HUBBLE SPACE TELESCOPE

       DAILY REPORT #2952

PERIOD COVERED:  0000Z (UTC) 09/06/01 - 0000Z (UTC) 09/07/01

Daily Status Report as of 250/0000Z

1.0 OBSERVATIONS SCHEDULED AND ACCOMPLISHED:

    1.1 Completed STIS/CCD 9148 (Light Echos and the Nature of Type Ia 
Supernovae)

        The Space Telescope Imaging Spectrograph (CCD) was used to take 
STIS snapshot images of a subset of 43 well observed Type Ia supernovae 
{SNIa}, most of which have been discovered in late type galaxies over the 
last 40 years to make a systematic search for light echos around SN 
Ia.  STIS will also observe a sample of 10 SN II and SN Ib/c, which are 
believed to be the result of massive star core collapse and, therefore, to 
be thin-disk population objects, in order to make an empirical calibration 
of the accuracy of our method for determining scale heights.  The SN Ia 
sample will provide a direct as well as accurate estimate of the scale 
height of SN Ia which is an important clue to the progenitors of these 
events.  The proposal completed nominally.

    1.2 Completed STIS/CCD/MA1 8244 (Probing Stellar Ejecta in SN 1006 
through UV Absorption Spectroscopy)

        The Space Telescope Imaging Spectrograph (CCD and MA1) was used to 
investigate the remnant of SN 1006 which provides a unique opportunity to 
study ejecta from a Type Ia supernova through UV absorption 
spectroscopy.  Absorption lines in the spectrum of the background 
Schweizer-Middleditch star have revealed the presence of cold Fe and Si 
with velocities up to 7000kms.  These lines surely are due to ejecta, but 
extrapolation from a single line of sight to the entire remnant suggests a 
mass of Fe less than half the ~ 0.5: Msun expected from a Type Ia 
supernova.  A reliable inventory of the ejecta requires several such ``core 
samples'' through the remnant, but until now no other suitable background 
UV sources had been identified.  The observations completed nominally.

    1.3 Completed Six 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.  As described in 2.1 and HSTAR 8330, the 
acquisition for the fifth iteration of this proposal defaulted to fine lock 
backup on one FGS only, possibly affecting the observations in that 
iteration.  Otherwise, the observations completed with no further anomalous 
activity.

    1.4 Completed Two Sets of STIS/CCD 8901 (Dark Monitor-Part 1)

        The Space Telescope Imaging Spectrograph (CCD) was used to 
monitor.  There was no anomalous activity.

    1.5 Completed STIS/CCD 8617 (Ultraviolet Spectroscopy of Hot 
Horizontal-Branch Stars in the Globular Cluster M13)

        The Space telescope Imaging Spectrograph (CCD) was used to observe 
blue horizontal-branch {BHB} stars in the metal-poor globular clusters M13, 
M15, NGC 288 and NGC 6752 that have recently been found to exhibit 
remarkable metallicity enhancements and helium depletions relative to the 
canonical cluster composition.  These abundance anomalies are most likely 
due to diffusion processes -- radiative levitation of the metals, and 
gravitational settling of helium --- in the stable radiative atmospheres of 
these hot stars.  With available ground-based facilities, we have observed 
stars in M13 as hot as 19000 K, but beyond this point we are constrained by 
low V- and B-band flux and an insufficient number of visible-wavelength 
spectral lines.  There were no reported problems.

    1.6 Completed Two Sets of FGS/1 9169 (An Interferometric Harvest of 
Double Degenerates)

        Fine Guidance Sensor #1R was used to observe the white dwarf mass 
and age distributions that hold clues to the star formation history of our 
Galaxy and the age of the disk.  As described in 2.1 and HSTAR 8330, the 
acquisition for the second iteration of this proposal defaulted to fine 
lock backup on one FGS only, possibly affecting the observations in that 
iteration.  Otherwise, no other problems were reported.

