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 to validate the radiometers ATSR-1, ATSR-2 and AATSR which were on-board ERS-1, ERS-2 and ENVISAT respectively. The self-calibration involves the use of two internal reference blackbodies. The filters used are 3.7 microns, 10.8 microns and 12.0 microns. During the life of AATSR, the instrument was on-board MS Color Festival (2006), MS Prinsessa Ragnhild (2008), and RMS Queen Mary 2 (2010-2012). The instrument is inactive on 2014, but it is still planned to be back on the RMS Queen Mary 2014, continuing to collect SST to bridge the gap between AATSR and SLSTR which will be on the Sentinel-3 due to be launched in 2015. The SISTeR is also planned to be used to validate SLSTR data.