Future European access to space telescopes

Bob Fosbury

The Hubble Space Telescope was launched in April 1990 and, after a
somewhat troubled early operation resulting from a spherically
aberrated primary mirror, has gone on to become a uniquely productive
tool for observational astronomy. In addition to its impact on almost
all fields of astrophysical research, it has become, by virtue of the
stream of spectacular pictures from its cameras, the dominant source of
material for the popularisation of astronomy throughout the world. NASA
have capitalised on this success in developing its "Origins" programme
which proposes major space and groundbased facilities for the next
decade and beyond.

Europe, through ESA, is a partner with NASA in the HST project and
there is a Memorandum of Understanding (MOU) between the two Agencies
extending for eleven years after launch. This ESA involvement,
expressed by the provision of an instrument, solar panels, staff at the
Space Telescope Science Institute in Baltimore etc., has been very
effectively utilised by European scientists who consistently receive in
excess of 20% of the competitively awarded telescope time in the annual
allocation cycles.

What are the prospects for the European involvement in HST and other
space telescopes after the MOU expires in 2001? ESA and NASA have for
some while been discussing the terms for the extension of the MOU and
it is possible that any agreement will include both HST and the Next
Generation Space Telescope (NGST). There have already been two
servicing missions to HST, in 1993 and 1997, and others are scheduled
for 1999 and 2002. After the last of these, NASA plan to operate the
telescope in a lower cost mode until retrieval by a Shuttle in 2010.
How to optimise the scientific programme of HST during this period will
be studied by a committee, "The Second Decade", of about 15 senior
scientists, including Europeans, chaired by Robert Brown at STScI.

The idea for an NGST with an aperture greater than 4m and a primary
wavelength coverage from 1 to 5 microns, came from the "HST and Beyond"
committee, chaired by Alan Dressler, which reported in 1996.
Feasibility studies in the US of NGST concepts up to 8m in aperture
rapidly built momentum and are described in the 1997 report: "NGST -
Visiting a time when galaxies were young" edited by Peter Stockman from
STScI. Current planning suggests a launch for NGST around 2007.

Following a formal invitation by NASA to cooperate in studies related
to the Origins programme, ESA formed an NGST Task Group which, during
mid 1997, recommended that studies be initiated in Europe to examine
specifically the technical aspects of using a 3AU orbit, multi-object
and integral field spectroscopy in the 1-5 micron region, and
independent concepts for an 8m class telescope and payload.

In January, ESA solicited "Letters of Interest" from scientists and
industry willing to participate in the last two of these studies (the
orbit will be studied by ESA itself) and, following receipt of these in
mid-February, is issuing "Invitations to Tender". An International
Workshop, "The Next Generation Space Telescope: Science Drivers and
Technological Challenges", has been organised in Liege (accent!) from
15-18 June this year and will act as a forum for European astronomers
and industry.

If funding can be found to convert these studies into a major
contribution to the NGST project, the prospects for European access to
large UV through IR telescopes in space look excellent for the next
decade or so. One possibility for doing this is through one of the
'flexi-missions' foreseen in the ESA long term science plan 'Horizon
2000+' with the decision taken a few years from now.

As has been so convincingly shown by the complementarity between the
HST and Keck 10m telescopes in, for example, the Hubble Deep Field
investigations, the synergy between groundbased and space telescopes
greatly amplifies the scientific value of both. With the heavy
investment in large groundbased telescopes by Europe, the prospect of
future restricted access to space telescopes becomes scientifically
unthinkable.

Bob Fosbury is at the Space Telescope - European Coordinating Facility
in Munich.
 
Useful web sites for HST and NGST 

ST-ECF:            http://ecf.hq.eso.org/ 
STScI:             http://www.stsci.edu/ 
NGST (NASA):       http://ngst.gsfc.nasa.gov/ 
Origins (NASA):    http://origins.jpl.nasa.gov/
HST second decade: http://sso.stsci.edu/second_decade/