Rapid Coordination Extends Space‐Based Sun‐Climate Record

Total solar irradiance (TSI), a measure of how much solar radiative energy hits the entirety of Earth, is the principle energy input to the global climate system.

Collecting accurate TSI data spanning multiple years helps scientists understand how much solar radiation is deposited in the atmosphere and at the surface and thus how much energy is available to influence weather, climate, the cryosphere, atmosphere dynamics, and ocean currents.

Because of TSI’s relevance for natural climate change, TSI has been identified within the US president’s National Plan for Civil Earth Observations [ Holdren, 2014 ] as a vital observation for determining the Earth’s net energy balance.

Similarly, within the National Oceanic and Atmospheric Administration (NOAA) Climate Data Record program, TSI is recognized as an important long‐term measurement for a robust, sustainable, and scientifically defensible approach to climate change
research.

Unfortunately, the main contributors to the TSI record have terminated their observations or are suffering degraded performance.

These include the NASA Active Cavity Radiometer Irradiance Monitor Satellite (ACRIMSat), whose mission ended in December 2013 due to battery problems after nearly 14 years in orbit; the Swiss Precision Monitor Sensor (PREMOS) instrument aboard the French Picard satellite, whose mission ended in March 2014; and the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) aboard the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO), which is still operational, albeit with degraded performance, after 18 years in orbit.

To ensure the longevity of the TSI record without data gaps, scientists had to work fast.

Extraordinary teamwork between NASA, the Laboratory for Atmospheric and Space Physics at the University of Colorado (CU‐LASP), NOAA, and the Air Force over the last few years has enabled the extension of TSI measurements.

This cooperation has included revitalizing the Solar Radiation and Climate Experiment (SORCE, see Image ), an aging NASA satellite launched in 2003; the launch and initial operations of the TSI Calibration Transfer Experiment (TCTE), a NOAA/NASA irradiance instrument aboard an Air Force satellite; and identifying a new opportunity for deployment on the International Space Station (ISS) in 2017 of the NOAA Total and Spectral Solar Irradiance Sensor (TSIS).

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