OSU researchers monitor hypersonic shockwaves as part of NASA OSIRIS-REx mission

Monday, September 25, 2023

Media Contact: Mack Burke | Associate Director of Media Relations | 405-744-5540 | mack.burke_iv@okstate.edu

Probe returns to Earth with samples from Bennu Asteroid 

As NASA’s OSIRIS-REx spacecraft completed its 1.2-billion-mile journey home and sent its sample return capsule back to Earth, a team of Oklahoma State University researchers was waiting and listening. 

The group, led by Drs. Jamey Jacob and Brian Elbing, is studying and classifying different sources of infrasound — which are sounds below the threshold for human hearing levels at 20 hertz or less — and the OSIRIS-REx return capsule provides a unique opportunity. 

To listen in on the reentry of the probe, which was carrying samples from the Bennu Asteroid, the team launched high-altitude balloons carrying specialized microphones near the Utah and Nevada border and deployed ground sensors near the landing site. 

“We're doing something that's never been done before. No one's ever tried to listen to these hypersonic shockwaves from these balloons,” said Zach Yap, research and development engineer at OSU’s Oklahoma Aerospace Institute for Research and Education (OAIRE). “Being part of a team that gets to do that — to try and hopefully succeed at getting these signals and further the knowledge of what we know about these kinds of sound waves and this way of measuring them is a real opportunity.”

And the team did succeed in its mission. 

“Overall, things went about as well as we could have hoped,” Elbing said. “Zach and Emalee [Hough] were able to successfully help launch balloons ahead of the entry, and our ground team got some really nice data. 

“We showed our data to Elizabeth Silber, a Sandia National Labs researcher and project lead for the ground efforts, and she said, ‘This is a beautiful, clean signal, like a textbook case.’” 

In addition, Elbing’s students are teaming up with infrasound researchers from the University of Hawaii.  

“They helped each other with identifying places to deploy sensors,” Elbing said. “This has created some unique opportunities for additional collaboration with them as we analyze our data.” 

OSU’s role in the OSIRIS-REx mission was part of multiple projects being led by NASA’s Jet Propulsion Laboratory and Sandia National Laboratory. 

“Organizations such as JPL and Sandia National Lab entrusting OSU as critical partners in the mission demonstrates the preeminence of our capabilities and personnel,” said Jacob, who serves as executive director of OAIRE. “Providing unique opportunities for students while simultaneously serving national interests and solving global challenges is part of our land-grant mission, and we look forward to helping solve the next grand challenge.” 

The use of infrasound-recording balloons is part of a project being led by Dr. Siddharth Krishnamoorthy at JPL.  

Being able to measure these infrasound sources from balloons will hopefully help researchers not only better understand our planet but be able to study other planets, like Venus. 

However, opportunities to listen to a known object reentering Earth’s atmosphere are rare.  

“This is only the fifth object re-entering from interplanetary space since the end of the Apollo mission,” said Elbing, an associate professor in mechanical and aerospace engineering, “So, it's a unique opportunity because we can measure meteors, but you never know when they are coming, so you can't put sensors where you'd like them to be.” 

The ground sensors are part of a project being led by Elizabeth Silber and Danny Bowman at Sandia National Labs. They were interested in using the OSIRIS-REx re-entry as an “artificial meteor” to better understand how we can use sound to determine the origin, speed, mass and shape of meteors, Elbing said. 

Characterization of these infrasounds is incredibly difficult, Elbing said.  

“That is where this research comes in,” Jacob said. “Since the reentry probe is a known quantity, namely mass and reentry trajectory, it gives us an opportunity to calibrate the systems and see how well they work.”  

The hardest part about researching infrasound is that it is a surprisingly noisy environment to work in, Elbing said.  

“Nobody is policing it because there's nobody that complains about those sounds,” he said. “So, it's actually quite noisy, and they carry over long distances.” 

Infrasound can come from many things such as tornadoes, earthquakes, volcanoes, air turbulence and even the heaving of the ocean, which one can hear everywhere on Earth at around 0.2 hertz — often called the sound of the sea, Elbing said. 

As the team characterizes more sounds, they can sort through the noise and better understand what their sensors are picking up, which means they can hear tornadoes before they become dangerous, (a previous research project of Elbing’s); listen for things entering the atmosphere, from meteors to intercontinental ballistic missiles; and better understand what is happening around the world, all by just listening. 

When the partnership originally started, NASA was looking for someone to help launch high-altitude balloons, or heliotropes, in Oklahoma.  

“Originally, they were going to come here and launch the balloons themselves,” Elbing said. 

However, after seeing the team’s expertise in this area, NASA decided that OSU would be responsible for all aspects of the launches. 

“I think we have had other people on site with us twice,” Elbing said. “You can see the confidence in the student researchers and the team when NASA show up and says, ‘You guys got it.’” 

Emalee Hough, a research and development engineer at OAIRE has been actively working on heliotrope research with NASA JPL and Sandia National Labs for the last two years and was part of the team responsible for launching the balloons for the reentry. 

“To be involved with the first-of-its-kind research efforts to detect the reentry of the asteroid sample is amazing in itself,” Hough said. “Being asked to help because of my experience in their previous campaigns is super exciting, and I am honored they wanted me to help out.” 

This opportunity also provides a steppingstone for further research in space. 

“This builds upon years of collaboration between Dr. Elbing and myself and both NASA JPL’s and Sandia National Laboratory,” Jacob said. “The long-term goal is to develop and demonstrate a platform for flight on Venus to search for the Venusian quakes.” 

The mission to Venus would be the first NASA mission of its kind to explore the geology of Venus and map out tremors, Jacob said.  

The longest surviving man-made object to land on Venus’ surface only survived 120 minutes, which means balloons may be the answer. 

“The Venusian atmosphere is pretty similar to our atmosphere at 60,000 feet," Yap said.  

The atmosphere is also denser than the Earth's atmosphere, meaning sound waves will propagate much better in the Venusian atmosphere than they will on Earth.  

“So, if we can hear something on Earth, you can definitely hear its equivalent on Venus,” Yap said. 

The project will use a balloon-borne infrasonic sensor to detect low-amplitude pressure waves from the ground as it shakes, much like one would get from a subwoofer, Jacob said. And, since Venus formed in ways like Earth, listening for earthquakes and tremors on its surface could provide valuable insight into Earth’s formation.   

From classifying sounds on Earth, to studying Venus, the impact of this research is far sweeping.  

“It ultimately improves national security and it's another example that there is a growing market and opportunities for the use of these high-altitude balloons,” Elbing said. “We are positioned as a leader in this area.”