HUBBLE SPACE TELESCOPE

   DAILY REPORT #2853

PERIOD COVERED:  0000Z (UTC) 04/17/01 - 0000Z (UTC) 04/18/01

Daily Status Report as of 108/0000Z

1.0 OBSERVATIONS SCHEDULED AND ACCOMPLISHED:

    1.1 Completed Two Sets of STIS/CCD 8864 (CCD Dark Monitor-Part 2)

        The Space Telescope Imaging Spectrograph (CCD) was used to monitor 
the darks for the CCD.  The proposal completed nominally.

    1.2 Completed WF/PC-2 8827 (Cycle 9 Supplemental Darks pt2/3)

        The WF/PC-2 was used to obtain three dark frames every day to 
provide data for monitoring and characterizing the evolution of hot 
pixels.  The proposal completed nominally.

    1.3 Completed STIS/CCD/MA1 8582 (UV Detectability of Bright Quasars in 
the Sloan Fields)

        The Space Telescope Imaging Spectrograph (CCD and MA1) was used to 
examine the He II Ly alpha absorption at 304{1+z} Angstrom which is a far 
more sensitive tracer of the intergalactic medium {IGM} than its H I 
counterpart.  The recent detections of such absorption in four quasars, 
albeit with limited data quality and a small sample size, demonstrate the 
great potential of such a probe.  There were no reported problems.

    1.4 Completed WF/PC-2 7407 (Continuation of Temporal Monitoring of the 
Crab Synchrotron Nebula)

        The WF/PC-2 was used to observe the synchrotron nebula surrounding 
the Crab pulsar that has been the subject of intensive study for 
decades.  It is generally accepted that the structure and activity in this 
region are due to wave phenomena near the termination shock of the pulsar 
wind, observations of which hold unique promise of leading to more complete 
models of the pulsar and its magnetosphere.  Unfortunately, this promise 
has not been fulfilled, largely because of the low spatial resolution and 
uneven temporal coverage of existing studies.  Recent WF/PC-2 observations 
of the Crab synchrotron nebula offer new hope in this quest.  These data, 
which reach the natural size scale defined by the Larmor radius of 
energetic electrons, resolve the majority of the known features in the 
Crab.  For the first time it is possible to reliably establish the physical 
conditions {e.g., emissivities, equipartition fields, and pressures} of 
features associated with the wind and its termination shock.  The 
observations completed as planned.

    1.5 Completed Four Sets of STIS/CCD 9248 (Probing the Large Scale 
Structure: Cosmic Shear Observations)

        The Space Telescope Imaging Spectrograph (CCD) was used to measure 
the distortion of light bundles from distant galaxies that probe the 
statistical properties of the intervening inhomogeneous {dark} matter 
distribution.  Its tidal gravitational field distorts the observable image 
shapes thereby causing a coherent ellipticity pattern {Cosmic Shear}.  The 
observations completed nominally.

    1.6 Completed FGS/1 9240 (Astrometric Mass Determination of an 
Extrasolar Planet Candidate)

        Fine Guidance Sensor-1R was used to perform astrometric 
observations that will allow a quick measure of the sky-plane motion of 55 
Cancri, a G star with an Msin{i} = 0.9 MJ radial velocity companion with a 
14 day period.  By using 7 pairs of visits, where each visit within a pair 
has the same parallax factor, we will be able to accurately determine the 
stars's proper motion.  The reflex motion of the star, due to its orbit 
about the star-companion barycenter, will manifest itself as a systematic 
residual to the measured proper motion if the companion is sufficiently 
massive.  There were no reported problems.

    1.7 Completed WF/PC-2 9244 (POMS Test Proposal: WFII Parallel Archive 
Proposal Continuation)

        The WF/PC-2 was used to perform a generic target version of the 
Archival Pure Parallel program.  The program will be used to take parallel 
images of random areas of the sky, following the recommendations of the 
Parallels Working Group.  The observations completed with no anomalous 
activity.

    1.8 Completed WF/PC-2 8683 (Imaging Of Brightest Cluster Galaxies: The 
High End Of The Black Hole Mass Distribution)

        The WF/PC-2 was used to make kinematic black hole detections in 
galaxies to decide whether they indicate that the mass correlates with both 
optical luminosity and radio power.  The observation completed with no 
reported problems.

