Status Report

NASA Hubble Space Telescope Daily Report #5135

By SpaceRef Editor
July 15, 2010
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Continuing to Collect World Class Science

PERIOD COVERED: 5am July 9 – 5am July 12, 2010 (DOY 190/09:00z-193/09:00z)


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


12325 – GSAcq(2,1,1) at 190/17:54:12z resulted in Fine lock Backup on FGS2. The subsequent REAcqs at 190/19:29:27z and 190/21:05:20z also resulted in fine lock backup on FGS2.

Observations possibly affected COS 98-109 Proposal ID# 11598; WFC3 135 Proposal ID# 11908

12326 – GSAcq(1,2,1) at 191/01:33:56z resulted in fine lock backup on FGS2 after scan step limit exceeded on FGS2. The subsequent REAcq at 191/02:52:29z also resulted in fine lock backup on FGS2.

Observations possibly affected: STIS 36, 37 Proposal ID# 11845; STIS 38-40 Proposal ID# 11847; WFC3 140-142 Proposal ID# 11661


18871-0 – Execute ROP NS-12 to Reset STIS FSW Error Count @ 190/1450z

17543-3 – Dump OBAD Tables After Failed OBAD @ 191/2048z, 191/2049z

18870-1 – Eclipse Management for 192/18:26 Eclipse (July 11) @ 192/2141z


FGS GSAcq 20 20
FGS REAcq 23 23
OBAD with Maneuver 16 16


Lunar Solar Eclipse 2010/192

OPS Request 18870 was successfully executed to configure the FSW processing of CSS data and temporarily disable Rate of Charge (ROC) safemode test during the moon shadow that occurred from 192/18:16z to 18:54z.

During the eclipse period, the minimum FSW SOC was approximately 438 A-hr, the maximum 482 A-hr and the FSW Benchmark was not reset. However, the batteries were charged nominally on the following orbit and benchmark reset was achieved.


S/C 12046

COS FUV DCE Memory Dump

Whenever the FUV detector high voltage is on, count rate and current draw information is collected, monitored, and saved to DCE memory. Every 10 msec the detector samples the currents from the HV power supplies (HVIA, HVIB) and the AUX power supply (AUXI). The last 1000 samples are saved in memory, along with a histogram of the number of occurrences of each current value.

In the case of a HV transient (known as a “crackle” on FUSE), where one of these currents exceeds a preset threshold for a persistence time, the HV will shut down, and the DCE memory will be dumped and examined as part of the recovery procedure. However, if the current exceeds the threshold for less than the persistence time (a “mini-crackle” in FUSE parlance), there is no way to know without dumping DCE memory. By dumping and examining the histograms regularly, we will be able to monitor any changes in the rate of “mini-crackles” and thus learn something about the state of the detector.

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.

WFC3/IR 11931

IR Signal Non-Linearity Calibration

These observations will be used to quantify the non-linear signal behavior of the IR channel, as well as to create the IR channel non-linearity calibration reference file. The non-linearity behavior of each pixel in the detector will be investigated through the use of flat fields, while the photometric behavior of point sources will be studied using observations of 47 Tuc.

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/UV 11923

UVIS Filter Wedge Check

The position of each UVIS filter will be checked to verify that the filters meet the CEI (Contract End Item) specification for image displacement. We will observe NGC 1850 with all full-frame UVIS filters using a subarray (UVIS1-C512A) without moving the telescope, as well as the quad filters with a 512×512 specifically designed subarray. We will also acquire one grism exposure. The relative displacement of the stars in each image will be measured from one filter to the next.

WFC3/UV 11918

WFC3 UVIS Image Quality

The UVIS imaging performance over the detector will be assessed periodically (every 4 months) in two passbands (F275W and F621M) to check for image stability. The field around star 58 in the open cluster NGC188 is the chosen target because it is sufficiently dense to provide good sampling over the FOV while providing enough isolated stars to permit accurate PSF (point spread function) measurement. It is available year-round and used previously for ACS image quality assessment. The field is astrometric, and astrometric guide stars will be used, so that the plate scale and image orientation may also be determined if necessary (as in SMOV proposals 11436 and 11442). Full frame images will be obtained at each of 4 POSTARG offset positions designed to improve sampling over the detector.

This proposal is a periodic repeat (once every 4 months) of visits similar to those in SMOV proposal 11436 (activity ID WFC3-23). The data will be analyzed using the code and techniques described in ISR WFC3 2008-40 (Hartig). Profiles of encircled energy will be monitored and presented in an ISR. If an update to the SIAF is needed, (V2, V3) locations of stars will be obtained from the Flight Ops Sensors and Calibrations group at GSFC, the (V2, V3) of the reference pixel and the orientation of the detector will be determined by the WFC3 group, and the Telescopes group will update and deliver the SIAF to the PRDB branch.

