NASA Hubble Space Telescope Daily Status Report #4353

Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.

HUBBLE SPACE TELESCOPE DAILY REPORT # 4353

– Continuing to collect World Class Science

PERIOD COVERED: UT May 01, 2007 (DOY 121)

OBSERVATIONS SCHEDULED

WFPC2 10468

Jupiter’s Upper Stratospheric Hazes Probed with Ganymede

I propose to observe a disappearance of Ganymede behind the dark limb of Jupiter with five filters of the ACS/HRC camera. Two exposures in each filter can be taken during such an event. The images will provide the spectral variation of the altitude of the apparent limb of Jupiter. The altitude of the apparent limb is dependent on the presence of hazes in Jupiter’s stratosphere. Hazes of vertical optical depths below 0.001 could be detected with these observations, providing an extremely sensitive probe of high hazes. The observations probe altitudes levels near the 1-mb pressure level, for which we have very limited data. The creation of aerosols, their growth, and their transport by winds is currently a mostly theoretical study. It would significantly benefit from constraints derived from the proposed observations. ACS/HRC is the only instrument capable of the required spatial resolution in the ultraviolet. Furthermore, a favorable geometry of Ganymede’s orbit occurs only once every six years. This proposal achieves unique results with a minimum of HST time.

WFPC2 10832

Solving the microlensing puzzle: An HST high-resolution imaging approach

We propose to use the HST Advanced Camera for Surveys High Resolution Channel to obtain high resolution imaging data for 10 bona-fide LMC microlensing events seen in the original MACHO survey. The purpose of this survey will be to assess whether or not the lens and source stars have separated enough to be resolved since the original microlensing event took place – about a decade has passed since the original MACHO survey and the HST WFPC2 follow-up observations of the microlensing events. If the components of the lensing event are resolved, we will determine the apparent magnitude and color of both the lens and the source stars. These data, in combination with Spitzer/IRAC data and Magellan near-IR JHK data, will be used to ascertain the basic properties of the lens stars. With the majority of the microlensing events in the original MACHO survey observed at the highest spatial resolution currently possible, we will be able to draw important conclusions as to what fraction of these events have lenses which belong to some population of dwarf stars in the disk and what fraction must be due to lenses in the halo or beyond. These data will greatly increase our understanding of the structure of the Galaxy by characterizing the stellar population responsible for the gravitational microlensing.

WFPC2 10896

An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars

We propose to finish our Cycle 11 optical survey for nearby debris disks using the ACS/HRC coronagraph. Out of 43 orbits originally proposed for the survey, 23 orbits were allocated, leading to a survey of 22 stars, from which two new debris disks were imaged for the first time. Our analysis of the initial survey gives an empirical estimate for the detection rate of debris disks relative to heliocentric distance and dust optical depth. Our target list for Cycle 15 is now optimized to yield more frequent disk detections. Likewise our observing strategy is improved to maximize sensitivity per telescope orbit allocated. Therefore we present the most efficient survey possible. The scientific motivation is to obtain scattered light images of previously unresolved debris disks to determine their viewing geometry and physical architecture, both of which may characterize the underlying planetary system. We choose 25 debris disk targets for which we predict a detection rate of 25% ? 5%. Four targets have extrasolar planets from which the viewing geometry revealed by a disk detection will resolve the v sin{i} ambiguity in the planet masses. These targets present the remarkable opportunity of finally seeing a debris disk in system with known planets.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration – CR Persistence Part 5

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.

NIC3 10792

Quasars at Redshift z=6 and Early Star Formation History

We propose to observe four high-redshift quasars {z=6} in the NIR in order to estimate relative Fe/Mg abundances and the central black hole mass. The results of this study will critically constrain models of joint quasar and galaxy formation, early star formation, and the growth of supermassive black holes. Different time scales and yields for alpha-elements {like O or Mg} and for iron result into an iron enrichment delay of ~0.3 to 0.6 Gyr. Hence, despite the well-known complexity of the FeII emission line spectrum, the ratio iron/alpha – element is a potentially useful cosmological clock. The central black hole mass will be estimated based on a recently revised back hole mass – luminosity relationship. The time delay of the iron enrichment and the time required to form a supermassive black hole {logM>8 Msol, tau ~0.5Gyr} as evidenced by quasar activity will be used to date the beginning of the first intense star formation, marking the formation of the first massive galaxies that host luminous quasars, and to constrain the epoch when supermassive black holes start to grow by accretion.

WFPC2 10845

HUNTING FOR OPTICAL COMPANIONS TO BINARY MILLISECOND PULSARS IN TERZAN 5 AND NGC6266

We propose deep WFPC2 and NICMOS observations to search for optical companions to binary millisecond pulsar {MSPs} in two Globular Clusters {GCs}: Terzan 5 and NGC6266. Terzan 5 has the largest MSP population of any GC: 33 MSP {17 in binary systems} have been discovered up to now in this stellar system. NGC6266 ranks fifth among the GC for wealth of MSPs but it is the only one in which all the {six} detected MSPs are in binary systems. Only 5 optical counterparts to binary MSP companions are known in GCs {two of them have been discovered by our group}: hence even the addition of a few new identifications are crucial to investigate the variety of processes occurring in binary MSPs in dense environment. The observations proposed here would easily double/triple the existing sample of known MSP companions, allowing the first meaningful study of the phenomena which drive the formation and evolution of these exotic systems. Moreover, since most of binary MSP in GC are formed via stellar interactions in the high density regions of the cluster, the determination of the nature of the companion and the incidence of this collisionally induced population have a significant impact on our knowledge of the cluster dynamics. Even more interesting, the study of the optical companions to NSs in a GC allows to derive tighter constraints {than those obtainable for NS binaries in the galactic field} on the properties {mass, orbital inclination and so on} of the compation star. This has, in turn, an intrisic importance for fundamental physics since it offers the opportunity of measuring the mass of the NS and hence to put constraints to the equation of state of matter at nuclear equilibrium density.

