Calibration, Noise & Signal-to-Noise: Observation, Measurement & Evidence

Common calibration data include bias or pedestal measurements, dark frames, flat fields, wavelength references, standard stars, point-spread functions, and time-dependent sensitivity corrections. Noise terms combine differently depending on detector and observing regime.

Repeated observations show predictable noise scaling, while observations of calibrated standards reveal sensitivity changes and detector nonuniformity. Mission pipelines document and propagate uncertainty into science products.

Photon counting follows statistical fluctuations, detector readout adds electronic uncertainty, thermal current accumulates with time, and sky emission contributes background photons. Calibration removes systematic instrument signatures without eliminating fundamental random noise.

Bias, dark, flat, wavelength, flux, and point-spread calibrations are tested on standards and repeated observations. Residual patterns reveal systematic errors that do not average away.