Causal Dispersive Plasma-Inversion Point-Ahead Tracking and Doubly-Stochastic Cox–Bessel Demodulation for Interplanetary Optical–RF Satellite Communications

Abstract

Near Superior Solar Conjunction (\alpha_SEP <= 5 deg), coronal electron wedges (\nabla_\perp STEC), temporal plasma drift (dSTEC/dt), and the 1517 s Round-Trip Light Time (RTLT at D = 1.52 AU) degrade Earth-referenced point-ahead tracking, while daytime scintillation and residual slot drift induce doubly-stochastic Cox photon bunching that saturates linear Poisson log-likelihood ratios (LLRs). This letter presents a causal two-node optical-RF transceiver requiring no ground laser beacon. Onboard the spacecraft, Deep Space Network (DSN) X/Ka-band uplinks are inverted via Lorentz-Appleton-Hartree group-phase duality, Gauss-Markov Best Linear Unbiased Estimation (BLUE), and radial Abel advection to compensate coronal orbit-determination bias. At the Earth receiver, a soft-posterior timing error detector (TED) with 1D Kalman tracking and a 3-slot Negative-Binomial co-spill demodulator (Theorem 1) reduce pointing error from 3.409 to 0.763 urad, slot drift by 11.4x, and coded Frame Error Rate (FER) by 9.3x (64.2x under 960-bit SCPPM), sustaining 36.97 Mbps at Mars conjunction (D = 1.52 AU, \alpha_SEP = 2.5 deg).