Is this flight software?

No. SIDUS models are educational reimplementations. Cross-check before any flight decision.

Horizon slant range

Geometric radio horizon distance from altitude (spherical body, no refraction).

SIDUS educational calculator. Category satellite. Tags: comms, operations, RF, satellite. Pure SI. Not flight software.

d = √(2 R h + h²)

Geometric radio horizon

Fundamentals of Astrodynamics and Applications (David A. Vallado): Standard reference for two-body, Lambert, maneuvers, and J2. Equations implemented independently in SIDUS.
Space Mission Engineering: The New SMAD (Wertz, Everett, Puschell (eds.)): Mission engineering handbook: RF links, constellations, and ops framing.
Free-space attenuation (ITU-R P.525-5) (International Telecommunication Union Radiocommunication Sector (ITU-R)): ITU-R P.525-5 Eqs. (5)–(6): L_bf = 20 log10(4πd/λ); practical form uses d in km and f in MHz with a 32.4 dB constant. SIDUS uses 32.44 dB as an approximation of the same Friis relation.

Read /llms.txt or call https://sidus.tools/api/mcp. Open the interactive page for live SI inputs.