Daily Report #5065

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5065

PERIOD COVERED: 5am March 31 - 5am April 1, 2010 (DOY 090/09:00z-091/09:00z)

OBSERVATIONS SCHEDULED

ACS/WFC 11715

The Luminous Galactic Cepheid RS Puppis: A Geometric Distance from its
Nested Light Echoes

RS Puppis is one of the most luminous Cepheids in the Milky Way (P =
41.4 days) and an analog of the bright Cepheids used to measure
extragalactic distances. An accurate distance would help anchor the
zero-point of the bright end of the period-luminosity relation, but at
a distance of about 2 kpc it is too far away for a trigonometric
parallax with existing instrumentation.

RS Pup is unique in being surrounded by a reflection nebula, whose
brightness varies as pulses of light from the Cepheid propagate
outwards. Members of our team have used ground-based imaging of the
nebula to derive phase lags in the light variations of individual
features in the nebula, and have inferred a seemingly very precise
geometric distance to the star. However, there is an unavoidable
ambiguity involving the cycle counts, which was resolved by assuming
that the features lie in the plane of the sky. If this assumption is
incorrect, a large systematic error would be introduced into the
distance measurement.

We show that polarimetric imaging using the high spatial resolution of
ACS/WFC and its ability to image close to the star can resolve this
ambiguity and yield a reliable geometric distance to RS Pup. We will
also obtain a wide-field multicolor image of the nebula, in order to
study its morphology and the mass-loss history of the Cepheid.

ACS/WFC 11995

CCD Daily Monitor (Part 2)

This program comprises basic tests for measuring the read noise and
dark current of the ACS WFC and for tracking the growth of hot pixels.
The recorded frames are used to create bias and dark reference images
for science data reduction and calibration. This program will be
executed four days per week (Mon, Wed, Fri, Sun) for the duration of
Cycle 17. To facilitate scheduling, this program is split into three
proposals. This proposal covers 320 orbits (20 weeks) from 1 February
2010 to 20 June 2010.

ACS/WFC3 11599

Distances of Planetary Nebulae from SNAPshots of Resolved Companions

Reliable distances to individual planetary nebulae (PNe) in the Milky
Way are needed to advance our understanding of their spatial
distribution, birthrates, influence on galactic chemistry, and the
luminosities and evolutionary states of their central stars (CSPN).
Few PNe have good distances, however. One of the best ways to remedy
this problem is to find resolved physical companions to the CSPN and
measure their distances by photometric main-sequence fitting. We have
previously used HST to identify and measure probable companions to 10
CSPN, based on angular separations and statistical arguments only. We
now propose to use HST to re-observe 48 PNe from that program for
which additional companions are possibly present. We then can use the
added criterion of common proper motion to confirm our original
candidate companions and identify new ones in cases that could not
confidently be studied before. We will image the region around each
CSPN in the V and I bands, and in some cases in the B band. Field
stars that appear close to the CSPN by chance will be revealed by
their relative proper motion during the 13+ years since our original
survey, leaving only genuine physical companions in our improved and
enlarged sample. This study will increase the number of Galactic PNe
with reliable distances by 50 percent and improve the distances to PNe
with previously known companions.

COS/FUV 11897

FUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity in each FUV
grating mode to detect any changes due to contamination or other
causes.

COS/NUV 11561

An Intensive COS Spectroscopic Study of the Planetary Debris Disks
Around two Warm White Dwarfs

