The National Institute of Standards and Technology Advanced Radiometer (NISTAR) instrument aboard NOAA’s Deep Space Climate Observatory (DSCOVR) spacecraft (which is a partnership between NOAA, NASA, and the U.S. Air Force) measures reflected sunlight and infrared emissions from Earth using three electrical substitution radiometers and a photodiode. NISTAR measures the absolute irradiance integrated over the entire sunlit face of Earth in four broadband channels minute-by-minute. These measurements provide an accurate energy balance measurement that improves our understanding of Earth’s radiation budget.