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Daily Report #5086



 
 
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Old April 30th 10, 05:27 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5086

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5086

PERIOD COVERED: 5am April 29 - 5am April 30, 2010 (DOY 119/09:00z-120/09:00z)

OBSERVATIONS SCHEDULED

COS/FUV 11687

SNAPing Coronal Iron

This is a Snapshot Survey to explore two forbidden lines of highly
ionized iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and
Fe XXI 1354 (T~ 10 MK) -- well known to Solar Physics -- have been
detected in about a dozen cool stars, mainly with HST/STIS. The UV
coronal forbidden lines are important because they can be observed
with velocity resolution of better than 15 km/s, whereas even the
state-of-the-art X-ray spectrometers on Chandra can manage only 300
km/s in the kilovolt band where lines of highly ionized iron more
commonly are found. The kinematic properties of hot coronal plasmas,
which are of great interest to theorists and modelers, thus only are
accessible in the UV at present. The bad news is that the UV coronal
forbidden lines are faint, and were captured only in very deep
observations with STIS. The good news is that 3rd-generation Cosmic
Origins Spectrograph, slated for installation in HST by SM4, in a mere
25 minute exposure with its G130M mode can duplicate the sensitivity
of a landmark 25-orbit STIS E140M observation of AD Leo, easily the
deepest such exposure of a late-type star so far. Our goal is to build
up understanding of the properties of Fe XII and Fe XXI in additional
objects beyond the current limited sample: how the lineshapes depend
on activity, whether large scale velocity shifts can be detected, and
whether the dynamical content of the lines can be inverted to map the
spatial morphology of the stellar corona (as in "Doppler Imaging'').
In other words, we want to bring to bear in the coronal venue all the
powerful tricks of spectroscopic remote sensing, well in advance of
the time that this will be possible exploiting the corona's native
X-ray radiation. The 1290-1430 band captured by side A of G130M also
contains a wide range of key plasma diagnostics that form at
temperatures from below 10, 000 K (neutral lines of CNO), to above
200, 000 K (semi-permitted O V 1371), including the important bright
multiplets of C II at 1335 and Si IV at 1400; yielding a diagnostic
gold mine for the subcoronal atmosphere. Because of the broad value of
the SNAP spectra, beyond the coronal iron project, we waive the normal
proprietary rights.

ACS/WFC 11715

The Luminous Galactic Cepheid RS Puppis: A Geometric Distance from its
Nested Light Echoes

RS Puppis is one of the most luminous Cepheids in the Milky Way (P =
41.4 days) and an analog of the bright Cepheids used to measure
extragalactic distances. An accurate distance would help anchor the
zero-point of the bright end of the period-luminosity relation, but at
a distance of about 2 kpc it is too far away for a trigonometric
parallax with existing instrumentation.

RS Pup is unique in being surrounded by a reflection nebula, whose
brightness varies as pulses of light from the Cepheid propagate
outwards. Members of our team have used ground-based imaging of the
nebula to derive phase lags in the light variations of individual
features in the nebula, and have inferred a seemingly very precise
geometric distance to the star. However, there is an unavoidable
ambiguity involving the cycle counts, which was resolved by assuming
that the features lie in the plane of the sky. If this assumption is
incorrect, a large systematic error would be introduced into the
distance measurement.

We show that polarimetric imaging using the high spatial resolution of
ACS/WFC and its ability to image close to the star can resolve this
ambiguity and yield a reliable geometric distance to RS Pup. We will
also obtain a wide-field multicolor image of the nebula, in order to
study its morphology and the mass-loss history of the Cepheid.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CC 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.

STIS/CCD 11567

Boron Abundances in Rapidly Rotating Early-B Stars

Models of rotation in early-B stars predict that rotationally driven
mixing should deplete surface boron abundances during the
main-sequence lifetime of many stars. However, recent work has shown
that many boron depleted stars are intrinsically slow rotators for
which models predict no depletion should have occurred, while
observations of nitrogen in some more rapidly rotating stars show less
mixing than the models predict. Boron can provide unique information
on the earliest stages of mixing in B stars, but previous surveys have
been biased towards narrow- lined stars because of the difficulty in
measuring boron abundances in rapidly rotating stars. The two targets
observed as part of our Cycle 13 SNAP program 10175, just before STIS
failed, demonstrate that it is possible to make useful boron abundance
measurements for early-B stars with Vsin(i) above 100 km/s. We propose
to extend that survey to a large enough sample of stars to allow
statistically significant tests of models of rotational mixing in
early-B stars.

STIS/CCD 11852

STIS CCD Spectroscopic Flats C17

The purpose of this proposal is to obtain pixel-to-pixel lamp flat
fields for the STIS CCD in spectroscopic mode.

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 11911

UVIS L-Flats and Geometric Distortion

Multiple pointing observations of the globular cluster Omega Centauri
(NGC 5139) will be used to measure the filter-dependent low frequency
flat field (L-flat) corrections and stability for a key set of 10
broadband filters used by GO programs. The selected filters are F225W,
F275W, F336W, F390W, F438W, F555W, F606W, F775W, F814W and F850LP. By
measuring relative changes in brightness of a star over different
portions of the detector, we will determine local variations in the
UVIS detector response.

The broad wavelength range covered by these observations will allow us
to derive the L-flat correction for the remaining wide, medium and
narrow-band UVIS filters. The same data will also be used to determine
and correct the geometric distortion that affects UVIS data. The broad
wavelength range covered by these observations will allow us to
measure the geometric distortion dependence with wavelength and
filters and to provide the most appropriate correction over the entire
wavelength range provided by UVIS.

WFC3/UVIS/IR 11909

UVIS Hot Pixel Anneal

The on-orbit radiation environment of WFC3 will continually generate
new hot pixels. This proposal performs the procedure required for
repairing those hot pixels in the UVIS CCDs. During an anneal, the
two-stage thermo-electric cooler (TEC) is turned off and the
four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20
deg. C. As a result of the CCD warmup, a majority of the hot pixels
will be fixed; previous instruments such as WFPC2 and ACS have seen
repair rates of about 80%. Internal UVIS exposures are taken before
and after each anneal, to allow an assessment of the procedure's
effectiveness in WFC3, provide a check of bias, global dark current,
and hot pixel levels, as well as support hysteresis (bowtie)
monitoring and CDBS reference file generation. One IR dark is taken
after each anneal, to provide a check of the IR detector.

ACS/WFC 11995

CCD Daily Monitor (Part 2)

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 320 orbits (20 weeks) from 1 February
2010 to 20 June 2010.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

12259 - GSAcq(2,3,3) at 119/10:11:22z was successful. REAcqs(2,3,3)
scheduled at 119/11:36:48z, 1312z, 1451z, 1633z, and 1815z all failed.

Observations affected: WFC3 111-130, proposal ID#11911.

12263 - GSAcq(1,2,1) results in fine lock backup (2,0,2) using FGS-2 @
120/0323z

Observations Possibly affected: COS 34-38 Proposal ID#11687, ACS
115-116 Proposal ID#11995, STIS 47 Proposal ID#11845

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 07 07
FGS REAcq 11 06
OBAD with Maneuver 05 05

SIGNIFICANT EVENTS: (None)


 




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