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Hubble Space Telescope
NICMOS STScI Analysis Newsletter 27

| STScI Analysis Newsletter
| December 2002
Visit the NICMOS web site
"New in the Last 45 Days" for all new information about 

CONTENTS (Optional):

- HST Cycle 12 Call for Proposals

- New NICMOS Instrument Handbook

- NICMOS Coronagraphy White Paper

- High S/N NICMOS Grism Capability

- post-NCS NICMOS Linearity Calibration

- post-NCS NICMOS Cold Mask Movement

- post-NCS Darks

- Cryocooler Status 

- post-NCS NICMOS Focus and Pointing

- NICMOS preprints


HST Cycle 12 Call for Proposals

NASA and The Space Telescope Science Institute (STScI) are
pleased to announce the Cycle 12 Call for Proposals for
Hubble Space Telescope (HST) Observations and funding for
Archival Research and Theoretical Research programs.
Participation in this program is open to all categories of
organizations, both domestic and foreign, including
educational institutions, profit and nonprofit
organizations, NASA Centers, and other Government agencies.
This solicitation will be open from October 16, 2002
through January 24, 2003 8:00pm EST, and proposals may be
submitted throughout this period. Results of the selection
will be announced in April 2003.


New NICMOS Instrument Handbook 

The post-NCS updated NICMOS Instrument Handbook for
Cycle 12 has been completed and released.  The new
Instrument Handbook is available on the NICMOS
home web page.


NICMOS Coronagraphy White Paper

A report comparing ground-based Adaptive Optics (AO)
observations with HST/NICMOS direct imaging and coronagraphy
has been prepared and released to STScI by Glenn Schneider,
Steward Observatory, University of Arizona, Tucson, AZ.  The
GROUND-BASED TELESCOPES," is available on the HST Cycle 12
Phase I web page and on the NICMOS home web page.


High S/N NICMOS Grism Capability

Results from a NICMOS calibration program to characterize
the high S/N capability of NICMOS grism spectroscopy has
been prepared and released. Instrument Science Report (ISR)
ISR-NIC-2003-001, title: "High Signal-to-Noise, Differential
NICMOS Spectrophotometry," is available on the NICMOS home
web page.


post-NCS NICMOS Linearity Calibration

Analysis of post-NCS long exposure images indicates that
the linearity of the NICMOS detectors has not changed with
the qualifier that the saturation limit is now lower.

The current linearity files delivered to CDBS for use by
the OPUS pipeline and calnica contain the
pre-NCS correction coefficients, but decreased saturation
values [node2]. These files are also available for NICMOS
users on the NICMOS web page.

New linearity reference files will be produced using the
post-NCS data and installed in CDBS in the near future.

post-NCS NICMOS Cold Mask Movement

Deep PSF images of calibration target LHS1846 (J=8.65;
J-K=0.75; sp.typ=M4V) were obtained in each NICMOS Camera
(program ID: 9704).  Analysis using phase retrieval
software show no appreciable change in cold mask position 
since January 1999.

post-NCS Darks

The NICMOS "dark current" is composed of three independent
components - a true dark-current which accumulates linearly
with exposure time, an "amplifier glow" which results from
operation of the four readout amplifiers near the detector
corners, injecting a spatially dependent signal each time
the detector is read out, and finally an amplifier-induced,
spatially varying bias component called "shading," whose
amplitude across the detector depends on the time since the
non-destructive readout.

All components of the darks have been characterized at the
post-NCS operating temp of 77.1~K. The observed changes in
characteristics were generally as-expected, based on data
taken through this temperature range during the end-of-life
(EOL) warmup in early 1999. The linear component of the dark
current shows an increased amplitude and a large number of
"hot" pixels across all the detectors. These pixels are
still functional and calibratable, but have a much higher
level of linear dark current than the mean of the rest of
the array, giving an uncalibrated image a "salty"
appearance. Small differences were seen in the amplifier
glow component, but in general the amplitude and spatial
extent of the glow are similar to the pre-NCS era. The
shading components also showed small differences from the
modeled values of EOL. New models were fit to the shading
at the 77.1~K operating temperature.  New reference files
for the fixed temperature of 77.1~K have been built and
installed into the calibration database.

Cryocooler Status

The cryocooler has held the NICMOS detector temperatures
quite well at ~77.1 K.  The amplitude of daily variations
of the detector temperatures is 0.05 K and larger
deviations occur when HST is oriented to unusually cold
or hot attitudes for extended periods of time.
Furthermore, a slow seasonal increase of the detector
temperatures to an average value of 77.19 K has occurred
as the aft-shroud warmed with the approach of Earth to 
perihelion.  An adjustment to decrease the NCC
temperature control-law set-point by 0.05 K was performed
on December 19, 2002 (day 2002.353 at 14:28:47 UT), which
reduced the detector temperatures by 0.04 K on average.  It
is anticipated that a corresponding increase in the
control-law set-point temperature will be required during
Spring 2003 once Earth recedes from the Sun.


post-NCS NICMOS Focus and Pointing

Monthly monitoring of the NICMOS focus will continue through
February 2003 and bi-monthly there after.  The latest
focus results show that the focus is as expected and
stable.  Trending indicates the focus oscillates about the
set values for each camera.

The HST Secondary mirror was moved on December 2, 2002
(day 2002.336 at 21:00 UTC) to correct the HST focus.  The
movement of the mirror completed with no problems.  The
NICMOS focus monitor executed two days after the mirror
movement and the results were nominal.

The NICMOS science aperture file was updated and will take
affect starting with observations on January 13, 2003.
This is a result of the calibration program following the
reactivation of NICMOS. Any data since the refurbishment
that is retrieved from the HST Archive will automatically
be recalibrated by OTFR with the new pointing values.


| Additional general section(s) (e.g. NICMOS preprints)

Gilliland, R.L. and Arribas, S. 2003, "High Signal-to-Noise,
Differential NICMOS Spectrophotometry," ISR-NIC-2003-001.

King, N.L., Nota, A., Walsh, J.R., Panagia, N., Gull, T.R.,
Pasquali, A., Clampin, M., and Bergeron, L.E. 2002, "A
Hubble Space Telescope Polarization Study of Dust in the
eta Carinae Homunculus," ApJ, 581, 285.

Noriega-Crespo, A., Cotera, A., Young, E., and Chen, H.
2002, "Hubble Space Telescope NICMOS Images of the HH 7/11
Outflow in NGC 1333," ApJ, 580, 959.

Schneider, G. 2002, "Domains of Observabilty in the Near-
Infrared with HST/NICMOS and (Adaptive Optics Augmented)
Large Ground-Based Telescope," STScI White Paper.

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