The ISAR instruments are calibrated against a Laboratory Black Body (CASOTS 2). The CASOTS 2 black body is an evolution of the CASOTS design and is based on the Giest & Fowler 3rd generation design used by NIST. The CASOTS 2 is slightly deeper than the NIST design and uses a stirred waterbath with no fixed calibration points. The temperature of the water bath is measured with a HART 1504 platinum resistance thermometer.CASOTS II The CASOTS 2 was characterised against the NIST black body at the University of Miami in March 2006.  Furthermore the ISAR team attended the the CEOS-IVOS infra-red isensor intercomparison workshop held  in 2009 at NPL and the University of Miami. All our measurments are tracable to SI standards.