QUESTION:
Does just the United States use the HST or is it an international tool?  How
do astronomers from other nations get to use the HST?

ANSWER from Elyse Wagner on June 13, 1996:
Scientists of any nationality or affiliation can propose for HST observing
time and may request to use any of the scientific instruments onboard.  Members
of the international scientific community respond to the "Hubble Space
Telescope Call for Proposals" that is sent to them every year, usually in
June.

There is an agreement between NASA and the European Space Agency (ESA) that
states "that a minimum of 15% of HST observing time (on the average over the
lifetime of the HST project) will be allocated to scientists from ESA member
states (Hubble Space Telescope Call for Proposals Pg. 12)."

There is a Telescope Allocation Committee (TAC), of about 70 scientists from
all over the world, that reviews the proposals and judges them according to
scientific merit.  The TAC selects the proposals that it feels are the best
use of HST observing time.