Ryan Malloy
ad7209d0db
Add observation functions for 19 planetary moons across four systems: - Galilean moons (Io, Europa, Ganymede, Callisto) via clean-room L1.2 theory - Saturn moons (Mimas through Hyperion) via TASS 1.7 - Uranus moons (Miranda through Oberon) via GUST86 - Mars moons (Phobos, Deimos) via MarsSat Add Jupiter decametric radio burst prediction for Radio JOVE operators: - io_phase_angle() — Io orbital phase from superior conjunction - jupiter_cml() — System III Central Meridian Longitude with light-time correction - jupiter_burst_probability() — Carr et al. (1983) source regions A, B, C, D L1.2 Galilean theory is a clean-room MIT implementation from the published IMCCE FORTRAN coefficients. All other ephemeris libraries are MIT-licensed extractions from Stellarium with static caching removed for PARALLEL SAFE. All 10 regression tests pass. Extension .so grows from 2.4MB to 2.5MB.
263 lines
8.2 KiB
C
263 lines
8.2 KiB
C
/*
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* radio_funcs.c -- Jupiter decametric radio burst prediction
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*
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* Jupiter emits intense radio bursts at 4-39.5 MHz, modulated by:
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* 1. Io's orbital phase around Jupiter (Io-related storms)
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* 2. Jupiter's Central Meridian Longitude (CML, System III)
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*
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* Radio JOVE operators use CML-vs-Io-phase lookup charts to predict
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* burst probability. This module computes both parameters from SQL,
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* enabling batch prediction queries over time series.
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*
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* References:
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* Carr, Desch & Alexander (1983), "Phenomenology of Magnetospheric
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* Radio Emissions", in Physics of the Jovian Magnetosphere.
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* Radio JOVE project: https://radiojove.gsfc.nasa.gov/
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*/
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#include "postgres.h"
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#include "fmgr.h"
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#include "funcapi.h"
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#include "utils/timestamp.h"
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#include "types.h"
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#include "astro_math.h"
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#include "vsop87.h"
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#include "l12.h"
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#include <math.h>
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PG_FUNCTION_INFO_V1(io_phase_angle);
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PG_FUNCTION_INFO_V1(jupiter_cml);
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PG_FUNCTION_INFO_V1(jupiter_burst_probability);
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/* ================================================================
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* io_phase_angle(timestamptz) -> float8
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*
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* Returns Io's orbital phase angle in degrees [0, 360).
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* Measured from superior geocentric conjunction:
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* 0 = Io behind Jupiter (as seen from Earth)
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* 90 = Io east of Jupiter (western elongation)
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* 180 = Io in front of Jupiter (inferior conjunction)
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* 270 = Io west of Jupiter (eastern elongation)
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*
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* This is the standard convention used by Radio JOVE charts.
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* ================================================================
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*/
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Datum
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io_phase_angle(PG_FUNCTION_ARGS)
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{
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int64 ts = PG_GETARG_INT64(0);
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double jd;
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double io_xyz[3];
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double jup_xyz[6], earth_xyz[6];
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double jup_geo[3];
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double io_rel_geo[3];
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double phase;
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double proj_x, proj_y;
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double jup_dist;
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double east_x, east_y, east_z;
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double north_x, north_y, north_z;
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double io_east, io_north;
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jd = timestamptz_to_jd(ts);
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/* Io position relative to Jupiter (VSOP87 ecliptic J2000, AU) */
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GetL12Coor(jd, L12_IO, io_xyz, NULL);
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/* Jupiter and Earth heliocentric positions */
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GetVsop87Coor(jd, 4, jup_xyz); /* VSOP87 body 4 = Jupiter */
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GetVsop87Coor(jd, 2, earth_xyz); /* VSOP87 body 2 = Earth */
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/* Jupiter geocentric direction */
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jup_geo[0] = jup_xyz[0] - earth_xyz[0];
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jup_geo[1] = jup_xyz[1] - earth_xyz[1];
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jup_geo[2] = jup_xyz[2] - earth_xyz[2];
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jup_dist = sqrt(jup_geo[0] * jup_geo[0] +
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jup_geo[1] * jup_geo[1] +
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jup_geo[2] * jup_geo[2]);
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/* Normalize Jupiter geocentric direction */
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jup_geo[0] /= jup_dist;
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jup_geo[1] /= jup_dist;
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jup_geo[2] /= jup_dist;
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/*
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* Project Io's position onto the plane perpendicular to
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* the Earth-Jupiter line of sight. We need two orthogonal
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* axes in this plane: "east" (position angle) and "north"
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* (toward north ecliptic pole).
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*
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* North ecliptic pole = (0, 0, 1) in ecliptic J2000.
