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NICMOS Polarimetry

NICMOS contains polarizing filters in Cameras 1 and 2. Each Camera contains three polarizing filters which are nominally offset from each other by ~120 deg. The angles, efficiencies and instrumental polarization were measured in Thermal-Vacuum tests. The on-orbit calibration set the ZERO point for the position angle (e.g., NICMOS coords to celestial coords) and determined the transmission coefficient term. The other terms were not adjusted. The position angle of the polarizers and their polarizing efficiencies are listed in the Polarimetry section of Chapter 5 of the NICMOS Instrument Handbook.

Observations in all three filters are needed to obtain the necessary information for calculating the degree of polarization and position angle at each pixel in the image. Saturating point sources is not recommended unless absolutely necessary. The array has to recover BEFORE the next iteration. Latent flux will make the final numbers suspect. This is also true for a number of iterations at the same position on the array. Dithering should move the target far beyond the saturated pixels. There are internal reflections and the observer should consider two rolls near 180 degrees. This places the ghosts on opposite sides of the object and allows a combination by "minimum" which should get rid of most of the ghost artifacts.

It is recommended that the observer review the data reduction techniques described in Chapter 5 of the NICMOS Data Handbook.

NICMOS Polarimetry Documentaion

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

Frequently Asked Questions.

Q: When using the WWW Exposure Time Calculator for polarimetry, what is the source flux I have to input? A: ...

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

NICMOS Polarimetry Update

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.

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.