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Index variables for GEO: terminology conventions? #320

@StevenCompernolle

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@StevenCompernolle

For a LEO like TROPOMI, one has

  • orbit_index
  • scan_subindex (across-track pixel position; along which the time does not vary). Matching TROPOMI's 'ground_pixel'
  • TROPOMI's scanline (along-track pixel position; along which the time does vary). There is no official HARP variable, but 'scan_index' seems a logical name.

Are there already plans for similar variable names for GEOs like S4, TEMPO and GEMS?

Specifically for S4, the ground_pixel (along which the time does not vary) and scanline (along which the time does vary) are taken over from the LEO like S5 and TROPOMI. So it seems logical to still have scan_subindex matching ground_pixel. Thereby my suggestion to add scan_subindex to the S4 ingestion.

However, I don't think there is already a HARP name for the repeated observation cycles of S4. In TEMPO this is called a 'scan' (there is a scan_num global attribute in TEMPO). 'scan_index' could therefore be a choice but this would conflict somewhat with the HARP logic, as a scan_index should only be '1 level higher' than a 'scan_subindex'. Any idea how we should call the index for the repeated observation cycle?

I do think such an index is valuable, in a similar way as the orbit_index is for a LEO.

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