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pg_orrery/CLAUDE.md
Ryan Malloy cd338c3c64 Vendor SGP4/SDP4 as pure C, drop g++ dependency 
Replace the sat_code git submodule (lib/sat_code/) with vendored
sources in src/sgp4/. The upstream .cpp files are renamed to .c —
the code is valid C99 with zero C++ features. This eliminates the
g++ and -lstdc++ build dependencies.

Adds 518 Vallado test vectors (AIAA 2006-6753-Rev1) as a 13th
regression suite to verify byte-identical numerical output.

Updates all documentation (CLAUDE.md, DESIGN.md, 11 MDX pages,
Dockerfile) to reflect the new layout and pure-C compilation.
2026-02-17 12:45:39 -07:00

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pg_orbit — Solar System Computation for PostgreSQL

What This Is

A PostgreSQL extension that moves orbital mechanics inside the database — the way PostGIS did for geography. Native C extension using PGXS, 68 SQL functions, 7 custom types, covering satellites (SGP4/SDP4), planets (VSOP87 + optional JPL DE441), Moon (ELP2000-82B), 19 planetary moons (L1.2/TASS17/GUST86/MarsSat), stars, comets, Jupiter radio bursts, and interplanetary Lambert transfers.

Current version: 0.3.0 on branch phase/solar-system-expansion Repository: https://git.supported.systems/warehack.ing/pg_orbit Documentation: https://pg-orbit.warehack.ing

Build System

make PG_CONFIG=/usr/bin/pg_config           # Compile with PGXS
sudo make install PG_CONFIG=/usr/bin/pg_config  # Install extension
make installcheck PG_CONFIG=/usr/bin/pg_config  # Run 13 regression test suites

Requires: PostgreSQL 17 development headers, GCC, Make.

Docker

make docker-build   # Build standalone image (pg17 + pg_orbit)
make docker-test    # Smoke test the image
make docker-push    # Push to git.supported.systems registry

Image: git.supported.systems/warehack.ing/pg_orbit:pg17

Project Layout

pg_orbit.control                # Extension metadata (version 0.3.0)
Makefile                        # PGXS build + Docker targets
sql/
  pg_orbit--0.1.0.sql           # v0.1.0: satellite types/functions/operators
  pg_orbit--0.2.0.sql           # v0.2.0: solar system (57 functions)
  pg_orbit--0.3.0.sql           # v0.3.0: complete extension (68 functions)
  pg_orbit--0.1.0--0.2.0.sql    # Migration: v0.1.0 → v0.2.0 (adds solar system)
  pg_orbit--0.2.0--0.3.0.sql    # Migration: v0.2.0 → v0.3.0 (adds DE ephemeris)
src/
  pg_orbit.c                    # PG_MODULE_MAGIC + _PG_init() (GUC registration)
  types.h                       # All struct definitions + constants + DE body ID mapping
  astro_math.h                  # Shared astronomical helpers + observe_from_geocentric()
  # --- Satellite (v0.1.0) ---
  tle_type.c                    # TLE custom type (I/O, binary, 15 accessors)
  eci_type.c                    # ECI position type + geodetic/topocentric types
  observer_type.c               # Observer type with flexible string parsing
  sgp4_funcs.c                  # sgp4_propagate(), _safe(), _series(), tle_distance()
  coord_funcs.c                 # eci_to_geodetic(), eci_to_topocentric(), ground_track()
  pass_funcs.c                  # next_pass(), predict_passes(), pass_visible()
  gist_tle.c                    # GiST operator class (&&, <->)
  # --- Solar System (v0.2.0) ---
  vsop87.c / vsop87.h           # VSOP87 planetary ephemeris (Bretagnon 1988)
  elp82b.c / elp82b.h           # ELP2000-82B lunar ephemeris (Chapront 1988)
  precession.c / precession.h   # IAU 1976 precession (Lieske 1979)
  sidereal_time.c / .h          # GMST calculation (Vallado Eq. 3-47)
  elliptic_to_rectangular.c/.h  # Orbital element conversions
  planet_funcs.c                # planet_observe(), planet_heliocentric(), sun/moon_observe()
  star_funcs.c                  # star_observe(), star_observe_safe()
  kepler_funcs.c                # kepler_propagate(), comet_observe()
  l12.c / l12.h                 # L1.2 Galilean moon theory (Lieske 1998)
  tass17.c / tass17.h           # TASS 1.7 Saturn moon theory (Vienne & Duriez 1995)
  gust86.c / gust86.h           # GUST86 Uranus moon theory (Laskar & Jacobson 1987)
  marssat.c / marssat.h         # MarsSat Mars moon theory (Jacobson 2014)
  moon_funcs.c                  # galilean/saturn/uranus/mars_moon_observe()
  radio_funcs.c                 # io_phase_angle(), jupiter_cml(), burst_probability()
  lambert.c / lambert.h         # Lambert transfer solver (Izzo 2015)
  transfer_funcs.c              # lambert_transfer(), lambert_c3()
  # --- JPL DE Ephemeris (v0.3.0) ---
  de_reader.h / de_reader.c     # Clean-room JPL DE binary reader (Chebyshev/Clenshaw)
  eph_provider.h / eph_provider.c # Provider dispatch, GUC, lazy init, frame rotation
  de_funcs.c                    # All _de() SQL function implementations
  sgp4/                         # Vendored SGP4/SDP4 (Bill Gray's sat_code, MIT license)
    sgp4.c                      # Near-earth propagator (period < 225 min)
    sdp4.c                      # Deep-space propagator (period >= 225 min)
    deep.c                      # Lunar/solar perturbations, resonance integration
    common.c                    # Shared initialization (Brouwer mean elements, Kepler solver)
    basics.c                    # select_ephemeris(), FMod2p()
    get_el.c                    # TLE parsing (parse_elements(), checksum)
    tle_out.c                   # TLE output (write_elements_in_tle_format())
    norad.h / norad_in.h        # Public + internal headers
    PROVENANCE.md               # Vendoring decision, modifications, verification
    LICENSE                     # MIT license (Bill Gray / Project Pluto)
test/
  sql/                          # 13 regression test suites
  expected/                     # Expected output
  data/vallado_518.json         # 518 Vallado test vectors (AIAA 2006-6753-Rev1)
docs/
  DESIGN.md                     # Architecture decisions, theory-to-code mappings
  Dockerfile                    # Starlight docs site (Astro + Caddy)
  package.json                  # Docs site dependencies
  astro.config.mjs              # Starlight configuration
  src/content/docs/             # MDX documentation pages

