Readnoise Variance

After the bad pixel mask has been applied, the readnoise variance is added into the VARIANCE component of the NDF. For all instruments, the readnoise value is obtained from the calibration system, having been previously calculted in the ARRAY_TESTS recipe. Since the readnoise value is stored in electrons, it must be converted into analogue-to-digital units.

[_ADD_READNOISE_VARIANCE_, _CALCULATE_NREADS_NOISE_FACTOR_]