The Scanning Infrared Sea surface Temperature Radiometer (SISTeR), developed at Rutherford Appleton Laboratory, is a self-calibrating filter radiometer for the in situ measurement of skin SST, that has been used to validate the radiometers ATSR-1, ATSR-2, AATSR and SLSTR which were on-board ERS-1, ERS-2 ENVISAT and Sentinel-3 respectively. The instrument has been deployed on MS Color Festival (2006), MS Prinsesse Ragnhild (2008), and RMS Queen Mary 2 (2010-present).