Scientists conduct first test of a cosmic ray radio navigation system – Ars Technica

Zoom in / Cosmic rays that rain down on Earth’s atmosphere are the basis for a new wireless alternative system for GPS navigation.

2015 Hiroyuki KM Tanaka

GPS is now a mainstay of everyday life, helping us with positioning, navigation, tracking, mapping and timing across a wide range of applications. But it does have some drawbacks, most notably the inability to pass through buildings, rocks, or water. That’s why Japanese researchers have developed an alternative radio navigation system that relies on cosmic rays, or muons, rather than radio waves, according to new leaf Published in the journal iScience. The team conducted its first successful test, and search and rescue teams could one day use the system to, for example, guide robots underwater, or help autonomous vehicles navigate underground.

“Cosmic ray muons fall evenly across the Earth and always travel at the same speed no matter what material they pass through, penetrating even kilometers of rock,” said co-author Hiroyuki Tanaka to Muographix at the University of Tokyo, Japan. “Now, using muons, we’ve developed a new type of GPS, which we’ve called muPS, that works underground, indoors, and underwater.”

As mentioned earlier, there is a long history of using muons in Image of archaeological structuresThe process is made easier because cosmic rays provide a steady supply of these particles. Muon is also used Chase illegally moved Nuclear material at border crossings and monitoring of active volcanoes, hoping to detect when they might erupt. In 2008, scientists at the University of Texas, Austin, workedAncient muon detectors reused to search for possible hidden Mayan ruins in Belize. Physicists at Los Alamos National Laboratory have developed portable versions of muon imaging systems to unlock the secrets of building the dome (Il Duomo) atop Cathedral of Saint Mary of Venus In Florence, Italy, it was designed by Filippo Brunelleschi in the early 15th century.

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In 2016, scientists used muon imaging Pick up the signals It points to a passage hidden behind the famous chevron blocks on the north face of the The Great Pyramid of Giza in Egypt. The following year, the same team discovered a mysterious void in another area of ​​the pyramid, believing it could be a hidden chamber, which was later painted using two different muon imaging Methods. And just last month, scientists used muon imaging to discover a chamber formerly hidden in the ruins of the ancient Neapolis necropolis, about 10 meters (about 33 feet) below present-day Naples, Italy.

Robots and autonomous vehicles could one day be common in homes, hospitals, factories and mining operations, as well as in search and rescue missions, but there is not yet a universal means of navigation and positioning, says Tanaka. et al. As noted, GPS cannot penetrate underground or underwater. RFID technologies can achieve good accuracy with small batteries, but it requires a control center with servers, printers, monitors, etc. A dead account suffers from chronic estimation errors with no external cue to provide a correction. Acoustic methods, laser scanning, and lidar also have drawbacks. So Tanaka and colleagues turned to muons when developing their alternative system.

Infographic showing the pros and cons of alternative technologies for indoor and underground spaces
Zoom in / Infographic showing the pros and cons of alternative technologies for indoor and underground spaces

2023 Hiroyuki as Tanaka

Muon imaging methods usually involve gas-filled chambers. As muons zip through the gas, they collide with the gas molecules and emit a flash of light (a flash), which is recorded by the detector, allowing scientists to calculate the particle’s energy and trajectory. It’s similar to X-rays or ground-penetrating radar, except that higher-energy muons occur naturally instead of X-rays or radio waves. This high energy makes it possible to image dense, dense matter. The denser the imaged object, the more muons are blocked. The Muographix system relies on four above-ground muon-detection reference stations that act as coordinates for muon-detection receivers, which are deployed either underground or underwater.

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The team conducted first trial from an array of muon-based underwater sensors in 2021, to be used to detect rapidly changing tidal conditions in Tokyo Bay. They have placed ten muon detectors inside the service tunnel of the Tokyo Bay Aqua Line, located about 45 meters (147 feet) below sea level. They were able to image the sea above the tunnel with a spatial resolution of 10 meters (about 33 feet) and a temporal resolution of 1 meter (3.3 feet), enough to demonstrate the system’s ability to sense powerful storm waves or tsunamis.

The array was tested in September of the same year, when a typhoon coming from the south hit Japan, resulting in an ocean swell and a tsunami. Excess volume of water slightly increased dispersion of muons, and this difference is in good agreement with other measurements of ocean inflation. And last year, Tanaka’s team reported that they had done just that Filmed successfully Tornado vertical profile using radiographs, showing tornado cross-sections and revealing differences in intensity. They discovered that the warm core had a low density, in contrast to the cold, high-pressure outer part. In combination with existing satellite tracking systems, radiographic imaging can improve hurricane forecasts.

The red line represents the path he walked
Zoom in / The red line represents the path that the “navigator” traveled. The white dotted line shows the trajectory recorded by MuWNS.

2023 Hiroyuki as Tanaka

Previous iterations of the team attached the receiver to the ground station with a wire, which greatly limited movement. This new version—the Muometric Wireless Navigation System, or MuWNS—as the name suggests, is completely wireless, and uses highly accurate quartz clocks to synchronize ground stations with the receiver. Combined, reference stations and synchronous clocks make it possible to determine the coordinates of the receiver.

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For the test run, the ground stations were placed on the sixth floor of the building and the “navigator” carrying the receiver walked around the basement corridors. The resulting measurements were used to calculate the navigator’s course and confirm the route taken. According to Tanaka, the MuWNS performed with an accuracy of between 2 and 25 meters (6.5 to 82 feet), with a range of up to 100 meters (about 328 feet). “This is as good as, if not better than, single-point GPS positioning over the ground in urban areas,” he said. “But it’s still far from practical. People need an accuracy of one meter, and the key to that is time synchronization.”

One solution is to incorporate commercially available chip-sized atomic clocks, which are twice as accurate as quartz clocks. But these atomic clocks are very expensive right now, though Tanaka expects the cost to drop in the future as the technology is more widely integrated into cell phones. The rest of the electronics used in MuWNS will be minimized from now on to make it a portable device.

DOI: iScience, 2023. 10.1016/j.isci.2023.107000 (about DOIs).

The folks at Muographix have created this charming sci-fi video to explain muon-based systems.

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