Ground Track for NOSE Path 156
Every 233 orbits, the EOS-Aura orbital repeat cycle, the spacecraft covers the exact same ground track. By describing the ground coverage for each orbit in the orbital repeat cycle, the ground coverage of a science data product can be described in terms of a reference to one of these pre-defined paths, rather than using bounding boxes or polygons. This method for describing the ground coverage of a science data product in metadata is called NOSE, Nominal Orbit Spatial Extent.
The NOSE metadata can be used for geo-spatial searches. To refine these searches, each ground track is split up in blocks. Each science data product then only needs to refer to the paths and blocks covered by the product in order to allow for geo-spatial searches. The definition of the NOSE paths and blocks needs to be included in the search system.
For OMI, 466 NOSE paths are defined. Paths 1 .. 233 specify the ground coverage of nominal global measurements for each orbit in the orbital repeat cycle, paths 234 .. 466 specify the ground coverage of spatial zoom-in measurements. The paths are split up in blocks: each block covers about two minutes of measurement time.
The eclipse side of the orbit is located in the figure where a discontinuity in the longitude occurs near the equator. The dayside of the orbit is located in the figure where the longitude changes continuously near the equator. Starting at the spacecraft midnight point the satellite moves southwards, then from south to north on the dayside and finally southwards again on the eclipse side of the orbit.