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:
|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|
|Possible effects of very energetic cosmic ray hits|
|NICMOS Count-rate Dependent Non-linearity|
|The linear component of the NICMOS dark current|
|Narrow stripes (a few pixels across) occurring at corresponding positions in all four quadrants|
(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|
|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|
|Excess dark current observed immediately after the observation of a bright target|
|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|
|An example of the effects of space junk|
|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.
Frequently Asked Questions.
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.
E. Bergeron and M. Dickenson 06 Oct 2003
B. Monroe 09 Nov 1999
T. Boeker 25 Oct 1999
M. Sosey 20 Sep 1999
L. Bergeron 01 Mar 1999
A. Storrs 26 Feb 1999
D. Gilmore 22 Jul 1998
A. Schultz 12 Mar 1998
D. Calzetti 05 Mar 1998
J. Najita 25 Feb 1998
D. Daou 31 Dec 1997
D. Daou 12 Sep 1997
D. Daou 16 Jun 1997
D. Calzetti 07 Jun 1997
D. Calzetti 27 Nov 1996
C. Skinner 01 Dec 1995
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 STScI Analysis Newsletter 19
Temperature dependent synthetic dark image generator
Polarizer Data Analysis Software
NICMOS Histroy Tool
NICMOS STScI Analysis Newsletter 17
Dealing With NICMOS Image Anomalies: Current Situation and Future Goals
Data header errors
NICMOS STScI Analysis Newsletter 8
Cosmic ray persistence
NIC3 pointed flats
NICMOS STScI Analysis Newsletter 2
Advice on the use of ORIENT, PATTERN-ORIENT, and POS TARG for Cycle 7
The Mr. Staypuft anomaly
The 'non-zero zeroth read problem'