August 13, 1999,  2:45pm


We would like to bring to your attention a new opportunity
with Cycle 9 Target Of Opportunity (TOO) proposals.

HST observers are advised that STScI is endeavoring to reduce the
turnaround time for activated TOO proposals that require such fast
response and are of the highest scientific importance.  The Cycle 9
Call for Proposals states that we can achieve turnaround times as
short as 2-5 days, where necessary to the science.  We are now working
with the HST Project at GSFC to identify ways to reduce this interval,
possibly to as short as half a day. This would require considerable
changes to the current commanding procedures, and would be undertaken
only if resources permit and if there is strong scientific pressure
from highly rated Cycle 9 proposals that demonstrate the need for this
capability. We therefore encourage the community to identify exciting
HST science that would be enabled by a less than 24-hour TOO
turnaround, and to submit Cycle 9 proposals accordingly.

In order to reflect the true cost of such fast TOOs, and to enable the
TAC to weigh science and resources appropriately, the TAC will be
advised that TOO proposals requesting a less than 24-hour turnaround
will incur a fixed overhead of 15 orbits per activation, which is the
average expected down-time due to this very fast TOO response.