Type System

All types are fixed-size, STORAGE = plain, ALIGNMENT = double. No TOAST overhead.

Type Bytes Description
tle 112 Parsed mean orbital elements for SGP4/SDP4
eci_position 48 x,y,z + vx,vy,vz (km, km/s) in TEME frame
geodetic 24 lat, lon (radians), alt (km) above WGS-84
topocentric 32 azimuth, elevation, range, range_rate
observer 24 lat, lon (radians), alt_m (meters)
pass_event 48 AOS/MAX/LOS times + max_el + AOS/LOS azimuth
heliocentric 24 x, y, z in AU (ecliptic J2000 frame)

Function Domains (68 total)

Domain Theory Key Functions Count
Satellite SGP4/SDP4 (Brouwer 1959) observe(), predict_passes(), ground_track() 22
Planets VSOP87 (Bretagnon 1988) planet_observe(), planet_heliocentric() 3
Sun/Moon VSOP87 + ELP2000-82B sun_observe(), moon_observe() 2
Planetary moons L1.2, TASS17, GUST86, MarsSat galilean_observe(), saturn_moon_observe() 4
Stars J2000 + IAU 1976 precession star_observe(), star_observe_safe() 2
Comets/asteroids Two-body Keplerian kepler_propagate(), comet_observe() 2
Jupiter radio Carr et al. (1983) jupiter_burst_probability() 3
Transfers Lambert (Izzo 2015) lambert_transfer(), lambert_c3() 2
DE ephemeris JPL DE440/441 (optional) planet_observe_de(), moon_observe_de() 11
GiST index Altitude-band approximation && (overlap), <-> (distance) 8
Diagnostics -- pg_orbit_ephemeris_info() 1

All functions are PARALLEL SAFE. VSOP87/ELP82B functions are IMMUTABLE (compiled-in coefficients). DE functions are STABLE (external file dependency).

Body IDs

Planets (VSOP87 convention)

ID Body ID Body
0 Sun 5 Jupiter
1 Mercury 6 Saturn
2 Venus 7 Uranus
3 Earth 8 Neptune
4 Mars 10 Moon

Planetary Moons (per-family indexing)

  • Galilean (0-3): Io, Europa, Ganymede, Callisto
  • Saturn (0-7): Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Iapetus, Hyperion
  • Uranus (0-4): Miranda, Ariel, Umbriel, Titania, Oberon
  • Mars (0-1): Phobos, Deimos

Constant Chain of Custody

The most critical design constraint. TLEs absorb geodetic model biases — using wrong constants silently corrupts positions by kilometers.

