Lars Lundin

VISIR upgrade overview and status

We present an overview of the VISIR upgrade project. VISIR is the mid-infrared imager and spectrograph at ESO’s VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan is based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array (Raytheon) which has been carefully characterized in ESO’s IR detector test facility (modified TIMMI 2 instrument). A prism spectroscopic mode will cover the N-band in a single observation. New scientific capabilities for high resolution and high-contrast imaging will be offered by sub-aperture mask (SAM) and phase-mask coronagraphic (4QPM/AGPM) modes. In order to make optimal use of favourable atmospheric conditions a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012 it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations and that VISIR was not ready to go back to science operations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise (ELFN). It is inherent to the design chosen for this detector and can’t be remedied by changing the detector set-up. Since this is a form of correlated noise its impact can be limited by modulating the scene recorded by the detector. We have studied several mitigation options and found that faster chopping using the secondary mirror (M2) of the VLT offers the most promising way forward. Faster M2 chopping has been tested and is scheduled for implementation before the end of 2014 after which we plan to re-commission VISIR. In addition an upgrade of the IT infrastructure related to VISIR is planned in order to support burst-mode operations. The upgraded VISIR will be a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It will offer synergy with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey work (e.g. VISTA, WISE). In addition it will bring confirmation of the technical readiness and scientific value of several aspects of potential mid-IR instrumentation at Extremely Large Telescopes.

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.

ERIS: preliminary design phase overview

The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the Max- Planck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio Astrofisico di Arcetri and will offer 1 - 5 μm imaging and 1 - 2.5 μm integral field spectroscopic capabilities with a high Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’ patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace, with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI upgrade strategy, which is part of the ERIS development plan and the overall project timeline.

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.

Upgrade of VISIR the mid-infrared instrument at the VLT

The European Southern Observatory (ESO) is preparing to upgrade VISIR, the mid-IR imager and spectrograph at the VLT. The project team is comprised of ESO staff and members of the original consortium that built VISIR: CEA Saclay and ASTRON. The goal is to enhance the scientific performance of VISIR and to facilitate its use by the ESO community. In order to capture the needs of the user community, we collected input from the users by means of a webbased questionnaire. In line with the results of the internal study and the input from the user community, the upgrade plan calls for a combination measures: installation of improved hardware, optimization of instrument operations and software support. The limitations of the current detector (sensitivity, cosmetics, artifacts) have been known for some time and a new 1k x 1k Si:As Aquarius array (Raytheon) will be the cornerstone of the VISIR upgrade project. A modified spectroscopic mode will allow covering the N-band in a single observation. Several new scientific modes (e.g., polarimetry, coronagraphy) will be implemented on a best effort basis. In addition, the VISIR operational scheme will be enhanced to ensure that optimal use of the observing conditions will be made. Specifically, we plan to provide a means to monitor precipitable water vapour (PWV) and enable the user to specify it as a constraint set for service mode observations. In some regions of the mid-IR domain, the amount of PWV has a fundamental effect on the quality of a given night for mid-IR astronomy. The plan also calls for full support by ESO pipelines that will deliver science-ready data products. Hence the resulting files will provide physical units and error information and all instrumental signatures will have been removed. An upgraded VISIR will be a powerful instrument providing diffraction-limited performance at an 8-m telescope. Its improved performance and efficiency as well as new science capabilities will serve the needs of the ESO community but will also offer synergy with various other facilities such as ALMA, JWST, VLTI and SOFIA. A wealth of targets for detailed study will be available from survey work done by VISTA and WISE. Finally, the upgraded VISIR will also serve as a pathfinder for potential mid-IR instrumentation at the European Extremely Large Telescope (E-ELT) in terms of technology as well as operations.

