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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
Editors: R. Albrecht, R. N. Hook and H. A. Bushouse

Nightly Scheduling of ESO's Very Large Telescope

A. M. Chavan, G. Giannone1 and D. Silva
European Southern Observatory, Karl Schwarzschild Str-2, D-85748, Garching, Germany

T. Krueger, G. Miller
Space Telescope Science Institute, Baltimore, MD 21218, USA

1Serco GmbH, at the European Southern Observatory



A key challenge for ESO's Very Large Telescope (VLT) will be responding to changing observing conditions in order to maximize the scientific productivity of the observatory. For queued observations, the nightly scheduling will be performed by staff astronomers using an Operational Toolkit. This toolkit consists of a Medium and a Short-Term Scheduler (MTS and STS), both integrated and accessible through a common graphical user interface. The MTS, developed by ESO, will be used to create candidate lists of observations (queues) based on different scheduling criteria. There may be different queues based on ``seeing'', or priority, or any other criteria that are selected by the staff astronomer. An MTS queue is then selected and supplied to the STS for detailed nightly scheduling. The STS uses the Spike scheduling engine, which was originally developed by STScI for use on the Hubble Space Telescope.


1. Introduction

  An Operational Toolkit (OT) is being developed at ESO as a front-end component of the Data Flow System (DFS). It is designed to react quickly to evolving weather, taking the best advantage of the current observing conditions. It will enable the observers to take the most valuable science data at any given time, with the goal of maximizing the observatory's scientific return. While it is aimed at supporting service mode operations, the toolkit can also be used by Visiting Astronomers.

The toolkit will make all observation preparation data available to the operator, and will allow the definition of queues and timelines of Observation Blocks (OBs). The OT will also interface to the VLT Control Software, providing observation instructions and recording OB-related run-time events. Finally, the toolkit will act as the interface to the OB repository for the whole Data Flow System.

2. Operating the front end of the Data Flow System

  Observation Blocks are modular objects, joining target information with the description of the technical setup of the observation. OBs are created by investigators using another DFS front-end tool, the Phase II Proposal Preparation System (P2PP; Chavan 1996), then checked into the ESO repository, where they are verified for correctness by ESO.

The operations team then uses the Operational Toolkit to browse the repository and build queues, based on object visibility, expected observing conditions, and user-defined scheduling constraints. A queue is a subset of the available OBs: it usually covers one to a few nights of observation, and several queues can be defined for the same night (e.g., based on different expectations of weather, or equipment availability). An OB can belong to more than one queue at a time.

Later, as the observing night begins and progresses, the staff observer can switch back and forth among the available queues, and build timelines (observing plans) for each individual queue. Timelines are based on the current weather conditions and OB priority, and can be built on several possible scheduling strategies.

Events originating from the VLT Control Software or other DFS subsystems -- such as a change in the current seeing conditions, the termination of an OB, an instrument configuration change, or a failure while reducing the science frames -- are also received by the OT, and fed back into the scheduling process and the OB repository.

3. Architecture of the Operational Toolkit

  Users of the OT will see a single graphical user interface, and access OT functionalities through a unified set of commands and display widgets. However, several independent components will cooperate behind the scenes to provide such features, as shown in Figure 1.
Figure 1: System architecture of the OT

4. Perspective

  A version of the MTS has been in operations at ESO's New Technology Telescope (NTT) in La Silla since the beginning of 1997, including a large fraction of the above listed features; feedback from early users proved invaluable in shaping the tool's behavior and looks. The first prototype of the STS was released in November 1997 for in-house testing, with field tests (at the NTT) foreseen for the beginning of 1998. We plan to have a fully operational OT by the time that service observing at the VLT starts.


Chavan, A. M. and Albrecht, M. 1997, in Astronomical Data Analysis Software and Systems VI, ASP Conf. Ser., Vol. 125, eds. Gareth Hunt and H. E. Payne (San Francisco, ASP), 367

Johnston, M. and Miller, G. 1994, in Intelligent Scheduling, ed. M. Zweben & M. S. Fox (San Francisco, Morgan Kaufmann), 391

© Copyright 1998 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA

Next: VLT Data Quality Control
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