It is very likely that the gas giants in our Solar system will survive
the evolution of the Sun into a white dwarf, and the same is thought
to be generally true for Jovian planets around solar-like stars if
their initial orbits are wider than ~3AU. Despite this prediction, no
unambiguous detection of a planet around a white dwarf has been
announced so far. However, over the past few years, about a dozen
white dwarfs have been identified which host metal-rich debris disks
that are thought to stem from the tidal disruption of asteroids. In
most cases the debris disks are observed in the form of an infrared
flux excess, and offer relatively little diagnostic potential for the
study of their structure. We have discovered three warm (T~20000K)
white dwarfs with metal-rich debris disks in a gaseous phase which
display strong double-peaked CaII emission lines in the I-band and
weak Fe 5169A emission. The line profiles can be modeled in terms of
Keplerian disks with an extension of ~1Rsun around the white dwarfs.
Photospheric MgII 4481A absorption demonstrates that the white dwarfs
are accreting from the debris disks. Besides these spectral features,
the optical wavelength range is devoid of other useful metal
transitions. Here, we propose an intensive spectroscopic ultraviolet
study of these systems, which will provide (a) ~1000 photospheric
absorption lines of 15 chemical elements, allowing an accurate
abundance study of the material accreted from the debris disks, and
(b) ~2 dozen additional emission lines of Mg, Cr, Ti, and Fe that will
provide detailed insight into the dynamical, thermal, and density
structure of these exo-planetary debris disks.

COS/NUV 11894

NUV Detector Dark Monitor

The purpose of this proposal is to measure the NUV detector dark rate
by taking long science exposures with no light on the detector. The
detector dark rate and spatial distribution of counts will be compared
to pre-launch and SMOV data in order to verify the nominal operation
of the detector. Variations of count rate as a function of orbital
position will be analyzed to find dependence of dark rate on proximity
to the SAA. Dependence of dark rate as function of time will also be
tracked.

COS/NUV/FUV/WFC3/UVIS/IR 11520

COS-GTO: QSO Absorbers, Galaxies and Large-Scale Structures in the
Local Universe

This is a program to probe the large scale structure of baryons in the
universe, including addressing questions of baryon fraction, physical
conditions and relationships between absorbers and large-scale
structures of galaxies. Besides these specific goals, this proposed
GTO program also probes a large enough total path length in Ly alpha
and OVI to add significantly to what STIS/FUSE has already observed.
Several Galactic High Velocity Cloud Complexes also are probed by
these sightlines, particularly the M Complex. The total path length of
this proposed program for Ly alpha large-scale structure surveys is
delta_z~5.5.

We have selected a variety of targets to address these questions,
under the following subcategories:

1. Target 8 bright BL Lac objects to search for low contrast Ly alpha
absorbers from the warm- hot interstellar medium (WHIM).

2. Ly alpha cloud sizes: The targets are a bright AGN pair which yield
tangential distance separations of 100--500 kpc at z=0.01--0.05, where
galaxy surveys are excellent. This pair has two filaments and two
voids in this distance range.

3. Probes of starburst outflows: The targets are bright AGN, = 100
kpc in projection out of the minor axis of nearby starburst galaxies.

4. A large galaxy's gaseous halo: Three probes of the kinematics and
metallicity of a single L* galaxy halo. These observations includes
G130M, G160M exposures at SNR~20 and G285M at 2850A and SNR~10 for
MgII. The 2L* galaxy, ESO 157-G049 (cz=1678 km/s), being probed by
these sightlines has an available H I 21cm map from ATCA, H alpha
imaging from CTIO and long- slit spectra from MSSSO.

5. Dwarf galaxy winds: These targets probe the kinematics and
metallicities of outflows from active and inactive (in terms of star
formation) dwarfs.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CC 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and 1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS/CC/MA 11516

COS-GTO: Cold ISM

With the COS, we will be able to observe interstellar spectra in a new
regime, translucent clouds, for atomic, ionic, and molecular lines and
bands, and extinction curves. The COS will allow us to observe stars
with total visual extinctions up to 10 magnitudes, and the grain size
indicator Rv up to 4.5. In translucent clouds we expect to see the
transition from neutral and ionized carbon to mostly C I, and then
from there, we should expect to see carbon increasingly locked up in
molecular form, as CO. Other species are expected to make similar
transitions, so we should find detectable abundances of molecules such
as H2O, OH, CS, CH2, SiO, and others; also, lower ionization fractions
of the metallic elements - and higher depletions of those elements as
well. Given that we expect to find higher depletions, we should see an
altered grain size distribution, which may show up in the extinction
curves, probably as lower far-UV extinction than in diffuse clouds.
Finally, we will search for neutral PAHs in absorption, as diffuse
bands in the UV, paralleling the optical DIBs (which are thought by
some scientists to be formed by singly-ionized PAHs). In translucent
clouds, models show that the PAHs will be neutral, not in cationic
form.

