NASA Hubble Space Telescope Daily Report #4089
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT #4089
PERIOD COVERED: UT April 10, 2006 (DOY 100)
OBSERVATIONS SCHEDULED
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 10545
Icy planetoids of the outer solar system
Early HST studies of satellites of Kuiper belt object focussed on the 50-200 km objects that were the largest known at the time. In the past 3 years we have discovered a population of much more rare and much larger {500-2000+ km} icy planetoids in the Kuiper belt. These objects are the largest and brightest known in the Kuiper belt and, in the era when we now know of more than 1000 Kuiper belt objects, these few planetoids are likely to be the focus of much of the research on physical properties of the outer solar system for years to come. We are currently engaged in an intensive program involving Spitzer, Keck, and other telescopes to study the physical and dynamical properties of this new population. HST is uniquely capable of addressing one parameter fundamental to completing the physical picture of these planetoids: the existence and size of any satellites. The detection and characterization of satellites to these large planetoids would allow us to address unique issues critical to the formation and evolution of the outer solar system, including the measurement of densities, internal properties, sizes and shapes of these objects, the study of binary formation as a function of primary size, and the context of the Pluto-Charon binary. For these bright objects, a satellite search takes less than a full orbit, allowing the opportunity for a new project on UV spectroscopy of the planetoids to piggyback at no added time cost. This poorly explored spectral range has the potential to show unique signatures of trapped gasses, cosmochemically important ices, and complex organic materials.
ACS/HRC 10556
Neutral Gas at Redshift z=0.5
Damped Lyman-alpha systems {DLAs} are used to track the bulk of the neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy, they could only be studied from the ground at redshifts z>1.65. However, HST has now permitted us to discover 41 DLAs at z<1.65 in our previous surveys. Followup studies of these systems are providing a wealth of information about the evolution of the neutral gas phase component of the Universe. But one problem is that these 41 low-redshift systems are spread over a wide range of redshifts spanning nearly 70% of the age of the Universe. Consequently, past surveys for low-redshift DLAs have not been able to offer very good precision in any small redshift regime. Here we propose an ACS-HRC- PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7] which we estimate will permit us to discover another 41 DLAs. This will not only allow us to double the number of low-redshift DLAs, but it will also provide a relatively high-precision regime in the low-redshift Universe that can be used to anchor evolutionary studies. Fortunately DLAs have high absorption equivalent width, so ACS-HRC-PR200L has high-enough resoultion to perform this proposed MgII-selected DLA survey.
ACS/HRC 10625
A Multiwavelength Investigation of Comet 73P/SW3-C
The nucleus of comet 73P/Schwassmann–Wachmann~3 experienced a non-tidal breakup in late 1995. The largest fragment {73P/SW3-C} survived its subsequent perihelion passage in 2001 and will return in 2006, when it will pass very close to {0.08 AU} Earth. This represents an outstanding opportunity to characterize a fresh cometary nucleus, and we propose an intensive investigation using both the Hubble and Spitzer telescopes. Employing the technique that our group has developed over the past decade to characterize 31 cometary nuclei, we will use HST/ACS to photometrically resolve the nucleus of 73P/SW3-C at optical wavelengths and SST/MIPS to do the same thing at thermal infrared wavelengths, thereby allowing us to determine both the size and albedo of this fragment. We also plan to measure the lightcurve of 73P/SW3-C to obtain detailed shape information, and use HST/NICMOS to probe the composition, in particular to search for evidence of icy material on the fresh surface. Previous observations indicate that most of the remaining mass of 73P/SW3 is in the form of numerous small fragments. A few of those may have been captured by the C fragment, and the determination of their orbits would allow the first, direct measurement of the mass of a cometary nucleus. Thus, we will also perform a deep search for any possible companions to the C-fragment.
ACS/HRC/WFC 10758
ACS CCDs daily monitor
This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.
ACS/WFC 10587
Measuring the Mass Dependence of Early-Type Galaxy Structure
We propose two-color ACS-WFC Snapshot observations of a sample of 118 candidate early- type gravitational lens galaxies. Our lens-candidate sample is selected to yield {in combination with earlier results} an approximately uniform final distribution of 40 early-type strong lenses across a wide range of masses, with velocity dispersions {a dynamical proxy for mass} ranging from 125 to 300 km/s. The proposed program will deliver the first significant sample of low-mass gravitational lenses. All of our candidates have known lens and source redshifts from Sloan Digital Sky Survey data, and all are bright enough to permit detailed photometric and stellar- dynamical observation. We will constrain the luminous and dark-matter mass profiles of confirmed lenses using lensed-image geometry and lens-galaxy structural/photometric measurements from HST imaging in combination with dynamical measurements from spatially resolved ground-based follow-up spectroscopy. Hence we will determine, in unprecedented detail, the dependence of early-type galaxy mass structure and mass-to-light ratio upon galaxy mass. These results will allow us to directly test theoretical predictions for halo concentration and star-formation efficiency as a function of mass and for the existence of a cuspy inner dark- matter component, and will illuminate the structural explanation behind the fundamental plane of early-type galaxies. The lens-candidate selection and confirmation strategy that we propose has been proven successful for high-mass galaxies by our Cycle 13 Snapshot program {10174}. The program that we propose here will produce a complementary and unprecedented lens sample spanning a wide range of lens-galaxy masses.
