Status Report

NASA Hubble Space Telescope Daily Report #4366

By SpaceRef Editor
May 22, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report #4366

Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.


– Continuing to collect World Class Science

PERIOD COVERED: UT May 18,19,20, 2007 (DOY 138,139,140)


WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure indvidual stars, given the proximity of these galaxies. The resulting H- R diagrams will enable studies of star-formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.

WFPC2 10903

Resolving the LMC Microlensing Puzzle: Where are the Lensing Objects?

We are requesting 12 HST orbits to continue to investigate the nature of the population that gives rise to the microlensing seen towards the LMC. This proposal builds on the cycle 14 HST program {10583} and will complement the study with 12 yet-to-be discovered microlensing candidates from Fall 2006. Our SuperMacho project is an ongoing ground- based survey on the CTIO 4m that has demonstrated the ability to detect LMC microlensing events via frame subtraction. The combination of high angular resolution and photometric accuracy with HST will allow us to 1} confrim that the detected flux excursions arise from LMC stars, rather than background supernovae or AGN, and 2} obtain reliable baseline flux measurements for the objects in their unlensed state. This latter measurement in important in determining the microlensing optical depth towards the LMC.

WFPC2 10896

An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars

We propose to finish our Cycle 11 optical survey for nearby debris disks using the ACS/HRC coronagraph. Out of 43 orbits originally proposed for the survey, 23 orbits were allocated, leading to a survey of 22 stars, from which two new debris disks were imaged for the first time. Our analysis of the initial survey gives an empirical estimate for the detection rate of debris disks relative to heliocentric distance and dust optical depth. Our target list for Cycle 15 is now optimized to yield more frequent disk detections. Likewise our observing strategy is improved to maximize sensitivity per telescope orbit allocated. Therefore we present the most efficient survey possible. The scientific motivation is to obtain scattered light images of previously unresolved debris disks to determine their viewing geometry and physical architecture, both of which may characterize the underlying planetary system. We choose 25 debris disk targets for which we predict a detection rate of 25% ? 5%. Four targets have extrasolar planets from which the viewing geometry revealed by a disk detection will resolve the v sin{i} ambiguity in the planet masses. These targets present the remarkable opportunity of finally seeing a debris disk in system with known planets.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick disks and halos of seven nearby, massive, edge-on galaxies using ACS, NICMOS, and WFPC2 in parallel. These observations will provide accurate star counts and color-magnitude diagrams 1.5 magnitudes below the tip of the Red Giant Branch sampled along the two principal axes and one intermediate axis of each galaxy. We will measure the metallicity distribution functions and stellar density profiles from star counts down to very low average surface brightnesses, equivalent to ~32 V-mag per square arcsec. These observations will provide the definitive HST study of extra-planar stellar populations of spiral galaxies. Our targets cover a range in galaxy mass, luminosity, and morphology and as function of these galaxy properties we will provide: – The first systematic study of the radial and isophotal shapes of the diffuse stellar halos of spiral galaxies – The most detailed comparative study to date of thick disk morphologies and stellar populations – A comprehensive analysis of halo and thick disk metallicity distributions as a function of galaxy type and position within the galaxy. – A sensitive search for tidal streams – The first opportunity to directly relate globular cluster systems to their field stellar population We will use these fossil records of the galaxy assembly process preserved in the old stellar populations to test halo and thick disk formation models within the hierarchical galaxy formation scheme. We will test LambdaCDM predictions on sub-galactic scales, where it is difficult to test using CMB and galaxy redshift surveys, and where it faces its most serious difficulties.

WFPC2 10877

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS}, have found hundreds of SNe, many of them in quite nearby galaxies {cz < 4000 km/s}. Most of the objects were discovered before maximum brightness, and have follow-up photometry and spectroscopy; they include some of the best-studied SNe to date. We propose to conduct a snapshot imaging survey of the sites of some of these nearby objects, to obtain late-time photometry that {through the shape of the light and color curves} will help reveal the origin of their lingering energy. The images will also provide high-resolution information on the local environments of SNe that are far superior to what we can procure from the ground. For example, we will obtain color-color and color-magnitude diagrams of stars in these SN sites, to determine the SN progenitor masses and constraints on the reddening. Recovery of the SNe in the new HST images will also allow us to actually pinpoint their progenitor stars in cases where pre- explosion images exist in the HST archive. This proposal is an extension of our successful Cycle 13 snapshot survey with ACS. It is complementary to our Cycle 15 archival proposal, which is a continuation of our long-standing program to use existing HST images to glean information about SN environments.

