Klaus Banse

VLT Data Flow System: from concepts to operations

In order to realize the optimal scientific return from the VLT, ESO has undertaken to develop an end-to-end data flow system from proposal entry to science archive. The VLT Data Flow System (DFS) is being designed and implemented by the ESO Data Management and Operations Division in collaboration with VLT and Instrumentation Divisions. Tests of the DFS started in October 1996 on ESOs New Technology Telescope. Since then, prototypes of the Phase 2 Proposal Entry System, VLT Control System Interface, Data Pipelines, On-line Data Archive, Data Quality Control and Science Archive System have been tested. Several major DFS components have been run under operational conditions since February 1997. This paper describes the current status of the VLT DFS, the technological and operational challenges of such a system and the planing for VLT operations beginning in early 1999.

Data reduction pipelines for the Very Large Telescope

With the completion of the first generation instrumentation set on the Very Large Telescope, a total of eleven instruments are now provided at the VLT/VLTI for science operations. For each of them, ESO provides automatic data reduction facilities in the form of instrument pipelines developed in collaboration with the instrument consortia. The pipelines are deployed in different environments, at the observatory and at the ESO headquarters, for on-line assessment of observations, instruments and detector monitoring, as well as data quality control and products generation. A number of VLT pipelines are also distributed to the user community together with front-end applications for batch and interactive usage. The main application of the pipeline is to support the Quality Control process. However, ESO also aims to deliver pipelines that can generate science ready products for a major fraction of the scientific needs of the users. This paper provides an overview of the current developments for the VLT/VLTI next generation of instruments and of the prototyping studies of new tools for science users.

Quality control systems for the Very Large Telescope

The operational applications needed to quantitatively assess VLT calibration and science data are provided by the VLT Quality Control system (QC). In the Data Flow observation life-cycle, QC relates data pipeline processing and observation preparation. It allows the ESO Quality Control Scientists of the Data Flow Operations group to populate and maintain the pipeline calibration database, to measure and verify the quality of observations, and to follow instrument trends. The QC system also includes models allowing users to predict instrument performance, and the Exposure Time Calculators are probably the QC applications most visible to the astronomical community. The Quality Control system is designed to cope with the large data volumes of the VLT, the geographical distribution of data handling, and the parallelism of observations executed on the different unit telescopes and instruments.

The common pipeline library: standardizing pipeline processing

The European Southern Observatory (ESO) develops and maintains a large number of instrument-specific data processing pipelines. These pipelines must produce standard-format output and meet the need for data archiving and the computation and logging of quality assurance parameters. As the number, complexity and data-output-rate of instrument increases, so does the challenge to develop and maintain the associated processing software. ESO has developed the Common Pipeline Library (CPL) in order to unify the pipeline production effort and to minimise code duplication. The CPL is a self-contained ISO-C library, designed for use in a C/C++ environment. It is designed to work with FITS data, extensions and meta-data, and provides a template for standard algorithms, thus unifying the look-and-feel of pipelines. It has been written in such a way to make it extremely robust, fast and generic, in order to cope with the operation-critical online data reduction requirements of modern observatories. The CPL has now been successfully incorporated into several new and existing instrument systems. In order to achieve such success, it is essential to go beyond simply making the code publicly available, but also engage in training, support and promotion. There must be a commitment to maintenance, development, standards-compliance, optimisation, consistency and testing. This paper describes in detail the experiences of the CPL in all these areas. It covers the general principles applicable to any such software project and the specific challenges and solutions, that make the CPL unique.

VLT Data Flow System: the NTT prototype experience

The data flow system (DFS) for the ESO VLT provides a global system approach to the flow of science related data in the VLT environment. It includes components for preparation and scheduling of observations, archiving of data, pipeline data reduction and quality control. Standardized data structures serve as carriers for the exchange of information units between the DFS subsystems and VLT users and operators. Prototypes of the system were installed and tested at the New Technology Telescope. They helped us to clarify the astronomical requirements and check the new concepts introduced to meet the ambitious goals of the VLT. The experience gained from these tests is discussed.