The Combined Power of Remote Earth Observations aboard the International Space Station

Understanding how Earth’s climate behaves is a significant, but important, challenge that NASA supports through data collection. When scientists better comprehend and monitor water and energy cycles, ecosystem changes, sea levels, geological hazards and population migrations, they can provide useful information to decision makers and the broader public regarding climate changes. Earth observations taken from space have provided decades of data that revolutionized weather tracking and forecasting, and provided insights into geophysical and atmospheric changes.

To celebrate the 50^th anniversary of Earth Day, we look at how the International Space Station has contributed to this important data set for the nearly 20 years that humans have been constantly on board, and its state-of-the-art tools monitoring our planet right now. The space station does much more than just snap photos of our planet. It has evolved into a robust platform for researchers studying Earth’s water, air, land masses, vegetation, and more, contributing new capabilities and unique data using systems mounted both inside and outside the orbiting laboratory.

At 51 degrees inclination and a 90-minute orbit, the station affords a unique perspective with an altitude of approximately 240 miles (400 kilometers) and an orbital path over 90 percent of the Earth’s population. This orbital path can provide improved spatial resolution and variable lighting conditions compared to the sun-synchronous orbits of typical Earth remote-sensing satellites.

Several external instruments, including ECOSTRESS, GEDI, OCO-3, DESIS, and HISUI, obtain useful information for researchers looking to better understand Earth’s atmosphere, oceans and surface. Though they individually collect data, in combination they provide a unique set of measurements that could push the leading edge of environmental research.

One Earth observation sensor on the space station, the NASA Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS), measures vegetation temperatures to examine how plants interact with the global water cycle and where they are experiencing heat stress. By observing how Earth’s foliage responds to water availability, scientists aim to identify crucial thresholds for water use, obtain factors that help predict plant water uptake, and measure agricultural use to aid in drought response planning.

Image of ECOSTRESS data taken over Peru during 2019 wildfires that shows vegetation temperatures in
response to water availability. The flame symbols show the locations of the fires whereas the colors indicate
the level of evaporative stress. The browner a region is, the less water is available for plants.

Credits: NASA

 

ESA (European Space Agency) astronaut Alexander Gerst preparing the DESIS instrument for installation aboard the space station. The DESIS instrument works by measuring hyperspectral reflections from Earth’s surface which contributes to resource management, ecosystem health monitoring and urban development.

Credits: NASA

 

A chart of OCO-3 data that shows solar-induced fluorescence in western Asia. Areas with lower plant glow, indicating lower photosynthesis activity, are shown in light green. Areas with higher photosynthesis activity are shown in dark green.

Credits: NASA

 

The GEDI suite in orbit over Earth. GEDI measures topography and vegetation primarily to help understand plants’ role in the carbon cycle.

Credits: NASA

 

Two instruments that collect detailed information about materials that make up Earth’s surface are the Hyperspectral Imager Suite (HISUI) developed by the Japanese Ministry of Economy, Trade, and Industry and the German Space Agency (DLR) Earth Sensing Imaging Spectrometer (DESIS). The sensors detect many wavelengths of light reflected by different materials. These light measurements define signatures that are unique to different materials, thus can support resource identification, exploration, agriculture, forestry and other environmental uses.

Other instruments on the station are looking at how Earth’s carbon cycles behave, as well as what factors influence it. The NASA Global Ecosystem Dynamics Investigation (GEDI) system uses high resolution lasers to collect observations of Earth’s 3D vegetation structure. These data help researchers understand the impact of carbon sinks, or areas such as forests that absorb carbon dioxide, on the carbon cycle. Scientists are using data collected from GEDI to gain insight into the carbon balance of Earth’s forests, how the planet’s surface reduces atmospheric carbon, and the implications forests have on biodiversity and habitat quality, as well as to support land use efficiency.

While GEDI is looking at the surface implications of changes to carbon sinks, NASA’s Orbiting Carbon Observatory-3 (OCO-3) sensor uses sunlight reflections through the atmosphere to quantify variations in atmospheric carbon dioxide. The variability in the space station’s orbit allows OCO-3 to build on similar data collected from free-flying satellites, particularly over low latitudes. Scientists are using OCO-3 to build targeted “snapshot” maps of Earth’s carbon exchange cycle over urban areas, forests, mangroves, oceans and agricultural regions. With OCO-3, researchers will gain a better understanding of how vegetation carbon sinks behave, as well as how human activities and development are affecting them.

Remote sensing instruments on the space station complement research on the ground to develop new models, calibrate data and contextualize existing information that can aid researchers in establishing baselines and improving predictive models. While information from each sensor can be interpreted individually, a single orbital platform that collects multiple types of data for the same site or region provides the opportunity for enhanced scientific discovery and deeper understanding. This creates a kind of “observational symbiosis” in which different sensor datasets can inform and expand the science analysis done with other sensor data. For example, the 3D observations obtained from GEDI can be used alongside HISUI’s hyperspectral surface material signatures to help visualize Earth’s ecosystems. Together, all of the space station Earth observation instruments are helping scientists understand how Earth is changing, as well as how to best use and manage the resources it provides.

Though every day may not be Earth Day, the work done by scientists and station instruments is continuously informing our understanding of the planet and how to protect it.

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