HST homepage http://ecf.hq.eso.org/ST-ECF-homepage.html
Under the terms of the ESA/NASA Memorandum of Understanding that runs until 2001 (11 years after launch), ESA's contribution to HST comprises:
In return for this contribution, European astronomers from ESA member states are guaranteed a minimum of 15% of HST observing time and the HST data archive is delivered to Europe (to the ESA/ESO European Coordinating Facility for Space Telescope, ST- ECF).
Since launch, the time awarded through the roughly annual AO and peer review process to European observers has bettered this minimum, as shown in Fig. 3.2.3/1. This figure also shows the evolution in the use of the FOC as a fraction of observing time.
Figure 3.2.3/1: The evolution from 1990 to 1996 of: the
fraction of time awarded to European observers on HST; the
fraction of observing time used by the FOC; the usage of the HST
ECF Archive (the new 'on-the-fly' recalibration process was made
available in spring 1996).
The period covered by the present report includes the routine operation of the HST Observatory throughout Cycle 6 and the preparation for the Instrument change that took place during the second Maintenance and Refurbishment Mission of February 1997. The period has been characterised by very smooth and efficient HST operation (no major malfunction has to be reported) and by a steady flow of high level astrophysical results. Most of these were presented during two dedicated Scientific Conferences: 'Science with the Hubble Space Telescope-II', 4-8 December 1995, Paris; 'HST and the High Redshift Universe', 1-5 July 1996, Cambridge, UK.
Possibly the most exemplary HST observing programme has been the Hubble Deep Field. The programme consisted in obtaining about 400 Wide Field Camera images of the same sky field through four different filters and then combining them to achieve the ultimate signal-to-noise ratio. The final image made available only a few weeks after the observations in December 1995, as shown in Fig. 3.2.3/2, revealed about 1600 galaxies (the faintest being of magnitude +30) with photometric redshifts between 0 and 6.
Figure 3.2.3/2: A subset of the Hubble Deep Field, a composite
image of about 400 individual Wide Field Camera frames showing
more than 1600 galaxies. Some objects are as faint as magnitude
+30. R. Williams (STScI), NASA/ESA.
Support to European astronomers is provided by the ST-ECF (comprising seven ESA and seven ESO staff) located within the European Southern Observatory in Garching. The main functions of the ST-ECF are to provide European astronomers with a convenient local source of up-to-date knowledge of the workings and status of HST's instruments for preparation of proposals and observations, software for calibration and data analysis, and access to the HST data archive for archival research.
During 1995, these ST-ECF activities were reviewed by an external board which recommended that, in addition to continuing to fulfil the above primary role, the ST-ECF could provide valuable support to the HST Project in areas which the STScI might otherwise have difficulty in undertaking. Following this recommendation, the ST-ECF took a new approach in the areas of calibration and data extraction of the new HST Instruments and in the HST Archive.
Given the increasing efficiency of the international networks, it is not necessary for the ST-ECF to maintain an 'exact' copy of the HST archive. During the past 2 years, the ST-ECF, in collaboration with the Canadian Astronomical Data Centre, has developed a new concept for the archive whereby, instead of storing all the HST data produced by the calibration pipeline on 12-inch (30.5 cm) optical disks, the raw data are stored on CD- ROMs and the relevant calibration process is run only when the data are retrieved. This concept, called 'on-the-fly recalibration', has the following advantages:
The down-side is the increase in computer power needed to run the recalibration process, but CPUs currently available are able to cope. The new concept of the ST-ECF archive has met with the approval of the users, with Fig. 3.2.3/1 showing the evolution in the usage of the archive.
The availability of the entire HST archive online has additional, far-reaching advantages. In particular, it opens the possibility of applying automatic processes to large sections of the data. One important example is the 'association' and merging of all the 'split' and 'dithered' Wide Field Camera images. Until now, the several images of the same field taken to reject the cosmic ray traces were stored individually in the archive and it was the task of the users to recognise them as a 'single observation'. While this is obvious to the prime observer, it is not so for the archive user. The ST-ECF is now running an automatic process that merges all the associated images into a single frame, with better signal-to-noise ratio and free of cosmic rays.
During the second M&R mission in February 1997, the Faint Object Spectrograph and Goddard High Resolution Spectrograph will be replaced by the Near-Infrared Camera and Multi-Object Spectrograph (NICMOS) and the Space Telescope Imaging Spectrograph (STIS). In support of NICMOS, and in collaboration with the STScI and the NICMOS teams, the ST-ECF developed the pipeline calibration and data extraction procedure for the GRISM spectrographic mode. In support of STIS, the ST-ECF is developing a complete software physical model of the spectrograph which will be essential, given the variety of possible observing modes, for a full calibration of the instrument.
The current HST MoU between NASA and ESA will end in 2001. Following the recommendation of the ESA Advisory bodies, a joint ESA/NASA Working Group has been appointed with the task of proposing mechanisms for extending the MoU.
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