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Draft document on dynamic scheduling - Tony Wong, ATNF
12 Nov 2001
======================================================

Dynamic scheduling adjusts the observing schedule in real time according
to system status and observing conditions. For example:
1) Point source projects are favoured when antennas are missing
2) Millimetre projects are favoured when weather is good

Currently the Compact Array is not well suited for dynamic scheduling,
since many CAOBS commands cannot be executed within SCHED files.
There are also observing-related tasks like CACAL, CATAG and SPD which
must be run outside of CAOBS. Thus, a substantial software effort
will be required to allow automated observing.

The advantages of dynamic scheduling are clear: the most efficient
possible use of the array. Indeed, the experience of the past year
suggests that without dynamic scheduling, very little useful
millimetre science will be possible at Narrabri.

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A PROPOSAL FOR IMPLEMENTING DYNAMIC SCHEDULING AT ATCA
------------------------------------------------------

Observing:
----------

1. Proposers will still be responsible for creating schedule files.
They may be present at Narrabri if they wish, and will certainly be
encouraged to come if they are unfamiliar with the instrument, but
they will have no control over time allocation.

2. The DA is responsible for making sure the scheduling software is
working. He/she is not responsible for ensuring that schedule files
are properly written, although help should be provided when practical.
If a schedule file has errors and cannot be observed, and the proposer
is not present at Narrabri or monitoring observations remotely, then
another project will be observed instead.

3. Because the responsibilities of the DA are increased, it may be
sensible to have 2 DA's at any given time, with alternate shifts.

4. Certain (technically difficult) projects may be designated as
"interactive only", i.e. they may still be dynamically scheduled, but
the proposer must observe the project either at Narrabri or remotely.
For dates on which the PI promises in advance to be "on call", and on
which observing conditions are appropriate, the software simply
relinquishes control of the array to the observer. On other dates,
the project will not be observed.

5. Certain (high-priority cm) projects may be designated "fixed
allocation", i.e. the observing times are fixed and cannot be
overridden. Obviously the number of such projects should be
minimised for dynamic scheduling to be effective.

6. Traditional, fixed-queue scheduling may remain for array
configurations in which there are no high-frequency proposals.
However, to reduce confusion, these observations would still be
handled by the scheduling software, unless designated "interactive."


Software Requirements:
----------------------

1. Automatic source selection: User should be able to specify LST
ranges for sources and prioritize calibrators. In other words, they
should be able to create a schedule that is robust against changes
to starting times/dates.

2. Hands-free operation: CACAL should not need to be run
interactively. Flux or bandpass calibrators should be included in
the same schedule file as the source and phase calibrator.


Decision making:
----------------

Project requirements will depend on:
* Frequency
* Desired system temperature
* Desired rms phase (e.g., using phase referencing or selfcal)

The decision on whether to stop observing current project will depend on:
* Project requirements
* How often the observing conditions are re-assessed
* Minimum time a project must be allowed to run.

The decision on which project to observe next will depend on:
* Project requirements
* Priority
* Number of allocated hours completed
* HA ranges completed and needed


Social impact:
--------------

Implementation of dynamic scheduling will reduce the number of
visitors to Narrabri. This can be compensated to some extent by
encouraging first-time PIs to be present at the array and doubling the
number of DA's. We might also increase the quality of staff-scientist
(and scientist-scientist) interactions by having an annual science
festival on-site.

Dynamic scheduling may also reduce the number of visitors to
Australia. However, the greatest impact will likely be on repeated
visits by overseas Australians or others familiar with the ATCA.
Other foreigners would probably want hands-on experience with the
instrument, or would ask a local collaborator do the observing anyway.
Ultimately, the increased productivity of ATCA should lead to better
science and hence more visitors.

Dynamic scheduling may increase the number of overseas proposals from
those who cannot afford to visit Australia for observations. This
would increase the visibility of ATCA, foster more collaborations with
Australian astronomers, and raise the standard of ATCA projects.


Implementation:
---------------

Phase One (2002) will involve continuously monitoring observing
conditions and running a dynamic scheduling program in simulation
mode. An ATNF-led committee will meanwhile develop software for
dealing efficiently with dynamically scheduled observations.
We will then assess the results of the simulation in mid-2002.

In Phase Two (starting in mid to late 2002), the array will actually be
scheduled dynamically, at least in certain array configurations.

In practice, we might expect the balance between fixed, interactive
observing and dynamic scheduling will shift gradually, as users become
more accustomed to the new system.