Orbit Tracker (CelesTrak GP)

SGP4 ground track, visibility footprint, topocentric look angles, and CelesTrak GP OMM ephemeris propagation for PocketQube and CubeSat missions.

Spacecraft & Ground Station
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TLE epoch: 2026-11-10 (0 days ago)

Catalog & Radio Reference

In Orbit

Operator: BME Budapest (HU)

Downlink: 437.390 MHz (GMSK 12500 Bd) · RF source

NORAD: 66670 · COSPAR: 2025-276E

SatNOGS DB CelesTrak GP
Sub-satellite point−26.79°, 162.25°In Earth eclipse (cylindrical model)
Altitude & velocity475 km7.63 km/s
Station elevation−74.2°Azimuth: 42°
Slant range12,758 kmBelow horizon (LOS)
Ground Track (−45 min to +90 min, SGP4 via satellite.js · TLE epoch: 2026-11-10 (0 days ago))Footprint r = 2388 km
GSHUNITY

DETERMINISTIC PHYSICS & DATA METHODOLOGY

How This Calculator Works

Source modules: lib/physics/sgp4-lite.ts, lib/data/gp-snapshot.json, satellite.js

Propagates active catalogued small satellites from build-time CelesTrak GP OMM snapshots (or user-triggered live CelesTrak sync) via Vallado/NORAD SGP4 (satellite.js), transforming TEME → ECF → geodetic coordinates, topocentric look angles, and cylindrical solar illumination.

Governing Equations & Physical Model

SGP4 TEME propagation & geodetic/topocentric transform
(r_TEME, v_TEME) = SGP4(OMM, t)  →  R_z(GMST)  →  (φ, λ, h), (Az, El, d)

Computes ground track over [t − 45 min, t + 90 min] and horizon footprint radius r_fp = R_E · arccos(R_E / (R_E + h)).

Cylindrical Earth eclipse check
r_sat · ŝ_☉ < 0   ∧   √(|r_sat|² − (r_sat · ŝ_☉)²) < R_E

Uses Vallado Algorithm 29 low-precision solar unit vector ŝ_☉(t) in ECI coordinates.

Inputs, Parameters & Units

ParameterUnitPhysical definition
SpacecraftNORAD CATNRActive orbital objects (e.g., HUNITY #66670, XI-IV #27848, CUTE-1 #27844, FUNcube-1 #39444, SwissCube #35932, SONATE-2 #59112) plus historical decayed records.
φ_gs, λ_gs°, °Observer geodetic latitude and longitude (default 52.01°N, 4.36°E Delft/ESTEC).

Assumptions & Validity Limits

  • Zero silent background requests are made to third parties on load; live CelesTrak GP OMM fetching runs strictly when the user clicks 'Sync CelesTrak' (cached 2 h in localStorage).
  • Re-entered spacecraft (e.g., Grizu-263A #51025) and rideshare payloads with unverified NORAD correlation disable SGP4 plotting rather than fabricating tracks.
  • SGP4 positional accuracy degrades with TLE/OMM epoch age, especially for high-B* 1P PocketQubes.

Worked Default Reference Case

Default active 3P PocketQube HUNITY (NORAD #66670, 2025-276E)

Propagates bundled CelesTrak OMM elements for HUNITY (437.390 MHz GMSK 12500 Bd) relative to 52.01°N, 4.36°E, displaying live TLE epoch age, AOS/LOS slant range, and sunlit/eclipse state.

Default tracked object
HUNITY (#66670, 3P)
Verified downlink
437.390 MHz (GMSK 12.5 kBd)
Ground track window
−45 min to +90 min
Network privacy policy
Offline snapshot until user sync
Model Validation & Analytical Test SuiteGround Segment & Tracking Architecture (SatWiki)

Engineering Specifications, Equations & Topic Hubs

TOPIC HUB · TOP.07 // ASTRODYNAMICSOrbital Mechanics, Thermospheric Drag & Lifetime
TOPIC HUB · TOP.08 // GROUNDGround Stations, TLE Tracking, Doppler & SatNOGS
TECHNICAL NOTE · NL-TN-2026-016Tracking a 5 cm satellite
SATWIKI SPECIFICATION · SQ-OP-006Tracking, TLEs & spacecraft identification
COURSE MODULE 10IARU/ITU Spectrum Coordination, Deployers & Operations