Status Report

Hubble Space Telescope Daily Report #2734 10/24/00

By SpaceRef Editor
October 24, 2000
Filed under

PERIOD COVERED:  0000Z (UTC) 10/23/00 – 0000Z (UTC) 10/24/00
Daily Status Report as of 298/0000Z
    1.1 Completed Four Sets of WF/PC-2 8826 (Cycle 9 Supplemental Darks pt 1)
        The WF/PC-2 was used to perform a T dark calibration program that obtains three dark frames every day in order to provide data for monitoring and characterizing the evolution of hot pixels.  There were no reported anomalies.
    1.2 Completed STIS/CCD 8837 (CCD Dark Monitor-Part 1)
        The Space Telescope Imaging Spectrograph (CCD) was used to monitor the darks.  The proposal completed with no reported problems.
    1.3 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.
    1.4 Completed Two Sets of WF/PC-2 8867 (Gamma-Ray Bursts: Discovering The Progenitors And Understanding The Explosion – Visits A0-R0)
        The WF/PC-2 was used to observe a gamma-ray burster,
GRB000926.  Gamma-ray burst astronomy, one of the most active and exciting frontiers in astrophysics, is now entering a critical stage — with dramatic leaps in understanding of these events, as well as new discoveries.  Improvements in triggering and positioning accuracy provided by the SAX and HETE-2 gamma-ray satellites will allow entirely new classes of events to be studied.  Given the recent progress in this field, the proposers are now in a position to design precision, broadband measurements that can provide quantitative information on the as-yet unknown energy sources, the explosion geometry, and the surrounding medium.  In particular, the growing evidence of an intimate connection between SNe and GRBs can be definitively tested.  The proposal completed with no reported problems.
    1.5 Completed Two Sets of STIS/CCD 8562 (Probing the Large Scale Structure: Cosmic Shear Observations)
        The Space Telescope Imaging Spectrograph (CCD) was used to probe the distortion of light bundles from distant galaxies, looking at the statistical properties of the intervening inhomogeneous {dark} matter distribution. The losses of lock described in HSTAR 7924 and 2.1 occurred during the final iteration of this proposal, undoubtedly affecting an observation.  Otherwise, the proposals completed nominally.
    1.6 Completed Four Sets of STIS/CCD 8260 (Searching for the Hydrogen Reionization Edge of the Universe at 5HST)
        The Space Telescope Imaging Spectrograph (CCD) was used to observe one of 36 parallel orbits {4–5 fields of 5–8 orbits each} to constrain the H Lyman-edge in emission that marks the transition from a neutral to a fully ionized IGM at a predicted zion~eq5–15.  This edge is due to recombination from the H Lyman series and Lyman continuum, and can be used to constrain zion, one of the most important unknown quantities in large scale structure and cosmology.  The proposal completed nominally.
    1.7 Completed STIS/CCD 8838 (Bias Monitor – Part 1)
        The Space Telescope Imaging Spectrograph (CCD) was used to monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.  The proposal completed nominally.
    1.8 Completed Six 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.
    1.9 Completed STIS/CCD/MA1 8149 (The Spectral Energy Distribution of a Neutron Star Photosphere)
        The Space Telescope Imaging Spectrograph (CCD and MA1) was used to make direct measurement of the radius or mass of any neutron star outside a binary system.  The proposal seeks to obtain the spectral energy distribution of the isolated neutron star, RXJ185635.  The observations completed with no reported problems.
    1.10 Completed 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.
    1.11 Completed WF/PC-2 8805 (POMS Test Proposal: WFII Parallel Archive Proposal Continuation)
        The WF/PC-2 was used to perform a generic target version of the WFPC2 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 proposal completed with no reported problems.
    1.12 Completed STIS/CCD 8603 (Secular Changes In The Temperatures And Radii Of Extreme Helium Stars)
        The Space Telescope Imaging Spectrograph (CCD) was used to make observations of 15 extreme helium stars (EHEs_ which, together with IUE data, will give a 20-year baseline of ultraviolet spectrophotometry.  EHEs are luminous stellar remnants evolving rapidly to become white
dwarfs.  They represent an important stage in the evolution of at least some low-mass stars, and are closely related to the R Coronae Borealis variables.  Models do not agree about their origin, nor about what fraction of normal stars pass through this phase, in which the stars have been completely stripped of their outer layers.  The models do predict that EHEs are contracting and provide rate predictions and evolutionary
lifetimes.  The observations completed with no reported problems.
    1.13 Completed WF/PC-2 8812 (Cycle 9 Internal Monitor)
        The WF/PC-2 was used to obtain routine internal monitors for WFPC2 in order to monitor the health of the cameras.  A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {gain 7 and gain 15}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows.  There were no reported problems.
    1.14 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 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 losses of lock described in HSTAR 7924 and 2.1 occurred during this proposal, undoubtedly affecting an observation.  Otherwise, the observations completed as planned.
    1.15 Completed WF/PC-2 8821 (Cycle 9 CTE Monitor)
        The WF/PC-2 was used to monitor CTE changes during cycle 9.  It is expected to determine CTE and zero points by comparison to ground based observations of clusters.  The observations completed nominally.
    2.1 Guide Star Acquisitions:
      Scheduled Acquisitions: 9
Successful: 9
        As documented in HSTAR 7924, there were multiple losses of lock at approximately 297/1936Z following a successful acquisition.  The proposals described in 1.5 and 1.14 were affected.
  Scheduled Re-acquisitions: 7
Successful: 7
    2.2 FHST Updates:
Scheduled: 23
Successful: 23
        HSTAR 7921 documents the fact that a full maneuver update at 297/100528Z succeeded with errors V1=-22.720, V2=8.090,
V3=-3.393.  However, a second full maneuver update at 297/100813Z succeeded with larger errors of V1=53.077, V2=-3.206, V3=9.516.  This pattern was consistent for the next four re-acquisitions at the same attitude.  All acquisitions/re-acquisitions were successful.
    2.3 Operations Notes:
        Using ROP SR-1A, correctable SSR EDAC errors were cleared on three occasions.
        As directed by ROP DF-18A, engineering status buffer limits were modified twice.
        A STIS flight software error counter was cleared at 297/1428Z per ROP NS-12.
        At 297/1446Z ,during orbit night, the VTFE curves for each of the six batteries was raised by 110 mV.  VTFE table dumps were performed before and after the uplink to verify the correct numbers were patched into the correct locations.  EPS SEs verified nominal functionality of the TRSWCC in the following orbit day.  Preliminary analyses indicate the adjustment compensated for the premature initiation of trickle charge observed since the K10 bypass relay was closed on day 286.
        SSA transmitter #2 was turned on at 298/0000Z and off at 298/0029Z, using ROP IC-2.
        The ephemeris table was uplinked at 298/0003Z.
        A TTR was written for an unrecoverable 43-second data loss, beginning at 298/0059Z, due to bad weather at WSGT.
        Per an operations note, the MAMA limits for threshold voltage were changed at 298/0910Z.
        Continuation of normal science observations and calibrations.

SpaceRef staff editor.