Status Report

NASA Hubble Space Telescope Daily Report # 3673

By SpaceRef Editor
August 14, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 10185

When does Bipolarity Impose itself on the Extreme Mass Outflows from
AGB Stars? An ACS SNAPshot 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? Our previous SNAPshot surveys of a PPNe sample {with
ACS & NICMOS} show that roughly half our targets observed are
resolved, with well-defined bipolar or multipolar morphologies.
Spectroscopic surveys of our sample confirm that these objects have
not yet evolved into planetary nebulae. Thus, the transformation from
spherical to aspherical geometries has already fully developed by the
time these dying stars have become preplanetary nebulae. From this
new and surprising result, we hypothesize that the transformation to
bipolarity begins during the very late AGB phase, and happens very
quickly, just before, or as the stars are evolving off the AGB. We
propose to test this hypothesis quantitatively, through a SNAPshot
imaging survey of very evolved AGB stars which we believe are nascent
preplanetary nebulae; with our target list being drawn from published
lists of AGB stars with detected heavy mass-loss {from millimeter-wave
observations}. This survey is crucial for determining how and when the
bipolar geometry asserts itself. Supporting kinematic observations
using long-slit optical spectroscopy {with the Keck}, millimeter and
radio interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the onset of
bipolar mass-ejection during late stellar evolution, and will provide
crucial input for theories of post-AGB stellar evolution. Our survey
will produce an archival legacy of long-standing value for future
studies of dying stars.

ACS/HRC 10272

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite nearby
galaxies {cz < 4000 km/s}. Most of the objects were discovered before
maximum brightness, and have follow-up photometry and spectroscopy;
they include some of the best-studied SNe to date. We propose to
conduct a snapshot imaging survey of the sites of some of these nearby
objects, to obtain late-time photometry that {through the shape of the
light and color curves} will help reveal the origin of their lingering
energy. The images will also provide high-resolution information on
the local environment of SNe that are far superior to what we can
procure from the ground. For example, we will obtain color-color and
color-magnitude diagrams of stars in these SN sites, to determine
their progenitor masses and constraints on the reddening. Recovery of
the SNe in the new HST images will also allow us to actually pinpoint
their progenitor stars in cases where pre-explosion images exist in
the HST archive. Use of ACS rather than WFPC2 will make our snapshot
survey even more valuable than our Cycle 9 survey. This Proposal is
complementary to our Cycle 13 archival proposal, in which we outline a
plan for using existing HST images to glean information about SN


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 10181

ACS/NICMOS Imaging of Bright Lyman Break Galaxy Candidates from SDSS

The recent surprising discovery of six unusually bright {r~20 mag}
Lyman break galaxy {LBG} candidates with z=2.45-2.80 in the Sloan
Digital Sky Survey {SDSS} raises a number of questions that only HST
can address. Specifically, what is the true nature of these objects,
and what role if any is played by gravitational lensing? We propose to
use the superior resolution and sensitivity of ACS and NICMOS to
obtain deep images of these objects and their environments. Compared
to SDSS images, HST will allow us to determine their morphologies
{extended, point-source, or lensed}, the appearance of their
environments {rich or poor}, and to detect any faint foreground groups
or clusters that might be responsible for lensing these objects. All
outcomes would be intriguing. If the objects are lensed, it increases
from 1 {MS1512-cB58} to 7 the number of normal LBGs bright enough to
study individually. If they are instead unlensed point sources, they
will represent a new class of previously unidentified absorption-line
quasars. Finally, if they are unlensed and extended star-forming
galaxies, they are at least 4mag brighter than L_* LBGs, thus making
them the most luminous star-forming objects yet seen, representing a
heretofore unknown extreme population of objects.

ACS/WFC 10260

The Most Massive Star Clusters: Supermassive Globular Clusters or
Dwarf Galaxy Nuclei?

