SpaceRef

SpaceRef


NASA Hubble Space Telescope Daily Report #5171

Status Report From: Space Telescope Science Institute
Posted: Wednesday, September 1, 2010

HUBBLE SPACE TELESCOPE DAILY REPORT #5171

Continuing to Collect World Class Science

PERIOD COVERED: 5am August 30 - 5am August 31, 2010 (DOY 242/09:00z-243/09:00z)

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

12367 - GSAcq(2,1,1) at 242/18:55:15z failed to gyro control due to search radius limit exceeded on FGS2.

Observations affected WFC3 17-18 Proposal ID#11644

12369 - GSAcq(2,1,1) at 243/06:33:18z and REAcq(1,2,1) at 243/07:47:55z acquired Fine Lock Backup on FGS 1 Due to Search Radius Limit Exceeded on FGS 2.

Observations possibly affected WFC3 32-25 Proposal ID#11840 and WFC3 36 Proposal ID#11929.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES:

2072-0 - Battery Pressure and FSW SOC Ground Limit Update


SCHEDULED SUCCESSFUL
FGS GSAcq 8 7
FGS REAcq 8 8
OBAD with Maneuver 6 6




SIGNIFICANT EVENTS:

Flash Report:

At approximately DOY 2010/242 16:52 GMT (12:52pm local), the EPS FSW SOC parameters and Battery Pressure (PSI) safing test limits were modified by 15 AH to accommodate the increase in battery capacity.

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.

COS/FUV 11895

FUV Detector Dark Monitor

Monitor the FUV detector dark rate by taking long science exposures without illuminating the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.

COS/FUV 11897

FUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity in each FUV grating mode to detect any changes due to contamination or other causes.

COS/FUV/STIS/CCD/MA1 11592

Testing the Origin(s) of the Highly Ionized High-Velocity Clouds: A Survey of Galactic Halo Stars at z>3 kpc

Cosmological simulation predicts that highly ionized gas plays an important role in the formation and evolution of galaxies and their interplay with the intergalactic medium. The NASA HST and FUSE missions have revealed high-velocity CIV and OVI absorption along extragalactic sightlines through the Galactic halo. These highly ionized high-velocity clouds (HVCs) could cover 85% of the sky and have a detection rate higher than the HI HVCs. Two competing, equally exciting, theories may explain the origin of these highly ionized HVCs: 1) the "Galactic" theory, where the HVCs are the result of feedback processes and trace the disk-halo mass exchange, perhaps including the accretion of matter condensing from an extended corona; 2) the "Local Group" theory, where they are part of the local warm-hot intergalactic medium, representing some of the missing baryonic matter of the Universe. Only direct distance determinations can discriminate between these models. Our group has found that some of these highly ionized HVCs have a Galactic origin, based on STIS observations of one star at z<5.3 kpc. We propose an HST FUV spectral survey to search for and characterize the high velocity NV, CIV, and SiIV interstellar absorption toward 24 stars at much larger distances than any previous searches (4< d<21 kpc, 3<|z|<13 kpc). COS will provide atomic to highly ionized species (e.g.,OI, CII, CIV, SiIV) that can be observed at sufficient resolution (R~22, 000) to not only detect these highly ionized HVCs but also to model their properties and understand their physics and origins. This survey is only possible because of the high sensitivity of COS in the FUV spectral range.

COS/NUV 11894

NUV Detector Dark Monitor

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 and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.

COS/NUV 11896

NUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity of each NUV grating mode to detect any changes due to contamination or other causes.

COS/NUV/FUV 12034

COS-GTO: Brown Dwarf Activity Part 2

Based on the Findings in our Cycle 17 program, we will focus on M-stars in Cycle 18.

S/C 11639

Catching Accreting WDs Moving into Their Instability Strip(s)

Our past HST studies of the temperatures of 9 accreting, pulsating white dwarfs in cataclysmic variables show that 3 are in the normal instability strip for single white dwarfs, but the other 6 are much hotter (15, 000-16, 500K). This dual strip has been proposed to be due to mass differences in the white dwarfs related to evolutionary history and driven by the ionization of different elements in their respective driving regions. In 2007, GW Lib (the brightest and best studied of the 6 hot accreting pulsators) and V455 And (the brightest and best studied of the 3 cool accreting pulsators) underwent rare large amplitude dwarf nova outbursts (known to heat the white dwarf) and their pulsations disappeared. We propose COS observations to: a) take advantage of the unprecedented opportunity to view the change in pulsation modes due to cooling of the white dwarf envelope and b) determine the masses of the white dwarfs to test the dual strip theory. In addition, a nova that had its outburst 22 yrs ago has begun non-radial pulsations as it returns to quiescence. We will use COS to determine its temperature in relation to the instability strip for the pulsating white dwarfs in dwarf novae.

