HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5168

PERIOD COVERED: 5am August 25 - 5am August 26, 2010 (DOY 237/09:00z-238/09:00z)

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS: (None)

COMPLETED OPS REQUEST:

18887-0 - Install COS CS FSW 4.11 @ 237/1542z

COMPLETED OPS NOTES: (None)

                       SCHEDULED  SUCCESSFUL

FGS GSAcq               05            05       

FGS REAcq               10            10       

OBAD with Maneuver 05            05       

SIGNIFICANT EVENTS:

COS FSW 4.11 was successfully installed and verified by the FSW team at 237/15:42.

OBSERVATIONS SCHEDULED:

ACS/WFC 11996

CCD Daily Monitor (Part 3)

This program comprises basic tests for measuring the read noise and dark

current of the ACS WFC and for tracking the growth of hot pixels. The

recorded frames are used to create bias and dark reference images for

science data reduction and calibration. This program will be executed

four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To

facilitate scheduling, this program is split into three proposals. This

proposal covers 308 orbits (19.25 weeks) from 21 June 2010 to 1 November

2010.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,

and 1x1 at gain = 4, to build up high-S/N superbiases and track the

evolution of hot columns.

WFC3/ACS/UVIS 11613

GHOSTS: Stellar Outskirts of Massive Spiral Galaxies

We propose to continue our highly successful GHOSTS HST survey of the

resolved stellar populations of nearby, massive disk galaxies using

SNAPs. These observations provide star counts and color-magnitude

diagrams 2-3 magnitudes below the tip of the Red Giant Branch of the

outer disk and halo of each galaxy. We will measure the metallicity

distribution functions and stellar density profiles from star counts

down to very low average surface brightnesses, equivalent to ~32 V-mag

per square arcsec.

This proposal will substantially improve our unique sampling of galaxy

outskirts. Our targets cover a range in galaxy mass, luminosity,

inclination, and morphology. As a function of these galaxy properties,

this survey provides: - the most extensive, systematic measurement of

radial light profiles and axial ratios of the diffuse stellar halos and

outer disks of spiral galaxies; - a comprehensive analysis of halo

metallicity distributions as function of galaxy type and position within

the galaxy; - an unprecedented study of the stellar metallicity and age

distribution in the outer disk regions where the disk truncations occur;

- the first comparative study of globular clusters and their field

stellar populations.

We will use these fossil records of the galaxy assembly process to test

halo formation models within the hierarchical galaxy formation scheme.

WFC3/IR 11694

Mapping the Interaction Between High-Redshift Galaxies and the

Intergalactic Environment

With the commissioning of the high-throughput large-area camera WFC3/IR,

it is possible for the first time to undertake an efficient survey of

the rest-frame optical morphologies of galaxies at the peak epoch of

star formation in the universe. We therefore propose deep WFC3/IR

imaging of over 320 spectroscopically confirmed galaxies between

redshift 1.6 < z < 3.4 in well-studied fields which lie along the line

of sight to bright background QSOs. The spectra of these bright QSOs

probe the IGM in the vicinity of each of the foreground galaxies along

the line of sight, providing detailed information on the physical state

of the gas at large galactocentric radii. In combination with our

densely sampled UV/IR spectroscopy, stellar population models, and

kinematic data in these fields, WFC3/IR imaging data will permit us to

construct a comprehensive picture of the structure, dynamics, and star

formation properties of a large population of galaxies in the early

universe and their effect upon their cosmological environment.

WFC3/IR 11708

Determining the Sub-stellar IMF in the Most Massive Young Milky Way

Cluster, Westerlund 1

Despite over 50 years of active research, a key question in galactic

astronomy remains unanswered: is the initial mass function (IMF) of

stars and sub-stellar objects universal, or does it depend on initial

conditions? The answer has profound consequences for the evolution of

galaxies as well as a predictive theory of star formation. Work to date

suggests that certain environments (high densities, e.g. Elmegreen 2004;

low metallicity, e.g. Larson 2005) should produce a top-heavy IMF, and

there are hints from unresolved star-bursts that this might be the case.

