Landsat-7 data are collected from a nominal altitude of 705 kilometers in a near-polar, near-circular, Sun-synchronous orbit at an inclination of 98.2 degrees, imaging the same 183-km swath of the Earth's surface every 16 days. Some of the browse images you encounter may appear black or empty. These are engineering data known as FAC=Full Aperture Calibrator. FAC is a white painted panel that is deployed in front of the ETM+ aperture and diffusely reflects solar radiation into the full aperture of the instrument. FAC scenes will typically be gathered on a daily basis and constitute roughly 10 scenes for each FAC collected. So, about 10 of the ~250 scenes per day that Landsat will be delivering to EDC will be FAC scenes. Eventually, this engineering data will be gleaned out of the database.
Direct_Spatial_Reference_Method Remote sensing image Raster_Object_Information Row_Count
<http://earthexplorer.usgs.gov> . The L0R data are reformatted, raw data acquired by the satellite as it views the Earth. The data are not radiometrically corrected, the pixels are not resampled or geometrically registered to an Earth location.
The L1R product is a radiometrically corrected image. Radiometric correction is performed using either gains in the Calibration Parameter File or gains computed on the fly from the Internal Calibrator. The choice is available to a user when the product is ordered. Radiometric corrections are not reversible. The L1R product geometry is identical to the input L0R data. These L1R data are available to approved researchers only.
The L1G product is a radiometrically and systematically corrected L0R image. The correction algorithms model the spacecraft and sensor, using data generated by onboard computers during imaging events. The radiometrically corrected pixels are resampled for geometric correction and registration to an Earth location with a geodetic accuracy of 5 to 25 times the sensor's ground instantaneous field of view.