)) +
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Float.floor(30.6001 * (m2 + 1)) +
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d + b - 1524.5
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frac = (h + mi / 60 + s / 3600) / 24.0
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jd_day + frac
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end
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defp greenwich_sidereal_hours(%DateTime{} = ts) do
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jd = julian_day(ts)
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t = (jd - 2_451_545.0) / 36_525.0
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# Mean sidereal time at Greenwich, in hours.
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gmst_sec =
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67_310.54841 +
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(876_600 * 3600 + 8_640_184.812866) * t +
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0.093104 * t * t -
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6.2e-6 * t * t * t
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hours = gmst_sec / 3600.0
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:math.fmod(:math.fmod(hours, 24.0) + 24.0, 24.0)
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end
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defp sin_deg(deg), do: :math.sin(deg * @deg_to_rad)
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end
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