Status Report

NASA Hubble Space Telescope Daily Report #3922

By SpaceRef Editor
August 15, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3922

PERIOD COVERED: UT August 11, 2005 (DOY 223)


ACS/HRC 10557

Probing Asteroid Families for Evidence of Ultraviolet Space Weathering

We propose six HST orbits to obtain UV reflectance spectra covering
200-460 nm of two Vesta asteroid family members, asteroid 832 Karin,
and two Karin family members. These observations extend work done
under a Cycle 13 AR grant, where we analyzed all of the existing IUE
and HST S-class asteroids in the MAST database to investigate the
effects of space weathering at UV wavelengths. Our hypothesis is that
the manifestation of space weathering at UV wavelengths is a spectral
bluing, in contrast with a spectral reddening at visible-NIR
wavelengths, and that UV wavelengths can be more sensitive to
relatively small amounts of weathering than longer wavelengths. The
proposed observations will address two objectives: {1} Measure the
UV-visible spectra of 832 Karin and two members of the young Karin
family {absolute age of 5.8 My}, in order to determine whether
intermediate space weathering is observable in objects likely pristine
when they originated from the interior of Karin’s pa rent body. {2}
Measure the UV-visible spectra of two members of the Vesta family to
compare with our analysis of IUE Vesta spectra. These observations
will probe Vesta’s interior, and test our hypothesis by contrasting
the apparent amount of alteration on the surfaces of Vestoids with
excavated material on Vesta.


CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks.
The CCD TECs will be turned off and heaters will be activated to bring
the detector temperatures to about +20C. This state will be held for
approximately 12 hours, after which the heaters are turned off, the
TECs turned on, and the CCDs returned to normal operating condition.
To assess the effectiveness of the annealing, a bias and four dark
images will be taken before and after the annealing procedure for both
WFC and HRC. The HRC darks are taken in parallel with the WFC darks.
The charge transfer efficiency {CTE} of the ACS CCD detectors declines
as damage due to on-orbit radiation exposure accumulates. This
degradation has been closely monitored at regular intervals, because
it is likely to determine the useful lifetime of the CCDs. We will now
combine the annealling activity with the charge transfer efficiency
monitoring and also merge into the routine dark image collection. To
this end, the CTE monitoring exposures have been moved into this
proposal . All the data for this program is acquired using internal
targets {lamps} only, so all of the exposures should be taken during
Earth occultation time {but not during SAA passages}. This program
emulates the ACS pre-flight ground calibration and post-launch SMOV
testing {program 8948}, so that results from each epoch can be
directly compared. Extended Pixel Edge Response {EPER} and First Pixel
Response {FPR} data will be obtained over a range of signal levels for
both the Wide Field Channel {WFC}, and the High Resolution Channel


ACS CCDs daily monitor – Cycle 13 – Part 2

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This program will be
for the entire lifetime of ACS.

ACS/SBC 10502

ACS Imaging of the Uranus Aurora and Hydrogen Corona

ACS SBC UV observations of Uranus are proposed with dual purposes that
can be achieved with a single set of observations. First, we propose
to observe the very unusual auroral of Uranus for the first time since
IUE and Voyager in the 1980’s. The Uranus aurora are centered on the
magnetic poles, corresponding to the 60 deg. tilted magnetic moment,
closer to the equator than the rotational poles. The brighter auroral
emission appears around the weaker magnetic pole. The auroral
emissions are highly variable, as recorded with IUE, and the
rotational phase of Uranus is not known. The observations will
therefore cover the extent of a Uranus rotation {17.29 hours}, and
will be repeated one-half solar rotation later to allow for variations
in the solar wind at Uranus. The high sensitivity of the ACS SBC at
long wavelengths will increase the sensitivity to auroral H2
emissions, and observations in cycle 14 near solar minimum will limit
the sky background and reflected solar emissions from the Uranus disc.
Secondly, these images will measure the extended hydrogen corona of
Uranus, first seen by the Voyager 2 UVS. We propose to model the
distribution of the hydrogen corona to determine the source processes
in the Uranus upper atmosphere, by comparison with model runs from an
exospheric code.

ACS/WFC/NIC3 10405

Probing the establishment of galaxy morphologies in the best-studied
high-redshift structure

We propose deep ACS I-band imaging of arguably the best-studied
high-redshift proto-cluster environment, a high-contrast structure in
the SSA22 field at z=3.1. Our on-going study of this region has
identified over 400 probable members of this structure across a
16-arcmin-square field, selected through narrow-band Lyman-alpha
emission, Lyman-break photometric criteria and far-infrared/radio
emission. Our proposed high-resolution imaging of galaxies in the
z=3.1 structure and in the nearby field, will provide morphological
information on galaxies over nearly two-orders of magnitude in local
density at this early epoch. This will allow us for the first time to
test whether galaxy morphology is defined at the formation of a galaxy
or reflects processes acting on it during its lifetime.