VLT VISIR: controlling data quality and instrument performance

VISIR is the new ESO VLT instrument mounted at the Cassegrain focus of Melipal (UT3) telescope. At Paranal it is the very first instrument capable of high sensitivity imaging in the N band and Q band mid infrared atmospheric windows. In addition, it features a long-slit spectrometer with a range of spectral resolutions between 150 and 30000. VISIR had been included in the standard VLT data flow operation even before regular observing started in March/April 2005. Data products are pipeline-processed and quality checked by the Data Flow Operations Group in Garching. The calibration data are processed to create calibration products and to extract Quality Control parameters. These parameters provide health checks and monitor instruments performance. They are stored in a database, compared to earlier data, trended over time and made available on the VISIR Quality Control web pages that are updated daily. We present the parameters that were designed to assess quality of the data and to monitor performance of the MIR instrument. We also discuss the general process of data flow and data inspection.

VISIR upgrade overview: all's well that ends well

We present an overview of the VISIR instrument after its upgrade and return to science operations. VISIR is the midinfrared imager and spectrograph at ESO’s VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan was based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array manufactured by Raytheon. In addition, a new prism spectroscopic mode covers the whole N-band in a single observation. Finally, new scientific capabilities for high resolution and high-contrast imaging are offered by sub-aperture mask and coronagraphic modes. In order to make optimal use of favourable atmospheric conditions, a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012, it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise. It is inherent to the design chosen for this detector and cannot be remedied by changing the detector set-up. Since this is a form of correlated noise, its impact can be limited by modulating the scene recorded by the detector. After careful analysis, we have implemented fast (up to 4 Hz) chopping with field stabilization using the secondary mirror of the VLT. During commissioning, the upgraded VISIR has been confirmed to be more sensitive than the old instrument, and in particular for low-resolution spectroscopy in the N-band, a gain of a factor 6 is realized in observing efficiency. After overcoming several additional technical problems, VISIR is back in Science Operations since April 2015. In addition an upgrade of the IT infrastructure related to VISIR has been conducted in order to support burst-mode operations. Science Verification of the new modes was performed in Feb 2016. The upgraded VISIR is a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It offers synergies with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey works like WISE. In addition, it will bring confirmation of the technical readiness and scientific value of several aspects for future mid-IR instrumentation at Extremely Large Telescopes. We also present several lessons learned during the project.

Quality control and data flow operations of SPHERE

ESO operates since April 2015 the new planet finder instrument SPHERE1 with three arms supported by a common path coronograph with extreme AO. Observing modes include dual band imaging, long slit spectroscopy, IFS and high contrast polarimetry. We report on the implementation of the SPHERE data flow and quality control system and on operational highlights in the first year of operations: This includes some unconventional parts of the SPHERE calibration plan like special rules for the selection of filters and the measures for an optimized calibration of the two polarimetric channels of the ZIMPOL arm. Finally we report on the significance of the SPHERE quality control system, its relation to the data reduction pipeline and which previously undocumented instrumental features have been revealed so far.

Detector Monitoring as part of VLT Science and Data Flow Operations

The ESO Paranal observatory is operating a heterogeneous set of science detectors. The maintenance and quality control of science detectors is an important routine task to retain the technical and science performance of the instrumentation. In 2006 a detector monitoring working group was built devoted with the following tasks: inventory of the currently existing detector calibration plans and monitored quality characteristics, completion and homogenization of the detector calibrations plans, design and implementation of cross-instrument applicable templates and data reduction pipeline recipes and monitoring tools. The instrument calibration plans include monthly and daily scheduled detector calibrations. The monthly calibrations are to measure linearity, contamination and gain including the inter-pixel capacitance correction factor. A reference recipe has been defined to be applicable to all operational VLT instruments and has been tested on archive calibration frames for optical, near- and mid-infrared science detectors. The daily calibrations measure BIAS or DARK level and read-out noise in different ways. This has until now prevented cross detector comparison of performance values. The upgrade of the daily detector calibration plan consists of the homogenization of the measurement method in the existing pipeline recipes.

Process control charts for dataflow operations of the ESO VLT

The Data Flow Operations Group of ESO in Garching, provides many aspects of data management and quality control of the VLT data flow. One of the main responsibilities is to monitor the performance of all operational instruments. We have investigated if the statistical methods of process control can be applied to the quality control of the VLT instruments and the data flow has been analyzed in this concern. The efficiency of these statistical methods is found to be related to the calibration plan, that determines the sampling size and frequency of calibrations. We apply these principles to ISAAC health check plots and give examples to demonstrate performance and limitations.