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article imageNASA's GOLD and ICON missions will study Earth's outer boundary

By Karen Graham     Jan 8, 2018 in Science
In a live feed on January 4, NASA researchers discussed the agency's January 25 mission: the launch of GOLD, the Global-scale Observations of the Limb and Disk mission.
GOLD will hitch a ride on the SES-14 communications satellite when it is launched from Kourou, French Guiana on January 25. The second mission, called ICON, the Ionospheric Connection Explorer will be launched at the end of the year. Both missions will examine the Earth's ionosphere, the boundary between our planet and outer space.
According to NASA, the two missions will allow scientists to explore and understand the area of 96 kilometers (60 miles) above Earth’s surface about which no one knows much. "For years, we've been studying the Earth's upper atmosphere — thermosphere and ionosphere — and we've been looking at those [layers] in detail from the ground and from low-Earth orbit missions.
We wanted to be able to back off and get the big picture, get a whole hemisphere at once. That lets us put things into context that we can’t understand when we’re just looking at one little piece," said Richard Eastes, the principal investigator for GOLD from the University of Central Florida.
NASA infographic showing the different layers of Earth’s atmosphere.
NASA infographic showing the different layers of Earth’s atmosphere.
NASA - Goddard Space Flight Center, Duberstein
The GOLD Mission
The GOLD craft's mission will be to analyze the ultraviolet radiation that the upper atmosphere releases. GOLD will also be the first craft to take comprehensive records of that atmospheric layer's temperature, Eastes added. The satellite carrying GOLD will orbit 35,400 kilometers (22,000 miles) above Earth in a geostationary orbit.
This means GOLD will stay fixed with respect to Earth's surface as the satellite orbits and the world turns. For comparison, the International Space Station cruises at about 400 kilometers (250 miles) above the Earth.
GOLD will be focused on the thermosphere, which extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to 621 miles) above our planet, and the layer called the ionosphere, which forms as radiation from the sun strips away electrons from particles to create charged ions.
"Thermo" means heat, and the temperature in this layer can reach up to 4,500 degrees Fahrenheit. Here is what's interesting - you would be very cold because there aren’t enough gas molecules to transfer the heat to you. This also means there aren’t enough molecules for sound waves to travel through. The ISS orbits Earth in the thermosphere and this where our low Earth orbit satellites can be found.
Relationship of the atmosphere and ionosphere.
Relationship of the atmosphere and ionosphere.
Bhamer, updated to SVG by tiZom
The Ionosphere is the ionized part of Earth's upper atmosphere, from about 60 km (37 mi) to 1,000 km (620 mi) altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere forms as radiation from the sun strips away electrons from particles to create charged ions.
And while solar flares and other interactions on the sun have an effect on these layers, scientists have learned that the Earth's own weather has an impact on the layers, too.
"In the past, people thought that this region of the Earth's upper atmosphere was affected primarily by what's happening at the sun and what's coming to the Earth from the sun," Sarah Jones, the GOLD mission scientist at Goddard said during the presentation. "The sun's radiation and charged particles of solar wind hit Earth's atmosphere, and in response, the planet's magnetic field can cause geomagnetic storms and other space weather."
Lightning strikes the United States about 25 million times a year.
Lightning strikes the United States about 25 million times a year.
Jones used tsunamis as an example of how what's going on here can affect the ionosphere. She pointed out that tsunamis create waves in the air and those waves move upwards, and the waves could potentially cause changes even at the very boundary between the Earth and space. "GOLD is studying in particular how to tease out the effects coming from the sun above and Earth below."
Why is GOLD's mission important?
While this is considered a scientific study, it is also more than just for pure science. For one thing, our aircraft, GPS systems and communication infrastructure will derive great benefits from our learning how to accurately map and model these regions.
At this time, we can only observe changes every few hours, and models of the upper atmosphere can predict only about a day of changes. However, GOLD will be able to monitor how the upper atmosphere changes and evolves throughout the day on an hourly basis so researchers can build better models.
This is where ICON's mission will add a greater dimension to GOLD's mission. ICON is scheduled to be launched later in the year and will fly through the upper atmosphere in low-Earth orbit — 350 miles (560 kilometers) This will allow ICON to get a much closer view of what's going on.
Solar Variability Affecting Earth. Incidents range from solar flares  sunspots.
Solar Variability Affecting Earth. Incidents range from solar flares, sunspots.
The cool thing about the combo between ICON and GOLD is the fact that we're getting this global view that's actually remote sensing, and then we have the in situ view, [where] we're actually sending something through it," Alex Young, the associate director for heliophysics science at Goddard during the live feed.
With GOLD and ICON in place, scientists will be able to pin down what causes changes between Earth's boundary and space. Young said, "It's interacting with spacecraft, sometimes disrupting them, and it even creates a really nasty environment for astronauts. Understanding that is important also for space travel near the Earth and through the rest of the solar system."
More about NASA, GOLD ICON missions, ionosphere, electricallycharged electrons and ions, Radio signals
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