The specific PSF metrics to be examined are encircled energy for aperture diameter 0.15, 0.20, 0.25, and 0.35 arcsec, FWHM, and sharpness. (See ISR WFC3 2008-40 tables 2 and 3 and preceding text.) about 20 stars distributed over the detector will be measured in each exposure for each filter. The mean, rms, and rms of the mean will be determined for each metric. The values determined from each of the 4 exposures per filter within a visit will be compared to each other to see to what extent they are affected by “breathing”. Values will be compared from visit to visit, starting with the values obtained during SMOV after the fine alignment has been performed, to see if the measures of the compactness of the PSF indicate degradation over time. The analysis will be repeated for stars on the inner part of the detector and stars on the outer part of the detector to check for differential degradation of the PSF.

As an example of the analysis, one can examine the sharpness of the F275W PSF exposures made during thermal vacuum testing (ISR WFC3 2008-40). To compare two samples, one can define the PSFs on each CCD chip as a sample of 8. The mean, rms, and rms of the mean sharpness are 0.0676, 0.0093, and 0.0035 for one chip, and 0.0701, 0.0085, and 0.0032 for the other. The difference of the means is 0.0025 and the statistical error in that difference is 0.0048, so the difference is not significant.

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 3×3 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 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).

ACS/WFC3 11882

CCD Hot Pixel Annealing

This program continues the monthly anneal that has taken place every four weeks for the last three cycles. We now obtain WFC biases and darks before and after the anneal in the same sequence as is done for the ACS daily monitor (now done 4 times per week). So the anneal observation supplements the monitor observation sets during the appropriate week. Extended Pixel Edge Response (EPER) and First Pixel Response (FPR) data will be obtained over a range of signal levels for the Wide Field Channel (WFC). This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing (program 8948), so that results from each epoch can be directly compared. The High Resolution Channel (HRC) visits have been removed since it could not be repaired during SM4.

This program also assesses the read noise, bias structure, and amplifier cross-talk of ACS/WFC using the GAIN=1.4 A/D conversion setting. This investigation serves as a precursor to a more comprehensive study of WFC performance using GAIN=1.4.

STIS/CC 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

ACS/WFC 11831

Probing X-Ray Jet Emission Mechanisms in a Complete Blazar Sample

We propose deep (70 ksec) followup Chandra X-ray observations and new HST ACS/WFC/F475W observations of two quasars, viz., 0106+013 and 1641+399, belonging to the complete flux-limited MOJAVE Chandra blazar sample. These two quasars have HST WFPC2/F702W data available in the archive. Combining the existing optical and radio data with the new Chandra and HST data at an additional optical band we aim to construct a significantly more accurate multi-waveband (four frequency) spectral energy distributions for distinct knots in the jets. This will serve as a first step towards resolving longstanding ambiguities surrounding the primary X-ray emission mechanisms in a well-defined sample of powerful FR-II class jets.


UV Spectroscopy of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe

Much of our information about galaxy evolution and the interaction between galaxies and the IGM at high-z has been provided by the Lyman Break Galaxies (LBGs). However, it is difficult to investigate these faint and distant objects in detail. To address this, we have used the GALEX All-Sky Imaging Survey and the SDSS to identify for the first time a rare population of low- redshift galaxies with properties remarkably similar to the high-redshift LBGs. These local “Lyman Break Analogs” (LBAs) resemble LBGs in terms of morphology, size, UV luminosity, star formation rate, UV surface brightness, stellar mass, velocity dispersion, metallicity, and dust content. We are assembling a wide range of data on these objects with the goal of using them as local laboratories for better understanding the relevant astrophysical processes in LBGs. These data include HST imaging (95 orbits in Cy15 and 16), Spitzer photometry and spectroscopy, Chandra and XMM X-ray imaging and spectroscopy, and near-IR integral field spectroscopy (VLT, Keck, and Gemini). In this proposal we are requesting the most important missing puzzle piece: far-UV spectra with a signal-to-noise and spectral resolution significantly better than available for typical LBGs. We will use these spectra to study the LBA’s galactic winds, probe the processes that regulate the escape of Ly-a and Lyman continuum radiation, determine chemical abundances for the stars and gas, and constrain the form of the high-end of the Initial Mass Function. Adding these new COS data will give us vital information about these extraordinary sites of star formation in the local universe. In so-doing it will also shed new light on the processes that led to the formation of stars, the building of galaxies, and the enrichment and heating of the IGM in the early universe.

