Reference Files

The ramp_fit step uses three reference file types:

• GAIN

• READNOISE

• DARK

During ramp fitting, the GAIN values are used to temporarily convert the pixel values from units of DN to electrons, and convert the results of ramp fitting back to DN. The READNOISE values are used as part of the noise estimate for each pixel. The DARK values are needed to estimate the Poisson noise. See Description: Optimized Least-squares with Uneven Ramps for more details.