### REDUCE_NOISE_PHOTON

determine photon noise contribution to total noise

#### Description:

This recipe derives the photon noise contribution by subtracting in quadrature noise measurements made with the shutter open and closed. The initial dark in the observation is used to estimate the dark noise, and the same number of samples in the first on-sky data are used to calculate the sky noise. The photon noise-equivalent-power (NEP) is then given by

NEP_ph = sqrt( NEP_sky$\ast$$\ast$2 - NEP_dark$\ast$$\ast$2 )The image for each subarray is derived separately.

The results are written to a log file called log.photnoise

#### Notes:

This recipe only works with raw time-series data and is designed to be used in an offline mode.

#### Available Parameters :

##### FLATSNR
Signal-to-noise ratio to use in the flatfield calculation.
##### NEP_CLIP
A comma-separated pair of numbers to indicate the low and high clipping levels for the NEP. If only one is given, it is assigned to the nepcliplow parameter.
##### NOI_CLIP
A comma-separated pair of numbers to indicate the low and high clipping levels for the noise. If only one is given, it is assigned to the noicliplow parameter.
##### NOISE_CFG
Name of an alternative config file used by calcnoise. File must be in ORAC_DATA_OUT.
##### RESIST_CFG
Name of an alternative list of resistor values used when calculating the flatfield. File must be in ORAC_DATA_OUT.
##### NOISE_SAMPLES
Number of samples to use when calculating the noise properties of on-sky data. Default is to use the same number as in the initial DARK.

None.