The next-generation Very Large Array (ngVLA) is an astronomical observatory planned to operate at centimeter wavelengths (25 to 0.26 centimeters, corresponding to a frequency range extending from 1.2 GHz to 116 GHz). The observatory will be a synthesis radio telescope constituted of approximately 214 reflector antennas each of 18 meters diameter, operating in a phased or interferometric mode.
We provide an overview of the current system design of the ngVLA. The concepts for major system elements such as the antenna, receiving electronics, and central signal processing are presented. We also describe the major development activities that are presently underway to advance the design.
We give an overview of the scientific commissioning and early operation of the Karl G. Jansky Very Large Array (VLA). The Expanded VLA Construction Project was a decade-long project to transform the capabilities of the VLA, culminating in its re-dedication in 2012 as the Jansky VLA. The need to keep a vibrant and engaged user community throughout the entire construction project translated into operational requirements (one of which was allowing the minimum down-time possible), and the need for a mechanism to provide the community with early access to the new capabilities alongside on-going construction and commissioning, using a staged approach. This access was enabled during the EVLA Construction Project by defining an Open Shared Risk Observing (OSRO) program for the general community, and a Resident Shared Risk Observing (RSRO) program for those requesting capabilities not fully commissioned in exchange for a period of residency to help commission and test those capabilities with the assistance of NRAO staff. The OSRO program has become the General Observing (GO) program in full operations, and the RSRO program has continued as a means of maintaining, and adding to, an active pool of users with innovative ideas for new capabilities, driven by their science. Besides the new technical capabilities, the start of full operations of the Jansky VLA also introduced full dynamic scheduling, including the ability for fast (less than 24 hour) response to triggers and targets of opportunity, and the delivery of pipeline-calibrated visibility data for continuum projects. We discuss some of the challenges resulting from the new capabilities and operational model for the VLA.
KEYWORDS: Data archive systems, Data storage, Calibration, Visibility, Telescopes, Standards development, Observatories, Algorithm development, Data modeling, Software development
The Expanded Very Large Array (EVLA) project is the next generation instrument for high resolution long-millimeter to
short-meter wavelength radio astronomy. It is currently in early science operations, with full science operations to
commence in January 2013. The EVLA construction project provided new software for all aspects of operation of the
telescope, including both that required for controlling and monitoring the instrument and that involved with the scientific
workflow. As the telescope transitions into full operations we are also developing the software and operations policies
that allow us to manage the large amounts of data collected by the instrument (up to terabytes for a single observation;
petabytes per year for all observations). We present an overview of our data management software and policies for the
EVLA, as well as some early experience we have gained with the storage and distribution of data, post-processing,
automatic processing, and centralized reprocessing of data, and storage of derived products back into our science
archive.
The Expanded Very Large Array (EVLA) is an international project to improve the scientific capabilities of the Very
Large Array (VLA), an aperture synthesis radio telescope consisting of 27, 25-meter diameter antennas distributed in a
Y-shaped configuration on the Plains of San Augustin in west-central New Mexico. The EVLA's major science themes
include measuring the strength and topology of magnetic fields, enabling unbiased surveys and imaging of dust-shrouded
objects that are obscured at other wavelengths, enabling rapid response to and imaging of rapidly evolving transient
sources, and tracking the formation and evolution of objects in the universe. The EVLA's primary technical elements
include new or upgraded receivers for continuous frequency coverage from 1 to 50 GHz, new local oscillator,
intermediate frequency, and wide bandwidth data transmission systems to carry signals with 16 GHz total bandwidth
from each antenna, and a new digital correlator with the capability to process this bandwidth with an unprecedented
number of frequency channels for an imaging array. The project also includes a new monitor and control system and new
software that will provide telescope ease of use. The project was started in 2001 and is on schedule and within budget.
Scientific observations with the new correlator started in March 2010. The structural modifications that convert the VLA
antennas to the EVLA design were completed in May 2010. The project will be complete in December 2012 when the
last receiver will be installed on an antenna.
Begun in 2001 with a total budget of around $100M, the Expanded Very Large Array (EVLA) project is the only major
upgrade to the VLA undertaken since the interferometer was dedicated in 1980. The goal of this 11-year long project is
to improve all the observational capabilities of the original VLA - except for collecting area and spatial resolution - by
at least an order of magnitude. To achieve this, the 28 VLA antennas have been modernized with new digital data
transmission systems that link to a new, wideband, fiber optic digital LO/IF system, and eight new sets of cooled
receivers are under construction that will offer full frequency coverage from 1 to 50 GHz, with instantaneous bandwidths
up to 8 GHz provided by two independent dual polarization frequency pairs. The new WIDAR correlator provided by
NRAO's Canadian EVLA partner replaced the old VLA correlator in early 2010 and is currently undergoing
commissioning.
