Numerical analysis of the LOFAR remote station beamformer

LOFAR (Low Frequency ARray) is a large new radio telescope aimed at unusually low frequencies under development at ASTRON. Using phased array technology, one of the instrumental components of this system is the beamformer using phase shifters. The use of phase shifters over physical time delay devices reduces cost of the system and increases flexibility. Phase shifters allow us to create multiple beams at hardly any extra cost and it opens the possibility of adaptive responses to interfering signals. The unusual frequencies, combined with the desire to use non regular array configurations for the system means that analytical analysis of the station beaxnformer is hard, if not impossible. We therefore introduce a numerical analysis of the station beamformer using simulations of the LOFAR station both in Matlab and in C++.

The Square Kilometre Array Science Data Processor Preliminary Compute Platform Design

The Square Kilometre Array is a next-generation radio-telescope, to be built in South Africa and Western Australia. It is currently in its detailed design phase, with procurement and construction scheduled to start in 2017. The SKA Science Data Processor is the high-performance computing element of the instrument, responsible for producing science-ready data. This is a major IT project, with the Science Data Processor expected to challenge the computing state-of-the art even in 2020. In this paper we introduce the preliminary Science Data Processor design and the principles that guide the design process, as well as the constraints to the design. We introduce a highly scalable and flexible system architecture capable of handling the SDP workload

On optimising cost and value in compute systems for radio astronomy

Large-scale science instruments, such as the distributed radio telescope LOFAR, show that we are in an era of data-intensive scientific discovery. Such instruments rely critically on significant computing resources, both hardware and software, to do science. Considering limited science budgets, and the small fraction of these that can be dedicated to compute hardware and software, there is a strong and obvious desire for low-cost computing. However, optimising for cost is only part of the equation; the value potential over the lifetime of the solution should also be taken into account. Using a tangible example, compute hardware, we introduce a conceptual model to approximate the lifetime relative science value of such a system. While the introduced model is not intended to result in a numeric value for merit, it does enumerate some components that define this metric. The intent of this paper is to show how compute system related design and procurement decisions in data-intensive science projects should be weighed and valued. By using both total cost and science value as a driver, the science output per invested Euro is maximised. With a number of case studies, focused on computing applications in radio astronomy past, present and future, we show that the hardware-based analysis can be, and has been, applied more broadly

Software-defined networks in large-scale radio telescopes

Traditional networks are relatively static and rely on a complex stack of interoperating protocols for proper operation. Modern large-scale science instruments, such as radio telescopes, consist of an interconnected collection of sensors generating large quantities of data, transported over high-bandwidth IP over Ethernet networks. The concept of a software-defined network (SDN) has recently gained popularity, moving control over the data flow to a programmable software component, the network controller. In this paper we explore the viability of such an SDN in sensor networks typical of future large-scale radio telescopes, such as the Square Kilometre Array (SKA). Based on experience with the LOw Frequency ARray (LOFAR), a recent radio telescope, we show that the addition of such software control adds to the reliability and flexibility of the instrument. We identify some essential technical SDN requirements for this application, and investigate the level of functional support on three current switches and a virtual software switch. A proof of concept application validates the viability of this concept. While we identify limitations in the SDN implementations and performance of two of our hardware switches, excellent performance is shown on a third