WFPC2 10870

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In between, we will have a rare opportunity to see the unlit face of the rings. With the nine optically thick rings essentialy invisible, we will observe features and phenomena that are normally lost in their glare. We will use this opportunity to search thoroughly for the embedded “shepherd” moons long believed to confine the edges of the rings, setting a mass limit roughly 10 times smaller than that of the smallest shepherd currently known, Cordelia. We will measure the vertical thicknesses of the rings and study the faint dust belts only known to exist from a single Voyager image. We will also study the colors of the newly-discovered faint, outer rings; recent evidence suggests that one ring is red and the other blue, implying that each ring is dominated by a different set of physical processes. We will employ near- edge-on photometry from 2006 and 2007 to derive the particle filling factor within the rings, to observe how ring epsilon responds to the “traffic jam” as particles pass through its narrowest point, and to test the latest models for preserving eccentricities and apse alignment within the rings. Moreover, this data set will allow us to continue monitoring the motions of the inner moons, which have been found to show possibly chaotic orbital variations; by nearly doubling the time span of the existing ACS astrometry, the details of the variations will become much clearer.

ACS/SBC 10864

Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems with ACS

One of the key problems in planetary system formation is understanding how rapidly, and over what time interval Jovian planets can form. Dust in the protoplanetary disk is critical in planetesimal formation, but it is the gas which produces giant planets, and which is essential for their migration. However, compared to data on the circumstellar dust, information on the gas component is sparse, especially in the planet-formation zone. This severely limits our ability to put observational constraints on giant planet formation, except to note that the process must be largely complete by 12 Myr, given the paucity of Herbig Ae or classical T Tauri stars older than 10-12 Myr. In the FUV, photo-excited molecular hydrogen transitions have the requisite contrast to the stellar photosphere, accretion shock, and reflection nebulosity, and can be traced 50-100 AU from the exciting stars in both envelopes and outflow cavities and protoplanetary disks. Central disk cavities, an expected consequence of planet formation, larger than 0.1″ are directly detectable in HST FUV spectra, while smaller cavities may be detected by comparison with protoplanetary disks which are still accreting onto their stars. We propose augmenting existing HST coronagraphic imagery of 6 Herbig Fe and T Tauri disks with ACS Solar-Blind Channel Lyman alpha imagery and slitless spectroscopy simultaneously sampling the disk in molecular hydrogen and small-grain reflection nebulosity. These data will be used to quantify the amount of vertical stratification in these disks, to map the mass-loss geometry from the star, and to determine whether removal of molecular material preceeds, lags, or is contemporary with clearing of the dust.

ACS/SBC 10862

Comprehensive Auroral Imaging of Jupiter and Saturn during the International Heliophysical Year

A comprehensive set of observations of the auroral emissions from Jupiter and Saturn is proposed for the International Heliophysical Year in 2007, a unique period of especially concentrated measurements of space physics phenomena throughout the solar system. We propose to determine the physical relationship of the various auroral processes at Jupiter and Saturn with conditions in the solar wind at each planet. This can be accomplished with campaigns of observations, with a sampling interval not to exceed one day, covering at least one solar rotation. The solar wind plasma density approaching Jupiter will be measured by the New Horizons spacecraft, and a separate campaign near opposition in May 2007 will determine the effect of large-scale variations in the interplanetary magnetic field {IMF} on the Jovian aurora by extrapolation from near-Earth solar wind measurements. A similar Saturn campaign near opposition in Jan. 2007 will combine extrapolated solar wind data with measurements from a wide range of locations within the Saturn magnetosphere by Cassini. In the course of making these observations, it will be possible to fully map the auroral footprints of Io and the other satellites to determine both the local magnetic field geometry and the controlling factors in the electromagnetic interaction of each satellite with the corotating magnetic field and plasma density. Also in the course of making these observations, the auroral emission properties will be compared with the properties of the near-IR ionospheric emissions {from ground-based observations} and non thermal radio emissions, from ground-based observations for Jupiter?s decametric radiation and Cassini plasma wave measurements of the Saturn Kilometric Radiation {SKR}.