STIS/CCD/MA 11668

Cosmo-chronometry and Elemental Abundance Distribution of the Ancient Star HE1523-0901

We propose to obtain near-UV HST/STIS spectroscopy of the extremely metal-poor, highly r-process-enhanced halo star HE 1523-0901, in order to produce the most complete abundance distribution of the heaviest stable elements, including platinum, osmium, and lead. These HST abundance data will then be used to estimate the initial abundances of the long-lived radioactive elements thorium and uranium, and by comparison with their observed abundances, enable an accurate age determination of this ancient star. The use of radioactive chronometers in stars provides an independent lower limit on the age of the Galaxy, which can be compared with alternative limits set by globular clusters and by analysis from WMAP. Our proposed observations of HE1523-0901 will also provide significant new information about the early chemical history of the Galaxy, specifically, the nature of the first generations of stars and the types of nucleosynthetic processes that occurred at the onset of Galactic chemical evolution.

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.

STIS/CCD 11853

Cycle 17 STIS CCD Imaging Flats

This program periodically monitors the STIS CCD imaging mode flat fields by using the tungsten lamps.

STIS/CCD/FGS 11848

CCD Read Noise Monitor

This proposal measures the read noise of all the amplifiers (A, B, C, D) on the STIS CCD using pairs of bias frames. Full-frame and binned observations are made in both Gain 1 and Gain 4, with binning factors of 1x1, 1x2, 2x1, and 2x2. All exposures are internals. Pairs of visits are scheduled monthly for the first four months and then bi-monthly after that.

WFC3/ACS/IR 11840

Identifying the Host Galaxies for Optically Dark Gamma-Ray Bursts

We propose to use the high spatial resolution of Chandra to obtain precise positions for a sample of Gamma-Ray Bursts (GRBs) with no optical afterglows, where the optical light is suppressed relative to the X-ray flux. These bursts are likely to be highly obscured and may have different environments from the optically bright GRBs. Our Chandra observations will (unlike Swift XRT positions) allow for the unique identification of a host galaxy. To locate these host galaxies we will follow up our Chandra positions with deep optical and IR observations with HST. The ultimate aim is to understand any differences between the host galaxies of optically dark and bright GRBs, and how these affect the use of GRBs as tracers of starformation and galaxy evolution at high redshift.

WFC3/ACS/IR 11563

Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to <0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields

The first generations of galaxies were assembled around redshifts z~7-10+, just 500-800 Myr after recombination, in the heart of the reionization of the universe. We know very little about galaxies in this period. Despite great effort with HST and other telescopes, less than ~15 galaxies have been reliably detected so far at z>7, contrasting with the ~1000 galaxies detected to date at z~6, just 200-400 Myr later, near the end of the reionization epoch. WFC3 IR can dramatically change this situation, enabling derivation of the galaxy luminosity function and its shape at z~7-8 to well below L*, measurement of the UV luminosity density at z~7-8 and z~8-9, and estimates of the contribution of galaxies to reionization at these epochs, as well as characterization of their properties (sizes, structure, colors). A quantitative leap in our understanding of early galaxies, and the timescales of their buildup, requires a total sample of ~100 galaxies at z~7-8 to ~29 AB mag. We can achieve this with 192 WFC3 IR orbits on three disjoint fields (minimizing cosmic variance): the HUDF and the two nearby deep fields of the HUDF05. Our program uses three WFC3 IR filters, and leverages over 600 orbits of existing ACS data, to identify, with low contamination, a large sample of over 100 objects at z~7-8, a very useful sample of ~23 at z~8-9, and limits at z~10. By careful placement of the WFC3 IR and parallel ACS pointings, we also enhance the optical ACS imaging on the HUDF and a HUDF05 field. We stress (1) the need to go deep, which is paramount to define L*, the shape, and the slope alpha of the luminosity function (LF) at these high redshifts; and (2) the far superior performance of our strategy, compared with the use of strong lensing clusters, in detecting significant samples of faint z~7-8 galaxies to derive their luminosity function and UV ionizing flux. Our recent z~7.4 NICMOS results show that wide-area IR surveys, even of GOODS-like depth, simply do not reach faint enough at z~7-9 to meet the LF and UV flux objectives. In the spirit of the HDF and the HUDF, we will waive any proprietary period, and will also deliver the reduced data to STScI. The proposed data will provide a Legacy resource of great value for a wide range of archival science investigations of galaxies at redshifts z~2- 9. The data are likely to remain the deepest IR/optical images until JWST is launched, and will provide sources for spectroscopic follow up by JWST, ALMA and EVLA.

