Hubble Space Telescope Daily Report #2942 23 Aug 2001
The Space Telescope Imaging Spectrograph (CCD) was used to measure
D/H in gas clouds seen against background QSOs. This provides a unique and
fundamental cosmological probe of the baryonic density parameter. To date,
most of the QSO absorption line D/H constraints have been derived at high
redshift. In this proposal the proposers investigate a lower redshift
range, because there are two potentially crucial advantages to be gained by
carrying out D/H measurements at intermediate redshift. First, the
background of HI forest lines is lower and contamination of the DI feature
is significantly reduced. Second, a far larger sample of very bright QSOs
exists. There were no reported problems.
2.0 FLIGHT OPERATIONS SUMMARY:
2.1 Guide Star Acquisitions:
Scheduled Acquisitions: 6
Successful: 6
As described in HSTAR 8314, the acquisition at 234/155929Z
defaulted to fine lock backup on FGS-3 only when the scan step limit was
exceeded on FGS-2. The proposals detailed in 1.9 and 1.10 may have been
affected.
Scheduled Re-acquisitions: 9
Successful: 9
2.2 FHST Updates:
Scheduled: 12
Successful: 12
2.3 Operations Notes:
The SSR EDAC error counter was cleared twice per ROP SR-1A.
Flight software 2.0B EEPROM and 2.0C RAM installation occurred
successfully at 234/1330Z. This installation, together with related
installations performed yesterday and another installation tomorrow,
changes the post-SM3B Diode Bus Controller commanding and fixes the
Magnetic Torquer echo check timing.
3.0 SIGNIFICANT FORTHCOMING EVENTS:
Installation of 2.0C EEPROM flight software today.
Continuation of normal science observations and calibrations.