An Interstellar Precursor Probe Carrying a Pulsed Beacon for a Transit-Timing Measurement Over a Thousand Astronomical Units

This paper presents a space mission design, computed from stated assumptions and not measured, built to measure one quantity: the accumulated beacon timing deviation predicted by the transit relation at 1,000 astronomical units, for which the design case adopts 2.8 seconds of timing deviation. The instrument is a nuclear-electric precursor probe carrying a phase-stable pulsed optical beacon referenced to an onboard atomic clock, receding from the Sun at about 7 astronomical units per year, with its beacon pulses timed at Earth against the same clock standard used to characterise the beacon before launch. It operates from a hyperbolic solar-system escape trajectory reaching 1,000 astronomical units in about 140 years, with the precision timing observing plan concentrated in the first decades for 30 years. The one-day measurement uncertainty is 11 seconds; averaged over the full mission of 1.10e+04 days it falls to 0.105 seconds, giving a signal-to-noise ratio of 26.6 for the design case and a five-sigma detection limit of 0.525 seconds. The spacecraft has a dry mass of 1400 kilograms, a wet mass of 2900 kilograms including propellant, and a total electrical load of 1739 watts supplied by a radioisotope power system, since solar power is negligible over most of the trajectory. Every performance figure in this paper comes from the deposited computation; the design is simulated, not measured, and no hardware described here has been built or flown.