Following ascents and descents, the BBR's can be out of thermal equilibrium (the inner dome temperature may take longer to stabilise than the outer dome) which can cause errors and negative values in the data.


Therefore it is recommended that the BBR data is used in straight and level runs only. For more information, please refer to the attached MRF technical note, which also suggests the BBRs are allowed 5 minutes following a profile to stabilise.

pdf MRF tech note13 - Thermal lag of Hercules' pyranometers (237 KB)

To help guarantee good BBR data quality during a campaign, there should be (1) regular cleaning of the domes, (2) maybe a couple of box pattern calibrations and (3) regular pirouettes on the runway.