Probing Evolution And Reionization Spectroscopically {PEARS}

While imaging with HST has gone deep enough to probe the highest
redshifts, e.g. the GOODS survey and the Ultra Deep Field,
spectroscopic identifications have not kept up. We propose an ACS
grism survey to get slitless spectra of all sources in a wide survey
region {8 ACS fields} up to z =27.0 magnitude, and an ultradeep field
in the HUDF reaching sources up to z =28 magnitude. The PEARS survey
will: {1} Find and spectrocopically confirm all galaxies between
z=4-7. {2} Probe the reionization epoch by robustly determining the
luminosity function of galaxies and low luminosity AGNs at z = 4 – 6.
With known redshifts, we can get a local measure of star formation and
ionization rate in case reionization is inhomogeneous. {3} Study
galaxy formation and evolution by finding galaxies in a contiguous
redshift range between 4 < z < 7, and black hole evolution through a census of low-luminosity AGNs. {4} Get a robust census of galaxies with old stellar populations at 1 < z < 2.5, invaluable for checking consistency with heirarchical models of galaxy formation. Fitting these galaxies' spectra will yield age and metallicity estimates. {5} Study star-formation and galaxy assembly at its peak at 1< z < 2 by identifying emission lines in star-forming galaxies, old populations showing the 4000A break, and any combination of the two. {6} Constrain faint white dwarfs in the Galactic halo and thus measure their contribution to the dark matter halo. {7} Derive spectro-photometric redshifts by using the grism spectra along with broadband data. This will be the deepest unbiased spectroscopy yet, and will enhance the value of the multiwavelength data in UDF and the GOODS fields to the astronomical community. To this end we will deliver reduced spectra to the HST archives.

FGS 10478

Dynamical Masses and Radii of Four White Dwarf Stars

The cool white dwarf stars WD1639+153 and WD1818+126 were recently
resolved by HST FGS1r to be double degenerate binary systems with
projected separations of 112 mas and 174 mas respectively. At a
distance of less than 50 pc they may both have periods shorter than
about 20 years, making them ideal candidates for follow up studies for
dynamical mass determinations. This will increase the number of white
dwarfs with dynamical mass measurements from the current 4 up to 8.
Continued observations of these white dwarfs along with nearby field
stars with the FGS will accuractely determine the orbital elements and
parallax of each system. The mass and radius of all four white dwarfs
can be determined to an unprecedented 1%, making it possible to test
and calibrate the theoretical white dwarf mass radius relation at the
cool end of the cooling curve for the DA and DC subclasses. Since the
components of the binary are coeval, once the mass and radius, and
hence the cooling age of each star is known, it will be possible to
estimate the relation between the initial mass and final mass for all
four white dwarfs. We are requesting a total of 4 HST orbits per year
for the next three cycles to initiate the process that will result in
a determination of the mass and radius of the four white dwarfs.

NIC1/NIC2/NIC3 10721

NICMOS dark current tests for newly implemented SPARS sequences

On June 12, 2005, 4 new NICMOS multiaccum sequences {SPARS4, SPARS16,
SPARS32, SPARS128} were implemented. The purpose of this observation
is to measure the dark currents for these new multiaccum sequences for
all three NICMOS detectors.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration – CR Persistence Part 4

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time 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 images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 10510

Morphology of massive early-type galaxies at z>1.2: constraining
galaxy formation models

We ask for NICMOS-NIC2 H-band imaging of a sample of 10 massive
early-type galaxies spectroscopically identified at 1.26500A, would map the mass
distribution of the bulk of their stellar content. The targets have
been revealed by our group on the basis of near-IR spectroscopy
obtained in the framework of a spectroscopic survey of a complete
sample of bright EROs {Ks<18.5}. Optical and near-IR photometry is available for all the targets, and low resolution near-IR spectra have allowed their identification and redshift measurement. Spectroscopic and photometric data in our hands show that they have already assembled stellar masses greater than 3 10^11 solar masses, and that the mean age of their stellar population is estimated older than 2-3 Gyr for 6 of them and about 1 Gyr for the other 4 galaxies. Thus, they are among the most luminous and massive evolved galaxies detected so far at z>1. Other data are needed to infer how they have assembled
such high stellar masses, i.e. to trace back their evolution. The
requested observations would allow us to reveal signs of past
interaction/merger event. A smooth r^{1/m} profile, coupled with no
other signs of interaction/merger {disturbed morphology}, would place
the possible merger event of formation 1-2 Gyr before their redshift z
pprox 1.5, i.e. at z > 2-3. On the other hand, if signs of recent
merger events will be found, the last merger event forming the local
massive spheroids will be constrained at 1.5 < z < 2. Thus, the requested HST observations will allow for the first time to see how massive early-type galaxies at z pprox 1.5 look like, constraining in any case the redshift of the possible merging event of their formation.

WFPC2 10534

Active Atmospheres on Uranus and Neptune

We propose Snapshot observations of Uranus and Neptune to monitor
changes in their atmospheres on time scales of weeks, months, and
years. Uranus is rapidly approaching equinox in 2007, with another 4
degrees of latitude becoming visible every year. Recent HST
observations during this epoch {including 6818: Hammel, Lockwood, and
Rages; 8680: Hammel, Rages, Lockwood, and Marley; 8634: Rages, Hammel,
Lockwood, Marley, and McKay; and 10170: Rages, Hammel, Lockwood, and
Marley} have revealed strongly wavelength-dependent latitudinal
structure and the presence of numerous visible-wavelength cloud
features in the northern hemisphere. Long-term ground-based
observations {Lockwood and Thompson 1999} show seasonal brightness
changes whose origins are not well understood. Recent near-IR images
of Neptune obtained using adaptive optics on the Keck Telesccope
together with images from our Cycle 9 Snapshot program {8634} show a
general increase in activity at south temperate latitudes as well as
the possible development of another Great Dark Spot. Further Snapshot
observations of these two dynamic planets will elucidate the nature of
long-term changes in their zonal atmospheric bands and clarify the
processes of formation, evolution, and dissipation of discrete albedo


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

HSTARS: (None)


17495-0 – Null Genslew for Proposal 10431-0 – Slot#8 @ 223/1915z

17496-0 – Null Genslews for Proposal 10431-0 – Slot#9,10,11,14 @ 223/1916z

                                SCHEDULED     SUCCESSFUL 
 FGS Gsacq                    12                      12 
 FGS Reacq                     5                        5 
 FHST Update                 18                       18 


SpaceRef staff editor.