NICMOS Coronagraphy
NICMOS coronagraphic imaging capability is
provided by a hole in the Camera 2 Field Divider
Assembly which provides a 0.3 arcsec radius
coronagraphic spot, with an effective useful
radius of 0.4 arcsec at the detector image plane.
Coronograph users should read this important advisory
for coronagraphic observing. Other important information on coronagraphy
can be found in
Chapter 5 of the NICMOS Data Handbook, section 5.1
of the NICMOS Instrument Handbook as well as in the following
performance summaries: Performance of
the Coronagraph in Cycle 7, and Motion of the Coronagraphic Hole Over
Time. For more specific details on coronagraphy, follow the links to the
documents listed below.
NICMOS Coronagraphy Documentation
Advisories:
Important updates, discoveries and developments
that could potentially affect NICMOS observations,
calibration, or data analysis.
NICMOS Coronagraphic Observing for Cycle 13 onwards
Information for NICMOS coronagraphic observers.
A. Schultz 06 Apr 2004 (html)
NICMOS Camera 2 ACQ Exposure Times
This announcement from August, 1998, notified users that the ACQ exposure times (keyword exptime) in the science headers were incorrect.
NICMOS Group 25 Aug 1998 (html)
FAQs:
Frequently Asked Questions.
Performance Summaries:
Status reports reflecting the current
understanding of instrument characteristics,
performance and calibration.
Motion of the Coronographic Hole Over Time
Animation, plots, and tables of
the position of the coronagraphic
hole over time
NICMOS Group 04 Nov 1998 (html)
Performance of the Coronagraph in Cycle 7
Past performance of the Coronagraph
and recommendations for proposers
NICMOS Group 28 Oct 1998 (html)
Handbooks:
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 2005-001: NICMOS Two Gyro Mode Coronagraphic Performance
In preparation for the Hubble Space Telescope (HST) entry into Two Gyro Mode (TGM)
operations, the NICMOS coronagraphic performance was assessed during the February
21, 2005 TGM on orbit test (ID: 10448) in two filter bands (F110W and F160W). The
gyroscope pair 2-4 was used for the TGM test. Observations were obtained of a previously
observed calibration target (GJ517; sp.type=K5Ve) coronagraphically and with direct
imaging. The F110W filter performance very closely tracks the three gyro mode (ID:
10177) results. The observed jitter of ~6.2 mas had little effect on the 1.1 ìm coronagraphy.
This result clearly shows that 1.1 ìm coronagraphy is robust against the
observed TGM jitter. The NICMOS coronagraph inner working angle (IWA) is 3.2 ë/D at
1.1 ìm. Consequently, there is sufficient performance compliance to target decentering of
these RMS amplitudes within the coronagraphic hole. There was a slight decline in performance
with the F160W filter with respect to three gyro mode which may be due to imaging
systematics; i.e., breathing and jitter. The 1.6 ìm coronagraphy is more susceptible to
imaging systematics primarily due its broader PSF (IWA=2.2 ë/D). At r=10 pixels, the
coronagraphic diffracted and scattered light suppression factor is ~3 compared to direct
imaging, while it is a factor of 4 in three gyro mode. The observed coronagraphic performance
is essentially unaffected at 1.1 ìm with TGM operations, while there is a marginal
decline at 1.6 ìm of similar amplitude to that arising from other well-known HST/NICMOS
orbit-driven instabilities. The improvement in image contrast (and dynamic range)
with coronagraphy and TGM is still substantial over direct imaging.
