NASA Hubble Space Telescope Daily Report #4090
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT #4090
PERIOD COVERED: UT April 11, 2006 (DOY 101)
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 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.
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 10738
Earth Flats
Sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the flats currently in the pipeline and to monitor any changes. Weekly coronagraphic monitoring is required to assess the changing position of the spots.
ACS/HRC/WFC 10514
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 10433
The Cepheid PL-Z
We are proposing to empirically calibrate the metallicity sensitivity of the Cepheid Period- Luminosity relation at the highest metallicity range so far observed in nearby galaxies. To do this we will obtain the I-band Population II Tip of the Red Giant Branch {TRGB} distances to two galaxies, NGC 3627 and NGC 3368, both of which have comparable {Cepheid} distances of 11 Mpc and have almost identical {very high} metallicities of 12 + log[O/H] = +9.3. At present, observers have extremely divergent views on the magnitude of the metallicity effect on the Cepheid zero point, and theorists cannot even agee upon the sign of the effect.
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/NC2/NC3 10723
Cycle 14 NICMOS dark current, shading profile, and read noise monitoring program
The purpose of this proposal is to monitor the dark current, read noise, and shading profile for all three NICMOS detectors throughout the duration of Cycle 14. This proposal is a slightly modified version of proposal 10380 of cycle 13 and 9993 of cycle12 that we cut down some exposure time to make the observation fit within 24 orbits.
NIC2 10603
Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust
Young, edge-on circumstellar disks are uniquely valuable laboratories for the study of planet formation. In these objects, the central star is occulted from direct view, significant PSF artifacts are absent, and the disk is clearly seen as a central dust lane flanked by faint disk reflected light. The detailed morphology of these nebulae and its variation with wavelength provide crucial information on the disk internal structure and the properties of its constituent dust grains. A key observable is the slope defining the wavelength dependence of the dust scattering opacity, which becomes shallower when grain growth has taken place; multiwavelength resolved disk images are the key dataset enabling such measurements. Recent analyses of three different edge-on disks have revealed a diversity in their dust properties that is indicative of different degrees of dust grain evolution having taken place in each system. This characterization of disk grain growth, when applied comparatively to a larger sample of these objects, would enable the construction of an evolutionary sequence of young disks at successive stages on the road to planet formation. In pursuit of this goal, we have identified a sample of 15 edge-on disks previously discovered by HST or groundbased telescopes, but for which high fidelity, high spatial resolution images do not yet exist in both the optical and near-infrared. We propose broad-band multicolor imaging with NICMOS of all these targets, and ACS imaging of nine of these targets In combination with existing data, the proposed images will form a complete database of high resolution optical/near-IR images for these 15 disk systems. Scattered light modeling will be used to derive the disk structure and dust properties, yielding results that will be of fundamental importance for our understanding of grain properties during protoplanetary disk evolution.
WFPC2 10745
WFPC2 CYCLE 14 INTERNAL MONITOR
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.
WFPC2 10748
WFPC2 CYCLE 14 Standard Darks
This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.
WFPC2 10751
WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly Monitor
Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 14 decon proposal 10744 for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 07 07
FGS REacq 08 08
OBAD with Maneuver 18 18
SIGNIFICANT EVENTS: (None)
