NASA Hubble Space Telescope Daily Report #4109

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT #4109

PERIOD COVERED: UT May 08, 2006 (DOY 128)

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 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 10627

A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae

We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects which have evolved from the AGB but may or may not become planetary nebulae {PNe}. This survey will complement existing HST images of proto-planetary nebulae {PPNe} and PNe in addressing circumstellar envelope morphology as a function of: 1} the progenitor star mass; 2} the chemical composition; and 3} evolutionary stage. We will connect the observed diversity of nebualar shapes with the main physical and chemical conditions characterizing post-AGB objects, to identify the mechanism that breaks the symmetry of AGB mass loss. To our knowledge, no previous HST projects have been specifically designed to address this issue. From our database of 360 post-AGB candidates, we have selected approximately 50 targets, none of which have been or are being observed with HST, to sample different central star masses, chemical compositions, and evolutionary stages, uniformly across the sky. These new data will also provide important constraints to a quantitative analysis of Spitzer Space Telescope {SST} observations planned for a similar sample of objects. We will model the HST images and SST spectra using our axisymmetric dust code 2-Dust, to derive dust density distributions, pole to equator density ratios, dust shell masses, inclination angles as well as dust composition.

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 10491

A Snapshot Survey of the most massive clusters of galaxies

We propose a snapshot survey of a sample of 124 high X-ray luminosity clusters in the redshift range 0.3-0.7. Similarly luminous clusters at these redshifts frequently exhibit strong gravitational lensing. The proposed observations will provide important constraints on the nature of the cluster mass distributions and a set of optically bright, lensed galaxies for further 8-10m spectroscopy. We acknowledge the broad community interest in this sample and waive our data rights for these observations.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.

ACS/WFC 10710

Hubble Heritage Observations of ESO 325-G004

The Hubble Heritage team will use a single pointing of ACS WFC to obtain F475W and F555W images as part of a public release image.

FGS 10482

Trigonometric Calibration of the Period- Luminosity Relations for Fundamental and First-Overtone Galactic

Cepheids are the primary distance indicators for the extragalactic distance scale and the Hubble constant. The Hubble Constant Key Project set the zero-point for their Cepheid distance scale by adopting a distance to the LMC, averaged over a variety of techniques. However, different methods give an LMC distance modulus ranging from 18.1 to 18.8, and the uncertainty in the Cepheid zero-point is now the largest contributor to the error budget for H_0. Moreover, the low metallicity of the LMC raises additional concerns, since the PL relation probably depends on metallicity. The zero-point can be determined from Hipparcos parallaxes of Galactic Cepheids out to several hundred parsecs, but with a typical parallax error of 0.5-1 mas, the Hipparcos error bars are uncomfortably large for this demanding application. By contrast, HST’s FGS1R interferometer can achieve astrometric accuracy of 0.2 mas. We propose to use FGS1R to determine trigonometric parallaxes for a sample of 9 nearby Cepheids, including both fundamental {F} and first-overtone {FO} pulsators. We show that the improvement in the PL relations for F and FO Cepheids will be dramatic. We will determine the PL slopes from our nearby solar- metallicity sample alone, without recourse to nearby galaxies and the issue of [Fe/H] dependence. The zero-point will be determined robustly to about 0.05 mag, based on accurate, purely geometrical measurements. All of this can be achieved in the next few years with HST, without having to wait for the SIM and GAIA missions well into the next decade.

NIC2 10540

Imaging Nearby Dusty Disks

Images of circumstellar debris disks around young stars display complex structures that suggest they harbor forming planets. Disks around stars of nearly the same age and mass show dramatically different morphologies including rings with brightness asymmetries and multiple warps. The reasons for this heterogeneity are not understood, nor given the small sample of imaged disks, can we be sure we have yet observed all possible outcomes of the planet formation process. Disk imaging programs have demonstrated that the Hubble Space Telescope is the only excellent platform for the high-contrast detection of scattered light disks in the presence of their bright parent stars. Therefore, we propose a NICMOS imaging survey of the nearest, youngest, stars to Earth with substantial disks known from infrared excess emission.

WFPC2 10744

WFPC2 Cycle 14 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check. FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10255 – OBAD Failed Identification ( ESB 1902) @ 128/22:53:25z

At 128/22:53:25, OBAD2 failed. A 486 ESB message 1902 (OBAD Failed Identification) was received. OBAD2 had (RSS) value of 27683.67 arcseconds. Per OPS REQUEST 17543-2, OBAD tables 369 and 370 were dumped at 128/23:27:36.

10256 – GSAcq(2,1,1) failed to RGA Control due to search radius limit exceeded on FGS-1 @ 128/22:54:47z

The GSAcq(2,1,1) scheduled at 128/22:54:47 – 23:02:52 failed to RGA control due to search radius limit exceeded on FGS-1. A 486 ESB “a05” (search radius limit exceeded) was received at 128/23:00:49. Pre-acquisition OBAD1 was successful, OBAD2 failed per(HSTAR# 10255.) Enough attitude error had been introduced that the acquisition could not succeed.

10257 – REAcq(1,3,3) failed to RGA Control @ 129/02:18:16z

REAcq(1,3,3) at 129/02:18:16 failed to RGA control due to stop flag (QF1STOPF) on FGS-1. Previous GSAcq(1,3,3) at 00:54:42 was successful. Pre-acquisition OBAD’s were successful with RSS error corrections of 2726.53 and 15.46, post-acquisition OBAD/MAP had (RSS) value of 20.71 arcseconds.

COMPLETED OPS REQUEST:

17543-2 – Dump OBAD tables after failed OBAD (Generic OR) @ 128/2329z

COMPLETED OPS NOTES:

1386-2 – User Class for Quick Updated Proc’s @ 128/1627z (CCS-H), 128/1851z (CCS-F)

1409-0 – Mnemonic Display Utility Work Around @ 128/1627Z (CCS-H),

128/1851z (CCS-F) 0900-1 – Command Problem @ 128/11:25:47z

                           SCHEDULED      SUCCESSFUL      FAILURE TIMES
FGS GSacq                11                     10                 (HSTAR # 
10256)
FGS REacq                03                     02                 (HSTAR # 
10257)
OBAD with Maneuver   28                      27                (HSTAR # 10255)

SIGNIFICANT EVENTS: (None)