NASA Hubble Space Telescope Daily Report #4134

Status Report From: Space Telescope Science Institute
Posted: Wednesday, June 14, 2006


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science


PERIOD COVERED: UT June 13, 2006 (DOY 164)


ACS/HRC 10512

Search for Binaries Among Faint Jupiter Trojan Asteroids

We propose an ambitious SNAPSHOT program to survey faint Jupiter Trojan asteroids for binary companions. We target 150 objects, with the expectation of acquiring data on about 50%. These objects span Vmag = 17.5-19.5, a range inaccessible with ground-based adaptive optics. We now have a significant sample from our survey of brighter Trojans to suggest that the binary fraction is similar to that which we find among brighter main-belt asteroids, roughly 2%. However, our observations suggest a higher binary fraction for smaller main-belt asteroids, probably the result of a different formation mechanism {evident also from the physical characteristics of the binaries}. Because the collision environment among the Trojans is similar to that of the Main Belt, while the composition is likely to be very different, sampling the binary fraction among the fainter Trojans should help us understand the collisional and binary formation mechanisms at work in various populations, including the Kuiper Belt, and help us evaluate theories for the origin of the Trojans. Calibration of and constraints on models of binary production and collisional evolution can only be done using these large-scale, real-life physical systems that we are beginning now to find and utilize.

ACS/HRC 10547

A SNAP Program to Obtain Complete Wavelength Coverage of Interstellar Extinction

We propose a SNAP program to obtain ACS/HRC spectra in the near-UV {PR200L} and near-IR {G800L} for a set of main sequence B stars with available IUE UV spectrophotometry, optical photometry, and 2MASS IR photometry. Together with these existing data, the new observations will provide complete photometric and spectrophotometric coverage from 1150 to 11000 A and enable us to produce complete extinction curves from the far-UV to the near-IR, with well- determined values of R{V}. The proposed set of 50 program sight lines includes the full range of interstellar extinction curve types and a wide range of color excesses. The new data will allow us to examine variability in the near-UV through near-IR spectral regions, including the UV-optical "knee" and the "Very Broad Structure." We will examine the response of these features to different interstellar environments and their relationship to other curve features. These are largely unexplored aspects of extinction curves which will provide additional constraints on the properties of interstellar grains. The curves will be derived using stellar atmosphere models to represent the intrinsic spectral energy distributions of the program stars, eliminating the need to observe unreddened "standard stars." This approach virtually eliminates "mismatch error", allowing us to derive extinction curves with much higher precision than previously possible. In addition, the new spectra will provide higher S/N data for the peak of the 2175 A bump than previously available.

ACS/HRC 10559

Astrometric monitoring of binary L and T dwarfs

We propose to obtain high angular resolution ACS images of five binary L and T dwarfs in order to determine their orbital parameters and dynamical masses, and directly constrain the evolutionary models of ultracool and substellar objects. The binaries have estimated periods ranging between 5 and 14 years. All of them have already been resolved at least twice {sometimes more} using HST, providing first and second epochs measurements. We propose to obtain two more ACS imaging observations separated by 9 to 12 months during cycle 14. The expected period coverage should therefore range between 35% and 117%, allowing us to compute precise orbital parameters and masses. Our sample is large enough and covers a sufficiently wide range of spectral types {from L3 to T5.5} to allow us to obtain strong constraints the evolutionnary models.


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 a Snapshot program using the ACS/HRC that has a potential discovery efficiency an order of magnitude higher than the HST observations that have already discovered the majority of known transneptunian binaries. By more than doubling the number of observed objects in dynamically hot and cold subpopulations we will be able to answer, with statistical significance, the question of whether these groups differ in the abundance of binaries as a result 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.

ACS/WFC 10523

The Halo Shape and Metallicity of Massive Spiral Galaxies

We propose to resolve the stellar populations of the halos of seven nearby, massive disk galaxies using a SNAP survey with WFC/ACS. These observations will provide star counts and color-magnitude diagrams 2-3 magnitudes below the tip of the Red Giant Branch 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 ~31 V-mag per square arcsec. This proposal will create a unique sampling of galaxy halo properties, as our targets cover a range in galaxy mass, luminosity, inclination, and morphology. As function of these galaxy properties this survey will provide:- the first systematic measurement of radial light profiles and axial ratios of the diffuse stellar halos and outer disks of spiral galaxies- a comprehensive analysis of halo metallicity distributions as function of galaxy type and position within the galaxy- an unprecedented study of the stellar metallicity and age distribution in the outer disk regions where the disk truncations occur- the first comparative study of globular clusters and their field stellar populations We will use these fossil records of the galaxy assembly process to test halo formation models within the hierarchical galaxy formation scheme.

