Preventing traffic accidents to the moon and back

Preventing traffic accidents to the moon and back

Purdue engineer aims to protect upcoming lunar missions from space debris

WEST LAFAYETTE, Ind. – With dozens of missions headed to space between Earth and the moon over the next 10 years, there’s bound to be traffic.

To prevent these spacecrafts from colliding with each other, Carolyn Frueh, an engineer at Purdue University, is researching how to monitor and track all human-made objects and predict the impact of their potential damage in this neighborhood of the Earth and the Moon, which is called the lunar region.

According to Frueh, an associate professor at Purdue University of Aeronautics and Astronautics, The fact is that space traffic solutions in the lunar region will be moving targets. The methods it develops aim to adapt to this area as traffic changes.

“There’s never really going to be a final answer to the space traffic management problem, because as the commercial sector grows and the capabilities and types of vehicles you have change, the problem will evolve as well,” she said. “So when we think about the technologies we want to use, we also have to make sure that what we have in mind can evolve over time.”

The economic potential of lunar space is estimated at more than $30 billion Over a 20-year period, taking into account government investment, demand for satellite communications services and other factors.

At 238,900 miles, the distance between Earth and the Moon is 18 times longer than the Great Wall of China. This may seem like enough space for spacecraft to move without colliding with each other, but the lunar zone is much less understood than near-Earth orbiters, which extend 24,000 miles beyond Earth’s surface to a “sweet spot” called the geosynchronous zone that enables satellites to keep up with the rotation of Earth. the earth. Near-Earth orbits are home to most satellites. Famous residents of this area include the Hubble Space Telescope and the International Space Station.

Even with more knowledge of near-Earth orbits, approximately 130 million pieces of space debris surround Earth. Much of this debris has broken off satellites that have exploded or collided with other objects. Debris has already reached the moon: a booster rocket crashed on the moon’s surface last March.

Fruit debris
This animation shows man-made space objects classified by the US Space Force. Red objects are in orbits close to Earth. Green objects are present in the lunar region. (Purdue University photo/Carolyn Frueh) Download image

To address the traffic coming into lunar space, Frueh pulled back from her research into how spacecraft turn into debris. It works with space agencies around the world to improve databases of space objects.

Doing the same for lunar space would be difficult without being able to see as much of that larger area as possible. For near-Earth orbits, telescopes in space, and to a limited extent telescopes on Earth, are among the satellites’ “traffic cameras.” But there are no telescopes in the lunar region because there is not much satellite activity that can be observed yet. Space telescopes will be better at tracking lunar satellites when more of them inhabit that region because ground-based telescopes can only detect an important satellite in cislunar space if the satellite, Moon, and Earth are in exactly the right alignment.

Frueh, in collaboration with her student Surabhi Bhadauria, is developing a method to create “sight maps” that show the best areas telescopes should use to find and track human-made objects in lunar space — including active satellites, dead satellites, and parts of satellites.

Compared with other methods, these maps better address a major challenge of observing the lunar region: space is always changing. The constantly moving positions of the Earth, Moon, and Sun affect what a telescope observes at any given moment and which orbits it can use to see spacecraft well. Current mapping methods must rerun a model of every state that would affect the telescope’s orbit and overall viewing geometry at every moment in time, which is computationally demanding.

Furwa map
“Vision maps” can show where to place telescopes in lunar space to improve detection and monitoring of man-made objects, helping to prevent satellite collisions. This view map takes into account all the limitations that might affect the orbits that telescopes must use to capture as much of the area as possible over a 30-day period. The map shows areas of lower visibility (pink) and higher visibility (yellow) independently of viewing direction. (Purdue University photo/Surabhi Bhadauria and Carolyn Frueh) Download image

Froeh’s view maps models that quickly and more comprehensively indicate where telescopes should go to observe as much of the lunar region as possible. Maps allow more of the area to be seen by averaging all the orbits a telescope might use rather than incorporating every change in orbit over time as other mapping methods do. Fruet’s method also does not require any additional computational time to show which satellites can be observed under what conditions from different locations.

“It’s like planning a road trip. We have now identified interesting points in the lunar region to observe with telescopes, but we have not yet found the way to put telescopes there,” Frueh said.

Even when telescopes are eventually placed in the lunar region, the satellites will likely appear as just white dots or lines in the images captured by these telescopes. But Frue is accustomed to collecting meaningful information from these shapes in telescope images of satellites in near-Earth orbits. They are working on a method that allows researchers and mission planners to distinguish which orbits a satellite uses to carry out its mission. This method will be designed to work under a range of scenarios – even when very little is known about the satellite.

Since traffic accidents are inevitable in lunar space, Frueh also thinks ahead about how to estimate the damage an accident could cause. In the event of a collision or explosion, where do all the pieces end up?

Her research suggests that pieces taken from a fragmented satellite can travel long distances in a relatively short period of time. She and her student Ariel Black recently presented a study at the 2023 AAS/AIAA Spaceflight Mechanics Meeting showing that these pieces could easily travel to Earth from the depths of lunar space.

Fragmentation of fur
In this graph, parts of a spacecraft exploded near the Moon would be expected to spread millions of miles away in just one month depending on the orbit in which the explosion occurred. The length of each colored line in this graph indicates how far fragments can spread in 30 days from a single explosion point along the Lyapunov orbit family around a location called the second Lagrange point “L2”. These orbits are being considered for lunar missions. In each orbit, the explosion point is assumed to be compatible with the Earth and the Moon. (Purdue University photo/Ariel Black and Carolyn Frueh) Download image

“We are laying the foundations that we believe will shape how space traffic management problems in the lunar region are addressed,” Frueh said.

About Purdue University

Purdue University is a public research institution of widespread distinction. Ranked among the top 10 public universities (Times Higher Education/Wall Street Journal and QS), with two colleges in the top four in the United States (US News & World Report), Purdue discovers and disseminates knowledge at a quality and scale second to none. nothing. More than 105,000 students study at Purdue University across modalities and locations, including 50,000 in-person students on the West Lafayette campus. In a commitment to affordability and accessibility, Purdue’s main campus has frozen tuition for 12 years in a row. See how Purdue never stops relentlessly pursuing the next giant leap, including its first comprehensive urban campus in Indianapolis, Mitchell E. College. Daniels Jr. New Business, Inc., Purdue Innovates, at https://stories.purdue. Edo.

Writer/Media: Kayla Albert, 765-494-2432,

source: Caroline Frueh,


Optical observation regions in lunar space using the geometry of the two-circle bound four-body problem

The paper is available online at the Advanced Optical and Satellite Observation Technologies Conference website in Maui.

Investigation of fragmentation events in the lunar domain

This study was presented at the 2023 AAS/AIAA Aerospace Mechanics Meeting. Please contact Kayla Albert at or 765-494-2432 to obtain a copy of the paper.

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