A Formation-Flying Gravitational Gradiometer Mapping the Gradient Field for a Fifth-Coordinate Signature

This paper presents a space mission design, computed from stated assumptions and not measured, built to measure one quantity: the gravity-gradient anomaly attributed to a fifth-coordinate coupling at orbital altitude, for which the design case adopts 85 milli-Eotvos. The instrument is four satellites in a tetrahedral formation, each carrying a three-axis electrostatic gradiometer, with inter-satellite laser metrology measuring the formation geometry continuously so that gradients can be formed both inside each instrument and between spacecraft separated by tens of kilometres. It operates from a 500-kilometre polar orbit, the tetrahedron maintained by differential drag and low-thrust control for 2.5 years. The one-day measurement uncertainty is 420 milli-Eotvos; averaged over the full mission of 913 days it falls to 13.9 milli-Eotvos, giving a signal-to-noise ratio of 6.12 for the design case and a five-sigma detection limit of 69.5 milli-Eotvos. The spacecraft has a dry mass of 660 kilograms, a wet mass of 770 kilograms including propellant, and a total electrical load of 1032 watts supplied by a solar array of 2.97 square metres at the operating distance. 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.