The channel correlation matrices (for independent or structured effects) should set fill_value for invalid channels. Certainly if all of the orbit is invalid.
This needs a project level decision (@Rhonaphipps), as it also affects AVHRR (@jmittaz @patternizer), microwave (@Burgdorf @ihansuhh) and MVIRI (@frarue).
The channel correlation matrices (for independent or structured effects) should set
fill_value
for invalid channels. Certainly if all of the orbit is invalid.