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ATLANTA — During the total solar eclipse on April 8, when the moon will temporarily obscure the sun's face from view for millions of people across Mexico, the United States and Canada, multiple experiments will be underway to better understand some of the biggest unresolved questions about the golden orb.
NASA will launch sounding rockets and WB-57 high-altitude planes to conduct research on aspects of the sun and Earth that's only possible during an eclipse. During the 2017 eclipse that crossed the U.S., NASA and other space agencies conducted observations using 11 different spacecraft and two high-altitude planes.
Data collected during that eclipse helped scientists to accurately predict what the corona, or the sun's hot outer atmosphere, would look like during eclipses in 2019 and 2021. Despite its blazing temperatures, the corona is fainter in appearance than the sun's bright surface, but it appears like a halo around the sun during an eclipse when the bulk of the sun's light is blocked by the moon, making it easier to study.
Observing the sun during eclipses also helps scientists better understand how solar material flows from the sun. Charged particles known as plasma create space weather that interacts with an upper layer of Earth's atmosphere, called the ionosphere. The region acts as a boundary between Earth's lower atmosphere and space.
Energetic solar activity released by the sun during solar maximum could interfere with the International Space Station and communication infrastructure. Many low-Earth orbit satellites and radio waves operate in the ionosphere, which means dynamic space weather has an impact on GPS and long-distance radio communications.
Sending rockets into an eclipse
Three sounding rockets will lift off in succession from NASA's Wallops Flight Facility in Virginia before, during and after the eclipse to measure how the sudden disappearance of sunlight impacts Earth's upper atmosphere.
Aroh Barjatya, professor of engineering physics at Embry-Riddle Aeronautical University in Daytona Beach, Florida, is leading the experiment, called the Atmospheric Perturbations around the Eclipse Path, which was first carried out during October's annular solar eclipse.
Each rocket will eject four soda bottle-size scientific instruments within the path of totality to measure changes in the ionosphere's temperature, particle density, and electric and magnetic fields about 55 to 310 miles above the ground.
"Understanding the ionosphere and developing models to help us predict disturbances is crucial to making sure our increasingly communication-dependent world operates smoothly," Barjatya said in a statement.
The sounding rockets will reach a maximum altitude of 260 miles during flight.
During the 2023 annular eclipse, instruments on the rockets measured sharp, immediate changes in the ionosphere.
"We saw the perturbations capable of affecting radio communications in the second and third rockets, but not during the first rocket that was before peak local eclipse," Barjatya said. "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."
Soaring above the clouds
Three different experiments will fly aboard NASA's high-altitude research planes known as WB-57s.
The WB-57s can carry almost 9,000 pounds of scientific instruments up to 60,000 to 65,000 feet above Earth's surface, making it the workhorse of the NASA Airborne Science Program, said Peter Layshock, manager of NASA's WB-57 High Altitude Research Program at Johnson Space Center in Houston.
The benefit of using WB-57s is that a pilot and an equipment operator can fly above the clouds for about 6½ hours without refueling within the eclipse's path of totality spanning Mexico and the U.S., allowing for a continuous and unobstructed view. The flight path of the planes means that the instruments will be within the moon's shadow for longer than they would be on the ground. Four minutes of totality on the ground equals closer to six minutes of totality in the plane, Layshock said.
One experiment will also focus on the ionosphere using an instrument called an ionosonde, which acts like radar by sending out high-frequency radio signals and listening for the echoes as they bounce off the ionosphere to measure the number of charged particles it contains.
The other two experiments will focus on the corona. One project will use cameras and spectrometers to uncover more details about the temperature and chemical composition of the corona, as well as capture data about large bursts of solar material from the sun known as coronal mass ejections.
Another project, led by Amir Caspi, a principal scientist at the Southwest Research Institute in Boulder, Colorado, has the goal of capturing images of the eclipse from 50,000 feet above the Earth's surface in the hopes of spying structures and details within the middle and lower corona. Using high-speed and high-resolution cameras, capable of taking images in visible light and infrared light, the experiment will also look for asteroids that orbit within the sun's glare.
"In the infrared, we don't really know what we're going to see, and that's part of the mystery of these rare observations," Caspi said. "Every eclipse gives you a new opportunity to expand upon things where you take what you learned at the last eclipse and you solve a new piece of the puzzle."
