There's a total solar eclipse coming up in North America, and NASA plans to shoot some rockets at it to see how the ionosphere changes as the Sun is obscured by the Moon.

NASA plans to launch a trio of sounding rockets before, during, and after the eclipse on April 8 as part of its Atmospheric Perturbations around Eclipse Path (APEP) program in the hopes of being able to better predict and prevent disruptions to terrestrial communications tech.

"Understanding the ionosphere and developing models to help us predict disturbances is crucial to making sure our increasingly communication-dependent world operates smoothly," said Aroh Barjatya, engineering physics professor at Embry-Riddle Aeronautical University and project leader. 

The ionosphere is part of the thermospheric layer of Earth's atmosphere and forms the boundary between the lower atmosphere and the vacuum of space. Stretching from around 50 to 400 miles above Earth's surface, the ionosphere is pelted by solar radiation during the day, separating electrons from atoms in the layer and creating a blanket of positively charged ions crucial to certain forms of communication. 

One of the reasons AM radio broadcasts can be heard so far from their sources is because the signals bounce off the ionosphere. FM waves, being shorter than AM ones, tend to escape the ionosphere.

By cutting the Sun's energy off, an eclipse can disrupt communications - even after a short duration of daytime darkness - affecting radio waves, GPS signals, and satellite communications. Relying on satellites to detect ionosphere changes from an eclipse isn't practical because satellites may not be in the right place at the right time, so rockets are the best bet, says NASA. 

The plan is to launch the trio of rockets 45 minutes before the eclipse, in the midst of it, and 45 minutes after to get a baseline degree of disruption, and to see how long it takes for atmospheric ionization to return to normal. Each rocket is expected to reach a maximum altitude of 260 miles, placing it smack-dab in the middle of the ionosphere.

Upon reaching their trajectory, each rocket will launch four two-liter bottle sized instruments, effectively delivering readings "from 15 rockets, while only launching three," Barjatya said. All 15 sensor-packed devices will measure charged and neutral particle density as well as surrounding electric and magnetic fields.

This will be the second time in as many years that APEP has had an opportunity to study ionosphere disruptions due to an eclipse, but the 2023 eclipse was annular, not total. The upcoming eclipse on April 8 is total, meaning measurements could be different.

"We are super excited to relaunch them during the total eclipse, to see if the perturbations start at the same altitude and if their magnitude and scale remain the same," Barjatya said. 

Here's hoping everything goes to plan - the next total solar eclipse to grace the skies in the United States won't happen until 2044. ®

https://www.theregister.com//2024/03/27/nasa_eclipse_rockets/