Notice: For the foreseeable future, the daily reports may
contain
apparent discrepancies between some
proposal descriptions and the listed
instrument usage. This is due to the
conversion of previously approved
ACS WFC or HRC observations into WFPC2,
or NICMOS observations
subsequent to the loss of ACS CCD science
capability in late January.
HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #
4328
PERIOD COVERED: UT March 27, 2007 (DOY 086)
OBSERVATIONS SCHEDULED
FGS 10612
Binary Stars in Cyg OB2: Relics
of Massive Star Formation in a
Super-Star Cluster
We propose to make a high angular resolution SNAP survey
of the massive
stars in the nearby, super-star
cluster Cyg OB2. We will use FGS1r TRANS
mode observations to search for astrometric companions in the separation
range of 0.01 to 1.00 arcsec and in the magnitude difference range
smaller than 4 magnitudes. The
observations will test the idea that the
formation of very massive stars involves
mergers and the presence of
nearby companions. Discovery of
companions to massive stars in this
relatively nearby complex will provide
guidance in the interpretation of
apparently supermassive
stars in distant locations. The search for
companions will also be important for verification
of fundamental
parameters derived from spectroscopy,
adjustments to main sequence
fitting and distance estimations,
determining third light contributions
of eclipsing binaries, identifying
wide colliding wind binaries,
studying the relationship between
orbital and spin angular momentum, and
discovering binaries amenable to future
mass determinations. The massive
star environment in Cyg OB2 may be similar to the kinds found in the
earliest epoch of star formation, so
that a study of the role of
binaries in Cyg
OB2 will help us understand the formation processes of
the first stars in the Universe.
FGS 10989
Astrometric Masses of Extrasolar
Planets and Brown Dwarfs
We propose observations with HST/FGS to estimate the astrometric
elements {perturbation orbit semi-major
axis and inclination} of
extra-solar planets orbiting six stars.
These companions were originally
detected by radial velocity techniques.
We have demonstrated that FGS
astrometry of even a short segment of
reflex motion, when combined with
extensive radial velocity information,
can yield useful inclination
information {McArthur et al. 2004},
allowing us to determine companion
masses. Extrasolar
planet masses assist in two ongoing research
frontiers. First, they provide useful
boundary conditions for models of
planetary formation and evolution of
planetary systems. Second, knowing
that a star in fact has a plantary mass companion, increases the value
of that system to future extrasolar planet observation missions such as
SIM PlanetQuest,
TPF, and GAIA.
NIC2 10603
Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the
Growth of Circumstellar Dust
Young, edge-on circumstellar
disks are uniquely valuable laboratories
for the study of planet formation.
In these objects, the central star is
occulted from direct view, significant
PSF artifacts are absent, and the
disk is clearly seen as a central
dust lane flanked by faint disk
reflected light. The detailed morphology
of these nebulae and its
variation with wavelength provide crucial
information on the disk
internal structure and the properties of
its constituent dust grains. A
key observable is the slope
defining the wavelength dependence of the
dust scattering opacity, which
becomes shallower when grain growth has
taken place; multiwavelength
resolved disk images are the key dataset
enabling such measurements. Recent
analyses of three different edge-on
disks have revealed a diversity in
their dust properties that is
indicative of different degrees of dust
grain evolution having taken
place in each system. This
characterization of disk grain growth, when
applied comparatively to a larger
sample of these objects, would enable
the construction of an evolutionary
sequence of young disks at
successive stages on the road to planet
formation. In pursuit of this
goal, we have identified a sample of
15 edge-on disks previously
discovered by HST or groundbased
telescopes, but for which high
fidelity, high spatial resolution images
do not yet exist in both the
optical and near-infrared. We propose
broad- band multicolor imaging
with NICMOS of all these targets,
and ACS imaging of nine of these
targets In combination with existing
data, the proposed images will form
a complete database of high
resolution optical/near-IR images for these
15 disk systems. Scattered light modeling will be used to
derive the
disk structure and dust properties,
yielding results that will be of
fundamental importance for our
understanding of grain properties during
protoplanetary disk evolution.
NIC2 10849
Imaging Scattered Light from Debris Disks Discovered by
the Spitzer
Space Telescope around 21 Sun-like Stars
We propose to use the high-contrast capability of the
NICMOS coronagraph
to image a sample of newly
discovered circumstellar disks associated
with Sun-like stars. These systems
were identified by their strong
thermal infrared {IR} emission with the
Spitzer Space Telescope as part
of the Spitzer Legacy Science
program titled "The Formation and
Evolution of Planetary Systems" {FEPS, P.I.: M.Meyer}. Modeling of the
thermal excess emission from the
spectral energy distributions alone
cannot distinguish between narrowly
confined high-opacity disks and
broadly distributed, low-opacity disks.
By resolving light scattered by
the circumstellar
material, our proposed NICMOS observations can break
this degeneracy, thus revealing the
conditions under which planet
formation processes are occuring or have occured. For
three of our
IR-excess stars that have known radial-velocity planets,
resolved
imaging of the circumstellar
debris disks may further offer an
unprecedented view of planet-disk
interactions in an extrasolar
planetary system. Even non-detections of
the light scattered by the
circumstellar material will place strong
constraints on the disk
geometries, ruling out disk models with
high optical depth. Unlike
previous disk imaging programs, our
program contains a well-defined
sample of ~1 solar mass stars covering
a range of ages from 3 Myr to 3
Gyr, thus allowing us to study the
evolution of disks from primordial to
debris for the first time. The results
from our program will greatly
improve our understanding of the
architecture of debris disks around
Sun-like stars, and will create a morphological context
for the
existence of our own solar system. This
proposal is for a continuation
of an approved Cycle 14 program
{GO/10527, P.I.: D. Hines}.
