&lt;p&gt;&lt;strong&gt;Radiometric calibration is critical to many NASA activities.&amp;nbsp; At NASA SSC, imaging cameras have been used in-situ to monitor propulsion test stand activities.&amp;nbsp; Radiometric calibration can help analyze the illumination produced by a test article during firing in order to detect defects or stop a test if required.&amp;nbsp; &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Laboratory calibrations are typically performed using stable NIST traceable integrating sphere-based calibrated sources.&amp;nbsp; After launch, calibration is maintained using on-board calibration sources, ground-based vicarious calibration campaigns, and sometimes stellar and/or lunar calibration approaches.&amp;nbsp;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;NIST traceable integrating sphere based radiometric calibration sources have been used for several decades. An integrating sphere source is a spherical shell coated with highly reflective diffuse material that is illuminated either internally or externally. &amp;nbsp;These spheres have ports that allow light to enter or exit. Sometimes the integrating sphere source will have a detector or spectrometer to monitor its output.&amp;nbsp;&lt;/strong&gt;&lt;strong&gt;An observatory class calibrator (~1.2-1.5 m in diameter) can radiometrically calibrate imaging systems over the 360-2500 nm (UV-SWIR) spectral range by incorporating tungsten lamps into the design. &amp;nbsp;In this project, LEDs were combined with tungsten lamps to produce a UV-SWIR source. &amp;nbsp;Operating the tungsten lamp at temperatures lower than their normal limits extends their lifetime while only slightly reducing their SWIR output. &amp;nbsp;Since operating at lower temperatures also lowers illumination in the UV and visible spectrum, LEDs were used to fill in that part of the spectrum. &amp;nbsp;In this way, the light source was made stable for better than a few percent for 1000 hours or more as compared to the typical 50 hours for traditional light sources. &amp;nbsp;This feature improved the robustness of the calibration source and potentially reduces future maintenance costs.&lt;/strong&gt;&lt;/p&gt;