Laser Interferometer Space Antenna could double as an asteroid scale

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

One of the hardest things to calculate for an asteroid is its mass—but it is such a critical feature. It determines how much of an impact it would have if it hits something, or how many resources are potentially available on it. But to accurately measure it, we typically use optical sensing and a guesstimate of its density based on its spectral profile.

A new paper suggests a completely novel way to use the Laser Interferometer Space Antenna (LISA) flagship mission to potentially provide highly accurate mass calculations for nearby asteroids without any change in hardware. The paper is published in the journal Astronomy & Astrophysics.

Obviously, the spectral density guess isn't ideal—we can estimate the mass of an asteroid with up to 10% uncertainty for less than 35% of near-Earth asteroids.

Most of those highly accurate measurements are actually done on binary asteroid systems, where we can use complex orbital dynamics to calculate how big each part of the pair is—or, in some cases, we get lucky and the asteroid is gravitationally bound to another object like a planet for a brief period of time. But the vast majority of our estimates of asteroid masses are just that—estimates.

The most accurate way to calculate an asteroid's mass is to send a probe to it. But that is prohibitively expensive for all 41,000 known near-Earth asteroids (NEAs). So why not use a multibillion-dollar mission we're already building to help?

LISA, which is planned to launch in July 2035, is designed as a gravitational wave detector. It will consist of three separate spacecraft flying in triangular formation, and will mainly be looking for the ripples in the fabric of spacetime caused by cataclysmic events like merging black holes. But its exquisitely sensitive instruments would also make it very susceptible to regular Newtonian dynamics.

Inside each of LISA's spacecraft, there is a free-falling test mass, and the instrumentation to measure picometer-level changes to those masses. If an NEA happens to get close enough to one of them—specifically inside what is called the Minimum Orbital Intersection Distance (MOID)—the asteroid's pull will tug on those masses, inducing a tiny velocity change that LISA's instrumentation will then be able to measure.

Originally, the designers of the mission thought this would be a bug rather than a feature—they saw any gravitational pull not caused by the waves th