RAIT: A Redundant Array of Inexpensive Telescopes for Distributed Optical Aperture Synthesis

RAIT (Redundant Array of Inexpensive Telescopes) is a staged architecture for low-cost distributed optical aperture synthesis, transposing the RAID storage framework (Patterson, Gibson & Katz, 1988) from data storage to astronomical instrumentation: a single monolithic optic is replaced by a scalable array of commercial off-the-shelf (COTS) small-aperture telescopes, whose performance is recovered at the synchronization, calibration, and reconstruction layers. This preprint is a citable priority record of the architecture, roadmap, cost-escalation model, and validation protocol — not a report of completed experimental results. Three-phase roadmap (with honest confidence levels): Phase 0 — incoherent multi-aperture lucky imaging (~17 k€, 12 months). Target: ~2× improvement in effective (seeing- and sampling-limited) resolution over a single station, bounded by the single-aperture diffraction limit (~2.4 km/pixel on the Moon for a 130 mm aperture). Confidence: high. Phase 1 — short-baseline coherent reconstruction (~+28 k€, ~45 k€ cumulative). Theoretical 10× scale (~240 m/pixel) set by the 1.3 m baseline (λ/B); requires a real Fizeau/beam-combination and piston-metrology subsystem, so it is an experiment to be falsified. Confidence: medium. Phase 2 — long-baseline intensity interferometry (HBT) (~1.6 M€, 5+ years). A feasibility path toward sub-metric-class angular scales (~80 cm/pixel) over a ~400 m baseline with SPAD detectors and White Rabbit timing. Confidence: speculative (HBT measures |V|2, not phase). What is claimed: the RAIT architecture and its RAID-level mapping; the three-phase, risk-separated roadmap; the cost-escalation model and its two physical thresholds; and the validation protocol (SNR-√N scaling, multi-aperture lucky-frame statistics, inter-tube atmospheric decorrelation, drizzle sampling recovery, empirical MTF, and forward-modelled comparison against LRO NAC). What is not claimed: any completed experimental result; any super-resolution beyond the single-aperture diffraction limit by incoherent combination (physically excluded); or a demonstrated feasibility of coherent recombination (Phase 1) or of lunar HBT imaging (Phase 2) — both are stated targets, conditional on dedicated experiments and photon-budget/phase-retrieval studies. The programme is milestone-driven: each phase is a verifiable step, and funding of the next phase is conditional on the minimum metrics actually measured in the previous one.