By Andy Tomaswick
March 6, 2025
The Gaia hypothesis theorizes that all of Earth’s systems are tied together, making one large, living organism. While there’s still some disagreement about whether or not that hypothesis is true, it is undeniable that many of Earth’s systems are intertwined and that changes in one can affect another. As our technology advances, we are becoming more and more capable of detecting changes in those systems and how those changes affect other systems as well. A new proposal from a robotics expert at NASA’s Jet Propulsion Laboratory (JPL) takes that exploration one step further by trying to develop a system that takes the “pulse” of a planet.
Planetary pULSe-tAkeR (PULSAR) was one of the most recent rounds of Institute of Advanced Concepts (NIAC) grants, handed out in January. The grant was awarded to Maro Quadrelli, group supervisor of the robotics modeling and simulation group at JPL. So, the obvious question is, why is a roboticist trying to develop a “pulse” sensor for a planet?
It has to do with positioning – or, more precisely, the exact positioning of a spacecraft compared to a ground station. As the exact location of spacecraft can be more precisely locked down, connections to ground stations become more concrete. So, as signals move through the medium connecting those two points, any disruption of the signals themselves would be due to the disturbances in the medium rather than perturbations of the location of either the spacecraft or the ground station.
NASA Goddard video on the ionosphere, one of the spheres of influence Dr. Quadrelli hopes to monitor.
Credit – NASA Goddard YouTube Channel
In plain English, that means that Dr. Quadrelli and his team will try to understand what is happening in the different layers of the Earth by monitoring several detector “baselines,” as they are called in the press release announcing the project. One famous example of an equivalent system is the interferometer that first detected gravitational waves.
The Laser Interferometer Gravitational Observatory (LIGO) consists of two 4 km long “arms” with a laser on one end and a detector on the other. That’s a gross oversimplification, but the detector can pick up that change when a gravitational wave disturbs the space around the laser. PULSAR would use a similar concept, but instead of lasers in vacuum tunnels to detect gravitational waves, it would use those same lasers between a geostationary satellite and a ground station to detect perturbations in a planet’s atmosphere.
Plenty of studies show that different layers of the atmosphere are coupled physically to one another and even to a planetary interior. For example, the ionosphere responds to space weather, as well as seismic events in the interior of a planet. PULSAR could shine a laser directly through different parts of the ionosphere from different geostationary orbiting satellites, and by analyzing the disruptions at each part of the ionosphere, it could provide an idea of what’s going on in both the atmosphere and under the surface of the planet. In essence, it would take the planet’s “pulse.”
Another YouTube video discussion about ICON, a mission that also studied the Ionosphere until it ended in July 2024.
Credit – NASA APPEL YouTube Channel
One of the most critical aspects of this system would be the precise control of the position of the geostationary satellites. They would be upwards of 20,000km away from their receiving station (compared to 4km for LIGO), so their signals could experience plenty of interference on their journey. Teasing out what that interference represents regarding physical processes could be a challenge.
But that is precisely what NIAC is for. The press release for the project doesn’t provide many details about what the Phase I grant will focus on in terms of simulations, modeling, or hardware implementation, but addressing the challenges facing such a project is certainly within the realm of physical possibility. Maybe someday in the future, we’ll have a system of robotic pulse takers measuring the health of our planet, whether it’s a fully living organism or not.
Learn More:
NASA – PULSAR: Planetary pULSe-tAkeR
UT – Millions of Phones Could Map the Earth’s Ionosphere
UT – Explore Earth’s Ionosphere with Google Earth
UT – A Gamma-ray Burst Disturbed the Earth’s Ionosphere