Simulated observation of an Earth twin by the HWO concept assuming a simplified noise and a higher-fidelity noise instances. Top panel: the simulated observed flux at a distance of 10 pc between 0.2 and 2 μm for the two noise scenarios: simplified noise at constant error bars (shaded dark gray area with solid edges) and higher-fidelity simulated noise obtained with PSG (shaded light gray area with dotted edges). Bottom panel: signal-to-noise ratio (S/N) as a function of wavelength for the two noise instances: simplified noise (solid line) and PSG-simulated noise (dotted line).