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NICMOS Anomalies

This is a list of "features" that might appear in NICMOS science data, even after pipeline calibration. Most of these are well-known imperfections of HgCdTe detectors which are also present in ground-based data taken with similar detectors. However, since NICMOS data has a much lower thermal background than ground-based instruments, these features stand out more clearly.

Many of the items in the list are driven by small temperature variations of the on-chip electronics. Because the calibration reference files are taken at slightly different temperature, the pipeline correction is not 100% accurate.

The NICMOS group provides a set of tools that improve the data quality significantly over the pipeline calibration by using temperature information in the science data headers. In the near future, NICMOS will take advantage of "On-the-Fly Recalibration" (OTFR) which is likely to incorporate these new tools so that many of the items in the list below will be corrected in the pipeline output.

The following references may prove useful in identifying and dealing with anomalies:

Amplifier Glow
A pattern of light, due to the reaout amplifiers, that is highest in the corners and decreases towards the center of the detector
Bad ('Photometrically Challenged') Central Column
The central row/column of apparent decreased sensitivity
Bias Jumps (Bands)
Wide bands (tens of pixels across) of fluctuating bias levels
Cosmic Ray Persistence
Spatially correlated persistent images from cosmic ray hits incurred during SAA passages
Cosmic Rays
Possible effects of very energetic cosmic ray hits
Count-rate Non-Linearity
NICMOS Count-rate Dependent Non-linearity
Dark Current
The linear component of the NICMOS dark current
Electronic Bars
Narrow stripes (a few pixels across) occurring at corresponding positions in all four quadrants
Electronic Ghosts
(Mr. Staypuft, Ringing & Streaking)
Electronic ghost images and bands appearing at points in the other three quadrants which correspond to the position of a bright source in one quadrant
Flat Fields
Sensitivity patterns for all three NICMOS cameras
High Noise Region
Sensitivity variations resulting in noise modulations across the detector
Hot and Cold Pixels
Pixels with abnormally high or low sensitivities
Image Persistence
Excess dark current observed immediately after the observation of a bright target
Optical Ghosts
Optical ghosts in the NIC1 polarizers
Particulate Contaminates (GROT)
Small spots of reduced sensitivity, generally extending only over a pixel or two
Residual Bias (Pedestal)
A DC offset which remains in an image after the dark current has been removed, producing an inverse flat field pattern in calibrated data
A time-dependent bias that changes across a quadrant as the pixels are sequentially read out
Space Junk
An example of the effects of space junk
Super Shading
An intermittent phenomenon similar to shading but with an increased amplitude
A decrease in observed brightness along the bottom edge of all three NICMOS cameras

NICMOS Anomalies & Image Artifacts Documentation

Important updates, discoveries and developments that could potentially affect NICMOS observations, calibration, or data analysis.

The NICMOS 'Pedestal' Effect

Memo Describing the 'Bars' Phenomenon

Frequently Asked Questions.

Performance Summaries:
Status reports reflecting the current understanding of instrument characteristics, performance and calibration.

The NICMOS Instrument Handbook is the primary guide regarding the characteristics and use of the instrument. The HST Data Handbook is the primary guide for calibration, reduction and analysis of NICMOS data.

Instrument Science Reports:
ISRs are technical reports written by members of the NICMOS Group about various aspects of the instrument and data. They usually contain in-depth information about specific topics.

NICMOS ISR 2003-010: Removal of Cosmic Ray persistence From Science Data using the Post-SAA Darks
E. Bergeron and M. Dickenson 06 Oct 2003

NICMOS ISR-99-010: NICMOS Temperature-Specific Darks
B. Monroe 09 Nov 1999

NICMOS ISR-99-009: NICMOS Dark Current Anomaly: Models and Test Plans
T. Boeker 25 Oct 1999

NICMOS ISR-99-008: GROT in NICMOS Cameras
M. Sosey 20 Sep 1999

NICMOS ISR-1999-012 NICMOS Calibration Lamp Stability
L. Bergeron 01 Mar 1999

NICMOS ISR-99-002: Color Dependence of NICMOS Flatfields
A. Storrs 26 Feb 1999

NICMOS ISR-98-011: NIC1 Narrow-band Earth Flats
D. Gilmore 22 Jul 1998

NICMOS ISR-98-003: NICMOS Camera 3 Pointed Flats
A. Schultz 12 Mar 1998

NICMOS ISR-98-002: First NICMOS On-Orbit Flat-Fields: Results from SMOV Data
D. Calzetti 05 Mar 1998

NICMOS ISR-98-001: Cosmic Ray Persistence in NICMOS Data
J. Najita 25 Feb 1998

NICMOS ISR-032: NICMOS SAA Contour Test: Results from SMOV data
D. Daou 31 Dec 1997

NICMOS ISR-024: Persistence in NICMOS: Results from On-Orbit data
D. Daou 12 Sep 1997

NICMOS ISR-023: Persistence in NICMOS: Results from Thermal Vacuum Data
D. Daou 16 Jun 1997

NICMOS ISR-022: Cosmic Rays on NICMOS: Results from On-Orbit Data
D. Calzetti 07 Jun 1997

NICMOS ISR 1996-019: Cosmic Rays on NICMOS: Results from Thermal Vacuum Data
D. Calzetti 27 Nov 1996

NICMOS ISR-95-006: Effects of the NICMOS Array Flat-field Response on Observations.
C. Skinner 01 Dec 1995

NICMOS ISR-95-005: Characterisation of NICMOS Array Flat-field Response.
C. Skinner 02 Nov 1995

Papers and Proceedings:
Selected NICMOS related published papers and workshop proceedings.

Cookbook style instructions, prescribed procedures, and helpful tips.

Space Telescope Analysis Newsletters:
STANs contain useful information regarding calibration and data reduction.

NICMOS STScI Analysis Newsletter 22
New NICMOS Exposure Time Calculator
Synthetic DARKs for NIC1
Release of the Visual Target Tuner
NICMOS Group 31 May 2000 (html)

NICMOS STScI Analysis Newsletter 19
Temperature dependent synthetic dark image generator
Polarizer Data Analysis Software
NICMOS Histroy Tool
NICMOS Group 30 Sep 1999 (html)

NICMOS STScI Analysis Newsletter 17
Dealing With NICMOS Image Anomalies: Current Situation and Future Goals
Data header errors
NICMOS Group 01 Mar 1999 (html)

NICMOS STScI Analysis Newsletter 8
Cosmic ray persistence
NIC3 pointed flats
NICMOS Group 01 Feb 1998 (html)

NICMOS STScI Analysis Newsletter 2
Focus update
Advice on the use of ORIENT, PATTERN-ORIENT, and POS TARG for Cycle 7
The Mr. Staypuft anomaly
The 'non-zero zeroth read problem'
NICMOS Group 31 May 1997 (html)