ACS/WFC 10592

An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These `luminous infrared galaxies' {LIRGs} are primarily interacting or merging disk galaxies undergoing enhanced star formation and Active Galactic Nuclei {AGN} activity, possibly triggered as the objects transform into massive S0 and elliptical merger remnants. We propose ACS/WFC imaging of a complete sample of 88 L_IR > 10^11.4 L_sun luminous infrared galaxies in the IRAS Revised Bright Galaxy Sample {RBGS: i.e., 60 micron flux density > 5.24 Jy}. This sample is ideal not only in its completeness and sample size, but also in the proximity and brightness of the galaxies. The superb sensitivity, resolution, and field of view of ACS/WFC on HST enables a unique opportunity to study the detailed structure of galaxies that sample all stages of the merger process. Imaging will be done with the F439W and F814W filters {B and I-band} to examine as a function of both luminosity and merger state {i} the evidence at optical wavelengths of star formation and AGN activity and the manner in which instabilities {bars and bridges} in the galaxies may funnel material to these active regions, {ii} the relationship between star formation and AGN activity, and {iii} the structural properties {AGN, bulge, and disk components} and fundamental parameters {effective radius and surface brightness} of LIRGs and their similarity with putative evolutionary byproducts {elliptical, S0 and classical AGN host galaxies}. This HST survey will also bridge the wavelength gap between a Spitzer imaging survey {covering seven bands in the 3.6-160 micron range} and a GALEX UV imaging survey of these galaxies, but will resolve complexes of star clusters and multiple nuclei at resolutions well beyond the capabilities of either Spitzer or GALEX. The combined datasets will result in the most comprehensive multiwavelength study of interacting and merging galaxies to date.


What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

Essentially all planetary nebulae {PNs} are aspherical, whereas the mass-loss envelopes of AGB stars are strikingly spherical. Our previous SNAPshot surveys of a morphologically unbiased sample of pre-planetary nebulae {PPNs} -- objects in transition between the AGB and PN evolutionary phases -- show that roughly half our observed targets are resolved, with bipolar or multipolar morphologies. Spectroscopic observations of our sample confirm that these objects have not yet evolved into planetary nebulae. Thus, the transformation from spherical to aspherical geometries has already fully developed by the time these dying stars have become PPNs. Although our current studies have yielded exciting results, they are limited in two important ways -- {1} the number of well-resolved objects is still small {18}, and the variety of morphologies observed relatively multitudinous, hence no clear trends can yet be established between morphology and other source properties {e.g., near-IR, far-IR colors, stellar spectral type, envelope mass}, and {2} the current samples are strongly biased towards small PPNs, as inferred from their low 60-to-25 micron flux ratios [R{60/25}<1]. However, the prototype of objects with R{60/25}>1, the Frosty Leo Nebula, has a puzzlingly large post-AGB age {almost 10^4 yr} and a fairly cool central star, very different from the expectations of single-star stellar evolutionary models. A proposed, but still speculative, hypothesis for such objects is that the slow evolution of the central star is due to backflow of material onto the mass-losing star, retarding its evolution towards the PN phase. This hypothesis has significant consequences for both stellar and nebular evolution. We therefore propose a survey of PPNs with R{60/25}>1 which is heavily weighted towards the discovery of such "stalled PPNs". Supporting kinematic observations using long-slit optical spectroscopy {with the Keck}, millimeter and radio interferometric observations {with OVRO, VLA & VLBA} are being undertaken. The results from this survey {together with our previous work} will allow us to draw general conclusions about the complex mass-outflow processes affecting late stellar evolution, and will provide crucial input for theories of post-AGB stellar evolution. Our survey will produce an archival legacy of long-standing value for future studies of dying stars.

WFPC2 10631

Intermediate-Age Globular Clusters in M31

We propose deep ACS/WFC imaging of four halo M31 globular clusters in order to derive their horizontal branch morphologies. Our spectroscopic investigation of their integrated light identifies them as members of an intermediate-age population of globular clusters in M31. Since our spectroscopic results are based on the analysis of Balmer absorption lines, we need to secure our results against an artificial juvenation due to extreme horizontal branch morphologies. The proposed observations will allow a clear-cut answer to the question of whether spectroscopically derived intermediate-age estimates are due to genuinely younger ages or are the result of anomalously hot horizontal branch morphologies. Either way, our results will have important implications for spectroscopically derived ages and metallicities of distant stellar populations. Because of the high spatial resolution of the proposed ACS/WFC observations we will also derive accurate surface brightness profiles of our target globular clusters and investigate the influence of stellar density on horizontal branch morphology. Moreover, together with deep parallel WFPC2 fields we will study the metallicity dispersion of the background stellar population in M31 as a function of galactocentric radius.