The long duration of the EVLA construction project coupled with the need to maintain the scientific productivity and
user base of the telescope obviously precluded shutting down the old array while new infrastructure was built and
commissioned. Consequently, the construction plan was based on the fundamental assumption that the old VLA would
continue to operate as new EVLA capabilities gradually came online; in some cases, additional complexity had to be
designed into new hardware in order to maintain transitional interoperability between the old analog and new digital
systems as the latter were installed and commissioned. As construction has advanced, operations has increasingly had to
coexist side by side with EVLA commissioning and verification. Current commissioning plans attempt to balance
making new EVLA capabilities available to the user community as soon as they have been installed and verified, and
maintaining a stable and robust end-to-end data acquisition and delivery process for the user community.
The Expanded Very Large Array (EVLA) project is the next generation instrument for high resolution long-millimeter
to short-meter wavelength radio astronomy. It is currently funded by NSF, with completion scheduled
for 2012. The EVLA will upgrade the VLA with new feeds, receivers, data transmission hardware, correlator,
and a new software system to enable the instrument to achieve its full potential. This software includes both
that required for controlling and monitoring the instrument and that involved with the scientific dataflow. This
manuscript presents an update on the overall design, and details for the pre-observing portions of the software,
including: user authentication; proposal preparation, submission, and handling; and observation preparation.
It will focus particularly on the observation preparation software, describing an implementation of a web-based
interface for creation of a detailed observation description, and plans to achieve common observation preparation
software with the ALMA telescope.
The "Project Data Model" (PDM) is a model of the information that describes an astronomical observing project. In this
paper we consider the PDM to cover the Proposal and Observing Preparation phases (also often called Phase 1 and Phase
2), and also the intermediate phase of reviewing and approving the project. At the back end of observing, the production
of calibrated or partially calibrated science data, such models or data structures have been common for some time, albeit
evolving (FITS, Measurement Set, etc.), but modelling the front end of observing is a relatively recent phenomenon, with
most observatories creating their own versions of the "PDM". This paper describes work towards a common PDM for
two radio observatories that are in development, ALMA and the EVLA. It goes further to explore the prospect of a wider
common PDM that could be shared across astronomy. Is there a case to produce such a common PDM? And is it
feasible? It is likely that a common model for Phase 1, an observing proposal, is possible. However, for a number of
reasons a common model for Phase 2 is a much tougher challenge.
The Expanded Very Large Array (EVLA) project is the next generation instrument for high resolution and high sensitivity long-millimeter to short-meter wavelength radio astronomy. It is currently funded by NSF, with completion scheduled for 2012. The EVLA will upgrade the VLA with new feeds, receivers, data transmission hardware, correlator, and a new software system to enable the instrument to achieve its full potential. This software includes both that required for controlling and monitoring the instrument and that with emphasis on the scientific functions related to the telescope. The primary goals of the software are: to maximize the scientific return of the EVLA; provide ease of use, for both novices and experts; exploit commonality amongst all NRAO telescopes where possible. The software design methodology includes detailed initial use-cases and requirements from the scientists, intimate interaction between the scientists and the programmers during design and implementation, and rapid prototyping and development cycles (as short as a week). This manuscript is an update of a similar description published for the SPIE meeting two years ago; a more full description and background can be found there, while this document concentrates on the changes since then, specifically in the area of the high level design and pre-observing software (user authentication; proposal preparation, submission, and handling; observation preparation; and observation scheduling).
The Expanded Very Large Array project has the top-level goal of
enhancing the performance of the Very Large Array by an order of
magnitude or more in all areas: sensitivity, frequency coverge,
spectral resolution, and spatial resolution. The project is being
implemented in two, overlapping phases: Phase I, which began in 2000
and will finish by 2012 addresses all new capabilities except spatial
resolution, and Phase II, which will improve tenfold the spatial
resolution, and which is planned to begin in 2006, and finish by 2013.
Progress in Phase I is very good, with first light and first fringes
having been achieved, and tests of the new hardware and software now
underway. A proposal for funding Phase II has now been delivered to
the National Science Foundation. A critical component of the project
is the new correlator, being designed and built by the Canadian
Herzberg Institute of Astrophysics at the DRAO in Penticton, BC
Canada. This new advanced correlator will be delivered beginning in
late 2008. First shared-risk science with the early portions of the
correlator will be done in late 2007.
The Expanded Very Large Array (EVLA) project is the next generation
instrument for high resolution long-millimeter to short-meter
wavelength radio astronomy. It is currently funded by NSF, with
completion scheduled for 2012. The EVLA will upgrade the VLA with new feeds, receivers, data transmission hardware, correlator, and a new software system to enable the instrument to achieve its full potential. This software includes both that required for controlling and monitoring the instrument and that involved with the scientific
dataflow. We concentrate here on a portion of the dataflow software,
including: proposal preparation, submission, and handling; observation preparation, scheduling, and remote monitoring; data archiving; and data post-processing, including both automated (pipeline) and manual processing. The primary goals of the software are: to maximize the scientific return of the EVLA; provide ease of use, for both novices and experts; exploit commonality amongst all NRAO telescopes where possible. This last point is both a bane and a blessing: we are not at liberty to do whatever we want in the software, but on the other hand we may borrow from other projects (notably ALMA and GBT) where appropriate. The software design methodology includes detailed initial use-cases and requirements from the scientists, intimate interaction between the scientists and the programmers during design and implementation, and a thorough testing and acceptance plan.
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