Changelog

0.1.0 — 2026-10-16

First release.

• SGP4 and SDP4 propagator written from scratch after Vallado et al. (2006), "improved" mode, WGS-72 constants. It matches Vallado's tcppver.out reference vectors to better than 1 mm.
• TLE parsing for 2-line and 3-line sets, with checksum validation, epoch decoding and lookup by name, alias or NORAD id.
• satpass tle update downloads CelesTrak groups into a cache (refreshes at most every 2 hours) and warns about stale elements. Sample TLEs are bundled so the tool works offline.
• Frames: TEME→ECEF via IAU-82 GMST, WGS-84 geodetic conversions, and topocentric az/el/range/range-rate.
• Low-precision Sun, a conical umbra/penumbra Earth-shadow model, twilight classification and diffuse-sphere visual magnitudes.
• Pass prediction: a coarse scan followed by Brent root-finding for AOS/LOS and Brent maximisation for culmination, plus visibility windows within each pass.
• Commands: passes, now, track (CSV), skyplot (SVG), groundtrack (SVG with Natural Earth coastlines), flyover-list, ical, tle update|list|info and config init|show.