KEYWORDS: Antennas, Field programmable gate arrays, Astronomy, Optical correlators, Data processing, Logic, Digital signal processing, Polarization, Data storage, Switches
The MeerKAT radio telescope consists of 64 Gregorian-offset antennas located in the Karoo in the Northern Cape in South Africa. The antenna system consists of multiple subsystems working collaboratively to form a cohesive instrument capable of operating in multiple modes for defined science cases. We focus on the channelizing subsystem (F-engine), the correlation subsystem (X-engine), and the beamforming subsystem (B-engine). In the wideband instrument mode, the channelizing can produce 1024, 4096, or 32,768 channels with correlation up to 64 antennas. Narrowband mode decomposes sampled bandwidth into 32,768 channels. The F-engine also performs delay compensation, equalization, quantization, and grouping and ordering. The X-engine provides both correlation and beamforming computations (independently). This document is intended to be a stand-alone entity covering the channelizing, correlation, and beamforming processes for the MeerKAT radio telescope. This includes data reception, pre- and post-processing, and data transmission.
A tracking sensor system for precise telescope time realization called the Karoo Telescope Time (KTT), for next generation precision radio astronomy is described in this article. This is a key enabler for precision timing science like transients, pulsar search and pulsar timing. A Mark I real time sensor called KTT-GNSS was already implemented and verified and needs to ensure receptor timing below the <30ns level. Some aspects and design and algorithm testing for a Mark II post facto sensor called KTT-UTC which has the goal of <5ns is described herein. The Mark II sensor also has accurate daily intermediary sensors, based on past data, and is not based on any extrapolations like the Mark I sensor is.
KEYWORDS: LIDAR, Receivers, Laser systems engineering, Antennas, Telescopes, Clocks, Time metrology, Astronomy, Temperature metrology, Signal processing
An optical fiber based laser radar time transfer system has been developed for the 64-dish MeerKAT radiointerferometer telescope project to provide accurate atomic time to the receivers of the telescope system. This time transfer system is called the Karoo Array Timing System (KATS). Calibration of the time transfer system is essential to ensure that time is accurately transferred to the digitisers that form part of the receivers. Frequency domain reflectometry via vector network analysers is also used to verify measurements taken using time interval counters. This paper details the progress that is made in the verification measurements of the system in order to ensure that time, accurate to within a few nanoseconds of the Universal Coordinated Time (UTC, is available at the point where radio signals from astronomical sources are received. This capability enables world class transient and timing studies with a compact radio interferometer, which has inherent advantages over large single dish radio-telescopes, in observing the transient sky.
KEYWORDS: Radio astronomy, Systems engineering, Radio telescopes, Signal processing, Telescopes, Antennas, Optical correlators, Phased arrays, Tolerancing, Image processing
The Square Kilometre Array (SKA) is a large science project planning to commence construction of the world's largest Radio Telescope after 2018. MeerKAT is one of the precursor projects to the SKA, based on the same site that will host the SKA Mid array in the central Karoo area of South Africa. From the perspective of signal processing hardware development, we analyse the challenges that MeerKAT encountered and extrapolate them to SKA in order to prepare the System Engineering and Project Management methods that could contribute to a successful completion of SKA.
Using the MeerKAT Digitiser, Correlator/Beamformer and Time and Frequency Reference Systems as an example, we will trace the risk profile and subtle differences in engineering approaches of these systems over time and show the effects of varying levels of System Engineering rigour on the evolution of their risk profiles. It will be shown that the most rigorous application of System Engineering discipline resulted in the most substantial reduction in risk over time.
Since the challenges faced by SKA are not limited to that of MeerKAT, we also look into how that translates to a system development where there is substantial complexity in both the created system as well as the creating system. Since the SKA will be designed and constructed by consortia made up from the ten member countries, there are many additional complexities to the organisation creating the system - a challenge the MeerKAT project did not encounter. Factors outside of engineering, for instance procurement models and political interests, also play a more significant role, and add to the project risks of SKA when compared to MeerKAT.
Tim Gibbon, Enoch K. Rotich Kipnoo, Romeo R. G. Gamatham, Andrew W. Leitch, Renier Siebrits, Roufurd Julie, Sias Malan, Warnich Rust, Francois Kapp, Thondikulam Venkatasubramani, Bruce Wallace, Adriaan Peens-Hough, Paul Herselman
Scientific curiosity to probe the nature of the universe is pushing the boundaries of big data transport and computing for radio telescopes. MeerKAT, the South African precursor to Square Kilometre Array, has 64 antennas separated by up to 12 km. By 2018, each antenna will stream up to 160 Gbps over optical fiber to a central computing engine. The antenna digitizers require highly accurate clock signals distributed with high stability. This paper outlines requirements and key design aspects of the MeerKAT network with timing reference overlay. Fieldwork results are presented into the impact of birefringence and polarization fluctuations on clock stability.
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