G. Schneider, A. Schultz, S. Malhotra & I. Dashevsky 08 Jul 2005 (pdf)
NICMOS ISR 2004-001: NICMOS Coronagraphic Calibration
The NICMOS coronagraphic imaging mode has been fully reactivated following SM3B,
performing slightly better than during Cycle 7. The diffractive rejection is essentially
unchanged (to first order) from Cycle 7 except there is a shift in the mean position of the
cold mask which gives better second-order rejection on the downsloping diffraction spikes
and slightly worse on the upsloping diffraction spikes. A target can be positioned within
~0.08 pixel (~5.8 mas) of the coronagraphic hole low-scatter position, with a repeatability
of ~0.04 pixel (~2.9 mas) for two visits executed within the same orbit, with a roll between
visits. The coronagraphic focus was checked and no adjustment was needed. The Cycle 7
coronagraphic focus position is still the best focus. A slight adjustment was made to the
PAMC tilt to remove some coma that was not present during Cycle 7. The "hole 32x32
pixel subarray" field-of-regard (FOR) was adjusted by a few pixels in each direction due
to displacement of the hole image on the detector caused by the warm up at the end of
Cycle 7 and subsequent cool down following SM3B. A new ACQ FOR "gain" table (flat
field) was installed to handle hot and cold pixels, allowing Mode-2 acquisitions for targets
from H=4 to 17. The coronagraphic hole low scatter point, the "sweet spot," was checked
and a slight adjustment was required to achieve light suppression about the coronagraphic
hole comparable to or slightly better than that achieved during Cycle 7.
A. Schultz 30 Jan 2004 (pdf)
NICMOS ISR 2003-003: NICMOS Monitoring Stability
A review of the NICMOS monthly flat field monitoring data (program IDs: 9326, 9640)
indicates that the NICMOS cameras are functioning as expected due in large part to the
stable temperature provided by the NICMOS Cooling System (NCS). The flat field data
(lamp-on) filter count rates have remained constant following SM3B/SMOV indicating
that detector sensitivity and the lamps fluxes have remained constant. Additionally, pixel
saturation levels have essentially remained unchanged since SMOV. The number of grot
affected pixels has not changed since SMOV indicating stability within the dewar. Note
that there was an increase in the number of grot affected pixels following Cycle 7 & 7N
with the addition of a large chunk in the lower right quadrant of NIC1. Dithering to
remove the affects of grot is recommended. A check of the NIC2 coronagraphic hole image
location shows hole motion similar to what was observed during Cycle 7 & 7N. Coronagraphic
observers should taylor their observations to minimize the effects of hole motion
on their data. Incremental monthly and super flat field reference files have been created
and delivered to the HST Archive for user support.
A.B. Schultz 01 Apr 2003 (pdf)
NICMOS ISR-99-006: NICMOS Coronagraphic Imaging Strategy
NICMOS Camera 2 reference images and observing strategies aimed at optimizing PSF subtraction are discussed.
A. Schultz 27 Aug 1999 (pdf)
NICMOS ISR-98-019: NICMOS Mode-1 Coronagraphic Acquisition
This report describes the acquisition of bright targets for NICMOS coronagraphic observations.
A. Schultz 19 Jan 1999 (pdf)
NICMOS ISR-98-012: NICMOS Camera 2 Coronagraphic ACQs
We have evaluated 38 Camera 2 on-board ACQs, and describe in this report the stability of coronagraphic target acquisitions.
A. Schultz 29 May 1998 (pdf)
NICMOS ISR-031: NICMOS Camera 2 Coronagraphic Acquisition
This report describes the NICMOS Camera 2 coronagraphic acquisition mode procedures for point sources, onboard software for faint targets and 'Reuse-Offset' for bright sources.
A. Schultz 13 Jan 1998 (pdf)
Papers and Proceedings:
Selected NICMOS related published papers and workshop
proceedings.
2004 AAS Poster--HST/NICMOS Coronography: Prospects for Cycle 13 and Beyond-A Choice of Coronagraphic Imagers
G. Schneider, M. Silverstone, D. Hines
Domains of Observability in the Near-Infrared with HST/NICMOS and (Adaptive Optics Augmented) Large Ground-Based Telescopes
G. Schneider
Domains of Observability in the Near-Infrared with HST/NICMOS and (Adaptive Optics Augmented) Large Ground-Based Telescopes
G. Schneider
Presentation from 2002 SPIE Meeting: Post-NCS Performance of the HST NICMOS
A. B. Schultz
Tutorials:
Cookbook style instructions, prescribed procedures, and
helpful tips.
Examples:
Examples of how to use various NICMOS-related tools, calibration and analysis techniques.
Space Telescope Analysis Newsletters:
STANs contain useful information regarding
calibration and data reduction.
|