STIS/CCD/MA2 11568

A SNAPSHOT Survey of the Local Interstellar Medium: New NUV
Observations of Stars with Archived FUV Observations

We propose to obtain high-resolution STIS E230H SNAP observations of
MgII and FeII interstellar absorption lines toward stars within 100
parsecs that already have moderate or high-resolution far-UV (FUV),
900-1700 A, observations available in the MAST Archive. Fundamental
properties, such as temperature, turbulence, ionization, abundances,
and depletions of gas in the local interstellar medium (LISM) can be
measured by coupling such observations. Due to the wide spectral range
of STIS, observations to study nearby stars also contain important
data about the LISM embedded within their spectra. However, unlocking
this information from the intrinsically broad and often saturated FUV
absorption lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding the kinematic structure of the gas along the line of
sight. This can be achieved with high resolution spectra of high-mass
ions, (FeII, MgII), which have narrow absorption lines, and can
resolve each individual velocity component (interstellar cloud). By
obtaining short (~10 minute) E230H observations of FeII and MgII, for
stars that already have moderate or high- resolution FUV spectra, we
can increase the sample of LISM measurements, and thereby expand our
knowledge of the physical properties of the gas in our galactic
neighborhood. STIS is the only instrument capable of obtaining the
required high resolution data now or in the foreseeable future.

STIS/MA1/MA2 11857

STIS Cycle 17 MAMA Dark Monitor

This proposal monitors the behavior of the dark current in each of the
MAMA detectors.

The basic monitor takes two 1380s ACCUM darks each week with each
detector. However, starting Oct 5, pairs are only included for weeks
that the LRP has external MAMA observations planned. The weekly pairs
of exposures for each detector are linked so that they are taken at
opposite ends of the same SAA free interval. This pairing of exposures
will make it easier to separate long and short term temporal
variability from temperature dependent changes.

For both detectors, additional blocks of exposures are taken once
every six months. These are groups of five 1314s FUV-MAMA Time-Tag
darks or five 3x315s NUV ACCUM darks distributed over a single
SAA-free interval. This will give more information on the brightness
of the FUV MAMA dark current as a function of the amount of time that
the HV has been on, and for the NUV MAMA will give a better measure of
the short term temperature dependence.

WFC3/UVIS/IR 11909

UVIS Hot Pixel Anneal

The on-orbit radiation environment of WFC3 will continually generate
new hot pixels. This proposal performs the procedure required for
repairing those hot pixels in the UVIS CCDs. During an anneal, the
two-stage thermo-electric cooler (TEC) is turned off and the
four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20
deg. C. As a result of the CCD warmup, a majority of the hot pixels
will be fixed; previous instruments such as WFPC2 and ACS have seen
repair rates of about 80%. Internal UVIS exposures are taken before
and after each anneal, to allow an assessment of the procedure's
effectiveness in WFC3, provide a check of bias, global dark current,
and hot pixel levels, as well as support hysteresis (bowtie)
monitoring and CDBS reference file generation. One IR dark is taken
after each anneal, to provide a check of the IR detector.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

12234 ? OBAD(1,3) at 091/07:56:38z failed due to too few stars on
FHST#1. GSAcq(1,2,1) at 091/08:02:11z was successful.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 9 9
FGS REAcq 7 7
OBAD with Maneuver 5 4

SIGNIFICANT EVENTS: (None)