Evolution of the HST Proposal Selection
Process: Changes for Cycle 9
June 30, 1999
Abstract
For Cycle 9 the Science Program Selection
Office (SPSO) has changed the selection process to ensure that HST will
continue to perform the best possible science with the best return for the
astronomical community. This report summarizes the changes to the selection
process and offers suggestions on writing an effective proposal that
accounts for these changes.
Introduction
Since Cycle 1 the number of submitted
proposals has more than doubled (to over 1000 proposals in Cycle 8), and
the fundamental structure of panels and the TAC has been scaled up
commensurately, with little structural change.
The TAC's primary responsibility has always
been to establish priorities among scientific disciplines, but now that it
has doubled in size -- to more than 20 people in the last cycle -- the kind
of in-depth, focused discussion needed to set these priorities has become
increasingly difficult. Also, in past cycles the proposal selection process
has worked against larger programs, which are increasingly seen as a vital
part of the HST program.
Changes in the Selection Process for
Cycle 9
To address these concerns and ensure that
HST will continue to produce the best possible science for the astronomical
community, the Science Program Selection Office has changed the selection
process. The major changes for Cycle 9 are:
- Fewer panels:
With more orbits to allocate, each panel will have more flexibility,
especially to approve the somewhat larger proposals.
- Fewer scientific categories:
Panels will be dedicated to very broad science topics, perhaps as few as
five -- one for solar system, two for Galactic science, two for
extragalactic science. Hence it will be essential for proposers to
describe the impact of the proposed science on astronomy in general (i.e.
the big picture). Science balance among subtopics, previously determined
by the TAC, will be achieved within the selection panels. This approach,
long practiced in the high-energy astrophysics community, also simplifies
the avoidance of conflicts of interest.
- TAC focus on large programs:
The main role of the TAC will be to approve the best large programs (100
r more orbits), for which they will have up to 1,000 orbits to allocate.
This means the TAC could approve 2 to 3 programs averaging 300 orbits each.
With scientific balance achieved within the broad selection panels, the TAC
is not expected to address the small proposals at all.
Large proposals will therefore have an excellent chance of success, and
are strongly encouraged.
- Incentives for medium proposals:
Starting in Cycle 7, there have been "orbit subsidies" to
encourage panels to approve medium proposals (more than 30 orbits). This
meant that a fraction of the orbit request was not charged against the panel
quota. This system worked reasonably well, leading in Cycle 8 to an average
acceptance rate that was independent of proposal size. For cycle 9 the
subsidized fraction will increase with size. We will adjust the algorithm
from one Cycle to the next to try to keep the oversubscription rate
approximately the same independent of the size of the proposal (under the
assumption that quality is independent of size). We strongly encourage
proposers to ask for the observing time they need to achieve their
scientific goals, without strategizing in response to perceived notions
of advantages or disadvantages with respect to size.
- Allocation of coordinated
Chandra/AXAF time: Proposals of a fundamentally multi-wavelength
nature, requiring both HST and the Chandra X-ray Observatory (AXAF), can
be submitted to either the present HST Cycle 9 or the next AXAF review.
By agreement with the AXAF Science Center (ASC), STScI will be able to
award up to 400 kiloseconds of AXAF observing time, and similarly the ASC
will be able to award up to 100 orbits of HST time, to highly-rated
proposals meeting the multi-wavelength criterion.
Suggestions for Proposers
These revised procedures should lead to a
stronger, better HST program. Here are some suggestions to keep in mind
when writing a proposal.
- Proposers must stress why their
science is critically important and why it requires HST. The
panelists reading the proposals will have a broader expertise -- and there
will be fewer specialists in the particular topic -- so more introductory
material may be necessary.
- Larger proposals are strongly
encouraged and are expected to be at least as successful as
small proposals. The oversubscription rate for HST hovers around 5:1, so
it is never easy to get time but the odds of success are the same for
proposals over 100 orbits and those under 10 orbits. So if you have
a project that requires a large investment of HST observing time, do not
hesitate to propose it.
- Science requiring both HST and
Chandra/AXAF can be proposed to only one Observatory, eliminating
the "double jeopardy" that unfairly disadvantages
multi-wavelength science. Proposals should be submitted to the observatory
that represents the prime science, i.e, where the predominant panel
expertise (IR/opt/UV vs. X-ray) is most relevant.
- Proposers should write clearly.
Reviewers have always had a difficult job reading ~100 or so proposals
carefully. In Cycle 9, that number may be doubled. So take the time to write
clearly and coherently, explaining what you want to do and why. This is good
proposal strategy whatever the review process may be.
As experience with these new procedures
accumulates, we will continue to fine-tune and improve the process. Our
primary goal remains to select the best possible science program for HST,
with an appropriate scientific balance.