NASA Hubble Space Telescope Daily Report #4937
Thursday, September 24, 2009
Source: Space Telescope Science Institute - Comments
HUBBLE SPACE TELESCOPE DAILY REPORT #4937
Continuing to Collect World Class Science
PERIOD COVERED: 5am September 23 - 5am September 24, 2009 (DOY 266/09:00z-267/09:00z)
CCD Daily Monitor (Part 1)
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 352 orbits (22 weeks) from 31 August 2009 to 31 January 2010.
NUV Detector Dark
The purpose of this proposal is to 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.
NUV Imaging Sensitivity, Cycle 17
The purpose of this proposal is to test NUV imaging sensitivity for a range of target spectral energy distributions. All targets have wide-slit STIS spectra in the HST Archive. We use eleven horizontal branch stars in the globular cluster NGC 6681 covering a range of effective temperatures, plus a solar-analog standard star.
NUV Internal/External Wavelength Scale Monitor
This program monitors the offsets between the wavelength scale set by the internal wavecal versus that defined by absorption lines in external targets. This is accomplished by observing two external radial velocity standard targets: HD187691 with G225M and G285M and HD6655 with G285M and G230L. The two standard targets have little flux in the wavelength range covered by G185M and so Feige 48 (sdO) is observed with this grating. Both Feige 48 and HD6655 are also observed in SMOV. The cenwaves observed in this program are a subset of the ones used during Cycle 17. Observing all cenwaves would require a considerably larger number of orbits. Constraints on scheduling of each target are placed so that each target is observed once every ~2-3 months. Observing the three targets every month would also require a considerably larger number of orbits.
Extended Dark Monitoring
This program takes a series of darks to obtain darks (including amplifier glow, dark current, and shading profiles) for all three cameras in the read-out sequences used in Cycle 17. A set of 12 orbits will be observed every two months for a total of 72 orbits for a 12 month Cycle 17. This is a continuation of Cycle 16 program 11330 scaled down by ~80%.
The first orbit (Visit A0) should be scheduled in the NICMOS SMOV after the DC Transfer Test (11406) and at least 36h before the Filter Wheel Test (11407). Data download using fast track.
The following 28 orbits (visit A1-N2) should be scheduled AFTER the SMOV Proposal 11407 (Filter Wheel Test). This is done in order to monitor the dark current following an adjustment of the NCS set-point. These visits should be executed until the final temperature is reached during SMOV.
NICMOS Post-SAA Calibration - CR Persistence Part 6
This is a new procedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and every time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA. The darks will be obtained in parallel in all three NICMOS cameras. The post-SAA darks will be non-standard reference files available to users with a 'Use After' date/time mark. The keyword 'UseAfter=date/time' will also be added to the header of each post-SAA dark frame. The keyword must be populated with the time, in addition to the date, because HST crosses the SAA ~8 times per day, so each post-SAA dark will need to have the appropriate time specified, for users to identify the ones they need. Both the raw and processed images will be archived as post-SAA darks. Generally we expect that all NICMOS science/calibration observations started within 50 minutes of leaving an SAA will need such MAPs to remove the CR persistence from the science images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.
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.
CCD Dark Monitor Part 1
The purpose of this proposal is to monitor the darks for the STIS CCD.
CCD Bias Monitor-Part 1
The purpose of this proposal is to 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.
COS FUV Line Spread Function Characterization
In this program we will observe the star Sk-155 (an O9b star in the SMC) with the high resolution E140H grating on STIS. Sk-155 was observed with COS during SMOV with the purpose of confirming the spectroscopic resolution of the FUV medium resolution gratings (G130M and G160M). Comparison of the E140H spectra with the COS spectra shows that the COS spectral resolution is likely significantly impacted by broad non- Gaussian wings in the COS LSF. Further tests and characterization of this effect is critical for evaluating the final spectroscopic resolution of COS. However, the existing STIS/E140H spectra of Sk-155 only cover the wavelength range 1165-1350 A (good for testing the G130M spectral resolution). They do not extend to long enough wavelenghts to test the COS G160M spectral resolution. Therefore, in this supplemental STIS program we will use 2 HST orbits to re-observe Sk 155 with STIS. We will utilize the E140H grating with the 0.2x0.09 aperture and central wavelength of 1598 angstroms which covers the missing wavelength range 1500-1700 angstroms.
Panchromatic WFC3 Survey of Galaxies at Intermediate z: Early Release Science Program for Wide Field Camera 3
The unique panchromatic capabilities of WFC3 will be used to survey the structure and evolution of galaxies at the peak of the galaxy assembly epoch. Deep ultraviolet and near-IR imaging and slitless spectroscopy of existing deep multi-color ACS fields will be used to gauge star-formation and the growth of stellar mass as a function of morphology, structure and surrounding density in the critical epoch 1 < z < 4. Images in the F225W, F275W, and F336W filters will identify galaxies at z < 1.5 from their UV continuum breaks, and provide star-formation indicators tied directly to both local and z > 3 populations. Deep near-IR (F125W and F160W) images will probe the stellar mass function well below 10^9 Msun for mass-complete samples. Lastly, the WFC3 slitless UV and near-IR grisms will be used to measure redshifts and star-formation rates from H- alpha and rest-frame UV continuum slope. This WFC3 ERS program will survey one 4 x 2 mosaic for a total area of 50 square arcminutes to 5-sigma depths of m_AB = 27 in most filters from the mid-UV through the near-IR.