WFPC2 10890

Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies

The formative phase of the most massive galaxies may be extremely luminous, characterized by intense star- and AGN-formation. Till now, few such galaxies have been unambiguously identified at high redshift, restricting us to the study of low-redshift ultraluminous infrared galaxies as possible analogs. We have recently discovered a sample of objects which may indeed represent this early phase in galaxy formation, and are undertaking an extensive multiwavelength study of this population. These objects are bright at mid-IR wavelengths {F[24um]>0.8mJy}, but deep ground based imaging suggests extremely faint {and in some cases extended} optical counterparts {R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain deep ACS F814W and NIC2 F160W images of these sources and their environs in order to determine kpc-scale morphologies and surface photometry for these galaxies. The proposed observations will help us determine whether these extreme objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity galaxies.

WFPC2 11027

Visible Earth Flats

This proposal monitors flatfield stability. This proposal obtains sequences of Earth streak flats to construct high quality flat fields for the WFPC2 filter set. These flat fields will allow mapping of the OTA illumination pattern and will be used in conjuction with previous internal and external flats to generate new pipeline superflats. These Earth flats will complement the Earth flat data obtained during cycles 4-14.

WFPC2 11029

WFPC2 CYCLE 15 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 15 decon proposal xxxx 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:

• 18054-0 – Preview KF Sun Vector Data via Telemetry Diags
• 18060-0 – MSS/Gyro1 KF Initialization Convergence Testing for SMS 120
• 18061-0 – MSS KF Adding Gyro1 Convergence Testing for SMS 120
• 18064-0 – PCS KF OOT Support, 121/18:20z
• 18065-0 – PCS KF OOT Support, 121/19:49z

COMPLETED OPS NOTES: (None)

                      SCHEDULED      SUCCESSFUL 

FGS GSacq               13                 13 
FGS REacq               02                 02 
OBAD with Maneuver      28                 28 

SIGNIFICANT EVENTS:

Evaluation of Universal Kalman Filter performance continued. Multiple text segments were executed, all of them successfully. Details follow.

Background Kalman Filter Operations Day 121:

The Kalman Filter (KF) was restarted on 120/14:35:30 after being halted on 116/21:00 for the Clock Roll-over.

The KF was halted at 121/11:22 (OR 18062-0) during orbit day and during a T2G guiding interval. The filter was restarted at 121/11:25 during orbit day and during a fast changing B-field while inertially fixed. The filter was activated with only the MSS enabled. All UKF parameters showed nominal operation. The test was an MSS Initialization Test Case with the vehicle inertially fixed during a fast changing B-field (M_0_INF, Test #3). The MSS/CSS default KF configuration was restored at 121/12:13.

The Gyro1 sensor input was added to the KF at 121/15:10 (OR 18059-1) during orbit day with no vehicle slew and during a T2G guiding interval. The filter was running with the MSS and CSS sensor inputs enabled and converged. All UKF parameters showed nominal operation. The test was an MSS/CSS/Gyro1 test case with the Gyro1 sensor input removed at 121/16:30 with the filter running. The Gyro1 input was removed during an M2G guiding interval, during orbit day, during a vehicle maneuver and during a slow changing B-field (MC_G1_HVS, Test #32). The response to the removal of the gyro input was nominal and the filter remained converged. The removal of the gyro input restored the default MSS/CSS configuration of the filter.

The KF was halted at 121/18:10 (OR 18060-0) during orbit day and during an M2G guiding interval. The filter was restarted at 121/18:21 during orbit day and during a slow changing B-field. The filter was activated with the MSS and Gyro1 sensor inputs enabled. All UKF parameters showed nominal operation. The test was an MSS/Gyro1 Initialization test case during a vehicle slew, during a slow changing B-field (M_G1_IVS, Test #12). The Gyro1 sensor input was removed at 121/18:34, however the CSS sensor input was intentionally left disabled to minimize the configuration changes needed for the next test at 19:57 and because the originally scheduled TDRSS service to execute the reconfiguration was deleted.

The Gyro1 sensor input was added to the KF at 121/19:57 (OR 18061-0) during orbit day, during a vehicle slew, during an M2G guiding interval and during a slow changing B-field. The filter was running with only the MSS sensor input enabled and converged. All UKF parameters showed nominal operation after the addition of the gyro sensor input enabling. The test was an MSS/Gyro1 test case with the Gyro1 sensor input added with the filter enabled and converged (M_G1_RVS, Test #20). The CSS sensor input was re-enabled, the Gyro1 sensor input removed and the filter restarted during a T2G guiding interval and during orbit night at 121/20:15. This reconfiguration restored the default MSS/CSS configuration of the filter.