Status Report

NASA Hubble Space Telescope Daily Report # 3450

By SpaceRef Editor
September 21, 2003
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DAILY REPORT        # 3450



ACS 9675

CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

ACS 9799

A Snapshot Survey of Galactic Bulge Globular Clusters

The globular clusters toward the Galactic bulge remain among the least
studied of the Galaxy’s globular clusters, primarily because severe
photometric crowding has hindered ground-based imaging. We propose a
snapshot survey {3 month proprietary period} using ACS onboard HST to
produce a complete sample of color-magnitude diagrams for these
clusters. The high spatial resolution of HST gives photometry vastly
superior to even the best ground-based color-magnitude diagrams.
Measurement of the horizontal and red giant branches gives reddening
and distance, from which physical parameters for the clusters are
derived. Ages to be derived are of special interest because this
population may contain the oldest clusters in the Galaxy.
Additionally, the separation of cluster members from contaminating
field stars will give far superior structural parameters than can be
derived from the ground. Many of these clusters have especially
concentrated cores; due to their proximity to the Galactic Center,
they may have experienced far greater dynamical evolution due to bulge
shocking. If stellar encounters are capable of modifying stellar
populations, these clusters probably are the best place to look for
such effects. Because ground-based study of these clusters has been so
difficult, we believe that this survey is potentially an important
part of HST’s legacy.

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter. Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the skewness of the shear distribution, and em the magnification effect. endlist Our measurements will determine the amplitude of the mass power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density Omega_m with s/n=4. They will be done at small angular scales where non-linear effects dominate the power spectrum, providing a test of the gravitational instability paradigm for structure formation. Measurements on these scales are not possible from the ground, because of the systematic effects induced by PSF smearing from seeing. Having many independent lines of sight reduces the uncertainty due to cosmic variance, making parallel observations ideal.

ACS/WFC 9744

HST Imaging of Gravitational Lenses

Gravitational lenses offer unique opportunities to study cosmology,
dark matter, galactic structure, galaxy evolution and quasar host
galaxies. They are also the only sample of galaxies selected based on
their mass rather than their luminosity or surface brightness. While
gravitational lenses can be discovered with ground-based optical and
radio observations, converting them into astrophysical tools requires
HST. HST has demonstrated that it is the only telescope that can in
each case precisely locate the lens galaxy, measure its luminosity,
color and structure, and search for lensed images of the source host
galaxy given the typical image separations of ~1”. We will obtain
ACS/WFC V and I images and NICMOS H images of 21 new lenses never
observed by HST and NICMOS H images of 16 lenses never observed by HST
in the IR. As in previous cycles, we request that the data be made
public immediately.

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration – CR Persistence Part 3

A new proceedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and everytime a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword ‘USEAFTER=date/time’ will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science i mages. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 9801

Are OH/IR Stars the Youngest post-AGB stars? A NICMOS Imaging Survey

Essentially all well-characterized preplanetary nebulae {PPNe}–
objects in transition between the AGB and planetary nebula
evolutionary phases – are bipolar, whereas the mass-loss envelopes of
AGB stars are strikingly spherical. In order to understand the
processes leading to bipolar mass-ejection, we need to know at what
stage of stellar evolution does bipolarity in the mass-loss first
manifest itself. We have recently hypothesized that most OH/IR stars
{evolved mass- losing stars with OH maser emission} are very young
PPNe. We are conducting a multiwavelength survey program of imaging
and spectroscopic observations of such objects, using a large,
morphologically unbiased sample selected using IRAS 12-to-25 micron
colors. Our ongoing HST/SNAP imaging survey of the optically bright
half of this sample with WFPC2 and ACS is highly successful: 19/32
objects observed are extended with bipolar/multipolar shapes
{remaining objects are unresolved}. Slightly more than 50% of our
sample are optically too faint or undetected but have strong near-IR
counterparts — we therefore propose a NICMOS SNAPshot imaging survey
of these optically-faint OH/IR stars. These observations are crucial
for determining how and when the bipolar geometry asserts itself. The
results from our NICMOS survey {together with the WFPC2/ACS survey}
will allow us to draw general conclusions about the onset of bipolar
mass-ejection during late stellar evolution. Our complementary program
of interferometric mapping of the OH maser emission in our sources is
yielding kinematic information with spatial resolution comparable to
that in the HST images. The HST/radio data will provide crucial input
for theories of post-AGB stellar evolution. In addition, these data
will also indicate whether the multiple concentric rings, “searchlight
beams”, and truncated equatorial disks recently discovered with HST
in a few PPNe, are common or rare phenomena.

