Bold claim: humanity has tracked Earth's energy conversation for over four decades, and the story keeps surprising us as new data keep arriving. But here’s where it gets controversial: our view of how the Sun, Earth, and clouds interact isn’t fixed; it evolves as technology improves and observations extend farther in time. This is the essence of a long-running scientific effort that began with a small satellite and grew into a robust, multi-mission program.
42 Years of Measuring Sun, Earth, and Energy in Between
5 min read
By Denise Lineberry
On January 31, 1958, Explorer 1 marked the United States’ first orbital mission. Its primary instrument, a cosmic ray detector, aimed to map the radiation environment around Earth. Although its final transmission occurred in May 1958, the satellite completed more than 58,000 orbits. As Explorer 1 orbited, NASA simultaneously built more sophisticated instruments to observe and understand Earth’s systems.
By 1975—five years after Explorer 1 burned up during atmospheric reentry—NASA launched its first Nimbus instrument. This mission delivered the first global, direct measurements of how much solar radiation enters and leaves Earth, helping validate and refine early climate models and laying the groundwork for NASA’s Earth Radiation Budget Experiment (ERBE).
In the 1970s, ERBE teams began planning the next step in Earth Radiation Budget measurements. Retired ERBE scientist Bruce Barkstrom recalls the first ERBE science meeting as an all-day effort to determine precisely where Earth’s top of the atmosphere lay. After extensive debate, they assigned one NASA Langley Research Center scientist the task of defining the altitude—about 18 miles (30 kilometers) above the Earth’s surface.
"That was the level of detail we had to get into as a science team," Barkstrom noted.
In October 1984, ERBE launched aboard NASA’s Earth Radiation Budget Satellite (ERBS) on the space shuttle Challenger (STS-41G).
"We had to rise at 3:30 a.m. to watch the launch at 7:30 a.m., and that morning the sky was overcast. When the shuttle’s exhaust brightened the sky below, it felt almost magical. Then the shuttle passed through the clouds, the light faded, and about a minute later the sun reflected off the exhaust and lit the sky again. It’s hard to describe this without getting emotional," Barkstrom recalled.
For a decade, ERBE delivered vital data about how energy from the Sun interacts with Earth, including how clouds influence the balance of incoming and outgoing radiation at the top of the atmosphere.
In the late 1980s, satellite instruments began providing the first direct evidence that clouds can cool Earth’s climate. Former CERES Principal Investigator Bruce Wielicki developed an algorithm to apply Nimbus and ERBE models to quantify cloud forcing—the difference in radiation budget components between typical cloud conditions and cloud-free conditions.
Armed with growing knowledge of clouds’ critical role in Earth’s energy budget, scientists pressed to collect more data. In 1997, the Clouds and the Earth’s Radiant Energy System (CERES) entered service, extending the ERBE-era measurements.
Since then, six additional CERES instruments have been launched to observe the solar energy reflected by Earth, the planet’s emitted heat, and clouds’ role in that process.
"The CERES instrument is small and elegant; it’s perhaps the most accurate radiometer NASA has flown," says CERES Principal Investigator Kory Priestley. "We’re already thinking about the next generation of instruments to meet the same exacting standards."
The seventh and final CERES instrument launched aboard NOAA’s Joint Polar Satellite System (JPSS)-1 in November 2017 and began operating with first-light observations anticipated in January 2018.
For 42 years, NASA has tracked Earth’s energy budget. The Langley Earth Radiation Budget Science Team remains the only global source for ERB data. Although our understanding of Earth’s energy budget and the technology used to measure it have advanced dramatically since Explorer 1 and Nimbus, the knowledge continues to evolve.
"With Earth observations, you never finish understanding everything," Barkstrom observed. "In observational science, there isn’t a final escape into absolute certainty where you never need to revise anything."
Why Measure Earth’s Energy Budget?
Barkstrom notes that efforts to understand the radiation budget began around 1880. Earth’s energy budget can be viewed as a balance: the Sun’s energy input versus the energy radiated back into space. Maintaining a continuous, stable, and accurate data record over decades is essential to understanding this balance and its fluctuations.
These data improve models that forecast seasonal and long-term trends, providing crucial information for industry and policymakers as they plan for the future.
The Latest
NASA’s Total and Spectral Solar Irradiance Sensor (TSIS-1) is currently aboard the International Space Station, measuring the Sun’s energy input to Earth.
Since 1978, satellites have maintained a continuous record of solar energy input. TSIS-1 builds on previous measurements, enabling scientists to study how the Sun’s variability affects Earth’s ozone layer, atmospheric circulation, clouds, and ecosystems.
These observations are essential for a scientific understanding of how solar variability influences the Earth system.
About the Missions: ERBE and CERES
ERBE
The radiation budget reflects the balance between incoming solar energy and the Earth’s outgoing longwave heat and reflected shortwave energy. In the 1970s, NASA recognized the need to improve our understanding of this budget and its climate effects. Langley Research Center led the development of new instrumentation capable of precise regional and global measurements of the budget’s components. The Goddard Space Flight Center built the Earth Radiation Budget Satellite (ERBS), on which the first ERBE instruments were launched by the Challenger in 1984. ERBE instruments were also flown on NOAA weather satellites NOAA 9 and NOAA 10 in 1984 and 1986.
CERES
The Clouds and Earth's Radiant Energy System (CERES) is a top-priority instrument for NASA’s Earth Observing System (EOS). The first CERES instrument launched in December 1997 aboard NASA’s Tropical Rainfall Measuring Mission (TRMM). CERES instruments have since flown on three major missions: the EOS Terra and Aqua satellites, the Suomi National Polar-orbiting Partnership (S-NPP), and the Joint Polar Satellite System (JPSS) collaboration between NASA and NOAA. In fall 2017, CERES FM6 launched on JPSS-1, marking the culmination of a successful CERES generation that enhances our ability to observe Earth’s interconnected systems with long-term data records.
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Last Updated
Feb 18, 2026
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