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IARPA Searches for Space Junk’s Trashed Signals

Novel signal detection methods may revolutionize space debris tracking.

Currently, the U.S. Space Force’s Space Fence is considered the world’s most advanced system for tracking objects in space. Although the system is capable of tracking objects as small as a marble, even smaller objects can cause catastrophic damage and cannot currently be tracked persistently. Credit Lockheed Martin image

The Intelligence Advanced Research Projects Agency’s (IARPA’s) goals under the Space Debris Identification and Tracking (SINTRA) program could be compared to the proverbial search for a needle in a haystack—if scientists didn’t know needles exist, what purpose they serve or whether they lie in haystacks.

IARPA is on a four-year mission to discover new ways of detecting tiny objects in space. Too small to be tracked with current technologies, those objects can cause catastrophic damage to space vessels, including the intelligence community’s mission-critical satellites. Space debris poses a risk to all space missions. With an average low-Earth-orbit (LEO) impact velocity of 22,500 mph, even the smallest of debris can cause significant damage, according to the SINTRA webpage.

The webpage explains that currently, more than 100 million objects greater than 1 millimeter orbit the Earth. However, less than 1% of the debris that can cause mission-ending damage is currently tracked. Debris larger than 10 centimeters can be detected and tracked, but current capabilities cannot track smaller objects.

The U.S. Space Force is building a new and improved “Space Fence,” which contractor Lockheed Martin describes as “the world’s most advanced radar,” that “provides uncued detection, tracking and accurate measurement” of space objects, including satellites and orbital debris, primarily in low-Earth orbit. The new radar permits the detection of much smaller microsatellites and debris than previous systems and “significantly improves the timeliness with which operators can detect space events,” the company says.

Although the Space Fence can track items as small as a marble, even smaller items can pose a threat, Alexis Truitt, IARPA’s SINTRA program manager, explained in an interview. “When they collide, it’s more like an explosion. Even a piece of 1-millimeter small debris can create an impact crater 10 times its size. A 1-centimeter piece of debris could create the equivalent amount of energy as a hand grenade explosion. And we just really can’t track things that small,” Truitt said.

While tracking methods continue to improve, especially with the new Space Fence, current capabilities offer a narrow field of view and can be adversely affected by weather and other conditions. “Even if you can detect something that’s a millimeter in size, with that small field of view, you’re not going to be able to track it persistently. You might get a blip across the radar, but you don’t know where it went after that,” Truitt offered.

IARPA’s approach with the SINTRA program is to search through signals data currently being ignored. “We are looking to revolutionize how we look at the data. There could be signatures in existing data that we’re not really picking up and there needs to be more research and development to understand those signatures,” Truitt said. “There could be signals in the data that we currently throw out as trash.”

She cited radar data to illustrate the point. “For example, if we’re looking at radar data, we’re expecting a return that could tell us the size of the object that we’re looking at. Let’s say we’re looking at a piece of debris 10 centimeters in size. If we’re off a little bit, if there’s some noise surrounding it, we may historically have thrown that noise out. We could get a more clear understanding of the radar return for that degree. But you know, I believe that there could be additional signatures.”

Those additional signatures could include “some electric fields, some plasma density, some other radiation that could be happening, that is caused by debris because it has a charged surface,” Truitt suggested. “It could be creating effects in space that could be reflected in that noise. And perhaps we just don’t understand what that signature looks like. And so right now, we’re just throwing it out.”

Astronomers, for instance, ignore signals from space debris. “If you think about the astronomy community as well, they’re looking at astronomical objects, and debris is polluting their space, and they’re throwing out debris in their collections. So, when I think about looking at data in a new way and looking at what we call signal to noise, there might be something small, very faint, but maybe it really represents a physical phenomenon,” she theorized.

Truitt drove home the point at the interview’s end. “With regard to the signatures and existing data, it could be like a very faint signal. One of the points I’d like to get across is that perhaps these signals can be created, even if you can’t see that piece of debris in the traditional radar return. This could be a means to detect something that doesn’t have a strong radar return, but maybe it still creates these faint effects around it. That’s how we plan to drive detection of smaller and smaller objects that aren’t traditionally detected with existing radar and optical systems.”

Truitt’s team will conduct the four-year SINTRA program in two phases, each lasting two years. The program will involve three milestone assessments each year with a testing and evaluation team of federally funded research and development centers, including the Massachusetts Institute of Technology (MIT) Lincoln Laboratory, the U.S. Naval Research Laboratory, Los Alamos National Laboratory and Johns Hopkins University Applied Physics Laboratory. “For every 75 cents we spend on performers, we’ll spend 25 cents on testing and evaluation,” Truitt reported.

The amount of space debris is growing at a rapid rate, but much of it is too small to be tracked with conventional technologies while still being large enough to cause major damage to satellites and other space vessels. The Intelligence Advanced Research Projects Agency aims to revolutionize space debris tracking with new approaches. Credit: NASA image

The first phase officially started June 29. The goal for the first phase is to establish a proof of concept for detection, tracking and characterization. The initial focus will be on space objects already cataloged to strengthen confidence in new techniques.

“At the beginning stages, we are trying to really advance the state of the art. We’re looking for things that are high risk, high payoff, low technical readiness levels at the beginning,” Truitt explained. “But at the end of the program, we hope to provide a demonstration and documentation from our rigorous testing and evaluation to hand it off to a transition partner who will test it in their operational environment. It’ll be at a technology level where it hasn’t been necessarily tested in an operational environment, but we’ll have all the information to allow that to occur and to support that.”

IARPA will not select a single winner at the end of the program. Each of the four teams, which are led by Advanced Space LLC, BlueHalo, SRI International and West Virginia University Research Corporation, are pursuing different solutions. If all goes well, all four solutions could ultimately be available to the intelligence agencies.

Truitt indicated multiple approaches might be needed. “We’re looking to supplement the current state of the art with novel innovative techniques and a holistic view to look at maybe a multi-phenomenology solution. We could look at a combination of different sensor types—optical data, radar data, plasma data, other types of data sources from ground and from space,” she said. “If they’re able to follow the same set of debris, and have different observables, perhaps the combination of those observables could help us further characterize that piece of debris.”

A multi-phenomenological approach could include the amount of drag and other characteristics. “It could tell us it’s a piece of aluminum or a piece of Styrofoam based on the drag, the spectral composition, the receptivity, the surface charge, things like that. Maybe we have a piece of information from each sensor type and the combination of those sensor types could yield more information,” Truitt elaborated.

Each team will contribute to a SINTRA database that will be available to the intelligence community at the program’s end. “At each milestone assessment, each performer is required to submit the data they use as part of their development ... with the understanding that it will be visible to other performers. We wanted to level the playing field, so that one performer couldn’t outperform another simply because of access to data,” Truitt said.

IARPA recently published the first iteration of the database for the performers. It includes data from the testing and evaluation team. “Some of that data includes some of the ground-based radar that MIT Lincoln Laboratory contributes to the Space Surveillance Network. We’re providing samples of data to the performers to help their development. We’re also reserving some for independent testing and evaluation,” Truitt reported.

Ultimately, intelligence agencies could use the SINTRA database for real-world operations. “We don’t have an operational mission, so we hope to hand this off as a comprehensive set of different types of data with a standardized set of metadata that our end users could potentially, if they like, integrate into their own operational database,” Truitt stated.

It also might be used as a gold standard to test new techniques or for students to test new algorithms, she added.