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NICMOS STScI Analysis Newsletter 11

NICMOS STScI Analysis Newsletter 11

May 1998


        - NICMOS NEWS
          + New NICMOS Information on the WWW
          + Change to HOPR policy as NICMOS end of life nears
          + CALNICA v3.2 and CALNICB v2.2 Coming Soon



New NICMOS Information on the WWW

Similar to all Space Telescope Instruments, the NICMOS home page on
the World Wide Web is updated with all instrument developments. The
NICMOS home page can be found by visiting the STScI WWW page
( and following Observing links to the NICMOS
Web pages.
Since last month, the following items have been newly posted:
    * NICMOS Focus Update page had been update (13 May 1998)
    * NICMOS Photometry page has been updated (22 May 1998)
    * NICMOS Coronographic Hole page has been updated (27 May 1998)
    * NICMOS PlateScale page has been updated (27 May 1998)
    * NICMOS reference files list has been updated (21 May 1998)
    * NICMOS Parallel Program page has been updated (27 May 1998)
Since last month, the following ISRs have been published:
    * NICMOS Camera 2 Coronagraphic ACQs
    * NICMOS Parallel Thermal Background: Results from SMOV and Cycle 7
    * Focus Variation and the Orbital Phase of Observations
    * Statistics of Accumulating Signal 
    * Possible Evidence for NICMOS Focus "Precessional Breathing"
    * Observed Camera 3 Performance

Change to HOPR policy as NICMOS end of life nears.

The Long Range Plan for HST is now very tightly managed in an
effort to complete as much NICMOS science as possible before the 
expected cryogen exhaustion date, and at the same time execute
STIS and WFPC2 science observations at an acceptably high rate.
As in past cycles with such tight scheduling conditions the 
policy for accepting and awarding Hubble Observation Problem
Report (HOPR) repeats has been modified as follows:
(1) Programs that are complete at more than the 75%
level in terms of executed and scheduled observations will not
in general be eligible for repeats of failed observations unless
the lost data can be justified to be of unique importance.  
(2) HOPRS filed after 1 August 1998 for NICMOS will not in 
general be accepted.

Observers are advised to file any HOPRs requesting repeats of 
failed observations as quickly as possible in order to improve their
chances of a favorable resolution.

Instructions for submitting a HOPR are available at

CALNICA v3.2 and CALNICB v2.2 Coming Soon

New versions of the NICMOS pipeline data calibration and reduction tasks
CALNICA and CALNICB are currently in testing and will be put into use in
the OPUS production pipeline in the near future. Changes to CALNICA mostly
involve enhancements to the MultiAccum zero read signal correction routine
and the implementation of two new data quality flag values. The new version
of CALNICB also includes the implementation of the new data quality flags,
as well as the addition of several new task parameters which will allow
users greater flexibility when reprocessing associated data sets.

In CALNICA v3.2 the MultiAccum zero read signal correction routine
(ZSIGCORR) is no longer automatically applied whenever a MultiAccum-mode
observation is processed. Two new keywords have been added to the primary
header of NICMOS science files - ZSIGCORR and ZSIGDONE - which now serve as
the calibration "switch" and "indicator" for the ZSIGCORR routine. This gives
users easy way to turn the step on and off as desired when reprocessing.
Another new keyword - SAMPZERO - has also been added to NICMOS primary
headers, which records the effective exposure time of the zero read image,
and is used by CALNICA v3.2 in estimating the amount of signal present in
the zero read image. When reprocessing old NICMOS images, which don't have
these keywords, CALNICA will use appropriate default values.

The ZSIGCORR routine itself has also been enhanced so that it is now
capable of estimating the signal present in the zero read for pixels that
had already reached saturation in the first read image. Data for such
pixels is carried through the remainder of the processing steps and used in
the CRIDCALC step to compute a signal level for storing in the output _cal
file. In previous versions of CALNICA, such pixels were simply set to zero
in the _cal file. The ZSIGCORR routine also now sets a DQ flag value, in
both the _ima and _cal output files, for all pixels identified as having
signal in the zero read image. The new DQ flag has a value of 2048, which was
previously unused. This DQ flag is treated by CALNICA as a warning only, as
it does not reject any data for pixels having this flag value. It is intended
to simply act as a warning to users that the data in such pixels may not be
as reliable as others.