This multicolor high spatial resolution data set will allow the user to gauge the growth of galaxies through star-formation and merging. High precision photometric and low- resolution spectroscopic redshifts will allow accurate determinations of the faint-end of the luminosity and mass functions, and will shed light on merging and tidal disruption of stellar and gaseous disks. The WFC3 images will also allow detailed studies of the internal structure of galaxies, and the distribution of young and old stellar populations. This program will demonstrate the unique power of WFC3 by applying its many diverse modes and full panchromatic capability to a forefront problem in astrophysics.
Star Formation, Extinction, and Metallicity at 0.7< z<1.5: H-Alpha Fluxes and Sizes from a Grism Survey of GOODS-N
The global star formation rate (SFR) is ~10x higher at z=1 than today. This could be due to drastically elevated SFR in some fraction of galaxies, such as mergers with central bursts, or a higher SFR across the board. Either means that the conditions in z=1 star forming galaxies could be quite different from local objects. The next step beyond measuring the global SFR is to determine the dependence of SFR, obscuration, metallicity, and size of the star-forming region on galaxy mass and redshift. However, SFR indicators at z=1 typically apply local calibrations for UV, [O II] and far-IR, and do not agree with each other on a galaxy-by-galaxy basis. Extinction, metallicity, and dust properties cause uncontrolled offsets in SFR calibrations. The great missing link is Balmer H-alpha, the most sensitive probe of SFR. We propose a slitless WFC3/G141 IR grism survey of GOODS-N, at 2 orbits/pointing. It will detect Ha+[N II] emission from 0.7< z<1.5, to L(Ha) = 1.7 x 10^41 erg/sec at z=1, measuring H-alpha fluxes and sizes for > 600 galaxies, and a small number of higher-redshift emitters. This will produce: an emission-line redshift survey unbiased by magnitude and color selection; star formation rates as a function of galaxy properties, e.g. stellar mass and morphology/mergers measured by ACS; comparisons of SFRs from H-alpha to UV and far-IR indicators; calibrations of line ratios of H-alpha to important nebular lines such as [O II] and H-beta, measuring variations in metallicity and extinction and their effect on SFR estimates; and the first measurement of scale lengths of the H-alpha emitting, star-forming region in a large sample of z~1 sources.
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).
Jovian Upheaval and Its Impact on Vortices
We propose observations of Jupiter with global coverage at high resolution to quantify changes in its atmosphere during and following the global upheaval. Only HST has the capability to obtain images with enough spatial resolution and contrast to extract velocity fields (we will use our newly developed technique to accomplish this), and with WFC3 we can image Jupiter in its entirety in a single exposure. We are in particular interested in the Red Oval BA: Will the Oval be long lived, remain red, or turn white again, disappear? Both the merger of its precursors, and change in color has never before been witnessed. The Great Red Spot: This storm system appears to decrease in size and has become rounder, both as derived from its associated cloud deck, but also from its potential vorticity, a more dynamically-relevant quantity. How will the GRS evolve? Will it swallow the new vortices detected in amateur images at this same latitude band? How will this effect the potential vorticity? In addition, we hope to understand disturbances and stagnation points, both of which were detected during the present global upheaval: are these cyclonic regions, can they spawn anticyclones (as suggested by amateur images)?
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).
A Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into the Formation of the Outer Solar System
The eight planets overwhelmingly dominate the solar system by mass, but their small numbers, coupled with their stochastic pasts, make it impossible to construct a unique formation history from the dynamical or compositional characteristics of them alone. In contrast, the huge numbers of small bodies scattered throughout and even beyond the planets, while insignificant by mass, provide an almost unlimited number of probes of the statistical conditions, history, and interactions in the solar system. To date, attempts to understand the formation and evolution of the Kuiper Belt have largely been dynamical simulations where a hypothesized starting condition is evolved under the gravitational influence of the early giant planets and an attempt is made to reproduce the current observed populations. With little compositional information known for the real Kuiper Belt, the test particles in the simulation are free to have any formation location and history as long as they end at the correct point. Allowing compositional information to guide and constrain the formation, thermal, and collisional histories of these objects would add an entire new dimension to our understanding of the evolution of the outer solar system. While ground based compositional studies have hit their flux limits already with only a few objects sampled, we propose to exploit the new capabilities of WFC3 to perform the first ever large-scale dynamical-compositional study of Kuiper Belt Objects (KBOs) and their progeny to study the chemical, dynamical, and collisional history of the region of the giant planets. The sensitivity of the WFC3 observations will allow us to go up to two magnitudes deeper than our ground based studies, allowing us the capability of optimally selecting a target list for a large survey rather than simply taking the few objects that can be measured, as we have had to do to date. We have carefully constructed a sample of 120 objects which provides both overall breadth, for a general understanding of these objects, plus a large enough number of objects in the individual dynamical subclass to allow detailed comparison between and within these groups. These objects will likely define the core Kuiper Belt compositional sample for years to come. While we have many specific results anticipated to come from this survey, as with any project where the field is rich, our current knowledge level is low, and a new instrument suddenly appears which can exploit vastly larger segments of the population, the potential for discovery -- both anticipated and not -- is extraordinary.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
FGS GSAcq 6 6
FGS REAcq 8 8
OBAD with Maneuver 6 6
SIGNIFICANT EVENTS: (None)
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