Detection Of A Space Capsule Entering Earth's Atmosphere Using Distributed Acoustic Sensing (DAS)

On December 3, 2018, NASA’s OSIRIS-REx mission made a significant milestone by meeting with the Near-Earth Asteroid 101955 Bennu. Over the next couple of years, it collected samples of rocks and dust from the surface of the asteroid. Fast forward to September 24, 2023, when the mission’s Sample Return Capsule (SRC) re-entered Earth’s atmosphere. NASA scientists successfully retrieved the capsule, and the analysis of its contents is already shedding light on the early conditions of our Solar System.

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Understanding the OSIRIS-REx Mission

OSIRIS-REx stands for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer. This ambitious NASA mission aimed to explore Bennu to understand better the materials that formed our planetary system. Asteroids like Bennu are seen as time capsules, preserving information from when the Solar System was just forming.

The sample collection phase involved the spacecraft analyzing the asteroid’s surface and gathering materials. This unique approach allows scientists to study the asteroid’s composition without needing an extensive amount of on-site exploration.

Project Highlights and Sample Retrieval

On its return journey, the capsule traveled at extremely high speeds, known as hypersonic speeds, when re-entering the atmosphere. Researchers had prepared thoroughly for this critical moment, having already tracked the SRC’s trajectory. This gave scientists a rare chance to capture the sonic boom created by the SRC during its re-entry.

A recent study highlighted this event’s significance, showcasing how new technology was used to collect geophysical data during the re-entry. The study, published in the journal Seismological Research Letters, detailed how this remarkable undertaking was led by Dr. Carly M. Donahue and her team from multiple institutions.

The Technology Used

The team deployed Distributed Acoustic Sensing (DAS) technology. This involved using specialized fiber-optic cables stretched along the ground to monitor sound waves. By using DAS, researchers could observe the sonic boom’s effects as it traveled across the ground. Unlike traditional methods which only capture data from one spot, DAS allows recordings from various locations, providing a clearer picture of how the sonic boom interacted with the landscape.

Dr. Donahue explained the advantages of using optical fibers to measure such phenomena, noting that this was one of the first times researchers had the chance to apply DAS to record a spacecraft’s re-entry.

A Unique Opportunity for Observation

Knowing the SRC’s specific trajectory allowed the team to position their sensors strategically. They set up two DAS interrogators and more than 12 kilometers (around 7.45 miles) of fiber-optic cables in the Nevada desert. They worked alongside other scientists deploying different sensors like seismic and infrasound systems.

After successfully installing the equipment, the researchers gathered invaluable data on the different sonic waves produced during the capsule’s re-entry. The results showed how the sound waves transformed when they struck various terrains.

Relevance and Impact

Understanding the dynamics of the sonic boom can help scientists better predict and analyze the potential impacts of meteoroids or asteroids that may come close to Earth. The ability to track these phenomena accurately could be crucial for future planetary defense initiatives.

Dr. Donahue explained that having a dense array of sensors could improve how meteor trajectories are characterized. This could lead to better assessments of potential impacts, especially when irregularities in the terrain come into play.

The Next Phase: OSIRIS-APEX

After OSIRIS-REx completed its primary mission, NASA prepared for its next phase. The spacecraft has been renamed OSIRIS-APEX (Apophis Explorer) and is set to rendezvous with another Near-Earth Asteroid, 99942 Apophis, in 2029. This exciting continuation underscores the importance of these missions in expanding our understanding of celestial bodies and their potential risks.

Conclusion

The successful sample collection from Bennu and the innovative methods employed during its capsule re-entry showcase the advancements in space exploration technology. The OSIRIS-REx mission not only brings us closer to understanding the early Solar System but also enhances our preparedness for addressing future cosmic threats. With ongoing analysis of the samples and upcoming missions, we eagerly anticipate further discoveries about our universe.