Rules

  1. SGP4 propagation: WGS-72 constants ONLY (mu, ae, J2, J3, J4, ke)
  2. Coordinate output (geodetic, topocentric): WGS-84 (a=6378.137km, f=1/298.257223563)
  3. TEME frame: Only 4 of 106 IAU-80 nutation terms (matching SGP4's internal model)
  4. Solar system pipeline: IAU 1976 precession, J2000 obliquity, GMST from Vallado Eq. 3-47
  5. Never mix: WGS-72 propagation + WGS-84 output. No other combination.
  6. DE frame rotation: DE positions (ICRS equatorial) pass through equatorial_to_ecliptic() at the provider boundary before entering the observation pipeline
  7. Same-provider rule: Both target and Earth must come from the same provider in any geocentric computation (never mix DE target with VSOP87 Earth)
  8. DE AU consistency: Verify DE header AU matches compiled-in AU_KM (149597870.7) at init time

WGS-72 Constants (from Hoots & Roehrich STR#3, propagation only)

#define WGS72_MU      398600.8            /* km^3/s^2 */
#define WGS72_AE      6378.135            /* km */
#define WGS72_J2      0.001082616
#define WGS72_KE      0.0743669161331734132  /* (min)^(-1) */

WGS-84 Constants (coordinate output only)

#define WGS84_A       6378.137            /* km */
#define WGS84_F       (1.0 / 298.257223563)

Astronomical Constants

#define AU_KM           149597870.7         /* IAU 2012 */
#define GAUSS_K         0.01720209895       /* AU^(3/2)/day */
#define OBLIQUITY_J2000 0.40909280422232897 /* 23.4392911 deg in radians */
#define J2000_JD        2451545.0           /* 2000 Jan 1.5 TT */

JPL DE Ephemeris (Optional)

v0.3.0 adds optional JPL DE440/441 ephemeris support (~0.1 milliarcsecond accuracy) alongside the existing VSOP87 pipeline (~1 arcsecond). DE functions are separate _de() variants — existing VSOP87 functions are completely unchanged.

Architecture

  • Clean-room DE reader (de_reader.c): ~250 lines of C. Parses the JPL binary format, evaluates Chebyshev polynomials via Clenshaw recurrence. No GPL dependency (avoids Bill Gray's jpl_eph).
  • Per-backend lazy init: Each PostgreSQL backend opens its own file descriptor on first _de() call. Never opens in _PG_init() (postmaster context). Safe for PARALLEL SAFE.
  • VSOP87 fallback: Every _de() function falls back to its VSOP87/ELP82B equivalent when DE is unavailable.
  • STABLE volatility: DE functions are STABLE (not IMMUTABLE) because output depends on an external file. Existing VSOP87 functions remain IMMUTABLE.

GUC Configuration

-- Set the path to a JPL DE binary file (requires superuser)
ALTER SYSTEM SET pg_orbit.ephemeris_path = '/var/lib/postgres/de441.bin';
SELECT pg_reload_conf();

-- Check which provider is active
SELECT * FROM pg_orbit_ephemeris_info();
GUC Type Default Context
pg_orbit.ephemeris_path string '' (empty = VSOP87 only) SIGHUP (superuser only)

DE Function Variants

Every _de() function mirrors an existing VSOP87 function:

DE Function VSOP87 Equivalent Volatility
planet_heliocentric_de() planet_heliocentric() STABLE
planet_observe_de() planet_observe() STABLE
sun_observe_de() sun_observe() STABLE
moon_observe_de() moon_observe() STABLE
lambert_transfer_de() lambert_transfer() STABLE
lambert_c3_de() lambert_c3() STABLE
galilean_observe_de() galilean_observe() STABLE
saturn_moon_observe_de() saturn_moon_observe() STABLE
uranus_moon_observe_de() uranus_moon_observe() STABLE
mars_moon_observe_de() mars_moon_observe() STABLE
pg_orbit_ephemeris_info() — STABLE

Vendored SGP4/SDP4

Bill Gray's sat_code (MIT license): https://github.com/Bill-Gray/sat_code

Vendored into src/sgp4/ from upstream commit ff7b98957dfa2979700a482bde9de9542807293e. The .cpp files were renamed to .c — the code is valid C99 with zero C++ features (no classes, templates, namespaces, exceptions, or STL). This eliminates the g++ and -lstdc++ dependencies.

Modifications from upstream are minimal and documented in src/sgp4/PROVENANCE.md:

  • Renamed .cpp → .c (no code changes — already valid C99)
  • Stripped Win32 DLL_FUNC/__stdcall decorators
  • Removed extern "C" wrapper (now compiled as C)
  • Removed unused SGP/SGP8/SDP8 model prototypes
  • Added forward declarations (-Wmissing-prototypes)
  • Changed bare inline to static inline for C99 compliance
  • Added equation citations referencing STR#3 and Vallado Rev-1

All numerical logic is byte-identical to upstream. Verified against 518 Vallado test vectors (AIAA 2006-6753-Rev1).