The final change to the ZSIGCORR routine is to have the estimated zero read
signal stored in the zero read imset of the output _ima file, so that users
can see the result of that calculation. Previously, the SCI image extension
of the zero read imset in the _ima file had a constant zero value, due to
the zero read image being subtracted from itself during the ZOFFCORR step.
In the new version of CALNICA the zero read SCI image will contain the
estimated countrate (or counts if UNITCORR is turned off) of the zero read,
the ERR extension will contain the corresponding statistical errors on that
signal, and the DQ extension will contain the new DQ flag value 2048 wherever
signal was detected (in addition to any other normal DQ flag values for bad

A second new DQ flag has been implemented throughout all CALNICA processing
steps. The flag value 16 will now be used to indicate pixels affected by
"grot" on the detectors. This flag value had previously been assigned to
indicate a bad pixel in the ILLMFILE reference file used by CALNICB, but had
never been implemented. The assignment of this value has now been changed
to indicate grot. The grot DQ flag values will soon be added to the MASKFILE
bad pixel reference files and will then be automatically propagated into data
processed with CALNICA during the MASKCORR step. As with the zero read signal
flag value of 2048, CALNICA v3.2 treats the grot DQ flag as a warning only,
and does not reject any data for affected pixels. The flag will appear in the
output _ima and _cal files as a warning to users.

CALNICB v2.2 also handles the two new DQ flag values. It also treats the zero
read signal flag (DQ=2048) as a warning only and does not reject data having
this flag, but it will reject pixels flagged as affected by grot (DQ=16). In
this way, mosaic images (_mos files) produced by CALNICB v2.2 will be cleaned
of grot where there is data from unaffected pixels in overlapping images.

The other major changes to CALNICB v2.2 are the addition of several new
task parameters, which will allow users more flexibility in controlling the
processing. Briefly, there will be parameters that allow you to turn the
scalar background subtraction on or off, set the cosmic-ray rejection
threshold, set the cross-correlation search window size, as well as the
capability to use an ASC table produced during a previous execution of
CALNICB as input for subsequent passes. This will allow users the option
of setting their own image background signal values and/or image offsets in
the table, and then have CALNICB use these supplied values rather than
computing them itself. More details concerning all of these features will be
announced in a later STAN after v2.2 has been publically released.


Data Analyst Position Available at STScI
The Space Telescope Science Institute currently has openings for
Data Analysts. Data Analysts in the Science Support Division help General
Observers and Archive Researchers analyze HST data, work with Instrument
Scientists in calibrating the HST instruments, and work with STScI staff
on grant-supported research projects. These research projects span a range
of size scales from comets and planets to the large scale structure of
the universe and a range of wavelengths from radio to X-ray astronomy.
Applicants should possess a B.S. degree (M.S. degree a plus) in astronomy
or physics, or equivalent; experience with astronomical research; familiarity
with scientific computing; expertise in data analysis; knowledge of IRAF, IDL
or other software packages for astronomical data analysis; and programming
ability. Additional mathematical, statistical, and computer skills are
desirable. Candidates should have the ability to work with a minimum of
direction, enjoy research, and possess skills to develop excellent working
relationships. Candidates should send a cover letter with current curriculum
vitae and the names of three references to:
Human Resources Manager
Space Telescope Science Institute
3700 San Martin Dr.
Baltimore, MD 21218
Women and minorities are strongly urged to apply. AAE/EOE.


                         RECENT PREPRINTS
We draw your attention to these papers, based on NICMOS data, that
will appear in the next few months.  This list includes all preprints received
by the STScI Library not yet published in the journals.  Please remember to
include our Library in your preprint distribution list.

PACKHAM, C.  "Evidence for a 20pc Disk at the Nucleus of
Centaurus A"  ApJ 6-2-98

                     APPENDIX: NICMOS Contacts
Any questions about the scheduling of your observations should be
addressed to your Program Coordinator. Post-Observation questions can
be addressed to your Contact Scientist. If you do not know who these
persons are, you can find the information on the WWW at
Analysis, STSDAS or any other HST-related questions can also be
addressed to
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