HUBBLE SPACE TELESCOPE

  DAILY REPORT #2858

PERIOD COVERED:  0000Z (UTC) 04/24/01 - 0000Z (UTC) 04/25/01

Daily Status Report as of 115/0000Z

1.0 OBSERVATIONS SCHEDULED AND ACCOMPLISHED:

    1.1 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.

    1.2 Completed Two Sets of WF/PC-2 8811 (Cycle 9 Standard Darks)

        The WF/PC-2 was used to obtain 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.  The proposal completed with no reported problems.

    1.3 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.

    1.4 Completed WF/PC-2 8581 (A Search For Low-Mass Companions To 
Ultracool Dwarfs)

        The WF/PC-2 was used to search for very low-mass {VLM} companions 
to a complete sample of 120 late-M and L dwarfs, drawn mainly from the 
2MASS and SDSS surveys.  The primary goal is to determine the multiplicity 
of M < 0.1 M_odot dwarfs.  In particular, we aim to identify binary systems 
suitable for long-term astrometric monitoring and mass measurement, and 
systems with cool, sub-1000K companions.  The proposal completed with no 
reported problems.

    1.5 Completed Three 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 
loss-of-lock described in 2.1 and HSTAR 8183 occurred during the second 
iteration of this observation.  Otherwise, the observations completed 
nominally.

    1.6 Completed STIS/CCD 8594 (H-Deficient Condensations In Pne -- A Key 
To Discrepancies In Abundance Determinations)

        The Space Telescope Imaging Spectrograph (CCD) was used to obtain 
deep long-slit spectra for the well-resolved H-deficient knots of A 30 and 
to search for such knots.  The data will yield the spatially resolved 
temperature, density and ionization structure of the knots in Abell 30, 
and, for the first time, accurate ORL C and O abundances for them.  The 
results will lead to a much better understanding of the physics of such 
knots and their effects on abundance determinations .  There were no 
reported problems.

    1.7 Completed Four Sets WF/PC-2 8816 (Cycle 9 UV Earthflats)

        The WF/PC-2 was used to obtain sequences of Earth streak flats to 
improve the quality of pipeline flat fields for the WFPC2 UV filter set and 
in order to monitor flat field stability.  There were no reported problems.

    1.8 Completed Eight Sets of 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 loss-of-lock described in 2.1 and HSTAR 8183 
occurred during the second iteration of this observation.  Otherwise, the 
observations completed with no other anomalous activity.

    1.9 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.  The loss-of-lock described in 2.1 and HSTAR 8183 occurred during 
this observation.  There were no other reported problems.

    1.10 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.

    1.11 Completed WF/PC-2 8682 (A Snapshot Study of 0bservational Cosmology)

        The WF/PC-2 was used to examine the observational constraints on 
the cosmic star formation history that is currently among the most active 
fields in observational cosmology.  The most widely used tracer of the 
co-moving volume-averaged star formation rate {SFR} is the UV luminosity 
density, which early results found to peak at z~1- 2.  The apparent 
identification of the primary epoch of metal production and star formation 
in the Universe led to intense theoretical and observational 
interest.  Nevertheless, and remarkably for such a fundamental observation, 
little is known about the history of star formation in the Universe beyond 
its global average.  There were no reported anomalies.

    1.12 Completed WF/PC-2 8634 (Atmospheric Variability on Uranus and Neptune)

        The WF/PC-2 was used to obtain snapshot observations of Uranus and 
Neptune to monitor changes in their atmospheres on time scales of months to 
years.  Uranus is rapidly approaching equinox in 2007, with another 4 
degrees of latitude in the northern hemisphere becoming visible every 
year.  Recent HST images during this unique epoch have revealed: {i} 
strongly wavelength-dependent latitudinal structure, {ii} the presence of 
numerous visible-wavelength cloud features in the northern hemisphere, and, 
{iii} in the near-IR, discrete features northward of 25degrees N that have 
the highest contrast ever seen for a Uranian cloud.  Long-term ground- 
based observations show seasonal brightness changes whose origins are not 
well understood.  Recent IR images of Neptune obtained using adaptive 
optics on the Keck Telescope indicate that a new "Bright Companion" type of 
feature has recently appeared in the southern hemisphere.  Snapshot 
observations of these two dynamic planets can supply context in which to 
discern the nature of long-term changes in their latitudinal atmospheric 
bands and to track the appearance, movement, and disappearance of discrete 
albedo features.  There were no reported problems.

    1.13 Completed Three Sets of STIS/MA1/MA2 8843 (Cycle 9 MAMA Dark 
Measurements)

        The Space Telescope Imaging Spectrograph (MA1 and MA2) was used to 
perform the routine monitoring of the MAMA detector dark noise.  The 
proposal completed nominally.

