Covering an Asteroid With Balls Could Characterize Its Interior

Exploring asteroids and other small bodies throughout the solar system has gotten increasingly popular, as their small gravity wells make them ideal candidates for resource extraction, enabling the expansion of life into the solar system. However, the technical challenges facing a mission to explore one are fraught – since they’re so small and variable, understanding how to land on one is even more so. A team from the University of Trieste in Italy has proposed a mission idea that could help solve that problem by using an ability most humans have but never think about.

Have you ever closed your eyes and tried to touch your fingers to one another? If you haven’t, try it now, and you’ll likely find that you can easily. It’s possible to do even without guidance from your five normal senses. That is what is known as proprioception – our hidden “sixth” sense. It is that ability to know where objects are in relation to one another – in this case, where your hands are in relation to one another without any other sensory indication.

Taking that basic idea and extrapolating it to a mission to an asteroid, the basic concept of the mission involves a lander with what seems like a dome with a ton of little balls on it, each facing a slightly different direction. Those balls are then ejected from the dome with varying degrees of force and land on various parts of the asteroid or comet.

They then create what is known in networking as a “mesh” system by connecting through one another and back to the main lander, which has a higher power output and larger communications array. They also contain a series of sensors, such as a camera, a magnetometer, and, importantly, an inertial measurement unit, or IMU.

IMUs are commonly used in cell phones to tell which direction the phone is oriented—that’s why your phone’s screen will flip upside down if you hold it upside down. They can also measure acceleration, which is why many are used in modern rocketry. They’re tiny and not very power-hungry, allowing them to fit into the ball format used for this mission.

Measurements from each of the remote sensors IMUs can be combined with data about the strength of the force that propelled them to their final resting place and fed into an algorithm, which will then help the base station determine the location of each sensor unit. That then allows measurements from the other sensors, such as the magnetometers and cameras, to paint a picture of the body’s external and internal structure – since magnetic fields, surface objects, and even gravity can vary significantly on small celestial bodies.

As a proof of concept for this mission design, the team ran a simulation of a mission to comet 67P/Churyumov-Gerasimenko, most widely known for being visited by Rosetta, the ESA mission whose lander, Philae, experienced some of the trouble that is so common on these missions. They found that, depending on the number of projectile sensors, the mission could cover even weird morphologies like 67P/Churyumov-Gerasimenko’s two-lobed form. 

No agency has yet taken up the mission, but as electronics and sensors get smaller and more power efficient and more small bodies become potential resource sources, there might be a place for testing these spaced-out sensors. We’ll have to wait and see—just not with proprioception alone.

Learn More:
Cottiga et al. – Proprioceptive swarms for celestial body exploration
UT – Could You Find What A Lunar Crater Is Made Of By Shooting It?
UT – Swarming Satellites Could Autonomously Characterize an Asteroid
UT – Swarms of Orbiting Sensors Could Map An Asteroid’s Surface

Lead Image:
Depiction of the mission’s lander and deployable sensor system.
Credit – Cottiga et al.

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