Publish Date: 
May 22, 2016


Artist concept of satellite in orbit above the Earth

Global-scale Observations of the Limb and Disk, or GOLD, is a NASA mission of opportunity that measures densities and temperatures in Earth’s thermosphere and ionosphere.

Historically difficult to observe, the upper atmospheric region responds both to terrestrial weather in the lower atmosphere below and the tumult of space weather from above. Big events in the lower atmosphere, like hurricanes or tsunamis, create waves that can travel all the way up to this interface to space, changing wind patterns and causing disruptions. On the opposite side, from above this region, flurries of energized particles and solar storms carry electric and magnetic fields and have the potential to disrupt Earth’s space environment.

This combination of factors makes it difficult to predict changes in the ionosphere — and these changes can have a big impact. The ionosphere stretches from roughly 50 – 360 miles above Earth’s surface. GOLD seeks to understand what drives change in this critical region. Resulting data has improved forecasting models of the space weather events that can impact life on Earth, as well as satellites and astronauts in space. GOLD is the first mission to provide us with observations fast enough to monitor the details of regular, hour-by-hour changes in space weather — not just its overarching climate.

Roughly the size of a mini fridge, the 80-pound GOLD instrument, hosted on the SES-14 commercial satellite, is an imaging spectrograph, an instrument that breaks light down into its component wavelengths and measures their intensities. Specifically, it measures far ultraviolet light, creating full-disk ultraviolet images of Earth from its geostationary vantage point above the Western Hemisphere

From these images, scientists can determine the temperature and relative amounts of different particles — such as atomic oxygen and molecular nitrogen — present in the neutral atmosphere, which is useful for determining how these neutral gases shape ionospheric conditions. These data have provided the first maps of the upper atmosphere’s changing temperature and composition all over the Americas.

Since entering service in 2018, GOLD has consistently scanned the entirety of the Earth’s disk every half hour.

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Full Name: 
Global-scale Observations of the Limb and Disk
Launch Date: 
January 25, 2018