Bias Parameter Files (BPFs) supply radiometric correction parameters that are applied during Level-1 processing of Landsat data.
There are separate BPFs for the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS), as the radiometric processing of the data from these instruments differs. The bias parameter for OLI is an estimate of the portion of the raw signal due to the electronics of the instrument and not due to light reaching the sensor. The TIRS bias parameter is an estimate of the portion of the raw signal that is due to the instrument electronics and to the thermal energy of the instrument.
Both BPFs contain two bias parameters per detector. The first bias parameter is an estimate derived from calibration data acquired before the scene interval for which the BPF is valid and the second is an estimate derived from calibration data acquired after. The OLI BPF also provides, for all operable detectors, a set of coefficients that can be used to estimate per frame variation in the bias as a polynomial function of the average of the Video Reference Pixel (VRP) response for a given band and Sensor Chip Assembly (SCA).
Landsat 8 BPF files can be downloaded.