I am hoping someone can help me determine the (absolute) orbit number for Sentinel 3 given only the relative orbit and cycle numbers in the filename. (I know that this is stored within the manifest .xml file, but I no longer have those for the files I downloaded.)
From documentation online (e.g. https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-3/satellite-description/orbit ) my understanding is 385 orbits per cycle. However on downloading a “fresh” file, I can’t reverse-engineer the formula, so must be missing something.
For example, file S3A_OL_1_ERR____20190815T045631_20190815T054045_20190816T083001_2654_048_119______LN1_O_NT_002 metadata says:
<sentinel-safe:orbitNumber type=“start” groundTrackDirection=“ascending”>18187</sentinel-safe:orbitNumber>
<sentinel-safe:relativeOrbitNumber type=“start” groundTrackDirection=“ascending”>119</sentinel-safe:relativeOrbitNumber>
The 119 and 48 match what’s in the filename. So from these I should be able to get orbit number 18187.
However, 48*385 + 119 = 18599 which does not match.
I then thought maybe cycles start from 1 not 0, in which case (48-1)*385+119 = 18214 which is closer but also doesn’t match.
Does someone know (and preferably can link to the source) for the correct calculation? I couldn’t find it in the reference documents linked above, or via a Google search.