    1.7 Completed Four Sets of STIS/CCD 9285 (POMS Test Proposal: STIS 
Non-scripted Parallel Proposal Continuation III)

        The Space Telescope Imaging Spectrograph (CCD) was used to make low 
galactic latitude, non-scripted parallel observations as part of a POMS 
test proposal.  As described in 2.1 and HSTAR 8330, the acquisition for the 
second and third iterations of this proposal defaulted to fine lock backup 
on one FGS only, possibly affecting the observations in those 
iterations.  Then, in the final iteration, the losses of lock discussed in 
2.1 and HSTAR 8331 occurred that possibly affected some of the observations 
in that iteration.  Otherwise, the observations were completed as planned, 
and no other anomalies were reported.

    1.8 Completed STIS/CCD 8903 (Bias Monitor - Part 1)

        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.  There were no problems.

    1.9 Completed WF/PC-2 9042 (An Archive To Detect The Progenitors Of 
Massive, Core-Collapse Supernovae)

         The WF/PC-s was used to search for supernovae which have massive 
star progenitors.  The already extensive HST archive and high-resolution 
ground-based images of galaxies within ~20 Mpc enables us to resolve and 
quantify their individual bright stellar content.  As massive, evolved 
stars are the most luminous single objects in a galaxy, the progenitors of 
core-collapse supernovae should be directly detectable on pre-explosion 
images.  One Type II progenitor has been observed this year, and the 
investigators have proposed a short, companion WFPC2 proposal to confirm 
this candidate and identify a second.  The observations completed nominally.

    1.10 Completed STIS/CCD/MA2 9040 (Baryons In Intermediate Redshift {Z > 
1} OVI Absorbers)

        The Space Telescope Imaging Spectrograph (CCD and MA2) was used to 
search for intervening OVI absorption systems in two further extremely UV 
bright intermediate redshift QSOs {HS 0747 + 4259, z = 1.9, V = 15.6; HS 
0818+2554, z = 1.5, V = 15.4} using the STIS E230M Echelle mode.  The 
scientific aim is to measure the baryonic fraction in the warm-hot 
intergalactic medium at redshifts 1 <=q z <=q 1.8.  Present existing data 
on HE 0515-4414 taken also with STIS E230M seem to indicate that the 
baryonic fraction at z = 1.5 is lower by a factor of ~ 15 than the high 
value found by Tripp et al. {2000} for z < 0.3.  Our results need to be 
confirmed by more lines of sight, and we plan to test hierarchical 
structure formation models which predict a rapid evolution between z = 1.5 
and z = 0.  The observations completed as planned with no reported 
anomalous activity.

2.0 FLIGHT OPERATIONS SUMMARY:

    2.1 Guide Star Acquisitions:
       Scheduled Acquisitions:  6
Successful:  6

        Per HSTAR 8330, the acquisition at 249/154118Z defaulted to fine 
lock backup on FGS-3 only due to FGS-2.  The proposals described in 1.3, 
1.6 and 1.7 may have been affected.

        During the proposal detailed in 1.7, losses of lock occurred at 
249/173746Z and at 249/175246Z.  HSTAR 8331 was generated as a result.
  Scheduled Re-acquisitions:  9
Successful:  9

    2.2 FHST Updates:
Scheduled: 15
Successful: 15

    2.3 Operations Notes:

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

        HSTAR 8333 relates that a STIS 641 status buffer message was posted 
at 250/015311Z that indicated that, while performing a MAMA Local Event 
Rate Check, the event rate check failed due to a checkbox sum exceeding the 
limit.  When this occurs, the MAMAs are automatically shuttered using the 
CIM and the calibration lamps are turned off.  Other such events occurred 
at 250/015759Z and at 250/032408Z.  This happened during STIS 9096, a 
proposal occurring during the period of the next report.  The STIS flight 
software error counter was rest at 250/0423Z per ROP SR-12.  Errors like 
these are expected to occur on the frequency of several times a year.  The 
STScI will be investigating the cause of the error and will be instituting 
steps to ensure that future visits to this target are appropriately 
adjusted..  In any event, an SMS review has shown that no more images of 
this particular target are scheduled this week.

3.0 SIGNIFICANT FORTHCOMING EVENTS:

        Continuation of normal science observations and calibrations.

/CAW