The SLSTR uses two independent scan chains each including a separate scan mirror. While more complex than the single scan system employed by the ATSR instrument, this configuration especially increases instrument swath coverage.
The nadir swath is asymmetrical with respect to the nadir point to provide identical and contemporaneous coverage with OLCI ocean/land colour measurements.
Figure 1: Outline sketch of the SENTINEL-3 SLSTR instrument viewing geometry highlighting the asymmetric nadir swath with respect to the nadir point
Following a trade-off analysis between topography and optical mission requirements, the choice of orbit for SENTINEL-3 is a sun-synchronous orbit at 814.5 km altitude (14 + 7/27 revolutions per day) with a local equatorial crossing time of 10:00 am. This satellite orbit provides a 27-day repeat.
The mean global coverage revisit time for dual view SLSTR observations is 1.9 days at the equator (one operational spacecraft) or 0.9 days (in constellation with a 180° in-plane separation between the two spacecraft) with these values increasing at higher latitudes due to orbital convergence.
Table 1: Global coverage revisit times for SLSTR optical measurements
Figure 2: SLSTR Mean Revisit Time with Two-Satellite Configuration