WFC3/UVIS 11697

Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies

Using the superior resolution of HST, we propose to continue our proper motion survey of Galactic dwarf galaxies. The target galaxies include one classical dwarf, Leo II, and six that were recently identified in the Sloan Digital Sky Survey data: Bootes I, Canes Venatici I, Canes Venatici II, Coma Berenices, Leo IV, and Ursa Major II. We will observe a total of 16 fields, each centered on a spectroscopically-confirmed QSO. Using QSOs as standards of rest in measuring absolute proper motions has proven to be the most accurate and most efficient method. HST is our only option to quickly determine the space motions of the SDSS dwarfs because suitable ground-based imaging is only a few years old and such data need several decades to produce a proper motion. The two most distant galaxies in our sample will require time baselines of four years to achieve our goal of a 30-50 km/s uncertainty in the tangential velocity; given this and the finite lifetime of HST, it is imperative that first-epoch observations be taken in this cycle. The SDSS dwarfs have dramatically lower surface brightnesses and luminosities than the classical dwarfs. Proper motions are crucial for determining orbits of the galaxies and knowing the orbits will allow us to test theories for the formation and evolution of these galaxies and, more generally, for the formation of the Local Group.

WFC3/IR 11696

Infrared Survey of Star Formation Across Cosmic Time

We propose to use the unique power of WFC3 slitless spectroscopy to measure the evolution of cosmic star formation from the end of the reionization epoch at z>6 to the close of the galaxy- building era at z~0.3.Pure parallel observations with the grisms have proven to be efficient for identifying line emission from galaxies across a broad range of redshifts. The G102 grism on WFC3 was designed to extend this capability to search for Ly-alpha emission from the first galaxies. Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will observe about 40 deep (4-5 orbit) fields with the combination of G102 and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.

Our primary science goals at the highest redshifts are: (1) Detect Lya in ~100 galaxies with z>5.6 and measure the evolution of the Lya luminosity function, independent of of cosmic variance; 2) Determine the connection between emission line selected and continuum-break selected galaxies at these high redshifts, and 3) Search for the proposed signature of neutral hydrogen absorption at re-ionization. At intermediate redshifts we will (4) Detect more than 1000 galaxies in Halpha at 0.52

We propose to obtain deep WFC3+G141 grism observations to spectroscopically confirm a remarkable z>2 cluster of galaxy candidate. Over a 1000 arcmin^2 field imaged with Spitzer’s IRAC we have discovered a compact (<30ÕÕ diameter) concentration of extremely red galaxies with a factor of >40 overdensity over the adjacent field. Among these galaxies for which we can derive meaningful photometric redshifts, 17 are consistent with zphot=2-2.5, making it very likely that the concentration is a real cluster at such high redshift. This is further supported by a 3.5 sigma detection of extended X-Ray emission on XMM-Newton data, by a likely color magnitude sequence of red galaxies, and by the presence of a giant galaxy consistent with a BCG at the cluster redshift. The general faintness of the red galaxies in all optical bands and their high redshifts prevent confirmation of this cluster with ordinary optical spectroscopy. The WFC3 camera with G141 grism provides the only way to confirm this record high-z cluster and measure its redshift from spectral breaks typical of old stellar populations. Our deep integrations will reveal redshifts for at least 19 ultra-red galaxies in the area and of a similar number of bluer galaxies at the cluster redshift. Knowledge of the cluster redshift based on the HST spectra will allow us to reach important scientific aims: find the most distant Xray emitting evolved galaxy cluster, determine membership of the other galaxies from photometric SED analysis, study their stellar population properties, characterize the color-magnitude relation with constraints on the formation redshift. The proposed observations will establish a first z>2 benchmark for cluster field comparisons of galaxy formation at this highest redshift and will firmly establish the progenitors of local rich Abell clusters.

STIS/CC 11626

Searching for the Upper Mass Limit in NGC 3603, the Nearest Giant H II Region

What is the mass of the highest mass star? 100Mo? 150Mo? 200Mo? Or higher? Theory gives us little guidance as to what physics sets the upper mass limit, presuming one exists. Is it due to limitations in the highest masses that can coalesce? Or is it due to stability issues in such a behemoth? Observationally, the upper mass limit is poorly constrained at present, with the strongest evidence coming from the K-band luminosity function of the Arches cluster near the Galactic Center. Here we propose to investigate this question by determining the Initial Mass Function of NGC 3603, the nearest giant H II region. This cluster is known to contain a wealth of O3 and hydrogen-rich Wolf-Rayets, the most luminous and massive of stars. By constructing an accurate H-R diagram for the cluster, we will construct a present day mass function using newly computed high mass evolutionary tracks, and convert this to an initial mass function using the inferred ages. This will allow us to see whether or not there is a true deficit of high mass stars, evidence of an upper mass cutoff. At the same time we are likely to establish good masses for the highest mass stars ever determined. We have laid the groundwork for this project using the Magellan 6.5-m telescope and the excellent seeing found on Las Campanas, plus analysis of archival ACS/HRS frames, but we now need to obtain spectra of the stars unobservable from the ground. This can only be done with HST and a reburbished STIS.