Evidence is mounting that the most massive globular clusters, such as
Omega Centauri and M31-G1, may be related to the recently discovered
"Ultra-Compact Dwarfs" and the dense nuclei of dE, N galaxies.
However, no systematic imaging investigation of these supermassive
globular clusters — at the level of Omega Cen and beyond — has been
done, and we do not know what fraction of them might bear the
signatures {such as large effective radii or tidal tails} of having
originated as dE nuclei. We propose to use the ACS/WFC to obtain deep
images of 18 such clusters in NGC 5128 and M31, the two nearest rich
globular cluster systems. These globulars are the richest star
clusters that can be found in nature, the biggest of them reaching
10^7 Solar masses, and they are likely to represent the results of
star formation under the densest and most extreme conditions known.
Using the profiles of the clusters including their faint outer
envelopes, we will carry out state-of-the-art dynamical modelling of
their structures, and look for any clear evidence which would indicate
that they are associated with stripped satellites. This study will
build on our previous work with STIS and WFPC2 imaging designed to
study the ‘Fundamental Plane’ of globular clusters. When our new work
is combined with Archival WFPC2, STIS, and ACS material, we will also
be able to construct the definitive mapping of the Fundamental Plane
of globular clusters at its uppermost mass range, and confirm whether
or not the UCD and dE, N objects occupy a different structural
parameter space.

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 9856

A near-IR imaging survey of submm galaxies with spectroscopic

Submillimeter {submm} surveys with SCUBA have identified a population
of obscured star-forming and active galaxies at high redshift. Our
recent spectroscopic campaigns with the Keck-10m telescope have
uncovered redshifts for 37 SCUBA galaxies. The wide redshift range of
the radio identified submm population {z=1-4} implies that many
varieties of sources driven by different physical processes may be
selected in a submm survey. Only HST observations have the resolution
to detect any changes in the morphologies of SCUBA galaxies with
increasing cosmic time. We propose to use HST-NICMOS, ACS to obtain
2-filter images of a sample of 15 SCUBA galaxies with redshifts
spanning z=0.8-3.5. Our goal is to understand what physical process
{major mergers?} drive their strong evolution and great luminosities,
and what the implications are for galaxy evolution models.

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


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

HSTAR 9511: GS Acquisition (2,1,2) @ 225/13:37:51Z resulted in FL
backup (2,0,2) using FGS 2 due to SSLE on FGS 1 after multiple
attempts. Prior FHST FM Updates @ 225/13:20:15Z and 13:23:00Z showed
good attitude error vector. Under investigation.

HSTAR 9512: FHST Roll Delay Update (U1,3RD) failure @ 225/19:42:21Z
with vehicle errors of QDVERRV0 = 377.867, QDVERRV1 = 165.543, and
QDVERRV2 = 183.370. No Attitude Error Vector was computed due to
QDVERRV0 being > 300 arcsec. Error Box results for QAEBSTFG0,
QEBSTFG1, and QEBSTFG2 all indicated "SUCCESS". A 486 ESB message 903
was received. Subsequent GS Acquisition (1,3,1) @ 225/20L03:06 was
successful. Under investigation.

HSTAR 9513: GS Acquisition (2,1,1) @ 226/01:52:21Z ended in FL backup
on FGS 1 due to SSLE on FGS 2 @ 226/01:56:01Z. Under investigation.


17245-2 Battery 1 Capacity Test (complete thru step 35);Step 36,bring
Batt#1 on-line to FSW @ 226/1415z)


                         SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              12                       12
FGS REacq              2                          2
FHST Update            20                        19             @225/1942 


Continued Battery 1 Capacity Test. Low rate discharge of Battery 1 was
concluded nominally @ 225/15:06Z. Commanding to reconfigure the EPS
for nominal CCC V/T levels, battery charging, and charge optimization
was completed @ 225/16:29Z. Restored Full-Rate-of-Charge (FULROC) back
to its nominal value of 21.3 Amps and re-enabled the Over Charge
Avoidance (OCA) routine @ 226/03:13Z. EPS SE monitored the system for
one full orbit to confirm Trim Relays opening/closing, as expected,
with the system reaching Trickle Charge and resetting during the
following orbit night period. Estimate returning Battery 1 online in
FSW, restoring EPS to its pre-test configuration, and updating the BM
SOC is expected to resume @ 226/14:15Z. Continuous ESTR Engineering
Coverage During Battery Capacity Test.

SpaceRef staff editor.