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9608

CCD Bias Monitor – Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1,
and 1×1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS 9855

Exploring Interstellar Krypton Abundance Variations at Kiloparsec Scales

We propose to obtain high-resolution STIS echelle observations of the
interstellar Kr I 1236 absorption toward eight stars situated in the
Galactic disk beyond the Carina/Sagittarius or Perseus Arms. The
measurement of interstellar krypton abundances is a relatively simple
way to investigate elemental abundance variations in the Galaxy, since
its dominant form is neutral and it is undepleted in the ISM.
Furthermore, the intrinsic strengths of krypton’s UV resonance lines
combined with its low relative abundance to hydrogen produce weak,
unsaturated features in typical Galactic sight lines. Previous GHRS
and STIS measurements have demonstrated that Kr/H abundance ratios
within the local spiral arm, the Orion Spur, are remarkably uniform;
however, anomalously high krypton abundances have been measured for
the only two sight lines extending also through gas outside the Orion
Spur. This program is designed to determine whether these sight lines
are isolated cases of enrichment, or if they are representative of
large scale krypton abundance variations outside the local arm. Since
krypton is undepleted in the ISM, these observations will also be
relevant to the study of total elemental abundance and depletion
variations for a variety of elements with resonance lines between 1170
and 1372 Angstroms.

STIS/CCD 10000

STIS Pure Parallel Imaging Program: Cycle 12

This is the default archival pure parallel program for STIS during
cycle 12.


Integrated Absorption- and Emission-Line Analysis of Nebulae

Serious discrepancies have arisen in CNONe abundance determinations
for galactic nebulae in the past ten years depending upon which type
of emission lines are used in the analysis: forbidden vs. permitted
lines. The cause of the discrepancies, which can exceed an order of
magnitude for some PNe, has been studied intensively but is still
unknown. Emission line abundances cannot be considered reliable until
the nature of these contradictory results is understood. We have
developed a technique for integrating absorption lines into emission
analyses for diffuse nebulae that provides an independent check on the
validity of emission-line analyses. It requires high resolution
observations of UV resonance absorption produced by the nebular gas in
imbedded or background stars together with optical spectra of the
nebulae. We propose to obtain UV spectra of four PNe central stars
with STIS that will provide data necessary to exploit the new
technique of integrated abundance determination that combines both
emission and absorption lines.

STIS/MA1 9790

Separating Activity and Accretion in T Tauri Stars

Due to their unique evolutionary state, the naked {non-accreting} T
Tauri stars {NTTS} are the only real proxies for what the underlying
magnetically active star of a classical TTS {CTTS} system looks like.
Comparative analysis then allows us to separate stellar properties
from accretion properties in CTTS. In addition, the late-type NTTS are
excellent candidates for studying rotation-activity relationships in
fully convective stars and probing the properties of turbulent
dynamos. With the limited data currently available, NTTS appear to be
very magnetically active stars with higher than expected H-alpha/X-ray
flux ratios but lower transition region fluxes relative to other
active stars. However, the data are very incomplete. We will use
HST-STIS observations of transition region line fluxes on 11 fully
convective NTTS to establish the level and structure of dynamo
generated emission in these young stars. In principal, these far
ultraviolet emission lines are sensitive diagnostics of mass accretion
onto CTTS, since accretion shocks on the stellar surface should
produce substantial emission measure at 10^5 – 10^6 K. However, it is
imperative that we first understand the emissions from NTTS before we
can use these lines to study accretion onto CTTS.

WFPC2 9595


This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be

HSTAR 9154:  GS Acquisition (1,2,1) @ 261/05:03:11Z resulted in FL
backup using FGS 2 due to SSLE on FGS 1 at AOS (261/05:14:45Z). Under



                           SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq               07                        07
FGS REacq               09                        09
FHST Update             16                        16


Returned Battery 1 to FSW 6-Battery System @ 261/10:20Z (OR17035-1).

SpaceRef staff editor.