System Noise

The sensitivity of SENTINEL-1 expressed by the noise equivalent sigma naught is specified to be -22 dB or better. The radiometric accuracy of its data products is within a statistical error (3σ) of 1.0 dB. For distributed targets the ambiguity ratio is specified to be -22 dB or better.

Radiometric Accuracy

Radiometric accuracy and stability are specified for SENTINEL-1 for all measurement modes to be within 1 dB (3σ) and 0.5 dB (3σ) respectively. The accuracy and stability numbers refer to measurement uncertainty of the radar backscattering coefficient using the image intensity excluding the effect of speckle and noise.

Radiometric Resolution

Radiometric resolution refers to the measurement uncertainty of the radar backscattering coefficient using the image intensity arising from speckle and noise for an otherwise perfect system. Radiometric resolution is expressed as the standard deviation of the measurement uncertainty normalised with respect to the mean. For an imaging system with noise bias subtraction, the radiometric resolution is given by:

The figure below shows the the radiometric resolution for a radar backscatter coefficient σ0 varying from -26 dB m2 m-2 up to 0 dB m255 m-2 for the different imaging modes of SENTINEL-1 over a 150 m by 150 m spatial resolution product with a NESZ of -22 dB. For comparison, the radiometric resolution of the ENVISAT ASAR Wide swath is also given.

Figure 1 Radiometric Resolution (in dB) as a Function of the Radar Backscatter Coefficient of a 150 × 150 m Spatial Resolution Product