Today the scientific community is facing an increasing complexity of the scientific projects, from both a technological and a management point of view. The reason for this is in the advance of science itself, where new experiments with unprecedented levels of accuracy, precision and coverage (time and spatial) are realised. Astronomy is one of the fields of the physical sciences where a strong interaction between the scientists, the instrument and software developers is necessary to achieve the goals of any Big Science Project. The Cherenkov Telescope Array (CTA) will be the largest ground-based very high-energy gamma-ray observatory of the next decades. To achieve the full potential of the CTA Observatory, the system must be put into place to enable users to operate the telescopes productively. The software will cover all stages of the CTA system, from the preparation of the observing proposals to the final data reduction, and must also fit into the overall system. Scientists, engineers, operators and others will use the system to operate the Observatory, hence they should be involved in the design process from the beginning. We have organised a workgroup and a workflow for the definition of the CTA Top Level Use Cases in the context of the Requirement Management activities of the CTA Observatory. Scientists, instrument and software developers are collaborating and sharing information to provide a common and general understanding of the Observatory from a functional point of view. Scientists that will use the CTA Observatory will provide mainly Science Driven Use Cases, whereas software engineers will subsequently provide more detailed Use Cases, comments and feedbacks. The main purposes are to define observing modes and strategies, and to provide a framework for the flow down of the Use Cases and requirements to check missing requirements and the already developed Use-Case models at CTA sub-system level. Use Cases will also provide the basis for the definition of the Acceptance Test Plan for the validation of the overall CTA system. In this contribution we present the organisation and the workflow of the Top Level Use Cases workgroup.
The X-shooter data reduction pipeline, as part of the ESO-VLT Data Flow System, provides recipes for Paranal
Science Operations, and for Data Product and Quality Control Operations at Garching headquarters. At Paranal,
it is used for the quick-look data evaluation. The pipeline recipes can be executed either with EsoRex at the
command line level or through the Gasgano graphical user interface. The recipes are implemented with the ESO
Common Pipeline Library (CPL).
X-shooter is the first of the second generation of VLT instruments. It makes possible to collect in one shot
the full spectrum of the target from 300 to 2500 nm, subdivided in three arms optimised for UVB, VIS and NIR
ranges, with an efficiency between 15% and 35% including the telescope and the atmosphere, and a spectral
resolution varying between 3000 and 17,000. It allows observations in stare, offset modes, using the slit or an
IFU, and observing sequences nodding the target along the slit.
Data reduction can be performed either with a classical approach, by determining the spectral format via
2D-polynomial transformations, or with the help of a dedicated instrument physical model to gain insight on the
instrument and allowing a constrained solution that depends on a few parameters with a physical meaning.
In the present paper we describe the steps of data reduction necessary to fully reduce science observations in
the different modes with examples on typical data calibrations and observations sequences.
We present a project aimed at establishing a set of 12 spectro-photometric standards over a wide wavelength range from
320 to 2500 nm. Currently no such set of standard stars covering the near-IR is available. Our strategy is to extend the
useful range of existing well-established optical flux standards into the near-IR by means of integral field spectroscopy
with SINFONI at the VLT combined with state-of-the-art white dwarf stellar atmospheric models. As a solid reference,
we use two primary HST standard white dwarfs. This ESO "Observatory Programme" has been collecting data since
February 2007. The analysis of the data obtained in the first year of the project shows that a careful selection of the
atmospheric windows used to measure fluxes and the stability of SINFONI make it possible to achieve an accuracy of 3-
6% depending on the wavelength band and stellar magnitude, well within our original goal of 10% accuracy. While this
project was originally tailored to the needs of the wide wavelength range (320-2500 nm) of X-shooter on the VLT, it will
also benefit any other near-IR spectrographs, providing a huge improvement over existing flux calibration methods.
We have developed a physical model of the VLT 2nd generation instrument X-shooter for use in wavelength
calibration. We describe here the model concept, its use during the development of the data reduction software
and the initial alignment of the spectrograph in the laboratory and the optimisation of the model to fit early
We present the current state of the Data Reduction Software (DRS) being developed at APC, Paris Observatory,
Amsterdam University and ESO for the X-shooter echelle spectrograph. X-shooter is the first VLT second
generation instrument, which will have its first light during the fall of the current year and will be available to
the astronomical community starting April 2009. The DRS will be fully integrated in the ESO VLT data flow
environment and it will use the ESO Common Pipeline Library. X-shooter data have two main characteristics,
on the one hand the exceptionally wide band (0.3 - 2.4 micron) covered in a single exposure, and on the other
hand the spectral format with highly curved orders and tilted lines. After a brief description of the reduction
process, the main results obtained up to now on simulated and laboratory data are reported. In particular the
precision of wavelength calibration and sky subtraction are discussed.
We present the Data Reduction Software (DRS) being developed at APC, Paris Observatory, Amsterdam University
and ESO for the X-shooter echelle spectrograph. X-shooter is the first VLT second generation instrument,
expected to be operational in 2008. The DRS will be fully integrated in the ESO VLT system and it will use the
ESO Common Pipeline Library. We discuss the data reduction related to slit and IFU observations. X-shooter
data have two main characteristics, on the one hand the exceptionally wide band (0.3-2.4 μm) covered in a single
exposure, and on the other hand the spectral format with highly curved orders and tilted lines. The reduction
process is described and the critical issues related to the above characteristics, notably the sky subtraction, the
optimal extraction, and the construction of 1D/2D/3D output products, are addressed. Some aspects of the
spectrophotometric calibration are also discussed.