    1.9 Completed  WF/PC-2 8677 (Extragalactic Novae: the Maximum Magnitude 
- Rate of Decline Relation in NGC 4472)

        The WF/PC-2 was used to accomplish two goals: {1} to provide the 
first homogeneous observational constraints on theoretical models for novae 
outbursts; and {2} to assess the reliability of novae as standard candles 
by using WFPC2 to collect well sampled light curves for 20-50 novae in the 
supergiant elliptical galaxy NGC 4472, the brightest galaxy within 30 
Mpc.  Both the length of the observing window and the temporal sampling of 
the observations are specifically designed to ensure that the novae peak 
magnitudes and decline rates are measured accurately.  These data will be 
used to construct the first `Maximum Magnitude versus Rate of Decline' 
{MMRD} relation for a galaxy beyond the Local Group.  This relation is not 
only a potentially powerful standard candle, but its shape and dispersion 
are directly linked to physical parameters which govern the physics of 
novae outbursts such as the white dwarf mass, temperature and mass 
accretion rate.  The proposal completed with no reported problems.

    1.10 Completed STIS/CCD 8607 (Completing the Local AGN Inventory: The 
AGN Content of Composite Nuclei)

        The Space Telescope Imaging Spectrograph (CCD) was used to increase 
the knowledge of the local space density of AGNs which is of fundamental 
importance to a number of astrophysical problems.  A significant fraction 
of nearby galaxies have nuclei whose spectra are intermediate between those 
of LINERs and nuclear starbursts.  These ``transition objects'' may be 
composite systems that contain both a central AGN and circumnuclear star 
formation.  We will test this hypothesis by obtaining spatially-resolved 
optical spectra of a well-defined sample of 15 nearby transition nuclei 
selected from the extensive ground-based survey of Ho, Filippenko, and 
Sargent.  The observations completed with no reported problems.

    1.11 Completed STIS/CCD 8865 (Bias Monitor-Part 2)

        The Space Telescope Imaging Spectrograph (CCD) was used to monitor 
the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1, and 1x1 at 
gain = 4, to build up high-S/N superbiases and track the evolution of hot 
columns.  The proposal completed with no anomalous activity.

    1.12 Completed STIS/CCD 8619 (Critical Spectroscopic Variations In Eta 
Carinae)

        The Space Telescope Imaging Spectrograph (CCD) was used to observe 
the very massive, unstable, persistently enigmatic star Eta Carinae that 
has implications for several branches of astrophysics.  While HST has 
produced a series of remarkable discoveries concerning this object, the 
nature of the central star remains elusive.  Now, however, recent 
developments offer, for the first time, an approach that can settle certain 
long-standing questions which have been obstacles to understanding this 
unique object.  A 5.5-year spectroscopic and X-ray cycle has been 
confirmed.  STIS now provides the most promising and very likely the only 
way to test whether Eta Car is a 5.5-yr binary system.  If it is, STIS will 
also allow us to constrain the parameters, needed to assess the companion 
star's possible role in past outbursts and ejecta.  If the data conflict 
with binary models, then the 5.5-yr effect is probably a thermal cycle 
which will give novel information about the star's structure.  In addition 
to the periodicity, a large, almost unprecedented brightening, first 
noticed in HST data, has occurred since 1997 and merits followup 
observations.  The observations completed with no reported problems.

    1.13 Completed WF/PC-2 8824 (Decontaminations and Associated 
Observations Pt. 3/4)

        The WF/PC-2 was used for the monthly 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.  There were 
no reported problems.

    1.14 Completed STIS/CCD/MA1 8638 (Temperature Scale And Metal 
Abundances Of Hot Hydrogen-Rich Central Stars Of Planetary Nebulae)

        The Space Telescope Imaging Spectrograph (CCD and MA1) was used to 
perform UV spectroscopy on a sample of hot hydrogen-rich central stars of 
PNe, covering the hottest phase of post-AGB evolution. The spectra will 
then be analyzed with fully metal line blanketed NLTE model atmospheres in 
order to determine T_eff, surface gravity, and chemical composition.  The 
proposal completed with no reported problems.

2.0 FLIGHT OPERATIONS SUMMARY:

    2.1 Guide Star Acquisitions:
       Scheduled Acquisitions: 10
Successful: 10

  Scheduled Re-acquisitions:  3
Successful:  3

    2.2 FHST Updates:
Scheduled: 18
Successful: 18

    2.3 Operations Notes:

        Using ROP SR-1A, the SSR EDAC error counter was cleared five times.

        A TTR was written when a command dropout occurred at 108/083613Z 
during a load uplink, necessitating a re-transmit.

        A CCS engineering status buffer limit was adjusted at 108/0844Z as 
directed by ROP DR-18A.

3.0 SIGNIFICANT FORTHCOMING EVENTS:

        Continuation of normal science observations and calibrations.

/CAW