Abstract
Recent imaging pushbroom radiometers with up to 30000 detectors per band in multiple modules and with dynamic ranges of up to 14 bits are a significant challenge to flat field. While there are various methods both pre-launch and on-orbit by which uniformity correction can be estimated, pre-launch calibration collects offer some of the lowest uncertainties. The Landsat-9 Operational Land Imager-2 (OLI2) prelaunch radiometric calibrations conducted at Ball Aerospace utilized spectral sources, large integrating spheres and rotation stages. The combination of these tools enables the calibration of the instrument’s radiometric response for the full field of view and dynamic range for each of its spectral bands. The uniformity characterization data for OLI2 were obtained by continuous motion yaw scans at multiple elevation angles, multiple source signal levels and wider angular range while the instrument is in the thermal vacuum chamber. The source used for the collects was a well-controlled tungsten halogen lamp illuminated integrating sphere. The yaw scans enables a creation of a sphere uniformity map for every band. The the uniformity map is 1° by 2.1° zone centered on the integrating sphere port. This extent is larger than the field of view of a single focal plan module (FPM). Effectively these data collects are mimicking the on-orbit side slither collects that are done on-orbit only now the target is a well-controlled stable calibration source with traceable absolute radiometric accuracy, and minimal atmospheric transmission error. The results of the radiometric uniformity characterization of OLI2 will be presented. The report will demonstrate that with the new collect method more information can be obtained in shorter amount of time and it ultimately resulted in better characterization dataset for OLI2. Description of the processing method used and the detailed information extracted from the data about quality of OLI2 and the sphere source will be provided. The uniformity corrections parameters and associated uncertainties for these uniformity correction factors will be discussed.
Radiometric Source Uniformity Characterization with Angular Scans: Landsat-9 OLI-2 Experience
Recent imaging pushbroom radiometers with up to 30000 detectors per band in multiple modules and with dynamic ranges of up to 14 bits are a significant challenge to flat field. While there are various methods both pre-launch and on-orbit by which uniformity correction can be estimated, pre-launch calibration collects offer some of the lowest uncertainties. The Landsat-9 Operational Land Imager-2 (OLI2) prelaunch radiometric calibrations conducted at Ball Aerospace utilized spectral sources, large integrating spheres and rotation stages. The combination of these tools enables the calibration of the instrument’s radiometric response for the full field of view and dynamic range for each of its spectral bands. The uniformity characterization data for OLI2 were obtained by continuous motion yaw scans at multiple elevation angles, multiple source signal levels and wider angular range while the instrument is in the thermal vacuum chamber. The source used for the collects was a well-controlled tungsten halogen lamp illuminated integrating sphere. The yaw scans enables a creation of a sphere uniformity map for every band. The the uniformity map is 1° by 2.1° zone centered on the integrating sphere port. This extent is larger than the field of view of a single focal plan module (FPM). Effectively these data collects are mimicking the on-orbit side slither collects that are done on-orbit only now the target is a well-controlled stable calibration source with traceable absolute radiometric accuracy, and minimal atmospheric transmission error. The results of the radiometric uniformity characterization of OLI2 will be presented. The report will demonstrate that with the new collect method more information can be obtained in shorter amount of time and it ultimately resulted in better characterization dataset for OLI2. Description of the processing method used and the detailed information extracted from the data about quality of OLI2 and the sphere source will be provided. The uniformity corrections parameters and associated uncertainties for these uniformity correction factors will be discussed.