GLIDE Mission: One Step Closer to Exploring the Exosphere

GLIDE will help us better understand the fundamental physics of our atmosphere and improve our ability to predict the impacts of the Sun’s activity.

NASA’s Global Lyman-alpha Imager of the Dynamic Exosphere, or GLIDE mission, passed a mission review on January 13, 2021, moving the mission into its next phase with a target launch readiness date of 2025.

The review, Key Decision Point C, evaluated the mission’s preliminary design and project plan to achieve launch by its target launch readiness date. With the successful review, GLIDE now moves into phase C, which includes the final design of the mission and building of the instruments.

GLIDE will survey the exosphere, the outermost layer of Earth’s atmosphere. GLIDE is the first mission dedicated to charting changes there. It seeks to answer basic questions about the nature of Earth’s exosphere, like its shape, size, and density, and what causes them change over time.

The little-understood exosphere constantly changes in response to space above and Earth below. This region is made almost entirely of hydrogen that mainly comes from methane or water in Earth’s oceans, which is broken down by sunlight and slowly rises to this hinterland between Earth’s atmosphere and space. Hydrogen then leaks from the exosphere, joining the sea of space. The exosphere stretches from about 310 miles above the surface to at least halfway to the Moon.

The exosphere plays an important role in Earth’s response to space weather, the changing conditions in space driven by the Sun. That weather can impact our technology, from satellites in orbit to communications signals in the upper atmosphere or power lines on the ground. During space weather storms, the exosphere experiences huge spikes of energy and mediates Earth’s recovery from these disturbances. GLIDE will help us better understand the fundamental physics of our atmosphere and improve our ability to predict the impacts of the Sun’s activity.

Studying Earth’s atmosphere, which makes life possible on our home planet, builds our understanding of atmospheres throughout the universe. GLIDE will observe the natural process of atmospheric escape, which occurs slowly at Earth. Atmospheric escape played an important role in the story of Mars’s atmosphere, where it siphoned water from the planet’s surface. This process also happens outside the solar system and impacts the habitability of exoplanets, shaping NASA’s search for life.

The solar wind soaring toward Earth
The GLIDE mission will provide insights into how Earth’s exosphere is influenced by changes in space, including the solar wind, shown here flowing from the Sun in this illustration. Credits: NASA

Orbiting the Sun at Lagrange point 1 (a gravitational balance point between Earth and the Sun), GLIDE will have the perfect vantage point to image the entire exosphere. At this distance, 1 million miles from Earth, GLIDE’s field of view around Earth will reach more than halfway to the moon – crucial for documenting the full extent of the exosphere and its changes.

GLIDE will ride to space along with IMAP, the Interstellar Mapping and Acceleration Probe, which will explore the boundaries of the heliosphere, the bubble that is inflated by the solar wind and surrounds the Sun and planets. GLIDE is a vital addition to NASA’s fleet of heliophysics satellites. NASA Heliophysics Division missions study a vast, interconnected system from the Sun to the space surrounding Earth and other planets to the farthest limits of the Sun’s constantly flowing streams of solar wind.

Led by University of Illinois Urbana-Champaign, GLIDE will provide key information about the dynamics of Earth’s outermost atmosphere and how, in turn, this region interacts with this complex space system at large.


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