NASA Hubble Space Telescope Daily Report #4091

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT #4091

PERIOD COVERED: UT April 12, 2006 (DOY 102)

OBSERVATIONS SCHEDULED

ACS/HRC 10564

Resolving Ultracool White Dwarf Binaries

We propose an ACS/HRC imaging survey of the coolest white dwarfs known in order to search for binarity. Current models fail to match observed spectral energy distributions of these sub- 4000K stellar remnants, consistently predicting much lower luminosities than observed. A possible explanation is that they are binary in nature. Because these cool degenerates have no spectral features, the only way to investigate their apparent overluminosity is with very high resolution imaging, which can only be done with HST {these stars are far too faint to be observed with adaptive optics on the ground}. Optical wavelengths are ideal because the spectral energy distributions of these old degenerates peak near 600 nm. With the F435W filter we will be able to partially resolve equally luminous binaries as close as 0.02″, which corresponds to within 0.6 AU for over half of the 12 proposed target stars. The collected data will be critical in determining whether these stars represent the oldest white dwarfs in the solar neighborhood.

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 10533

The IMF in NGC6611: the environmental influence on the formation of low-mass stars and brown dwarfs

We propose to use HST with ACS and NICMOS to survey the central area of the young {2 Myr} cluster NGC6611 in the Eagle Nebula, with the goal of constructing the low-mass and substellar Initial Mass Function {IMF}. We plan to obtain deep images in I {F775W} and Z {F850LP} with ACS/WFC, and deep images in J {F110W} and H {F160W} for 25 NICMOS/NIC2 fields within the 202″ x 202″ ACS/WFC field. Using a proven technique based on the use of IZJH color-magnitude and color-color diagrams to identify and determine the masses of the low-mass pre-main sequence cluster members, we are thus able to construct the IMF down to masses of 0.02-0.03 Msun. With an intense ionizing radiation field but a relatively low density, NGC6611 provides a unique laboratory in which to test the importance of photoevaporation and density on the formation of low-mass stars and brown dwarfs, through comparison with the IMFs determined for the different environments in the Orion Nebular Cluster, Taurus and IC348. This will not only offer substantial new insight into the physics of star formation, but also have important ramifications for estimating the global star formation rates at high redshift, the efficiency of galactic chemical evolution and the contribution of sub-stellar mass objects to the baryonic dark matter content of the Universe.

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 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.

S/C 10718

The Exosphere of a Newly Discovered Transiting Planet

We propose to use HST to directly detect the atmosphere and extended envelope {exosphere} of a recently discovered planet that transits the relatively bright star HD 149026. Absorption of background stellar Lyman-alpha emission is an extremely sensitive exospheric diagnostic that only HST can measure. If the HD 149026 planet is evaporating, then hydrogen in the exosphere should fill or overfill the Roche lobe, which has a size 4 times the diameter of Jupiter. If we do not detect a decrease in Lyman-alpha flux during several transits, then the hydrogen exosphere does not fill the Roche lobe of the planet and significant evaporation is unlikely. This would be a surprise, given that Vidal-Madjar et al. {2003} detected the exosphere of the planet that transits HD 209458, and the models of Lecavelier des Etangs et al. {2004} predict an order of magnitude more evaporation for the planet around HD 149026, due to its lower mass and smaller orbital distance. The newly discovered planet has 3 times the mean density and at least 3 times the core mass of the planet that transits HD 209458, which is consistent with significant exospheric evaporation in the past. We will also use ACS/PR200L observations to measure stellar limb darkening in the NUV, to detect Mg in the lower atmosphere of the planet, and to search for evidence of a moon or planetary rings.

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:

10218 – REACQ(2,1,2) Fine Lock Backup on FGS 2 @ 102/1014z REACQ(2,1,2) at 102/10:09:35 failed to Fine Lock Backup on FGS 2 at 10:14:10 with QF1STOPF on FGS 1. Primary GSACQ(2,1,2) at 07:06:39 and one previous REACQ at 08:34:35 was successful. No flags other than QF1STOPF on FGS 1 were seen. There were no OBAD’s scheduled prior to REACQ and no mapping OBAD afterward.

COMPLETED OPS REQUEST:

• 17702-0 – Genslew for proposal 10539 – slot 8 @ 102/1638z
• 17703-0 – Genslew for proposal 10539 – slot 9 @ 102/1639z
• 17704-0 – Genslew for proposal 10539 – slot 10 @ 102/1640z
• 17705-0 – Genslew for proposal 10539 – slot 11 @ 102/1641z
• 17706-0 – Genslew for proposal 10539 – slot 14 @ 102/1642z
• 17707-0 – Lower VTFE Curves by 50mV @ 102/2254z
• 17695-2 – Monitor VehConLaw.Integral Path Data via TMDIAG Slot 0 (Generic OR) @ 102/2351z

COMPLETED OPS NOTES:

• 1469-0 – Adjust Battery Temperature Limits for High Suntime @ 102/1330z
• 1470-2 – OTA Thermal Yellow Limit Updates @ 102/1932z

                           SCHEDULED      SUCCESSFUL
FGS GSacq                08                     08
FGS REacq                 07                     07
OBAD with Maneuver   28                     28

SIGNIFICANT EVENTS: (None)

VTFE Curve Adjustment Flash Report

In conjunction with the high suntime which started on DOY 2006/101, battery 1-3 temperatures began to increase resulting in a divergence in temperatures between the battery modules (~5 DegC difference between modules).

As per the high suntime contingency, EPS SEs lowered the VTFE curves on all the batteries by 50mV via Ops Request 17707 on DOY 2006/102 at 22:54 GMT. The system was monitored for 2 full orbit day periods. (The battery temperatures began to converge yielding ~3 DegC difference between modules.)