Early Radiometric Performance Assessment of the Landsat-8 Operational Land Imager (OLI)

摘要

Landsat-8, the latest in the Landsat series of satellites, was launched on February 11, 2013 and carries on board the Operational Land Imager (OLI) as one of its payloads. The satellite's mission is to continue the long history of moderate resolution imaging of the Landsat program. The OLI follows the highly successful Landsat-5 and Landsat-7 in continuing to populate a global archive of Earth images that dates back to 1972. The design of the Landsat-8 instruments is a significant departure from earlier Landsats. The OLI is a pushbroom instrument; all previous recent Landsat instruments were electromechanical (whiskbroom) instruments. OLI also has two new spectral bands and refined bandpasses; the thermal imaging capability on Landsat-8 is in a separate instrument. The pushbroom design provides significantly better signal to noise performance than historically available, but at the expense of circa 70,000 detectors versus the 100 or so on previous instruments. The large focal plane and large number of detectors makes detector to detector relative calibration more challenging, increasing the propensity for banding and striping in imagery. On-board radiometric calibration devices include a shutter to measure the dark levels, a full aperture solar panel for calibration against the sun, and multiple sets of lamps for short-term stability monitoring. Early results from the on-board calibration devices indicate that the OLI is outperforming the Landsat-7 instrument in signal-to-noise ratio by an order of magnitude, consistent with pre-launch measurements. Over the first five months, the instrument is stable to within 0.7%, as measured by the lamps and solar diffuser. A relative calibration (detector-to-detector) and a linearization parameter update have been performed that reduce visible striping; with this update, the residual striping has been reduced by half in all OLI bands.