How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos

We propose to address two of the biggest open questions in galaxy formation – how galaxies acquire their gas and how they return it to the IGM – with a concentrated COS survey of diffuse multiphase gas in the halos of SDSS galaxies at z = 0.15 – 0.35. Our chief science goal is to establish a basic set of observational facts about the physical state, metallicity, and kinematics of halo gas, including the sky covering fraction of hot and cold material, the metallicity of infall and outflow, and correlations with galaxy stellar mass, type, and color – all as a function of impact parameter from 10 – 150 kpc. Theory suggests that the bimodality of galaxy colors, the shape of the luminosity function, and the mass-metallicity relation are all influenced at a fundamental level by accretion and feedback, yet these gas processes are poorly understood and cannot be predicted robustly from first principles. We lack even a basic observational assessment of the multiphase gaseous content of galaxy halos on 100 kpc scales, and we do not know how these processes vary with galaxy properties. This ignorance is presently one of the key impediments to understanding galaxy formation in general. We propose to use the high-resolution gratings G130M and G160M on the Cosmic Origins Spectrograph to obtain sensitive column density measurements of a comprehensive suite of multiphase ions in the spectra of 43 z < 1 QSOs lying behind 43 galaxies selected from the Sloan Digital Sky Survey. In aggregate, these sightlines will constitute a statistically sound map of the physical state and metallicity of gaseous halos, and subsets of the data with cuts on galaxy mass, color, and SFR will seek out predicted variations of gas properties with galaxy properties. Our interpretation of these data will be aided by state-of-the-art hydrodynamic simulations of accretion and feedback, in turn providing information to refine and test such models. We will also use Keck, MMT, and Magellan (as needed) to obtain optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In addition to our other science goals, these observations will help place the Milky Way's population of multiphase, accreting High Velocity Clouds (HVCs) into a global context by identifying analogous structures around other galaxies. Our program is designed to make optimal use of the unique capabilities of COS to address our science goals and also generate a rich dataset of other absorption-line systems. WFC3/UVIS 11594 A WFC3 Grism Survey for Lyman Limit Absorption at z=2 We propose to conduct a spectroscopic survey of Lyman limit absorbers at redshifts 1.8 < z < 2.5, using WFC3 and the G280 grism. This proposal intends to complete an approved Cycle 15 SNAP program (10878), which was cut short due to the ACS failure. We have selected 64 quasars at 2.3 < z < 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar Sample, for which no BAL signature is found at the QSO redshift and no strong metal absorption lines are present at z > 2.3 along the lines of sight. The survey has three main

observational goals. First, we will determine the redshift frequency dn/dz of the LLS over the column density range 16.0 < log(NHI) < 20.3 cm^-2. Second, we will measure the column density frequency distribution f(N) for the partial Lyman limit systems (PLLS) over the column density range 16.0 < log(NHI) < 17.5 cm^-2. Third, we will identify those sightlines which could provide a measurement of the primordial D/H ratio. By carrying out this survey, we can also help place meaningful constraints on two key quantities of cosmological relevance. First, we will estimate the amount of metals in the LLS using the f(N), and ground based observations of metal line transitions. Second, by determining f(N) of the PLLS, we can constrain the amplitude of the ionizing UV background at z~2 to a greater precision. This survey is ideal for a snapshot observing program, because the on-object integration times are all well below 30 minutes, and follow-up observations from the ground require minimal telescope time due to the QSO sample being bright. 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 (46) galaxies that might be responsible for this process, but the progress is hampered partly by the difficulty of obtaining physical information (stellar mass, age, star formation rate/history) for individual sources. This is because the number of z>6 galaxies that have both secure spectroscopic redshifts and high-quality infrared photometry (especially with Spitzer/IRAC) is still fairly small. Considering that only several photometric points are available per source, and that many model SEDs are highly degenerate, it is crucial to obtain as many observational constraints as possible for each source to ensure the validity of SED modeling. To better understand the physical properties of high-redshift galaxies, we propose here to conduct HST/NICMOS (72 orbits) and Spitzer/IRAC (102 hours) imaging of spectroscopically confirmed, bright (z<26 mag (AB)) Ly-alpha emitters (LAEs) and Lyman-break galaxies (LBGs) at 5.76 as suggested recently? (2) Is Ly-alpha emission systematically suppressed at z>6 with respect to continuum emission? (i.e., are we reaching the epoch of incomplete reionization?), and (3) Do we see any sign of abnormally young stellar population in any of the z>6 galaxies?

SpaceRef staff editor.