KEYWORDS: Quality control, Calibration, Equipment, Data processing, Data archive systems, Large telescopes, Data storage, Data acquisition, Process control, Signal processing
We present the tool qcFlow designed to handle the quality control process at ESO’s LaSilla-Paranal Observatory in the ELT era. We highlight the top-level requirements and the way they are implemented in the tool. We also describe the supporting data flow software that allows the quality control process for a large suite of different astronomical instruments to be efficient and automated to a high degree.
The GRAVITY instrument installed at VLTI uses differential fibered delay lines to spatially filter the incoming wavefronts and accurately control the optical path difference between the Fringe Tracker (FT) and Scientific Detector (SC) parts of the instrument. On top of the differential dispersion occurring in the air, the chromatic dispersion introduced by these fibers impacts the real time performances of the fringe tracker by generating a second-order chromatic phase shift. Moreover, differential dispersion also affects GRAVITY dual-feed measurements that require a length adjustment of both FT and SC fibers. In this contribution, we show how chromatic dispersion can be corrected both in the fringe tracker real-time control as well as in the astrometric data reduction.
A comparison of the FWHM of standard stars observed with VISIR, the mid-IR imager and spectrometer at ESO's VLT, with expectations for the achieved mid-IR Image Quality based on the optical seeing and the wavelength-dependence of atmospheric turbulence, shows that for N-band data (7{12μm), VISIR realizes an image quality about 0.1" worse than expected based on the optical seeing. This difference is large compared to the median N-band image quality of 0.3-0.4" achieved by VISIR. We also note that other mid-IR groundbased imagers show similar image quality in the N-band. We attribute this difference to an under-estimate of the effect of the atmosphere in the mid-IR in the parameters adopted so far for the extrapolation of optical to mid-IR seeing. Adopting an average outer length-scale of the atmospheric turbulence above Paranal L0 = 46 m (instead of the previously used L0 = 23 m) improves the agreement between predicted and achieved image quality in the mid-IR while only having a modest effect on the predicted image quality at shorter wavelengths (although a significant amount of scatter remains, suggesting that l0 may not be constant in time). We therefore advocate adopting L0 = 46 m for the average outer length scale of atmospheric turbulence above Cerro Paranal for real-time scheduling of observations on VLT UT3 (Melipal).
The high multiplex advantage of VIMOS, the VLT visible imager and multi-object/integral-field spectrometer, makes it
a powerful instrument for large-scale spectroscopic surveys of faint sources. Following community input and
recommendations by ESO's Science and Technology Committee, in 2009 it was decided to upgrade the instrument. This
included installing an active flexure compensation system and replacing the detectors with CCDs that have a far better
red sensitivity and less fringing. Significant changes have also been made to the hardware, maintenance and operational
procedures of the instrument with the aim of improving availability and productivity. Improvements have also been
made to the data reduction pipeline. The upgrade will end in 2012 and the results of the program will be presented here.
CRIRES is a cryogenic, pre-dispersed, infrared Echelle spectrograph designed to provide a nominal resolving
power ν/Δν of 105 between 1000 and 5000 nm for a nominal slit width of 0.2". The CRIRES installation at
the Nasmyth focus A of the 8-m VLT UT1 (Antu) marks the completion of the original instrumentation plan
for the VLT. A curvature sensing adaptive optics system feed is used to minimize slit losses and to provide 0.2"
spatial resolution along the slit. A mosaic of four Aladdin InSb-arrays packaged on custom-fabricated ceramic
boards has been developed. It provides for an effective 4096 × 512 pixel focal plane array to maximize the free
spectral range covered in each exposure. Insertion of gas cells is possible in order to measure radial velocities with
high precision. Measurement of circular and linear polarization in Zeeman sensitive lines for magnetic Doppler
imaging is foreseen but not yet fully implemented. A cryogenic Wollaston prism on a kinematic mount is already
incorporated. The retarder devices will be located close to the Unit Telescope focal plane. Here we briefly recall
the major design features of CRIRES and describe the commissioning of the instrument including a report of
extensive testing and a preview of astronomical results.
