A novel method for characterising near-Earth asteroids with LISA

Near-Earth asteroids (NEAs) follow heliocentric trajectories similar to Earth's, yet despite their proximity this population remains poorly characterised, particularly with respect to physical properties such as mass. We present a novel approach to  characterising this population using the Laser Interferometer Space Antenna (LISA), the European Space Agency's upcoming gravitational-wave observatory.

 

LISA's measurement principle relies on high-precision interferometry to detect picometer-level variations induced by passing gravitational waves in the inter-spacecraft distances. This extreme sensitivity also renders LISA susceptible to more conventional gravitational perturbations, including the pull exerted by asteroids passing close to one of its spacecraft. While such signatures could be regarded as a noise source that degrades the gravitational-wave signal, they equivalently offer an opportunity to detect and characterize the perturbing bodies themselves.

 

We present the first systematic assessment of the signals produced by asteroid encounters with LISA and the resulting parameter resolution. Our results demonstrate that LISA can detect and characterize NEAs, provided the object passes sufficiently close to a spacecraft. The mass accuracies achievable from a single encounter are unmatched by any current observational technique, except dedicated probes that orbit the asteroid for an extended period. Furthermore, the method is largely insensitive to the observational biases that affect ground-based surveys, thereby improving access to the intrinsic properties of the population. The localization accuracies obtained within our framework further translate into a preliminary orbit determination and a constrained sky region, enabling targeted follow-up observations by other facilities.