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* East = North x LineOfSight (cross product)
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*/
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north_x = -(jup_geo[2] * jup_geo[0]); /* north - (north.los)*los */
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north_y = -(jup_geo[2] * jup_geo[1]);
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north_z = 1.0 - jup_geo[2] * jup_geo[2];
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{
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double nmag = sqrt(north_x * north_x + north_y * north_y + north_z * north_z);
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if (nmag > 1e-10) {
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north_x /= nmag;
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north_y /= nmag;
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north_z /= nmag;
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}
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}
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/* East = North x LOS */
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east_x = north_y * jup_geo[2] - north_z * jup_geo[1];
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east_y = north_z * jup_geo[0] - north_x * jup_geo[2];
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east_z = north_x * jup_geo[1] - north_y * jup_geo[0];
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/* Project Io relative position onto east/north */
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io_east = io_xyz[0] * east_x + io_xyz[1] * east_y + io_xyz[2] * east_z;
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io_north = io_xyz[0] * north_x + io_xyz[1] * north_y + io_xyz[2] * north_z;
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/* Along LOS component (positive = behind Jupiter from Earth) */
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proj_x = io_xyz[0] * jup_geo[0] + io_xyz[1] * jup_geo[1] + io_xyz[2] * jup_geo[2];
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proj_y = io_east;
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/*
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* Phase angle convention (Radio JOVE):
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* 0 = superior conjunction (Io behind Jupiter)
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* Measured counter-clockwise as seen from north ecliptic pole
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*/
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phase = atan2(-proj_y, proj_x) * RAD_TO_DEG;
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if (phase < 0.0)
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phase += 360.0;
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PG_RETURN_FLOAT8(phase);
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}
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/* ================================================================
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* jupiter_cml(observer, timestamptz) -> float8
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*
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* Jupiter's Central Meridian Longitude in System III (1965.0).
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* Returns degrees [0, 360).
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*
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* System III is defined by Jupiter's magnetic field rotation,
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* with period 9h 55m 29.711s (IAU).
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*
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* The CML is the System III longitude of the sub-observer point.
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* For Earth-based observation, this is approximately the
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* sub-Earth longitude.
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*
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* Reference: IAU (1976) System III longitude definition.
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* ================================================================
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*/
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Datum
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jupiter_cml(PG_FUNCTION_ARGS)
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{
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pg_observer *obs = (pg_observer *) PG_GETARG_POINTER(0);
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int64 ts = PG_GETARG_INT64(1);
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double jd;
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double jup_xyz[6], earth_xyz[6];
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double dx, dy, dz, geo_dist;
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double light_time_days;
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double jd_lt;
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double d;
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double cml;
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(void)obs; /* observer not needed for CML (geocentric is sufficient) */
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jd = timestamptz_to_jd(ts);
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/* Jupiter and Earth positions */
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GetVsop87Coor(jd, 4, jup_xyz);
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GetVsop87Coor(jd, 2, earth_xyz);
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/* Geocentric distance for light-time correction */
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dx = jup_xyz[0] - earth_xyz[0];
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dy = jup_xyz[1] - earth_xyz[1];
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dz = jup_xyz[2] - earth_xyz[2];
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geo_dist = sqrt(dx * dx + dy * dy + dz * dz);
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/* Light-time correction (speed of light = 173.1446 AU/day) */
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light_time_days = geo_dist / 173.1446327;
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jd_lt = jd - light_time_days;
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/*
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* System III longitude of central meridian.
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*
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* Reference epoch: J1965.0 = JD 2438761.5
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* Initial longitude: 305.38 deg (IAU 1976 convention)
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* Rotation rate: 870.536 deg/day (System III, 9h 55m 29.711s period)
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*
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* The sub-Earth longitude decreases with time (Jupiter rotates
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* prograde), so CML = initial + rate * elapsed_days.
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*/
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d = jd_lt - 2438761.5; /* Days since J1965.0 */
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cml = 305.38 + 870.536 * d;
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/* Normalize to [0, 360) */
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cml = fmod(cml, 360.0);
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if (cml < 0.0)
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cml += 360.0;
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PG_RETURN_FLOAT8(cml);
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}
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/* ================================================================
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* jupiter_burst_probability(io_phase float8, cml float8) -> float8
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*
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* Estimated probability of Jupiter decametric radio burst
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* based on Io phase angle and CML (System III).
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*
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* Returns a value 0.0-1.0 representing relative likelihood.
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*
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* Based on the empirical source regions from Carr et al. (1983):
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* Source A: CML 200-260, Io phase 195-265 (Io-A)
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* Source B: CML 90-200, Io phase 70-110 (Io-B)
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* Source C: CML 290-10, Io phase 215-260 (Io-C)
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* Source D: CML 0-50, no Io dependence (non-Io-D)
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*
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* This is a simplified model. Real-world burst probability
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* depends on additional factors (frequency, solar activity,
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* antenna orientation).
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* ================================================================
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*/
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Datum
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jupiter_burst_probability(PG_FUNCTION_ARGS)
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{
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double io_phase = PG_GETARG_FLOAT8(0);
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double cml = PG_GETARG_FLOAT8(1);
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double p;
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/* Normalize inputs */
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io_phase = fmod(io_phase, 360.0);
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if (io_phase < 0.0) io_phase += 360.0;
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cml = fmod(cml, 360.0);
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if (cml < 0.0) cml += 360.0;
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p = 0.0;
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/* Source A (Io-A): strongest, most predictable */
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if (cml >= 200.0 && cml <= 260.0 && io_phase >= 195.0 && io_phase <= 265.0)
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p = 0.8;
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/* Source B (Io-B): second strongest */
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if (cml >= 90.0 && cml <= 200.0 && io_phase >= 70.0 && io_phase <= 110.0)
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{
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double pb = 0.6;
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if (pb > p) p = pb;
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}
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/* Source C (Io-C): wraps around 360/0 boundary */
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if ((cml >= 290.0 || cml <= 10.0) && io_phase >= 215.0 && io_phase <= 260.0)
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{
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double pc = 0.5;
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if (pc > p) p = pc;
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}
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/* Non-Io-D: CML-dependent only, weaker */
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if (cml >= 0.0 && cml <= 50.0)
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{
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double pd = 0.15;
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if (pd > p) p = pd;
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}
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PG_RETURN_FLOAT8(p);
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}
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