WFPC2 11030
WFPC2 WF4 Temperature Reduction #3
In the fall of 2005, a serious anomaly was found in images
from the WF4
CCD in WFPC2. The WF4 CCD bias level appeared
to have become unstable,
resulting in sporadic images with either
low or zero bias level. The
severity and frequency of the problem
was rapidly increasing, making it
possible that WF4 would soon become
unusable if no work-around were
found. Examination of bias levels
during periods with frequent WFPC2
images showed low and zero bias
episodes every 4 to 6 hours. This
periodicity is driven by cycling of the
WFPC2 Replacement Heater, with
the bias anomalies occurring at the
temperature peaks. The other three
CCDs {PC1, WF2, and WF3} appear to
be unaffected and continue to operate
properly. Lowering the Replacement
Heater temperature set points by a
few degrees C effectively
eliminates the WF4 anomaly. On 9 January 2006,
the upper set point of the WFPC2
Replacement Heater was reduced from
14.9C to 12.2C. On 20 February 2006, the upper
set point was reduced
from 12.2C to 11.3C, and the lower
set point was reduced from 10.9C to
10.0C. These changes restored the WF4 CCD bias level;
however, the bias
level has begun to trend downwards
again, mimicking its behavior in late
2004 and early 2005. A third temperature reduction
is planned for March
2007. We will reduce the upper set point of the heater
from 11.3C to
10.4C and the lower set point from
10.0C to 9.1C. The observations
described in this proposal will test the
performance of WFPC2 before and
after this temperature reduction.
Additional temperature reductions may
be needed in the future, depending
on the performance of WF4. Orbits:
internal 26, external 1
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal
performance that will be investigated.)
HSTARS:
10757 - GSAcq(2.3.2) results in Fine Lock Back-up (2,0,2) using FGS-1
At
087/02:13:56 GSAcq (2,3,2)
scheduled from 02:10:10-02:17:24 resulted
in Fine Lock Back-up (2,0,2) using FGS 1.
OBAD #1 RSS:
1783.55
OBAD #2 RSS:
8.39
COMPLETED OPS REQUEST:
18024-2 - ACS Bus C On-Orbit Test, Phase I - Part 1
18025-2 - ACS Bus C On-Orbit Test, Phase I - Part 2
18026-6 - ACS Bus C On-Orbit Test, Phase I - Part 3
18027-3 - ACS Bus C On-Orbit Test, Phase I - Part 4
18029-0 - Patch WF2 UIDLE replacement htr
set point, adjustment #3
COMPLETED OPS NOTES:
1585-1 - Update WF-2 Temp Limits
1582-0 - Change JERRCNT Limit after Replacement Heater
adj#3
SCHEDULED SUCCESSFUL
FGS GSacq 06 06
FGS REacq 00 00
OBAD with Maneuver 12 12
SIGNIFICANT EVENTS:
Flash Report: ACS Main Bus C On-orbit Test
As of 086/14:05:20 UTC, all commanding for the ACS Main
Bus C on-orbit
test has been successfully completed
through execution of Ops Requests
18024 - 18028. During the course of execution of Macro 3
to close the
ACS Side 2 Hold relay for 50 ms, the PDU2 fuse was
observed to clear,
indicating the likely location for the
short circuit is in the Hold bus.
The engineering team is now reviewing the high-rate
T-Prime telemetry
data collected during the test for a
detailed analysis of the results.
The primary Main Bus C relay has been successfully
re-opened, the FHSTs
have been powered on, and the
remaining vehicle configuration has been
restored to normal as part of the
post-test clean-up.
Flash Report: ACS Bus C Test, Post-Test Monitoring
The Fixed-Head Star Trackers are performing nominally
following their
power cycle as part of the ACS Main
Bus C test. OBAD corrections of
approximately 0.5 and 0.005 degrees RSS were
performed prior to the
successful guide star acquisition at
086/20:58.
Flash Report: WF/PC-II CCD4 replacement Heater In-Flight
Temperature
Adjustment #3
The 3rd in-flight adjustment of the WF/PC-II replacement
heater
temperature control was successfully
completed with the execution of Ops
Request 18029-0 at 086/18:20. All activities proceeded
nominally.
The NSSC-1 executive limit table action value for the
pyramid bulkhead
temperature was changed from 8.13 to 2.38 degC in accordance with the
updates to CARD item 2.4.6.1, and the
UIDLE dead band control range was
shifted from 9.99 - 11.3 to 8.7 to 9.99
degC. The behavior of the
replacement heaters under the control of
UIDLE and the optical bench
temperatures will continue to be monitored
in real-time until such time
as the new settings can be
functionally verified, likely within the next
hour. Another Flash Report will be
sent following this verification.
Flash Report: Post WF/PC-II CCD4 Replacement Heater
In-Flight Temperature
Adjustment #3 Monitoring
At 86/23:08 the replacement heaters were observed turning
on when Bay1
fell to 8.74 degs,
~ 7 minutes later they were disables when Bay1
reached 9.99 deg as expected,
functionally verifying the patch.
____________________________________________________________
Lynn F. Bassford
Hubble Space Telescope
CHAMP
Lockheed Martin
NASA GSFC PH#: 301-286-2876
"The Hubble Space Telescope is the astronomical
observatory and key to unlocking the most cosmic mysteries of the past, present
and future." - 7/26/6