This program is a smaller version of our routine CCD monitoring program,
designed to run throughout SMOV, after which our regular Cycle 17 CAL
proposal will begin. This program obtains the bias and dark frames
needed to generate reference files for calibrating science data, and
allows us to monitor detector noise and the growth of hot pixels.

DESCRIPTION: This activity confirms COS sensitivity versus wavelength
over the entire observable spectrum for all FUV gratings and central
wavelength settings. Obtain quicklook sensitivity visit early in SMOV.
Later, after wavelength calibration is verified, perform a
precise-centering acquisition and observe an appropriate HST flux
standard star (chosen from the HST prime standard and FASTEX lists) with
the PSA. (A limited BOA characterization is obtained in Visit 13 using
primary standard GD153.) No off aperture-center observations are
performed in this activity (see COS32, program 11490, for off-center
characterizations). Spectra will be obtained to meet a Poisson S/N
criterion of ~30 per sensitivity extraction bin or higher; substantially
higher S/N characterization will be utilized in routine Cycle 17
calibration.

Measure the NUV detector dark rate by taking long science exposures with
no light on the detector. The detector dark rate and spatial
distribution of counts will be compared to pre-launch data in order to
verify the nominal operation of the detector, and for use in the CalCOS
calibration pipeline. Variations of count rate as a function of orbital
position will be analyzed to find dependence of dark rate on proximity
to the SAA.

The current census of binaries among the massive O-type stars is
seriously incomplete for systems in the period range from years to
millennia because the radial velocity variations are too small and the
angular separations too close for easy detection. Here we propose to
discover binaries in this observational gap through a Faint Guidance
Sensor SNAP survey of relatively bright targets listed in the Galactic O
Star Catalog. Our primary goal is to determine the binary frequency
among those in the cluster/association, field, and runaway groups. The
results will help us assess the role of binaries in massive star
formation and in the processes that lead to the ejection of massive
stars from their natal clusters. The program will also lead to the
identification of new, close binaries that will be targets of long term
spectroscopic and high angular resolution observations to determine
their masses and distances. The results will also be important for the
interpretation of the spectra of suspected and newly identified binary
and multiple systems.

The UV throughput of WFC3 during SMOV is monitored via weekly standard
star observations in a subset of key filters (as many as will fit into a
single orbit but to include at a minimum F218W, F225W, F275W, and
F606W). The data will provide a measure of throughput levels as a
function of time and wavelength, allowing for detection of the presence
of possible contaminants. In addition, a small set of internal exposures
are included with the externals, to provide verification of detector
stability.

This test will provide calibration data to characterize the performance
of the WFC3 UVIS shutter. Images with exposure times ranging from 0.5 to
17 seconds will be used to quantify shutter shading, accuracy, and
stability.

This proposal corresponds to WFC3-20, and depends on the completion of
the IR initial alignment (proposal 11425, WFC3-12). In this test, we
will study the stability and structure of the IR channel flat field
images through all filter elements in the WFC3-IR channel. Flat field
images for each filter will be combined in order to produce a
calibration-quality flat field image. High signal observations will
provide a map of the pixel-to-pixel flat field structure, as well as
identify the positions of any dust particles.

This proposal obtains the photometric zero points in 16 WFC3/UVIS
priority-1 filters, 20 WFC3/UVIS priority-2 filters, and 1 WFC3/UVIS ERO
filter using a hot DA white dwarf. The observations are repeated at
intervals of 1 day, 7 days, and 30 days, to monitor photometric
stability in 8 of the priority-1 filters, with emphasis in the UV where
contamination would have the strongest effects.

This proposal obtains the photometric zero points in all 15 WFC3/IR
filters using two stars with distinct temperatures (a hot DA white dwarf
and a solar analog). The observations are repeated at intervals of 1
day, 7 days, and 30 days, to monitor photometric stability in all
filters.

The UVIS detector was observed during ground testing to occasionally
exhibit flat field and dark variations with a bowtie pattern. These
variations are most significant as ~1% flat field (gain) variations
across the field of view. It is believed that this represents a state or
condition into which the detector can transition for reasons and under
circumstances which are not currently understood. It is also very
unlikely that most science observations will determine the state (bowtie
or no-bowtie) of the detector. Ground test data indicates that this
state is long lived (many hours to ~one day). Hysteresis or memory of
past light exposure is also associated with this state.

Recent evidence suggests that exposing the detector to ~200k to 500k
electrons may quench this state. This proposal obtains an internal flat
field sequence of three exposures: one at 10x full well with two at 0.5x
full well immediately before and after. Each exposure is 3x3 binned to
reduce the data volume required.