The objectives and general requirements for long-wave infra-red (LWIR) spaceborne sensor calibration are presented and assessed. The development and capabilities of existing ground calibration facilities (calibrators) are summarized. Recent calibrations and spaceborne measurements have identified major deficiencies in the calibrators and sensor response anomalies. These deficiencies, the response anomalies, and the operational conditions that influence the anomalies will be described. Changes in calibration methodology to characterize these effects will be reviewed. A review of the current "effective" method of data presentation and alternate methods will be provided. An assessment of the overall calibration status will be provided along with recommendation for critical calibration technology development.