SWAPI L3 metadata updates

[jtniehof]

This is a list of ISTP metadata that needs to be changed for SWAPI

Bold items need SWAPI team input; others are informational or Menlo can handle directly.

l3a_proton-sw

No issues

l3a_pui-he

• pui_background_count_rate_uncert has a VALIDMAX of 1 and several values over that (test file is imap_swapi_l3a_pui-he_20260419_v012.cdf). The uncertainty really is a lot larger than the calculated background rate in these cases, although that's also true for a lot of other places where the uncertainty is still less than 1. How should we handle this? Is this indicative of an issue to fix in the code, something we should replace with fill (and then maybe also replace the background count rate with fill), increase the VALIDMAX? Wait for updated code?

l3a_alpha-sw

• alpha_sw_temperature_uncert and alpha_sw_density_uncert similarly have values over the VALIDMAX; similar options to the PUI. How should we handle this?

l3b_combined

• combined_differential_flux references combined_energy_label but that variable doesn't exist, needs to be added
• Units are in IDL strings and should be according to IMAP nomenclature. I think that's #/(cm^2-s-sr-eV/q)