1.1.4 Geographical Coverage

MERIS scans the Earth's surface by the so-called push-broom method. CCD arrays provide spatial sampling in the across-track direction, while the satellite's motion provides scanning in the along-track direction. The instrument's 68.5° field of view, nadir pointing, covers a swath width of 1,150 km. at a nominal altitude of 800 km.

Resolutions

MERIS products are available at two spatial resolutions:

· Full Resolution (FR) with a resolution at subsatellite point 300 m

· Reduced Resolution (RR) with a resolution at subsatellite point 1200 m

Segment Concept

Product partition is performed by segments of 43.5 minutes for the MERIS RR, which consist of that part of the orbit for which the Sun zenith angle is below 80^°. A MERIS RR segment corresponds to 17,400 km along track.

The MERIS FR segment corresponds to the same Sun illumination limitations as for the reduced-resolution mode; however, the acquired data is not necessarily contiguous.

Scene Concept

For the purpose of distribution, the MERIS product is packaged in multiple of scenes of 1,150 km ×1,150 km for the reduced-resolution product; and in scenes of 575 km × 575 km or 296 km × 296 km for the full-resolution products.

RR scenes contain 71 × 71 tie points for an 1,150 km × 1,150 km image; FR-1 scenes contain 36 × 36 tie points for an 575 km × 575 km image; FR-2 scenes contain 18 × 18 tie points for an 296 km × 296 km image.

Only a part (called a “Child”) of a acquisition segment could be ordered.

Global Coverage

MERIS's 68.5° field of view allows global coverage to be provided in two to three days, as required by oceanographic, land, and atmospheric investigations. See figure 1.5

Figure 1.7 - Global coverage