Amir Caspi, Southwest Research Institute senior research scientist, talks about the NASA WB-57F jet that will used for research during the eclipse shown at Ellington Airport Thursday, Aug. 10, 2017, in Houston.
Two former weather reconnaissance planes at Ellington Airport have waited seven years to record something they've never spied before. They aim to help capture 7 ½ minutes of video as the moon creeps across the face of the sun to create a total eclipse visible across a long swath of the United States.
The planes will take off from Ellington with powerful telescopes and use the rare window of darkness to make observations of the sun's corona and its nearest planetary neighbor, Mercury, that would be impossible in normal daylight. Scientists hope those observations could ultimately help shed light on a host of mysteries, including big-picture questions about the sun's inner workings and more practical applications such as predicting space weather created by the sun that can damage satellites and knock out power grids.
"I'm a little anxious ... to make sure that everything goes well and that we get the data that we need," said Amir Caspi, principal investigator of the project and a senior research scientist in Southwest Research Institute's Colorado office.
Scientists have spent about a year preparing for the eclipse mission. Using NASA's WB-57 aircraft for astronomical research, however, has been about seven years in the making. This is the first time they will be used for astronomy.
"What we're hoping for is that this not only gets us really amazing data for this particular mission," Caspi said, "but also essentially showcases the potential of this platform for future astronomical missions. So hopefully we'll be able to do this, and things like this, again many times."
The NASA planes will take off from Ellington Airport around 10 a.m. Monday and fly west of St. Louis, where they'll pick up the projected eclipse path and aim their telescopes at Mercury.
The dirt on Mercury
The brilliance of the sun makes Mercury difficult to observe during the day. And viewing along the horizon at dusk or dawn presents challenges because, compared with looking straight up into the sky, scientists have to look through more of the Earth's atmosphere. That can distort images.
Caspi said scientists don't fully know what materials make up the top few centimeters of Mercury's soil or how compact it is. A heat map comparing the portion of the planet facing the sun with the portion rotated away from the sun, which is about 1,000 degrees colder, could help determine the surface composition as different materials heat up and cool down at different speeds.
Understanding the soil could give scientists a better idea of how rocky planets like Mercury and Mars form. The mission led by San Antonio-based Southwest Research Institute will use infrared telescopes in an attempt to make the first-ever thermal images of Mercury's surface, Caspi said.
"We don't exactly know what we're going to see or if we're going to be successful at it," he said, "because it's the first time that we will have tried it."
The planes will fly along the projected total eclipse path at about 450 miles per hour as they collect data on Mercury.
The umbra, or dark inner shadow of the moon where observers see the total solar eclipse, will travel from Oregon to South Carolina at varying speeds. It will be going about 1,450 miles per hour when it catches up to the planes, Caspi said.
At this point of total darkness, telescopes with a green filter will focus on the sun's corona.
The space weather forecast
Caspi said there's much to glean from studying the sun's corona.
"Partly it's because we're nerds and we like to learn about physics and astronomy," he said.
Studying the sun could ultimately help scientists learn about other stars and, thus, about whether planets orbiting those stars could sustain life.
On the more practical side, he said the sun drives space weather. Coronal mass ejections, where the sun throws off billions of tons of material, can damage satellites, disrupt GPS service or knock out power grids.
"To better understand the source and cause of these space weather hazards, we need to understand how the corona works," Caspi said. "And that will help us hopefully predict when these hazards might occur, especially at the dangerous level, and eventually therefore put preparation programs in place."
Scientists hope to answer two main questions: Why the corona is millions of degrees hotter than the sun's surface and why magnetic structures in the corona don't get tangled into a big knot.
For the first question, he said scientists know that energy is being transferred to the corona, making it hot. But scientists don't know how the energy is being transferred. The normal methods of heat transfer - radiation, convection or conduction - don't work effectively because the corona is too thin.
So scientists have two theories about how heat travels there: wave heating and nanoflares.
Wave heating involves the corona's magnetic structures, which can be seen as loops, arcades and fans. It theorizes that waves are carrying energy along these magnetic structures to the corona. That energy would heat up the corona.
Nanoflares, on the other hand, are like miniature solar flares. Scientists say these small yet powerful explosions could be happening all the time in the corona.
To detect which method is heating the corona, Caspi said scientists will look for moving sequences of brightening and dimming, resembling ripples in a pond. If these sequences are moving away from the sun, then wave heating could be occurring. If these sequences are moving toward the sun, that could indicate nanoflares.
It's likely that scientists will detect a combination of the two, he said.
As for the tangling of the corona's magnetic structure, Caspi said these structures are rooted in the constantly moving surface of the sun. So in theory, they should be twisted into something resembling bed head. But they don't appear to get tangled, and scientists would like some insight into why.
Seating is limited
Observations from the WB-57s during the total eclipse will be used to create a 7½-minute video. Viewers on the ground in that area will only get 2 minutes and 40 seconds of total darkness.
The planes will be separated by about 70 miles, meaning there will be 10 or 20 seconds with both planes in the total eclipse, and their footage will be stitched together to create the 7½ minutes. After the total eclipse passes both planes, they will spend another half hour observing Mercury before returning to Ellington.
The entire trip is expected to take 5½ to six hours.
"It's an exciting project," said Charles Mallini, program manager for NASA's WB-57s. "It's a good opportunity. We had the aircraft, the sensors, so it was a perfect match."
The cameras and telescopes were initially developed after the Space Shuttle Columbia accident. Birmingham, Ala.-based Southern Research developed the technology to better observe shuttle launches.
Southern Research has since upgraded the instruments so they could be used for astronomical science during Monday's mission. The test on Monday is being funded by a NASA grant, and Mallini said it could inspire other scientists to use the WB-57s for astronomical research.
And since the planes have just two seats - one for the pilot and one for the telescope operator - Caspi and his team will have to watch the solar eclipse from a screen at Ellington. Video from the mission will be livestreamed to the ground.
"This is my first total solar eclipse, and I get to watch it on a video monitor," Caspi said. "It's the sacrifice for science."
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