    1.14 Completed WF/PC-2 8712 (The Wind Accretion Wake In A Detached 
Binary System)

        The WF/PC-2 was used to observe RW Hya {= HD 117970}, the only 
known detached binary system, where direct observational evidence for wind 
accretion onto a white dwarf is found.  UV
observations will enable the investigator to advance knowledge in a field 
which has for long had to remain a theoretical subject.  RW Hya is an 
eclipsing system containing a mass-losing M-giant and a hot white dwarf on 
circular orbits {370 days}.  The observation completed with no reported 
problems.

    1.15 Completed STIS/CCD/MA1/MA2 8635 (A Test Of Pulsation And Diffusion 
Theory For Subluminous B Stars)

        The Space telescope Imaging Spectrograph (CCD, MA1 and MA2) was 
used to confirm the recent discovery of radial and nonradial mode 
pulsations in nearly 20 sdB stars that makes it possible to use 
asteroseismology to probe the internal structure of these stars and discern 
their evolutionary status. This is needed for reasons as diverse as 
understanding the late stages of stellar evolution and the calibration of 
the observed ultraviolet upturn in giant elliptical galaxies as an age 
indicator.  The observations completed with no anomalous activity.

    1.16 Completed STIS/CCD/MA1 8662 (A Snapshot Survey of the Hot 
Interstellar Medium)

        The Space Telescope Imaging Spectrograph (CCD And MA1) was used to 
obtain snapshot STIS echelle observations of key tracers of hot 
interstellar gas {C IV, N IV, and Si IV} for selected FUSE Team O VI survey 
targets with known UV fluxes.  By taking advantage of the snapshot 
observing mode we will efficiently obtain a large number of spectra 
suitable for the study of the highly ionized hot component of the 
interstellar medium {ISM}.  Our goals are to explore the physical 
conditions in and distribution of such gas, as well as to explore the 
nature of the interfaces between the hot ISM and the other interstellar gas 
phases.  The observations completed with no reported problems.

    1.17 Completed STIS/CCD/MA2 8595 (Does the D/H Ratio Vary in Local 
Interstellar Gas?)

        The Space Telescope Imaging Spectrograph (CCD and MA2) was used to 
take measurements of the D/H ratio in the Local Interstellar Cloud {LIC} 
that are consistent with 1.5 +/- 0.1 X 10^-5, while for other clouds within 
~ 100 pc, the measurement uncertainties are larger.  Two target white 
dwarfs {WDs}, HZ 43 and GD 153, are chosen because EUVE data show low HI 
column densities, thereby reducing the probabilities of multiple velocity 
components and saturation of the DI line.  The WDs have pure-H atmospheres, 
so contamination of the interstellar lines by photospheric metal lines is 
not an issue.  The measurements completed with no reported problems.

2.0 FLIGHT OPERATIONS SUMMARY:

    2.1 Guide Star Acquisitions:
       Scheduled Acquisitions: 11
Successful: 11

        After a successful acquisition, there was a loss-of-lock at 
114/122553Z during an astrometry observation.  Recovery was not completed 
until 114/124411Z.  HSTAR 8183 was written.  Proposals detailed in 1.5, 1.8 
and 1.9 were affected.
  Scheduled Re-acquisitions:  4
Successful:  4

    2.2 FHST Updates:
Scheduled: 30
Successful: 30

    2.3 Operations Notes:

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

        The CCS engineering status buffer limits were adjusted five times 
as directed by ROP DF-18A.

        Per ROP RD-7A, ESTR-2 reconditioning was completed at 114/0917Z.

        At 114/122506Z, per HSTAR 8182, while guiding, the gyro #5 motor 
current spiked to 254.8 mAmps and then settled down to a toggle between 204 
mAmps and 210 mAmps.  This is the second current spike on this gyro in two 
days. This event occurred during the loss-of-lock event described in 2.1 
above.  The spike was only six mAmps from the 270 mAmp threshold which 
would have caused the gyro to be taken offline, resulting in a subsequent 
Zero Gyro safemode entry.   Initial indications are that there was a 
decrease in the gyro duty cycle and a bias shift increase.  The gyro #5 
motor current operational yellow limits were again adjusted upward at 
114/2258Z per an operations request.  At a meeting held at 3:00 p.m., it 
was decided to perform data extractions on the original gyro #4 motor 
current, the origianl gyro#5 spin down, and motor currents for all prior 
gyro power ups.  PCS and flight software personnel were given the action to 
modify the gyro #5 motor current limit test to reflect 299.6 mAmps.

        SSA transmitter #2 was turned on at 114/1739Z and turned off at 
114/1748Z, using ROP IC-2.

        TTRs were generated for required re-transmits during at NSSC-1 
uplink at 115/0416Z and during a 486 uplink at 115/0735Z.  After the first 
occurrence, using ROP NS-5, a NSSC-1 error was reset at 115/0424Z.

3.0 SIGNIFICANT FORTHCOMING EVENTS:

        Continuation of normal science observations and calibrations.

/CAW