WFPC2 10832

Solving the microlensing puzzle: An HST high-resolution imaging approach

We propose to use the HST Advanced Camera for Surveys High Resolution Channel to obtain high resolution imaging data for 10 bona-fide LMC microlensing events seen in the original MACHO survey. The purpose of this survey will be to assess whether or not the lens and source stars have separated enough to be resolved since the original microlensing event took place – about a decade has passed since the original MACHO survey and the HST WFPC2 follow-up observations of the microlensing events. If the components of the lensing event are resolved, we will determine the apparent magnitude and color of both the lens and the source stars. These data, in combination with Spitzer/IRAC data and Magellan near-IR JHK data, will be used to ascertain the basic properties of the lens stars. With the majority of the microlensing events in the original MACHO survey observed at the highest spatial resolution currently possible, we will be able to draw important conclusions as to what fraction of these events have lenses which belong to some population of dwarf stars in the disk and what fraction must be due to lenses in the halo or beyond. These data will greatly increase our understanding of the structure of the Galaxy by characterizing the stellar population responsible for the gravitational microlensing.

WFPC2 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have relatively fragile test particles which can be used as tracers of the early dynamical evolution of the outer Solar System. We propose to continue a Snapshot program using the ACS/HRC that has a demonstrated discovery potential an order of magnitude higher than the HST observations that have already discovered the majority of known transneptunian binaries. With this continuation we seek to reach the original goals of this project: to accumulate a sufficiently large sample in each of the distinct populations collected in the Kuiper Belt to be able to measure, with statistical significance, how the fraction of binaries varies as a function of their particular dynamical paths into the Kuiper Belt. Today’s Kuiper Belt bears the imprints of the final stages of giant-planet building and migration; binaries may offer some of the best preserved evidence of that long-ago era.

WFPC2 10786

Rotational state and composition of Pluto’s outer satellites

We propose an intricate set of observations aimed at discovering the rotational state of the newly discovered satellites of Pluto, S/2005 P1 and S/2005 P2. These observations will indicate if the satellites are in synchronous rotation or not. If they are not, then the observations will determine the rotational period or provide tight constraints on the amplitude. The other primary goal is to extend the wavelength coverage of the colors of the surface and allow us to constrain the surface compositions of both objects. From these data we will also be able to significantly improve the orbits of P1 and P2, improve the measurement of the bulk density of Charon, and search for albedo changes on the surface of Pluto.


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


10817 – GSacq(2,3,2) failed due to search radius limit exceeded During LOS GSacq(2,3,2) scheduled at 140/04:31:31 failed due to search radius limit exceeded on FGS 2. ESB a05 (exceeded search radius limit) was received. OBAD2 at 04:26:31 showed errors of V1= 38.65, V2=28.45, V3=40.61, RSS=62.87.

During LOS the REacq(2,3,2) scheduled at 140/06:10:02 also failed due to search radius limit exceeded on FGS 2.

10818 – GSAcq (1,2,2) failed to RGA Hold (Gyro Control) At 140/18:15:30 GSAcq (1,2,2) scheduled from 18:12:08-18:19:32 had failed to RGA Hold (Gyro Control) due to mnemonic QSTOP on FGS 1. At 18:04:26 received one 486 STB message 1805 “FHST Moving Target Detected”.

OBAD #1 RSS: 3054.12

OBAD #2 RSS: 14.96

OBAD MAP: not scheduled

10819 – ACS 779 Fold Mechanism Move was Blocked

At 140/18:20:24 “Fold Mechanism Move Was Blocked P=0, T=38393. This was the result of the failed GSAcq at 18:12:08 so the TDF was down when the fold mechanism move to the SBC position was commanded. The move is blocked and SBC MAMA HV will remain on. The MAMA HV staying on is a new feature for ACS FSW CS4.01.



                        SCHEDULED      SUCCESSFUL 
FGS GSacq               24                 22 
FGS REacq               13                 12 
OBAD with Maneuver      74                  74 


SpaceRef staff editor.