Status Report

NASA Hubble Space Telescope Daily Report # 3680

By SpaceRef Editor
August 25, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 10050

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronagraphic
monitoring is required to assess the changing position of the spots.

ACS/HRC 10182

Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations

Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe


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/WFC 9717

Low Redshift Cluster Gravitational Lensing Survey

This proposal has two main scientific goals: to determine the dark
matter distribution of massive galaxy clusters, and to observe the
high redshift universe using these clusters as powerful cosmic
telescopes. Deep, g, r, i, z imaging of a sample of low-z {0.2-0.4}
clusters will yield a large sample of lensed background galaxies with
reliable photometric redshifts. By combining strong and weak lensing
constraints with the photometric redshift information it will be
possible to precisely measure the cluster dark matter distribution
with an unprecedented combination of high spatial resolution and area
coverage, avoiding many of the uncertainties which plague ground-based
studies and yielding definitive answers about the structure of massive
dark matter haloes. In addition, the cosmological parameters can be
constrained in a largely model independent way using the multiply
lensed objects due to the dependence of the Einsteining radius on the
distance to the source. We can also expect to detect several highly
magnified dropout galaxies behind the clusters in the redshift ranges
4-5 5-6 and 7-8, corresponding to a drop in the flux in the g, r, and
i bands relative to longer wavelength. We will obtain the best
information to date on the giant arcs already known in these clusters,
making possible detailed, pixel-by-pixel studies of their star
formation rate, dust distribution and structural components, including
spiral arms, out to a redshift of around z~2.5 in several passbands.

ACS/WFC 9727

Exploration of the SN Ia Hubble Diagram at z > 1.2

In the spirit of a Treasury proposal, we propose to organize, and
deliver to the astronomical community, non-proprietary follow-up
observations of ~10 Type Ia supernovae at 1<z<1.7 that are expected to
be discovered in a Cycle 12 Treasury proposal. Together with the
currently available sample, this would provide a Hubble diagram with
over 20 SNe Ia in this redshift range, where it is possible to test
the current cosmological model in the epoch of deceleration: If z ~
0.5 SNe Ia are fainter due to evolution rather than an accelerating
expansion, they should continue to get fainter at even higher
redshifts. This size sample will show trends and outliers, and permit
a more rigorous treatment of the asymmetric amplification distribution
from gravitational lensing. This is a key redshift range for the
studies of dark energy that will be done with future surveys {and
future instruments now being designed}; this dataset will lay the
ground-work for these studies by establishing the simple properties of
the supernovae in this redshift range, including magnitudes, colors,
and timescales. If considered more appropriate, this proposal could be
treated as a part of a Treasury or Director’s Discretionary program,
since the data would be available to everybody immediately, and we
would welcome others who would want to work with us on it.

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 9867

How Do Brown Dwarfs Form?

With NICMOS/NIC2 imaging of five brown dwarfs and one low mass star
that we have identified in a young cluster in OMC2/3, we plan to
assess the similarities between brown dwarf formation and low mass
star formation by searching for the presence of shocked H2 line
emission from jets/outflows, close binary companions, and/or
reflection nebulosity from protostellar envelopes and outflow
cavities. The detection of these phenomena would be evidence that
brown dwarfs result from the continuation of the star formation
process to masses below the hydrogen burning limit, and not through
the dynamical ejection of stellar embryos as has been recently
proposed. This proposal is complementary to our SIRTF GTO program
designed to search for circumstellar disks by measuring the spectral
energy distribution of these sources out to 8 microns. This task
requires not only high spatial resolution, but also a stable,
unchanging PSF such as HST provides.

NIC3 9846

The Origins of Sub-stellar Masses: Searching for the End of the IMF

Is there a preferred scale that defines the end of the IMF? We propose
to test this hypothesis by conducting a deep spectroscopic survey of
extremely low mass objects in the embedded young cluster associated
with NGC1333. At a distance of only 300pc, this cluster is one of the
nearest examples of a dense young cluster. We will be able to obtain
R=200 spectra and photometry for 40-60 cluster members with masses
between 5-40 Jupiter masses at an age of 1 Myr observed through
A{v}<10 mag. This will enable us to estimate temperatures and
luminosities for all sources detected in the survey. We will compare
their positions in an H-R diagram to PMS evolutionary tracks in order
to estimate their ages and masses. For a solar metallicity cloud at a
temperature of 10 K, the minimum mass for fragmentation is thought to
be 10 Jupiter masses. A statistically significant sample of objects
detected below this limit would challenge the role of hierarchical
fragmentation in limiting substellar masses. The proximity of this
cluster combined with the unique sensitivity, wavelength coverage, and
multi-object spectroscopic capability of NICMOS on HST make this
experiment possible.

WFPC2 10068

WFPC2 CYCLE 12 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

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

WFPC2 10072


This calibration proposal is the Cycle 12 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A
variety of internal exposures are obtained in order to provide a
monitor of the integrity of the CCD camera electronics in both bays
{gain 7 and gain 15}, a test for quantum efficiency in the CCDs, and a
monitor for possible buildup of contaminants on the CCD windows.

WFPC2 10080

Wavelength Stability of Narrow Band and Linear Ramp Filters

Verify the mapping of wavelength as a function of CCD position on
LRFs; check for changes in central wavelengths of narrow band filters.


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None



                          SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              06                        06
FGS REacq              10                        10
FHST Update            08                         08


Successfully modified the Battery 3 Capacity Test, Battery Pressure
Test limit @ 236/12:06Z (OR 17260 with attached COP 4.33). Following
the Battery 3 Capacity Test, the Battery Pressure Test limits will be
restored to their nominal limits.

Successfully started the Battery 3 Capacity Test, Step 1 @ 236/12:07Z
(OR 17259-1 with attached Battery 3 Capacity Test script). Estimate
discharge termination approximately 51 hours from start of discharge.
Battery 3 high-rate discharge terminated @ 236/21:28Z via the ACR
indicating Voltage had reached 26.34 Volts. Low-rate discharge was
started at this time and will continue until Battery 3 Voltage exceeds
the second Voltage limit of 15.09 Volts, at which time the ACR will
terminate the discharge.

SpaceRef staff editor.