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/IR/S/C 12089

Persistence - Part 2

The IR detectors on WFC3, like other IR detectors, trap charge when exposed to sources near or above the full well of the detector diodes. This charge leaks out, producing detectable afterglow images for periods which can last for several hours, depending on the amount of over exposure. These visits, which consist of tungsten lamp exposures of varying durations followed by darks, are intended to provide a better calibration of persistence over the full area of the IR detector of WFC3.

WFC3/UV 12091

WFC3/UVIS Fringe Calibration - Part 2

Fringing has been observed in flat fields of 12 narrowband filters (4 full-frame and 3 quad spectral elements) longer than 600 nm, with peak-to-peak fringe amplitude variations ranging from 0.5% to 14.2% (WFC3 ISR 2010-04). Two filters (F953N and F656N) will be tested in program 11922, supporting 88 Cycle 17 GO exposures in these filters. Here we propose to observe globular cluster Omega Centauri (NGC 5139) in the other 10 filters affected by fringing, supporting 319 Cycle 17 GO exposures in these filters. By measuring the relative changes in brightness of stars at different positions on the detector, we will determine the local variations induced by the fringing pattern.

The data will serve two purposes: characterize the effect of fringing on photometry of on-orbit data, and verify models used to correct for fringing effects. The models rely on Thermal Vacuum Test 3 (TV3) data between 845-990 nm and NASA/GSFC Detector Characterization Laboratory (DCL) test data from 700-1060 nm. Only the F953N filter in program 11922 overlaps with the test data wavelength range, making it difficult to compare the efficacy of fringe models. This program will expand the on-orbit fringing data so that we can compare models at 6 new wavelengths within the ground test data wavelength range, as well as 4 new wavelengths not covered by the ground test data. Flight data in these 4 filters can be corrected by extrapolating the model beyond the wavelength range of the test data used to create the model.

WFC3/UVIS 11657

The Population of Compact Planetary Nebulae in the Galactic Disk

We propose to secure narrow- and broad-band images of compact planetary nebulae (PNe) in the Galactic Disk to study the missing link of the early phases of post-AGB evolution. Ejected AGB envelopes become PNe when the gas is ionized. PNe expand, and, when large enough, can be studied in detail from the ground. In the interim, only the HST capabilities can resolve their size, morphology, and central stars. Our proposed observations will be the basis for a systematic study of the onset of morphology. Dust properties of the proposed targets will be available through approved Spitzer/IRS spectra, and so will the abundances of the alpha- elements. We will be able thus to explore the interconnection of morphology, dust grains, stellar evolution, and populations. The target selection is suitable to explore the nebular and stellar properties across the galactic disk, and to set constraints on the galactic evolutionary models through the analysis of metallicity and population gradients.

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.

WFC3/UVIS 11914

UVIS Earth Flats

This program is an experimental path finder for Cycle 18 calibration. Visible-wavelength flat fields will be obtained by observing the dark side of the Earth during periods of full moon illumination. The observations will consist of full-frame streaked WFC3 UVIS imagery: per 22- min total exposure time in a single "dark-sky" orbit, we anticipate collecting 7000 e/pix in F606W or 4500 e/pix in F814W. To achieve Poisson S/N > 100 per pixel, we require at least 2 orbits of F606W and 3 orbits of F814W.

For UVIS narrowband filters, exposures of 1 sec typically do not saturate on the sunlit Earth, so we will take sunlit Earth flats for three of the more-commonly used narrowband filters in Cycle 17 plus the also-popular long-wavelength quad filters, for which we get four filters at once.

Why not use the Sunlit Earth for the wideband visible-light filters? It is too bright in the visible for WFC3 UVIS minimum exposure time of 0.5 sec. Similarly, for NICMOS the sunlit-Earth is too bright which saturates the detector too quickly and/or induces abnormal behaviors such as super-shading (Gilmore 1998, NIC 098-011). In the narrowband visible and broadband near- UV its not too bright (predictions in Cox et al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat Fields." and observations in ACS Program 10050).

Other possibilities? Cox et al.'s Section II.D addresses many other possible sources for flat fields, rejecting them for a variety of reasons. A remaining possibility would be the totally eclipsed moon. Such eclipses provide approximately 2 hours (1 HST orbit) of opportunity per year, so they are too rare to be generically useful. An advantage of the moon over the Earth is that the moon subtends less than 0.25 square degree, whereas the Earth subtends a steradian or more, so scattered light and light potentially leaking around the shutter presents additional problems for the Earth. Also, we're unsure if HST can point 180 deg from the Sun.

WFC3/UVIS/IR 11644

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.

// end //

More status reports and news releases or top stories.

Please follow SpaceRef on Twitter and Like us on Facebook.

SpaceRef Newsletter