Radio Occultation: Sounding a Planet's Atmosphere

Every time a planetary probe passes behind its target body as seen from Earth, its radio downlink becomes a free atmospheric instrument. This simulator flies a probe through a real occultation geometry — planet, exponential atmosphere, and a fixed Earth direction — and computes the actual refractive bending angle and Doppler residual the ray would produce at every impact parameter, exactly as the Deep Space Network measures it. A live Abel inversion of the recorded bending angles reconstructs the vertical refractivity profile in real time, so you can watch the atmosphere being "measured" from a radio shadow alone, the same technique that first revealed the thin CO₂ atmosphere of Mars in 1965.