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Daily #4084



 
 
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Old April 4th 06, 02:44 PM posted to sci.astro.hubble
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Default Daily #4084


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4084

PERIOD COVERED: UT April 03, 2006 (DOY 093)

OBSERVATIONS SCHEDULED

ACS/HRC 10474

Shooting Stars: Looking for Direct Evidence of Massive Central Black
Holes in Globular Clusters

We propose to make observations that directly test the proposition
that globular clusters contain massive black holes. Our targets are
the bulge globular clusters NGC 6388 and NGC 6441. These are probably
among the most massive in the galaxy, but are understudied compared to
more familiar objects such as M15. Our analysis suggests that these
two clusters are the most likely to show unambiguous evidence for a
central massive black hole if such things exist in globular clusters.
The observations proposed will give us the first thorough kinematic
and photometric studies of these two clusters. The combination of the
two epochs will give us proper motions good to of order 6 km/s. In
addition, they will provide us with the first good, deep,
color-magnitude diagrams for these clusters. These diagrams will be
used to investigate the make up of the stellar population in the
clusters, to more firmly establish their distances, ages, and
metallicities, and to search for a binary sequence.

ACS/HRC 10563

Accurate dark-matter mass profiles in 3 elliptical galaxies as a test
of CDM

A critical test of the successful Lambda-CDM picture for structure
formation is the measurement of the power law exponent, gamma, of the
centre of dark matter density profiles, predicted to lie in the range
1.0-1.5. Measurements of gamma derived from rotation curves of LSB
galaxies appear to contradict CDM, but rely on assumptions that are
difficult to verify {e.g. axisymmetry}. We have recently demonstrated,
using our new `semi-linear' inversion method, how strong gravitational
lensing by galaxies can provide a clean and accurate measurement of
gamma, free of such ambiguities. HST images of lensed non-AGN galaxies
provide hundreds of resolution elements, each a constraint on the mass
profile. Such lenses are exceedingly rare, but we have recently
discovered new systems. We propose deep ACS-HRC observations of 3
systems to measure gamma in each, accurate to 0.15 {95% confidence}
and to obtain an indication of its variation between galaxies. To
establish the required number of orbits we have undertaken an
end-to-end simulation of the problem, creating and analysing synthetic
ACS images. Additionally the semi-linear method simultaneously
reconstructs the pixelised source surface brightness distribution. Our
simulations demonstrate that the fine sampling and small pixel
scattering of the HRC, resolves the morphology of the sources with
exquisite detail.

ACS/HRC 10738

Earth Flats

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 in the pipeline and to monitor any changes. Weekly
coronagraphic monitoring is required to assess the changing position
of the spots.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

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 programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

ACS/SBC 10535

High Temperature Accretion Flows and Reprocessing in X-ray Binaries:
The ADC Source 4U 1822-371

The eclipsing low-mass X-ray binary 4U 1822-371 is the ideal system in
which to observe hot accretion and the effects of strong irradiation.
Its orbital period is 5.57~hr and its orbital inclination is high
enough that flux from the neutron star is blocked by the edge-on
accretion disk in the system. Because the neutron star is hidden its
Accretion Disk Corona is visible. These ADCs are present in most if
not all low-mass X-ray binaries but are generally not visible. 4U
1822-371 provides a unique opportunity to study an ADC and disk
irradiation because the eclipse by the secondary star allows their
geometry and flux to be mapped. We will perform a multiwavelength
light curve synthesis and eclipse analysis of 4U 1822-371. The
scientific goal is to map the geometry and flux from its ADC and from
its irradiated accretion disk. The crucial and irreplaceable role of
HST is to provide the UV data needed to disentangle the ADC from the
irradiated accretion disk. We will obtain time-resolved,
objective-prism UV spectroscopy of 4U 1822-371 with the ACS/SBC with
the PR130L prism, covering most of its orbit and all of the eclipse.
This combination will yield excellent orbital light curves in the UV
continuum and in the integrated line fluxes.

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.

