One of the primary mission objectives of the SLSTR instrument is to extend the long-term, consistent set of global Sea Surface Temperature (SST) measurements. SLSTR provides data continuity back to 1991 as its data permit the continuation of data-sets from previous instruments: Along Track Scanning Radiometer (ATSR) on ERS-1, ATSR-2 on ERS-2 and the Advanced Along Track Scanning Radiometer (AATSR) on Envisat.
From left to right: ATSR launched on ERS-1 (1991-2000); ATSR-2 launched on ERS-2 (1995-2008); AATSR launched on Envisat (2002-2012); and the first of the Sentinel series SLSTR-A launched in 2016, followed by SLSTR-B in 2018 (not viewed here).
Following AATSR/Envisat, 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 instrument includes channels in the visible (VIS), thermal (TIR) and short wave (SWIR) infra-red spectrum.
The SLSTR design incorporates the basic functionality of AATSR, with the addition of some new, more advanced, features. These include wider swath coverage which completely overlaps the OLCI swath, more spectral bands, and a spatial resolution of 0.5 km for visible and SWIR bands. Unlike AATSR which had a forward and nadir viewing configuration, SLSTR has a backwards and nadir viewing configuration. Both the SLSTR and OLCI instruments require a clear view to the sun for calibration purposes and accommodating both on the same platform resulted in the SLSTR oblique view pointing backwards.
SLSTR provides equivalent or better performance (see comparative table below) when compared to its predecessors in the following ways:
Comparison of SLSTR specification with respect to previous AATSR and ATSR-1/2 instrument performance.
SSI is the spatial sampling interval at sub-satellite point (SSP), λ is central wavelength, a is top of atmosphere albedo, T is top of atmosphere brightness temperature, SNR is signal-to-noise ratio, and NEΔT is noise equivalent difference temperature.