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The basic SLSTR technique is inherited from the technique used by the series of scan radiometers on ATSR. The instrument includes the set of channels used by ATSR-2 and AATSR, ensuring continuity of data, together with two new channels at wavelengths of 2.25 and 1.375 microns in support of cloud clearing for surface temperature retrieval.

The SLST radiometer measures a nadir and an along track scan, each of which also intersects the calibration black bodies and the visible calibration unit once per cycle (two successive scans). The requirement for a wider nadir swath and for enhanced resolution in coastal regions means the number of instrument pixels to be measured per scan exceeds the corresponding figure for AATSR. The SLST radiometer uses two independent scan mirrors rotating in opposite directions each scanning at a rate of 200 scans per minute. Each scan measures two along track pixels of 1 km (four or eight pixels at 500 m resolution for visible/NIR channels and SWIR channels, respectively) simultaneously. This configuration increases the swath width in both views, as well as providing 500 m resolution in the solar channels. The width of the nominal image swath is 1 400 km for the nadir view, and 740 km for the along track view.

The SLSTR Optical Scanning Unit. (Credit IABG)

The SLSTR instrument is a conical scanning imaging radiometer employing the along track scanning dual-view technique to provide robust atmospheric correction over a dual-view swath.

The design also includes the capability to measure active wildfires, achieved by extending the dynamic range of the 10.8 µm channel and including dedicated detectors at 3.7 µm that are capable of detecting fires at ~650 K without saturation.

The SLSTR is separated into two physical units that are integrated onto a single plate: the SLSTR Optical Scanning Onit (see figure above) housing the Optomechanical Enclosure (OME) and Detection Assembly (DA), and a separate SLSTR control and processor electronics unit.

SLSTR Visible Channel Detector (Credit OSI)
Structural and Thermal Model of the SLSTR (showing the large kidney-shaped Earth-view baffles of nadir (bottom) and oblique (top) views) (Credit IABG)