WFPC2 10748

WFPC2 CYCLE 14 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 10749

Earth Flats

This proposal monitors flatfield stability. This proposal obtains
sequences of Earth streak flats to construct high quality flat fields
for the WFPC2 filter set. These flat fields will allow mapping of the
OTA illumination pattern and will be used in conjuction with previous
internal and external flats to generate new pipeline superflats. These
Earth flats will complement the Earth flat data obtained during cycles
4-13.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10194 - GSAcq (1,2,2) failed due to search radius limit exceeded on
FGS 1 @ 093/13:37:22z

At AOS 093/13:36:30, GSAcq (1,2,2) scheduled for 093/13:32:35 -
13:39:53 was observed to have failed due to search radius limit
exceeded on FGS 1. Also at AOS, Two ESB "1805" FHST moving target
detected noted. Received ESB "a05" Exceeded SRL. OBAD #1 data
unavailable. OBAD #2: V1 21.55, V2 15.22, V3 16.87, RSS 31.31. OBAD
MAP: V1 -0.19, V2 1.16, V3 -0.33, RSS 1.22. At AOS 093/15:28:10, REAcq
(1,2,2) scheduled for 093/15:08:31-15:15:49 was observed to have
failed due to search radius limit exceeded on FGS 1. Received ESB
"a05" Exceeded SRL. OBAD #1: V1 -38.80, V2 -3244.27, V3 -15.09, RSS
3244.54. OBAD #2: V1 -16.45, V2 17.10, V3 -23.73, RSS 33.56. OBAD MAP:
V1 2.01, V2 0.76, V3 1.88, RSS 2.85.

10195 - GSAcq (1,2,2) failed due to search radius limit exceeded on
FGS 1 @ 093/16:49:09z

At AOS 093/16:49:09, GSAcq (1,2,2) scheduled for 093/16:44:27 -
16:51:45 was observed to have failed due to search radius limit
exceeded on FGS 1. Received ESB "a05" Exceeded SRL. OBAD #1: V1
-184.56, V2 -2100.48, V3 637.18, RSS 2202.75. OBAD #2 V1 -6.01, V2
-5.40, V3 -4.82, RSS 9.41. OBAD MAP unavailable due to LOS. REAcq
(1,2,2) scheduled for 093/18:20:23-18:27:41 failed due to search
radius limit exceeded on FGS 1. Received ESB "a05" Exceeded SRL. OBAD
#2 RSS value = 12.69 arcseconds. OBAD MAP RSS value = 4.26 arcseconds.

10196 - GSacq(2,1,2) failed due to search radius limit exceeded @
093/20:12:13z

GSacq(2,1,2) scheduled at 093/20:08:57 failed due to search radius
limit exceeded on FGS 1. OBAD1 showed errors of V1= -2370.76,
V2=-1278.60, V3=727.90, RSS=2790.19. OBAD2 showed errors of V1=3.32,
V2=3.76, V3=-1.04, RSS=5.12.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 09 06 Hstar#
10194,10195 & 10196
FGS REacq 07 04 Hstar#
10194,10195 & 10196
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS:

Flash Report - Two Gyro Acquisition Modifications

The first 6 guide star acquisitions have succeeded using the new
Primary FGS to Fine Lock (PFFL) Acquisition Logic, and PCS observed no
issues with any of the other changes accompanying the logic change.
On-orbit performance is close to predicted values for the number of
Coarse Track cycles required for CTDV, T2G rates at the transition
time to F2G-CT, T2G rate damping time under F2G-CT control, duration
of the F2G open-loop walkdown, and Fine Lock walkdown length. The
predicted location for Fine Lock Data Valid was verified in flight,
demonstrating that observed vehicle drifts during the open-loop F2G
interval match predictions. Preliminary results show that vehicle
rates in T2G are reduced, as expected, with the new T2G Attitude Hold
gains. Preliminary analysis of the control law integral path indicates
that peak-to-peak residual environmental torques are now lower with
the updated vehicle inertia tensor.


 




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