Testing

13 regression test suites via make installcheck:

Suite What it tests
tle_parse TLE I/O round-trip, malformed input rejection, all 15 accessors
sgp4_propagate SGP4/SDP4, propagation series, tle_distance
coord_transforms TEME-to-geodetic, TEME-to-topocentric, ground_track
pass_prediction predict_passes, next_pass, pass_visible, min elevation filter
gist_index && overlap, <-> distance, GiST index scan, KNN ordering
convenience observe(), observe_safe(), tle_from_lines(), observer_from_geodetic()
star_observe Star observation, IAU 1976 precession, heliocentric type I/O
kepler_comet Keplerian propagation (elliptic/parabolic/hyperbolic), comet_observe
planet_observe VSOP87 planets, sun_observe, moon_observe (ELP2000-82B)
moon_observe Galilean/Saturn/Uranus/Mars moons, Io phase, Jupiter CML, burst probability
lambert_transfer Lambert solver, lambert_c3, pork chop grid, error handling
de_ephemeris DE function fallback to VSOP87, cross-provider consistency, error handling
vallado_518 518 Vallado test vectors (AIAA 2006-6753-Rev1), per-satellite breakdown

Error Handling Patterns

  • _safe() variants (sgp4_propagate_safe, observe_safe, star_observe_safe) return NULL on error instead of raising exceptions. Use these for batch queries over potentially invalid data.
  • SGP4 error codes: -1 (nearly parabolic), -2 (negative semi-major axis/decayed), -3/-4 (orbit within Earth, returns with NOTICE), -5 (negative mean motion), -6 (convergence failure)
  • Pass prediction: propagation failures return -pi elevation (below horizon), shedding the failed timestep without aborting the scan.
  • Input validation: same-body Lambert check, arrival-before-departure, invalid body_id, RA out of [0,24), negative perihelion distance.

Documentation Site

Live: https://pg-orbit.warehack.ing

Starlight docs at docs/ — 36 MDX pages covering all domains.

Sections: Getting Started, Guides (9 domain walkthroughs incl. DE ephemeris), Workflow Translation (Skyfield/Horizons/GMAT/Radio Jupiter Pro comparisons), Reference (all 68 functions incl. DE variants), Architecture (Hamilton's principles, constant custody, observation pipeline), Performance (benchmarks).

Local Development

cd docs && npm run dev      # Dev server on :4321
cd docs && npm run build    # Static build to dist/

Production Deployment

The docs site deploys to the warehack.ing VPS (149.28.126.25) which runs caddy-docker-proxy with wildcard DNS for *.warehack.ing.

Deploy (or redeploy after changes):

ssh -A warehack-ing@pg-orbit.warehack.ing
cd ~/pg_orbit
git pull origin phase/solar-system-expansion   # or the current branch
cd docs
make prod                                       # builds image + starts container

First-time setup on VPS:

ssh -A warehack-ing@pg-orbit.warehack.ing
git clone git@git.supported.systems:warehack.ing/pg_orbit.git
cd pg_orbit && git checkout phase/solar-system-expansion
cat > docs/.env << 'EOF'
COMPOSE_PROJECT_NAME=pg-orbit-docs
NODE_ENV=production
VITE_HMR_HOST=pg-orbit.warehack.ing
EOF
cd docs && make prod

Makefile targets:

  • make prod — build + start production (Caddy serves static files)
  • make dev — build + start dev mode (hot-reload, volume mounts)
  • make down — stop containers
  • make restart — stop + start production
  • make clean — stop + remove volumes
  • make logs — tail container logs

Infrastructure: Container pg-orbit-docs joins external caddy network. caddy-docker-proxy reads labels to auto-configure reverse proxy + TLS (Let's Encrypt via Vultr DNS challenge). TLS cert provisioning takes ~2 minutes on first deploy.

Do NOT run the docs container locally if also deployed on the VPS — competing ACME DNS challenges will corrupt each other's TXT records.

Coding Style

  • Standard PostgreSQL extension C style
  • ereport(ERROR, ...) for user-facing errors, never elog(ERROR, ...)
  • All memory via palloc/pfree (PostgreSQL memory contexts)
  • Comments explain "why", not "what"
  • No global mutable state — all computation from function arguments (exceptions: per-backend DE handle via on_proc_exit; 3 statics in vendored deep.c + 1 cache in sdp4.c, safe in PostgreSQL's fork model, never modified by pg_orbit)
  • Every function handling SGP4 must check the error return code
  • All functions marked PARALLEL SAFE
  • DE functions: always fall back to VSOP87/ELP82B on any error

Git Conventions

  • One commit per logical change
  • Branch per phase: phase/solar-system-expansion
  • Tag releases: v0.1.0, v0.2.0
  • Commit messages: imperative mood, no AI attribution