### Neptune

The Legacy and 2024 temperatures are in good agreement above 130 GHz (less than 2% offset), except around 230 and 345 GHz, where the CO atmospheric lines are taken into account in the 2024 models. The brightness temperature in the 2024 spectrum is 10% lower than the Legacy values in these lines.

Below 80 GHz the 2024 temperature values are more than 5% lower than the Legacy values.

The CASA model is very similar to the 2024 spectrum, with offset lower than 1%.

The use 2024 brightness temperature spectrum of Neptune will have a small impact on the NOEMA flux calibration, except in the vicinity of atmospheric lines.