Yet, there is no clear evidence for an IMF that differs from that

characterizing the Galactic field stars in a resolved stellar population

down to one solar mass. Westerlund 1 is the most massive young star

cluster known in the Milky Way. With an estimated mass of 5x10^4 Msun,

an age of 3-5 Myr, and located at a distance of 3-4 kpc, it presents a

unique opportunity to test whether the IMF in such a cluster deviates

from the norm well down into the brown dwarf regime. We propose WFC3

near-IR imaging to probe the IMF down to 40 Jupiter masses. The data

will enable use to: 1) provide a stringent test of the universality of

the IMF under conditions approximating those of star-bursts; 2) search

for primordial or dynamic mass segregation in the clusters; and 3)

assess whether the cluster is likely to remain bound (as a massive open

cluster) or disperse into the field. We will obtain images in the F125W,

F160W, and F139M filters. The F139M filter covers a strong water

absorption feature and the color F125W/F139M is a powerful temperature

diagnostic in the range 2800-4000 K. This information will enable us to:

a) confirm membership for low mass stars suspected on the basis of their

position in the color-magnitude diagram; b) place the members in the HR

diagram; and c) estimate the masses and ages of cluster members for

low-mass stars and sub-stellar objects. This new capability offered with

the WFC3 (through a novel combination of filter complement, high spatial

resolution, and large field of view) will enable us to make a

fundamental test of whether the IMF is universal on a unique resolved

stellar population, as well as assess the clusters structure, dynamics,

and ultimate fate.

WFC3/IR 11926

IR Zero Points

We will measure and monitor the zeropoints through the IR filters using

observations of the white dwarf standard stars, GD153, GD71 and GD191B2B

and the solar analog standard star, P330E. Data will be taken monthly

during Cycle 17. Observations of the star cluster, NGC 104, are made

twice to check color transformations. We expect an accuracy of 2% in the

wide filter zeropoints relative to the HST photometric system, and 5% in

the medium- and narrow-band filters.

WFC3/IR 11928

WFC3/IR Low-Frequency Flat and Geometric Distortion

Multiple observations of globular cluster Omega Cen at multiple infrared

wavelengths of IR detector will be used to derive filter dependency of

low-frequency sensitivity (L_flat fields) across of IR detector and its

time variation. Additionally, the same data will be also used to derive

filter-dependant geometric distortion of the detector and its

time-dependency.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more

reliably removed from science data using darks taken with the same

exposure sequences as the science data, than with a single dark current

image scaled by desired exposure time. Therefore, dark current images

must be collected using all sample sequences that will be used in

science observations. These observations will be used to monitor changes

in the dark current of the WFC3-IR channel on a day-to-day basis, and to

build calibration dark current ramps for each of the sample sequences to

be used by Gos in Cycle 17. For each sample sequence/array size

combination, a median ramp will be created and delivered to the

calibration database system (CDBS).

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of

full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K

subarray biases are acquired at less frequent intervals throughout the

cycle to support subarray science observations. The internals from this

proposal, along with those from the anneal procedure (Proposal 11909),

will be used to generate the necessary superbias and superdark reference

files for the calibration pipeline (CDBS).

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the

UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.

Initially found via an unexpected bowtie- shaped feature in flatfield

ratios, subsequent lab tests on similar e2v devices have since shown

that it is also present as simply an overall offset across the entire

CCD, i.e., a QE offset without any discernable pattern. These lab tests

have further revealed that overexposing the detector to count levels

several times full well fills the traps and effectively neutralizes the

bowtie. Each visit in this proposal acquires a set of three 3x3 binned

internal flatfields: the first unsaturated image will be used to detect

any bowtie, the second, highly exposed image will neutralize the bowtie

if it is present, and the final image will allow for verification that

the bowtie is gone.