Radiometric measurements performed by the PV Solar Radiometric Measurements Task support NREL’s centers for Measurements and Characterization, Performance Engineering and Reliability, and Renewable Energy Resources. The task provides characterization, measurements, testing, designs, and analysis of radiometric instrumentation and data for the performance of PV cells, modules, and systems. We describe recent characterization of the radiometric performance of pyranometers deployed for PV system testing at the NREL Outdoor Test Facility (OTF) and improvements undertaken in NREL broadband radiometer characterization. Typical measurement and calibration issues with diode array spectroradiometers used for absolute spectral measurements applied to PV performance and characterization are discussed.