WFPC2 10745


This calibration proposal is the Cycle 14 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 -- to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.


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


10305 - GSAcq(2,1,2) requires two attempts to achieve CT-DV @ 158/1602z

OTA SE review of PTAS processing revealed that GSAcq(2,1,2) required two attempts to achieve CT-DV on FGS2. The acquisition was successful

10306 - GSAcq(2,1,1) requires two attempts to achieve CT-DV @ 158/2303z

OTA SE review of PTAS processing data revealed that GSAcq(2,1,1) required two attempts to achieve CT-DV on FGS2. The acquisition was successful.

10307 - GSAcq(2,1,1) requires two attempts to achieve CT-DV @ 162/0032z

OTA SE review of PTAS processing revealed that GSACq(2,1,1) required two attempts to achieve CT-DV. The acquisition was successful.

10309 - OBAD1 failure @ 065/1254z

On 2006/065 at 12:54:23, OBAD 1 using FHSTs 1 & 3 failed with indication of Attitude Determination Error. The second OBAD at 13:30 using FHSTs 2 & 3 posted a 1 degree correction and the subsequent GS Acquisition succeeded.

10311 - Zero Gyro +V3 Sunpoint entry @ 164/2035z

At 20:30:13 the 486 ESB error counter SESBSLD incremented due to an 1805 "T2G Moving Target Detected" event. OBAD at 20:34:22 showed extremely huge errors of V1= -327127.89, V2= -17.1978.30, V3= -6276.11, RSS= 369633.04 arc seconds with GCHACLO9 = 1. Shortly after this, telemetry was lost due to HST slewing away from desired attitude. Telemetry was reacquired in AN format at 20:55, indicating that vehicle was in "Zero Gyro +V3 Sunpoint". Safemode Fault Recorder indicates that Magnetic Field Position test (SMAGANGA) failed at 164/20:35:27


17786-1 - **Contingency BCT Scripts** Appendix A (Early termination of battery discharge) @ 164/2231z

17785-2 - Battery 1 Capacity Test Script & 5 Battery Pressure Limit COP (thru step 32) @ 164/2303z

17796-0 - Power on GEA's Following Safing @ 165/0001z

17795-0 - Dump HST486 ESB @ 165/0055z

17797-0 - Transition NICMOS to SAA Oper @ 165/0217z

17798-0 - Recovery from ZGSP (thru step 36) @ 165/0424z


1490-0 - Update SOC Ground Low Yellow Limit value @ 164/1345z

               SCHEDULED   SUCCESSFUL 
 FGS GSacq        04             04 
 FGS REacq        03             03 
 OBAD with Maneuver   14             14 


Battery 1 Capacity Test Flash Report

Commanding for the Battery 1 Capacity Test started as scheduled on DOY 164/1155 GMT (6/13 at 7:55 am) with the setting of the Battery Pressure Test for a 5-battery system. Battery 1 was taken off-line and the discharge began on the first opportunity at 1302 GMT (6/13 at 9:02 am). The discharge was proceeding nominally; however, the test was terminated upon entry to Zero-Gyro Sunpoint Safemode.

DOY 164/2006 Zero-Gyro Sunpoint (ZGSP) Safemode Flash Report

At GMT 164/20:35:26 the vehicle entered ZGSP Safemode due to the failure of the Magnetic Field Position safemode test. The initial investigation shows no signs of hardware issues. The battery 1 capacity test was terminated as expected upon safemode entry with the removal of the discharge resistor. Contingency Section A of the Battery Capacity Test script was executed successfully which reconnected the SA section to the battery and disabled the capacity test macro. Recovery steps to return the payload safing sequences to the nominal RTCSs were also performed. HST Safemode Recovery Status

The recovery of HST from the Zero Gyro Sun Point safemode entry is proceeding nominally. At 165/02:56 HST was transitioned back to Two Gyro Science mode. An attitude update was uplinked and the aperture door opened. Recovery procedures have now been completed until uplink of the Health and Safety (H&S) SMS. The H&S SMS is expected to begin execution at 165/14:00. The first science SMS will begin at 166/02:00.

The safemode entry was likely caused by the Fixed Head Star Tracker (FHST) 2 locking on to a satellite at a transition to the Tracker-Two Gyro (T2G) mode. This was at the stage where FHST data is used to damp the vehicle rates. As a result, vehicle rates actually accelerated to over 0.03 degrees/second. The magnetic field angle test failed when the attitude error exceeded 12 degrees, initiating the Zero Gyro Sun Point safemode. Evaluation of the event will continue.

// end //

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