20 years of Earth observation from the Space Station – An extraordinary view from space

After 20 years of continuous human presence, the International Space Station (ISS) provided 241 visitors with an extraordinary view of the Earth from space, which they shared with the rest of the world.

Astronaut photography, formally called Crew Earth Observations (CEO), has produced over 3.5 million photographs of the ever-changing blue planet. But camera-wielding astronauts aren’t the only ones watching Earth from their perch in the sky. An impressive suite of Earth Science instruments also visited the station to acquire huge amounts of data on our planet.

However, space aboard the station itself is limited and the spots are highly coveted. The tools go through a rigorous approval process and review every two years, transforming the station into a virtual Swiss Army knife of interchangeable remote sensing tools. A particularly comprehensive suite of Earth observation instruments is currently aboard the station, with two more approved and many more set to become future ISS instruments.

These tools complement each other to provide a more complete picture of Earth’s systems, according to William Stefanov, Branch Chief of the Exploration Science Office of NASA‘s Johnson Space Center and principal investigator for the Crew Earth Observations Facility on the International Space Station. “That’s why it’s fortunately great that all of these instruments are on the International Space Station and are working simultaneously,” Stefanov said.

ECOSTRESS

The human crew was particularly helpful with the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument, which records the temperature of plants on the earth’s surface by measuring the heat they give off. The tool required the addition of Wi-Fi modules to transmit its data to the station, which in turn required astronauts to conduct a spacewalk to install them.

Since then, ECOSTRESS has provided new insights into the relationship between plant temperatures and water use. It can identify plant stress all the way to a single farmer’s field, when intervention and water management may still be possible to save crops.

Lead researcher Simon Hook says scientists have just begun scratching the surface of how the tool can be used based on its frequent, high-resolution temperature measurements. Work is underway to use temperature data to observe fires, droughts, volcanoes and heat waves or even to identify heat patterns within urban cities.

GEDI

From fields to forests, another plant-focused tool is the Global Ecosystem Dynamics Investigation (GEDI). Using lidar, a method of bouncing a laser off the planet and measuring how long it takes the signal to return, GEDI is creating a record of the three-dimensional structure of the world’s tropical and temperate forests so that the canopies of Earth’s trees can be mapped. and follow. time.

The vertical structure of the forests, which is essentially the height of the trees and the way their leaves and branches are arranged vertically, can help determine the amount of carbon storage lost from deforestation or gained from growing forests. GEDI principal investigator Ralph Dubayah, a professor of geographic sciences at the University of Maryland, College Park, says this is the largest uncertainty we have about the global carbon cycle, and why there is so much attention paid to understanding how deforestation and tree growth contribute to atmospheric concentrations of carbon dioxide. GEDI is a collaborative effort between NASA and UMD.

To provide its high-powered laser, GEDI makes use of the massive solar panels on the station. “Right now on the International Space Station we have an incredible confluence of instruments that together are capable of observing the function of the ecosystem, the structure and composition of plants,” Dubayah said. “And it was completely made possible because we have this amazing science platform on the ISS.”

LIS

Being high above the clouds also makes the station a good platform for observing the weather. NASA’s Lightning Imaging Sensor (LIS) records the time, energy production and locations of lightning events around the world in the lower atmosphere. It can provide information on when storms are growing or decaying, thereby helping to improve weather forecasting models and safety precautions for aircraft / spacecraft.

Complete the Geostationary Lightning Mapper (GLM) aboard the Geostationary Operational Environmental Satellite (GOES-16), which is a collaboration between NASA, the National Atmospheric and Oceanic Administration (NOAA) and the European Space Agency’s industrial and monitoring partners ( ESA) of thunderstorms and lightning in the upper atmosphere through the Atmosphere Space Interaction Monitor (ASIM) instrument located on the ISS.

Data from ASIM and LIS are both capable of capturing the impacts of dust storms, pollution, fires and volcanic eruptions on cloud formation and electrification. This is just one example of how ESA and other international agencies including the German Aerospace Center (DLR) and the Japanese Aerospace Exploration Agency (JAXA), they are also helping to advance a global understanding of our planet through the tools of the ISS with their observations of the Earth.

