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Block Scheduling of 1.5-m Telescope (1Sep95)
(from CTIO, NOAO Newsletter No. 43, September 1995)

In scheduling next semester, we have resumed enforcing a policy that
has been "on the books" for over a decade, namely limiting the number
of instrument changes on the 1.5-m telescope. Instrument changes
represent one of the primary burdens on the mountain staff and can also
take significant amounts of scientific staff time. Furthermore,
statistics show that the percentage of down time on the first night of
an instrument run is higher than on subsequent nights. Since we stopped
enforcing the policy, the number of instrument changes on the 1.5-m
telescope grew to be equal to the number of changes on the 4-m
telescope, and in some semesters even exceeded the number of 4-m
changes.

                             Implementation

What we have done is limit the total number of changes on the 1.5-m
telescope during the semester to 15. This corresponds to one change at
each quarter moon, plus a couple more for flexibility. When the actual
schedule is made up, proposals are scheduled by moving down the Time
Allocation Committee's ranking until the 15 changes are used up, at
which point only proposals that require no further instrument changes
are scheduled. This is done while trying to block-schedule the use of
any given instrument.

The main effect of the rules is that little-used instruments tend not
to be scheduled, since one needs one better-than-average proposal to
create a block of time with a given instrument. On the 1.5-m, these
instruments turned out to be ASCAP (single channel photometer), the
Bench-Mounted Echelle, and the IR Spectrometer.

Visitor instruments are counted as an instrument change as well, on the
same basis as facility instruments. That is, they are neither
discriminated against nor given preference.

                              Implications

If you are applying for time on the 1.5-m, with any instrument, make
sure you provide as wide a range of acceptable dates as possible.
Also, in the case of conferences, teaching, and social engagements,
you should distinguish between dates you cannot observe and dates you
prefer not to observe. In the absence of the distinction, the
scheduler has to assume that all such dates are unusable, even if this
means that you will not get telescope time. If you are requesting time
with a less-used instrument, the best strategy is to write a really
good proposal. In order to be assured of getting time, you need to be
in the top third of the proposals.

Jay Elias, Malcolm Smith

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