An automated occultation network for gravitational mapping of the trans-neptunian solar system

Abstract

We explore the potential of an array of O(100) small fixed telescopes, aligned along a meridian and automated to measure millions of occultations of Gaia stars by minor planets, to constrain gravitational signatures from a "Planet X" mass in the outer solar system. The accuracy of center-of-mass tracking for the occulters is limited by photon noise, uncertainties in asteroid shapes, and Gaia's astrometry of the occulted stars. Using both parametric calculations and survey simulations, we assess the total information obtainable from occultation measurements of main-belt asteroids (MBAs), Jovian Trojans and trans-Neptunian objects (TNOs). We find that MBAs are the optimal target population due to their higher occultation rates and abundance of objects above LSST detection thresholds. A 10-year survey of occultations by MBAs and Trojans using an array of 200 40 cm telescopes at 5 km separation would achieve $5σ$ sensitivity to the gravitational tidal field of a $5M_\oplus$ Planet X at 800 AU for $>90\%$ of potential sky locations. This configuration corresponds to an initial cost of $\approx $15 million. While the occultation survey's sensitivity to tidal forces improves rapidly with increasing number of telescopes, sensitivity to a Planet X becomes limited by degeneracy with the uncertain masses of large moonless TNOs. The 200-telescope survey would additionally detect $\approx $1800 TNO occultations, providing detailed shape, size, and albedo information. The survey would also measure the Yarkovski effect on many individual MBAs, measure the masses of many asteroids involved in mutual gravitational deflections, and enable better searches for primordial black holes and departures from General Relativity.