Test Results from an Imager for Scenes with High Dynamic Range and Low Light Levels

摘要

Ball Aerospace has field tested an Engineering Design Unit (EDU) of a Low Light Imager instrument capable of high dynamic range imaging in the Visible to Near Infrared wavelength range. The instrument design is well-suited to imaging scenes at low illumination levels or with radiance levels spanning a high dynamic range, including night scenes with clouds or anthropogenic light sources, and scenes that span the earth's terminator. A novel operating mode autonomously sets gains individually for each pixel and continuously updates the settings. Utilizing this scheme, the LLI EDU achieves a measured dynamic range > 10~7 in each image pixel of a scene. The upper and lower ends of the LLI dynamic range enable imaging of scenes illuminated by full sunlight or by a quarter moon only, as well as terminator scenes that span the two. The modular instrument configuration facilitates designs with different total Fields of View, including a three-module design with a cross-track FOV of 113 degrees. Testing and validation performed on the EDU include stray light testing, calibration and acquisition of ground images from an airborne platform. Radiometric test results demonstrate compliance with all radiometric requirements for the day/night imager for the National Polar Orbiting Environmental Spacecraft and Sensor program.