Brian Glendenning

Hydrogen Epoch of Reionization Array (HERA)

The Hydrogen Epoch of Reionization Array (HERA http://reionization.org) is a staged experiment that uses the unique properties of the 21-cm line from neutral hydrogen to probe the Epoch of Reionization (EOR). During this epoch, roughly 0.3-1 billion years after the Big Bang, the first galaxies and black holes heated and reionized the early Universe. Direct observation of the large scale structure of reionization and its evolution with time will have a profound impact on our understanding of the birth of the first galaxies and black holes, their influence on the intergalactic medium (IGM), and cosmology. This paper will provide an overview of the project and describe the design of the HERA receiving element.

First year of ALMA site software deployment: where everything comes together

Starting 2009, the ALMA project initiated one of its most exciting phases within construction: the first antenna from one of the vendors was delivered to the Assembly, Integration and Verification team. With this milestone and the closure of the ALMA Test Facility in New Mexico, the JAO Computing Group in Chile found itself in the front line of the projects software deployment and integration effort. Among the groups main responsibilities are the deployment, configuration and support of the observation systems, in addition to infrastructure administration, all of which needs to be done in close coordination with the development groups in Europe, North America and Japan. Software support has been the primary interaction key with the current users (mainly scientists, operators and hardware engineers), as the software is normally the most visible part of the system. During this first year of work with the production hardware, three consecutive software releases have been deployed and commissioned. Also, the first three antennas have been moved to the Array Operations Site, at 5.000 meters elevation, and the complete end-to-end system has been successfully tested. This paper shares the experience of this 15-people group as part of the construction team at the ALMA site, and working together with Computing IPT, on the achievements and problems overcomed during this period. It explores the excellent results of teamwork, and also some of the troubles that such a complex and geographically distributed project can run into. Finally, it approaches the challenges still to come, with the transition to the ALMA operations plan.

The ALMA computing project: initial commissioning

The Atacama Large Millimeter/Submillimeter Array (ALMA) is a large radio interferometric telescope consisting of 66 antennas with variable positions, to be located at the Chajnantor 5000mat a high site (5000m) in Chile. ALMA commissioning has now started with the arrival of several antennas in Chile and will continue for the next 4 years. The ALMA Software was from the beginning has been developed as an end-to-end system including: proposal preparation, dynamic scheduling, instrument control, data handling and formatting, data archiving and retrieval, automatic and manual data processing systems, and support for observatory operations. This presentation will expand mostly on ALMA software aspects issues on which we are concentrating in this phase: management, procedures, testing and validation. While software development was based on a common software infrastructure (ALMA Common Software - ACS) from the beginning, end-to-end testing was limited by the hardware available, and was possible for years until recently only on computer models. Although the control software was available early in prototype stand-alone form to support testing of prototypes antennas, it was only recently that dynamic interferometry was reached and software could be tested end to end with a somewhat stable hardware platform. The lessons learned so far will be explained, in particular the need for a realistic validation environment, the balance to be achieved between incremental development and the needed for stability and usability, and the way to achieve all the above with a development team distributed over three four continents. Some general lessons can be drown drawn on the potential conflicts between software and system (hardware) testing, or in other words on the danger in taking short-cuts in software testing and validation.

The last mile of the ALMA software development: lessons learned

At the end of 2012, ALMA software development will be completed. While new releases are still being prepared following an incremental development process, the ALMA software has been in daily use since 2008. Last year it was successfully used for the first science observations proposed by and released to the ALMA scientific community. This included the whole project life cycle from proposal preparation to data delivery, taking advantage of the software being designed as an end-to-end system. This presentation will report on software management aspects that became relevant in the last couple of years. These include a new feature driven development cycle, an improved software verification process, and a more realistic test environment at the observatory. It will also present a forward look at the planned transition to full operations, given that upgrades, optimizations and maintenance will continue for a long time.

The Hydrogen Epoch of Reionization Array Dish III: Measuring Chromaticity of Prototype Element with Reflectometry

Spectral structures due to the instrument response is the current limiting factor for the experiments attempting to detect the redshifted 21 cm signal from the Epoch of Reionization (EoR). Recent advances in the delay spectrum methodology for measuring the redshifted 21 cm EoR power spectrum brought new attention to the impact of an antenna’s frequency response on the viability of making this challenging measurement. The delay spectrum methodology provides a somewhat straightforward relationship between the time-domain response of an instrument that can be directly measured and the power spectrum modes accessible to a 21 cm EoR experiment. In this paper, we derive the explicit relationship between antenna reflection coefficient (S11) measurements made by a Vector Network Analyzer (VNA) and the extent of additional foreground contaminations in delay space. In the light of this mathematical framework, we examine the chromaticity of a prototype antenna element that will constitute the Hydrogen Epoch of Reionization Array (HERA) between 100 and 200 MHz. These reflectometry measurements exhibit additional structures relative to electromagnetic simulations, but we find that even without any further design improvement, such an antenna element will support measuring spatial k modes with line-of-sight components of k∥ > 0.2h Mpc− 1. We also find that when combined with the powerful inverse covariance weighting method used in optimal quadratic estimation of redshifted 21 cm power spectra the HERA prototype elements can successfully measure the power spectrum at spatial modes as low as k∥ > 0.1h Mpc− 1. This work represents a major step toward understanding the HERA antenna element and highlights a straightforward method for characterizing instrument response for future experiments designed to detect the 21 cm EoR power spectrum.

ALMA software management and deployment

The ALMA Software (~ 80% completed) is in daily use at the ALMA Observatory and has been developed as an end-toend system including: proposal preparation, dynamic scheduling, instrument control, data handling and formatting, data archiving and retrieval, automatic and manual data processing, and support for observatory operations. This presentation will expand on some software management aspects, procedures for releases, integrated system testing and deployment in Chile. The need for a realistic validation environment, now achieved with a two antenna interferometer at the observatory, and the balance between incremental development and stability of the software (a challenge at the moment) will be explained.

Ten things we would do differently today: reflections on a decade of ALMA software development

The software for the Atacama Large Millimeter/submillimeter Array (ALMA) that has been developed in a collaboration of ESO, NRAO, NAOJ and the Joint ALMA Observatory for well over a decade is an integrated end-to-end software system of about six million lines of source code. As we enter the third cycle of science observations, we reflect on some of the decisions taken and call out ten topics where we could have taken a different approach at the time, or would take a different approach in today’s environment. We believe that these lessons learned should be helpful as the next generation of large telescope projects move into their construction phases.