KEYWORDS: Sensors, Calibration, Telescopes, Data processing, Imaging spectroscopy, Temperature metrology, Large telescopes, Observatories, Spectrographs, Process control
Quality Control (QC) of calibration and science data is an integral part of the data flow process for the ESO
Very Large Telescope (VLT) and has guaranteed continuous data quality since start of operations. For each
VLT instrument, dedicated checks of pipeline products have been developed and numerical QC parameters to
monitor instrumental behavior have been defined. The advent of the survey telescopes VISTA and VST with
multi-detector instruments imposes the challenge to transform the established QC process from a detector-by-detector
approach to operations that are able to handle high data rates and guarantee consistent data quality.
In this paper, we present solutions for QC of multi-detector instruments and report on experience with these
concepts for the operational instruments CRIRES and VIMOS. Since QC parameters scale with the number of
detectors, we have introduced the concept of calculating averages (and standard deviations) of parameters across
detectors. This approach is a powerful tool to evaluate trends that involve all detectors but is also able to detect
outliers on single detectors. Furthermore, a scoring system has been developed which compares QC parameters
for new products to those from already existing ones and gives an automated judgment about data quality. This
is part of the general concept of information on demand: detailed investigations are only triggered on a selected
number of products.
By 2010, the Paranal Observatory will host at least 15 instruments. The continuous increase in both the complexity and
quantity of detectors has required the implementation of novel methods for the quality control of the resulting stream of
data. We present the new and powerful concept of scoring which is used both for the certification process and the Health
Check monitor. Scoring can reliably and automatically measure and assess the quality of arbitrarily amounts of data.
The purpose of the recent installation of eight interference filters in UVES is to isolate certain echelle orders to allow the use of a maximal slit length of 30". The typical decker height of the spectrograph slit for science operations is usually of the order of 10-12". The central wavelength of each filter was chosen to permit observations of the most important emission lines in extended objects. We discuss the performance of these filters and show the first science images obtained with the test run.
The performance of all scientific instruments of the Very Large Telescope (VLT) is monitored by the Quality Control (QC) Group of the European Southern Observatory. Basic goals are to detect instrumental failures on a short time basis and to evaluate and detect long-term trends. The QC process mainly involves pipeline-produced calibration products and is set up on a file by file
basis. This implies that currently each detector or channel of an instrument is checked separately. All operational VLT instruments have a low number of detectors but with the advent of multi-detector instruments like OmegaCAM and VISTA, which have up to 32 individual detectors, this approach becomes unfeasible. In this paper, we present solutions for this problem for the VLT instrument VIMOS. With four detectors operating simultaneously, VIMOS can be regarded as a test bed for studying new QC concepts which can be implemented for other instruments with higher multiplicity.
Four years after its announcement at SPIE, FLAMES, the VLT fibre facility, has been completed, integrated into the VLT observatory and commissioned. It has been in operation since February 2003. More than 250000 scientific (single) spectra have been obtained, which have enabled the on-sky performance of the instrument to be compared to the predictions. We show that in several relevant aspects the real instrument significantly outperforms the specified astronomical performance. Some of the early scientific results are finally presented.
UVES-fiber is part of the FLAMES instrument mounted on the 8.2m
Kueyen Telescope (UT2) of the ESO VLT. Up to eight single object fibers can be linked from the FLAMES focus to the red arm of the echelle spectrograph UVES. Science and calibration data are pipeline-processed by the Data Flow Operations group of ESO. Parameters to monitor the performance of the instrument are routinely extracted from calibration frames, stored into a database, and monitored over time. In addition to the Quality Control parameters already present for UVES in slit mode, several specific procedures had to be added in
order to monitor the performance in the multi-object case. Particular attention is required for the positioning of the fibers on the detector and the transmission of the fibers. In this paper, we present details of the Quality Control process for UVES-fiber and results from the first year of operations.
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