Chapter 4:
Anomalies and Error Sources

4.1 NICMOS Problems Checklist

4.2 NICMOS Dark Current and Bias

4.2.1 Dark Current

4.2.2 Bias, Shading, and “Pedestal”

4.2.3 Dark Reference Files

4.2.4 Cures: How To Get Rid of What's Left

4.3 Bars

4.4 Detector Nonlinearity Issues

4.4.1 Nonlinearity Calibrations

4.4.2 Non-Zero zeroth Read Correction for Bright Sources

4.4.3 Uncorrected Saturation

4.5 Count Rate Non-Linearity

4.6 Flat Fielding

4.6.1 Characteristics of NICMOS Flat Fields

4.6.2 Temperature-dependent Flat Fields

4.6.3 Color Dependence of Flat Fields

4.7 Pixel Defects and Bad Imaging Regions

4.7.1 Hot Pixels, Cold Pixels, and Grot

4.7.2 Erratic Middle Column/Row.

4.7.3 Coronagraphic Hole

4.7.4 Vignetting

4.8 Effects of Overexposure

4.8.1 Photon Persistence

4.8.2 Cosmic Ray Persistence

4.8.3 Bright Earth Persistence (BEP)

4.8.4 Amplifier Ringing (The “Mr. Staypuft” Anomaly)

4.8.5 Optical Ghost Images

4.9 Cosmic Rays of Unusual Size

4.10 Scattered Earthlight