### Uranus

The 2024 brightness temperature spectrum gives lower values than the Legacy model. Above 130 GHz the 2024 temperatures are 4% lower than the Legacy values. The offset increases towards lower frequencies, with 5% at 120 GHz and 10% below 80GHz.

The CASA model shows a different profile, with values in very good agreement with the Legacy values below 100 GHz and above 220 GHz, and 5% lower temperatures between 110 and 200 GHz.

Uranus is commonly used as a primary flux calibrator at NOEMA. Since the 2024 brightness temperatures are lower than the Legacy values, the secondary calibrator fluxes and the antenna efficiencies based on Uranus measurements will be lower. The amplitude of this effect will be of 4% above 130GHz, and in the 5–10% range between 80 and 115GHz.