CAPE CANAVERAL, Fla. — A long-awaited NASA mission designed to probe Earth's upper atmosphere has finally taken off after years of delays.

The Ionospheric Connection Explorer (ICON) spacecraft launched tonight (Oct. 10) at 10:00 p.m. EDT (0200 GMT on Oct. 11) aboard a Northrop Grumman Pegasus XL rocket, which was released in midair from its carrier plane, a Stargazer L-1011. The aircraft had taken off about an hour and a half earlier from Cape Canaveral Air Force Station here.

ICON will make its way to Earth orbit on a mission to study the planet's ionosphere, a massive layer of our atmosphere that overlaps with the boundary of space. The spacecraft's measurements will help scientists better understand the link between space weather and terrestrial weather, and how the two interact in the ionosphere, mission team members said.

Video: Watch NASA Air-Launch the ICON Space Weather Satellite

Related: Earth's Atmosphere: Composition, Climate & Weather

A Northrop Grumman Pegasus XL rocket streaks toward space carrying NASA's Ionosphere Connection Explorer satellite, or ICON, on Oct. 10, 2019. The rocket was launched from mid-air after being dropped by an L-1011 Stargazer carrier plane that took off from the Skid Strip runway at Cape Canaveral Air Force Station. (Image credit: NASA TV)

"The ionosphere is continually changing, and it's very dynamic," Nicky Fox, head of NASA's heliophysics division, explained during a prelaunch news briefing on Tuesday (Oct. 8).

"The ionosphere is a remarkable physics lab," Fox said. "It's not only a great place to go and study plasma physics, but it's also a region that has a big space weather impact on us."

Scientists have long been eager for the vending-machine-size satellite to get off the ground to see what it might tell us about this mysterious region. According to Fox, the ionosphere gets its name thanks to radiation from the sun , which bombards the atoms and molecules in this part of the atmosphere, essentially giving them a charge — a process called ionization.

It's here where strange and unique phenomena, such as the auroras and geomagnetic storms , are created. It's hard to forecast when these types of events will occur, because the ionosphere is an incredibly difficult region to study.

Related: Aurora Photos: Amazing Northern Lights Display from Solar Storms

An artist's view of NASA's Ionospheric Connection Explorer, or ICON, satellite. NASA has delayed the ICON satellite's planned June 14 launch due to rocket issues. (Image credit: NASA)

Until about a decade ago, scientists thought the sun caused most of the changes in the ionosphere, but more recent research suggests that is not the case; daily changes in the region are observed even when the sun isn't generating powerful storms. Fox explained that this is because terrestrial weather patterns and extreme events such as hurricanes also cause changes in the ionosphere.

This dynamic region where Earth weather meets space weather is home to the International Space Station and is a critical pathway for communications satellites. Radio waves and Global Positioning System (GPS) signals pass directly through this turbulent layer, and those signals can be distorted by patches of ionized material.

This is an issue because space weather can not only have an impact on communications systems but also electronics and even power grids. To mitigate these effects, scientists are hoping to better understand the sun and its many processes. And ICON can help with that, mission team members said.

Related: NASA's ICON Satellite Mission in Pictures

The $252 million probe is going right into the thick of the ionosphere, heading for a circular orbit 357 miles (575 kilometers) above Earth's surface. Equipped with various instruments that are designed to measure winds and particles, ICON will also measure how dense the atmosphere is and analyze its chemical composition.

Such data were supposed to be rolling in already. ICON was originally scheduled to launch in 2017, but issues with the Pegasus caused multiple lengthy delays. (Bad weather also scuttled an attempt yesterday, Oct. 9.)

ICON finally got aloft tonight. Stargazer L-1011 took off from the Skid Strip runway at Cape Canaveral Air Force station at 8:32 p.m. EDT (0032 GMT) and headed for its planned drop zone about 50 to 100 miles (80 to 160 km) east of Daytona Beach.

The crew released the 57-foot-long (17 meters) rocket at 10:00 p.m. (0200 GMT), on its second approach to the drop zone. (On the first try, mission control briefly lost communication contact with the carrier plane, leading to an abort.) Five seconds after the drop, the three-stage Pegasus ignited and began to climb to orbit.

Don Walter, Northrop Grumman's chief pilot for the L-1011, said the flight is like an attraction at Disney World. "When the rocket launches, the airplane wants to go up, and you get pushed back in your seat," he told Space.com. "Which is a good thing for us. When the rocket lights, we want to be a long way away."

He went on to explain that the experience is also quite noisy. "It sounds like a freight train underneath the plane," he added.

This flight was the 44th launch of a Pegasus rocket on a satellite delivery mission and the seventh out of Cape Canaveral.

While in space, ICON will work in tandem with another NASA mission called GOLD (Global-scale Observations of the Limb and Disk), which launched as a tagalong payload aboard a commercial communications satellite in January 2018. From its orbital perch 22,000 miles (35,400 km) above the Earth, GOLD has been monitoring the ionosphere from above. The two missions will work together to provide a complete picture of the inner workings of the ionosphere.