Ryan Malloy
adfb6949e1
Range rate: topocentric residuals now include an optional 4th component (dot(Δr, v_ecef) / |Δr|) with OD_RR_SCALE=10.0 for unit balancing. Controlled via fit_range_rate parameter on tle_from_topocentric(). Weighted observations: per-observation weights applied as √w scaling to both residuals and Jacobian rows, producing the weighted normal equations H'WH without explicit W construction. Weights parameter added to tle_from_eci, tle_from_topocentric, and tle_from_angles. Gauss angles-only IOD: Vallado Algorithm 52 implementation for seed-free orbit recovery from 3+ RA/Dec observations. New RA/Dec residual function with cos(dec) scaling and wrap-around handling. New tle_from_angles() and tle_from_angles_multi() SQL functions accepting RA in hours [0,24), Dec in degrees [-90,90]. New standalone test suite: test_od_gauss (17 assertions). New regression tests: Tests 18-25 covering range rate, weights, angles-only with/without seed, and error cases.
110 lines
3.5 KiB
C
110 lines
3.5 KiB
C
/*
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* od_solver.h -- TLE fitting via weighted least-squares differential correction
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*
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* Implements Vallado & Crawford (2008) AIAA 2008-6770:
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* - Equinoctial element perturbation
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* - SGP4 as the propagation engine
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* - Jacobian by finite differencing
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* - SVD solve via LAPACK dgelss_()
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* - Tiered step limiting (Vallado 2008 Section V.B)
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* - Brouwer-to-Kozai Newton-Raphson for TLE output
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*/
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#ifndef PG_ORRERY_OD_SOLVER_H
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#define PG_ORRERY_OD_SOLVER_H
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#include "norad.h"
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/* Maximum number of DC iterations */
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#define OD_MAX_ITER 25
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/* Convergence thresholds (Vallado 2008 Section V.A) */
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#define OD_RMS_REL_TOL 0.0002
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#define OD_RMS_ABS_TOL 0.0002
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/* Number of equinoctial states (6 orbital + optional B*) */
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#define OD_NSTATE_6 6
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#define OD_NSTATE_7 7
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/*
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* Observation type flag
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*/
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typedef enum
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{
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OD_OBS_ECI = 0, /* 6-component: x, y, z, vx, vy, vz (km, km/s) */
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OD_OBS_TOPO = 1, /* 3-component: az, el, range (rad, rad, km) */
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OD_OBS_RADEC = 2 /* 2-component: RA, Dec (radians, equatorial) */
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} od_obs_type_t;
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/*
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* Single observation for the DC solver
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*/
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typedef struct
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{
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double jd; /* Julian date of observation */
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double data[6]; /* ECI: [x,y,z,vx,vy,vz], topo: [az,el,range,...] */
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int observer_idx; /* index into config->observers[] (topo mode) */
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} od_observation_t;
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/*
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* Observer location (needed for topocentric mode)
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*/
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typedef struct
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{
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double lat; /* radians */
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double lon; /* radians */
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double alt_m; /* meters */
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double ecef[3]; /* pre-computed ECEF position (km) */
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} od_observer_t;
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/*
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* Solver configuration
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*/
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typedef struct
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{
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od_obs_type_t obs_type; /* ECI or topocentric */
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int fit_bstar; /* include B* as 7th state */
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int fit_range_rate; /* include range_rate in topo residuals */
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int max_iter; /* iteration limit */
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od_observer_t *observers; /* array of observers (topo mode) */
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int n_observers; /* count (0 for ECI mode) */
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double *weights; /* per-observation weights (NULL=uniform) */
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int n_weights;
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} od_config_t;
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/*
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* Solver result
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*/
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typedef struct
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{
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tle_t fitted_tle; /* resulting TLE (Kozai mean motion) */
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int iterations; /* iterations performed */
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double rms_initial; /* RMS residual before fitting (km) */
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double rms_final; /* RMS residual after fitting (km) */
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int converged; /* 1 if converged, 0 if hit max_iter */
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char status[64]; /* human-readable status */
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double covariance[28]; /* upper triangle of (H^T H)^{-1}, row-major */
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int cov_size; /* 21 (6-state) or 28 (7-state), 0 if failed */
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double condition_number; /* s_max / s_min from final SVD */
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} od_result_t;
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/*
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* Primary entry point: fit a TLE from observations.
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*
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* obs: array of N observations
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* n_obs: number of observations (must be >= 6, or >= 7 if fit_bstar)
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* seed: initial TLE guess (if NULL, computed from first/last obs)
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* config: solver configuration
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* result: output (caller allocates)
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*
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* Returns 0 on success, -1 on error.
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*
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* Memory: all working arrays allocated via palloc() (when used from
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* PostgreSQL) or malloc() (standalone). Freed before return.
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*/
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int od_fit_tle(const od_observation_t *obs, int n_obs,
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const tle_t *seed, const od_config_t *config,
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od_result_t *result);
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#endif /* PG_ORRERY_OD_SOLVER_H */
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