Hubble Space Telescope Daily Report #2952 – 7 Sep 2001

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 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. 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.