ACS/WFC 10732
ACS internal CTE monitor
The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be closely monitored at regular intervals, because it is likely to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. 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. Extended Pixel Edge Response {EPER} and First Pixel Response {FPR} data will be obtained over a range of signal levels for both the Wide Field Channel {WFC}, and the High Resolution Channel {HRC}.
ACS/WFC 10775
An ACS Survey of Galactic Globular Clusters
We propose to conduct an ACS/WFC imaging survey of Galactic globular clusters. We will construct the most extensive and deepest set of photometry and astrometry to-date for these systems reaching a main sequence mass of ~0.2 solar mass with S/N >= 10. We will combine these data with archival WFPC2 and STIS images to determine proper motions for the stars in our fields. The resultant cleaned cluster CMDs will allow us to study a variety of scientific questions. These include [but are not limited to] 1} the determination of cluster ages and distances 2} the construction of main sequence mass functions and the issue of mass segregation 3} the internal motions and dynamical evolution of globular clusters, and 4} absolute cluster motions, orbits, and the Milky Way gravitational potential. We anticipate that the unique resource provided by the proposed treasury archive will play a central role in the field of globular cluster studies for decades, with a stature comparable to that of the Hubble Deep Field for high redshift studies.
NIC1/NIC2/NIC3 8793
NICMOS Post-SAA calibration – CR Persistence Part 4
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 USEAFTER 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 DARKSs. 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.
NIC2 10519
Testing the Stellar Coalescence and Accretion Disk Theories of Massive Star Formation with NICMOS
The importance of massive stars cannot be underestimated – they produce most of the heavy elements in the universe and dominate the evolution of the interstellar medium in their vicinity. In spite of their significance, our understanding of their formation is meager. Both accretion through disks, analogous to the process of low-mass star formation, and coalescence of low-mass stars through collisions in the dense cores of stellar clusters have been suggested. Possibly both mechanisms occur. High spatial resolution polarization measurements of the closest massive young stellar objects {YSOs} will enable us to search for evidence of disk accretion or coalescence in the form of patterns indicative of light scattered off a coherent disk or off a disk disrupted by an infalling star, respectively. Here we propose to use 2 micron polarimetry with NICMOS to identify the presence of accretion disks around massive YSOs or to characterize their environments as possibly disrupted from a close stellar encounter. There are only a few sources that meet the stringent selection criteria for this investigation {even with HST}, which we will examine here. High spatial resolution is required, but even more important, the point spread function {PSF} must be stable with time. Furthermore, the PSF must put minimal flux into large spatial scales, something that cannot be achieved with adaptive optics. This combination of high Strehl ratio and stable PSF can only be achieved from space.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10209 – GSacq(1,3,1) failed @ 100/15:01:47z
During LOS the GSacq(1,3,1)scheduled at 100/15:01:47 failed. At AOS (15:15:15) the QSTOP and QF1STOPF were flagging. There were no other flag indicating SRLEX or SSLEX. Also there were no ESB messages. The map at 15:09:38 showed errors of V1=-0.06, V2=11.94, V3=-2.77, RSS=12.26.
10210 – OBAD failed and GSacq failed @ 100/16:41:15z
OBAD 2 at 100/16:32:55 failed due to too few starts. ESB 1901 (OBAD too few stars)was received. The GSacq(1,3,1) at 16:38:12 also failed. Only QSTOP and QF1STOPF flagged out of limits.
10211 – FHST OBAD Failure, due to lack of sufficient stars @ 100/16:32:50z
OBAD scheduled at 100/16:32:50 using trackers 1 and 2 failed due to insufficient percentage of stars identified. 486 ESB 1901 (OBAD_TOO_FEW_STARS) was received. OBAD success flag (mnemonic GCHACLO9) remained at the same state. Subsequent acquisition failed per HSTAR 10210.
10212 – FHST OBAD Failure @ 101/02:17:37z
OBAD scheduled at 101/02:14:48 using trackers 1 and 2 failed. ESB message 1901 “OBAD_TOO_FEW_STARS” was received at 02:17:37. Subsequent guide star acquisition was successful. OBAD tables 369 and 370 were dumped in accordance with Ops Request 17543-2.
10214 – FHST OBAD Failure @ 101/05:23:13z
OBAD scheduled at 101/05:20:15 using trackers 1 and 2 failed. ESB message 1901 “OBAD_TOO_FEW_STARS” was received at 05:23:13. Subsequent guide star acquisition was successful. OBAD tables 369 and 370 were dumped in accordance with Ops Request 17543-2.
10216 – FHST OBAD Failure @ 101/06:59:01z
OBAD scheduled at 101/06:56:10 using trackers 1 and 2 failed. ESB message 1901 “OBAD_TOO_FEW_STARS” was received at 06:59:01. Subsequent guide star acquisition was successful. OBAD tables 369 and 370 were dumped in accordance with Ops Request 17543-2.
COMPLETED OPS REQUEST: 17543-2 – Dump OBAD tables after failed OBAD @ 101/02:24:25z, 101/05:27:26z, 101/05:44:30z, 101/07:03:53z, 101/07:17:45z
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 14 12 (HSTAR 10209) (HSTAR 10210) FGS REacq 01 01 OBAD with Maneuver 30 26 (HSTAR 10211) (HSTAR 10212) (HSTAR 10214) (HSTAR 10216)
SIGNIFICANT EVENTS: (None)