OCO-3

Several instruments currently aboard the station are not the first of their kind. As its name might suggest, Orbiting Carbon Observatory-3 (OCO-3) is a third iteration tool for long-term monitoring of atmospheric carbon dioxide distributions around the world, complementing long-term terrestrial observations. It provides information on regional carbon sources and sinks and monitors changes in the carbon cycle related to human activity.

Together with GEDI and ECOSTRESS, OCO-3 contributes to a more complete picture of terrestrial ecosystems. While its predecessor, the OCO-2 satellite, followed a polar orbit, the OCO-3 path aboard the station offers a denser dataset for areas with large carbon fluxes, including biologically more diverse regions of the Land like the Amazon rainforest.

The orbit also allows measurements at different times of the day, especially for the benefit of ECOSTRESS and OCO-3 as plants and their contribution to the carbon cycle fluctuate with the time of day due to variations in the sun, temperature and availability of water.

SAGE III

Like OCO-3, the Stratospheric Aerosol and Gas Experiment (SAGE) III, is a third generation instrument. Subsequent SAGE instruments have provided a continuous record of Earth’s upper atmospheric water vapor, aerosol and ozone, which form the protective “sunscreen” layer for the planet.

As sunlight passes through the upper atmosphere, its unique blend of particulate matter and gas creates the picturesque colors of spectacular sunsets and sunrises. To replicate a sunset or sunrise view from the space station, SAGE III looks at the Earth from a side angle, capturing a similar view of the atmosphere at its edges as someone watching the sunset from the ground. But from its perspective of space, SAGE III can visualize the entirety of these atmospheric layers according to project scientist Dave Flittner, and sees 15 sunrises and sunsets every day.

Scientific director Marilee Roell says the longevity of these observations was crucial in monitoring and maintaining the protective ozone layer in the upper atmosphere. SAGE II closely monitored the decline in ozone from common aerosols into hair sprays and flame retardants that degraded the layer, and its data informed the Montreal Protocol Treaty, which phased out the use of these. harmful chemicals.

“It’s one of the greatest success stories in science informing politics,” Roell said. “And not only is it a first-rate scientific instrument, it is also found on the International Space Station, a manned platform. In a way we are getting the best of science and becoming a part of the human spaceflight program in a peripheral way. “

TSIS-1

Further atmospheric measurements of the sun come from the Total and Spectral Solar Irradiance Sensor (TSIS-1), which actually consists of two instruments: the Total Irradiance Monitor (TIM) and the Spectral Irradiance Monitor (SIM).

TSIS-1 continues the work of NASA’s Solar Radiation and Climate Experiment satellite by measuring the amount of sunlight reaching Earth and how it is distributed in wavelength.

These measurements of solar energy, together with model-based calculations of its absorption and reflection by the atmosphere and the earth’s surface, provide information on the sun’s influence on climate, the ozone layer, atmospheric circulation, and ecosystems. Data are fundamental inputs for modeling the earth’s climate and atmospheric systems.

COMING SOON: EMIT & CLARREO-PF

There is still much to learn about Earth and new tools that can further contribute to our understanding such as the Pathfinder of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) and the Earth Surface Mineral Dust Source Investigation (EMIT) are already scheduled to achieve station within the next two years.

The CLARREO Pathfinder will measure the sunlight reflected from the Earth and make direct measurements of the Sun, with unprecedented results precision. The data can then help calibrate other sensors starting in 2021. EMIT is scheduled to launch next year in 2022 to map dust source regions on the Earth’s surface and assess the impact of dust on warming and cooling. of the atmosphere.

“It was really satisfying to see the range of things we had on the space station,” Stefanov said. From imaging systems to lasers and radars, and more recently to hyperspectral instruments Stefanov believes the limit to what they can do in the future is really limited only by what scientists and engineers are able to design and the number of instrument ports. available.

“There will be opportunities for new sensors to go up to the station,” he said. “And I think it will continue to develop as a very useful remote sensing platform for Earth observations in the future.”