Landsat "Real-Time" (RT) scenes contain valid Image file data and are usable as is. Newly acquired Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS) data require a period of evaluation and calibration adjustment after acquisition, but are processed immediately based on preliminary calibration coefficients, assigned to the temporary RT Tier, and made available for download. When definitive calibration information becomes available, RT scenes are reprocessed and assigned to the appropriate Tier 1 (T1) or Tier 2 (T2) category. The Landsat Product Identifier correctly reflects the new category. The details about the follow-on processing for both L7 and L8 are described below. After the follow-on processing is complete and the data is available as T1 or T2, the RT data is removed.
Landsat 7 ETM+ data use predicted ephemeris and initial bumper mode parameters during initial processing. During a short period of instrument trending/characterization (about 1 week), calibration parameter adjustments finalize the geometric correction model, the data are reprocessed.